Sherman Tank Site News Post 17: Summer is here, I have all kinds of content for updates, but less time than I would like.
I am always tweaking the site and doing minor edits, but in the past few weeks, I’ve had time for some more major projects. There have been a few minor projects worth noting as well.
The Editor over at Tank and AFV News sent me some very interesting reports that give a very interesting look into the Army’s search for a suitable tank Motor.
THE NEW REPORTS! (They are new to the site, not new)
Ordnance Development of the Wright-Continental R-975 Radial Engine: This report is very interesting. It shows how long, and just how far the Army and Continental went to try and improve the life of the R-975 tank motor. By the time they were done, it was almost a new motor, but still not a great tank motor. Good enough for sure, but no Ford GAA, or as reliable as even the A-57!
Ordnance Development of the Chrysler a-57 Multibank Tank Engine:This report is just like the one on the R-975, but all about my favorite tank motor, the Mighty A-57! This motor became shockingly reliable for how complicated it was. What made it great was the complication only came in mating the five motors, the banks themselves were solid, wells designed, motors.
These reports will give you a very good look into why the US Army chose the motors they did and the story behind getting each one to work as a tank motor. They are interesting stories in their own right.
Sherman Tank Site Post 73: Articles from Army Motors Episode #1
This is the first in a series of posts I’m going to do highlighting the Sherman or M4 series-related vehicle, articles I’ve found. With some commentary, though some of these articles are so good they speak for themselves.
Give Your Tank a Brake!
This article surprised me, because in the world of 4 wheel drive, compression braking is commonly used to control a vehicle on steep hill descents, and some vehicles have very low gears in their transfer case for this purpose, among others. I bought a Jeep Rubicon because it came with a Transfercase to do this.
A tank is not a Jeep though, so I clearly get the point of the article. Also, as for using the engine to brake, I’ve never been big on downshifting for that reason, even in cars and Jeeps. I once had a conversation with my wife, who was big on downshifting, about the cost and labor of a new set of brake pads, versus a new clutch. She agreed once we talked about the labor involved.
I started a new image improvement series based on the Shermans Motors. I was not entirely happy with the first series of images I cleaned up regarding the Ford GAA and the M4A3. There were several reasons, the main being, I just got a lot better at using the imaged editing software over the process of doing that first set. This left a lot of images of less quality than they could be, and that annoys me so I’m going to fix that. On the upside, many of these images already are almost done, so fixing them does not take that long.
Another problem with the early parts diagrams is they only have simple part names. If I don’t know for sure the name of the port, a cover plate is covering and the diagram just says cover, it makes it less useful. What’s interesting is you can find the same images just labeled differently in the different parts catalogs and Technical Manuals. On the improved images, I’m using the actual commonly used parts name. Digging through the various manuals to figure this out can be time-consuming, but I always learn something so it’s ok.
I‘ll post a bunch of the updated images at the end of this post.
I put up Clothing and Gear store, you can click on the first link to go directly to the link, or the second link to go to the preview page on this website, with some larger images of some of the shirts. The idea behind the store is even if it only makes a few bucks a month, it can help offset some of the web pages hidden costs. I think I have some amusing T-shirts up, check it out.
I put in a small forum, so people have an easier venue to discuss things since the comment system is clunky for that. To start it off, I put a post up about my feelings on the Sherman Stabilizer system and if it not being commonly used is a myth or not. Please pop over and add your feedback.
Coming soon, more huge Technical drawings and parts breakdowns.
I downloaded this PDF, Report on The New Weapons Board 1944, someplace, but since I don’t remember where I hosted it too. The report documents the feedback the troops gave to the board on the various weapons they demonstrated.
The report was put together in early 44 to document feedback from the troops on current weapons, and proposed improvements, and replacements. There is a good amount of information on the M4 medium tank, and US Armor in general. Most of the combat feedback comes from the fighting in Italy, and North Africa.
The report also sheds an interesting light and gives evidence for the view that the US Army didn’t consider the improved early Sherman bad, and only wanted it replaced with something much better. It also gives some interesting insight into the Shermans and what condition they were in when they got to the using units.
Feedback on current equipment and changes.
The first thing is this to note about the Sherman is the first mention of it is praise for the current models. This quote stands out, “No new type is desired unless the improvement in military characteristics is sufficient to warrant the changes and defects in the present standard tanks are avoided.”
They did have a list of improvements they did want either done to the Sherman and to make sure the follow-on model, the T20 series incorporated them.
They wanted a 76mm gun like the 3-inch gun on the M10. The news of the 76mm M1 series and the new Shermans mounting the gun interested the troops a lot. They brought an M4E6 76mm Sherman to show to the troops.
Improved suspension and tracks. It turns out the rubber block tracks with no chevron were not well liked and wore out very quick in rocky, hilly terrain. The steel chevron blocks with rubber backs were well like and lasted much longer. This feedback is mostly from the MTO, the mountainous and rocky landscape was hard on tanks and even the Sherman had some issues. The complaints about the suspension had more to do with width than durability.
They wanted armored air cleaners on the M4 and M4A1 tanks. It turns out the Air cleaners mounted under the overhang on the rear hull of the M4 and M4A1 tanks were prone to damage, and this damage was not expected and didn’t pick up until Italy so there was a shortage. All other models had the air cleaners inside the hull. Some units added improvised armor and some were added later in the production runs.
Better ballistic angle around the front of the transmission housing. The old three-part differential is what they are talking about. Most early Shermans had this type, and the armor was thinner than the later cast single piece units. There were two cast versions, an early thinner, but still no worse than the three-piece unit, and a later improved thicker one. There was a demand for add-on armor over this area, but it was never approved.
More power. Yet, when the M4A3 Ford GAA powered Shermans came online, they did not want to swap them in as replacements, and only wanted whole units who trained on them stateside first to be issued the improved tanks. The M4A4 and M4A2 were not big enough improvements to switch to those motors.
Diesel engine. The US Army rejected the GM 6046, claiming it was not as reliable as the R975, but all the nations that did use this motor liked it.
They wanted better sights and fire control equipment. Many tanks in the MTO and NATO(North African Theater of Operation) had not gotten the M34A1 gun mounts with telescopic sights. The mount for the periscope sight had not seen major improvements, though there were field mods to make it work. The using arm was enthusiastic about the changes in the second gen Shermans fire control, but wanted even more advanced features, like rangefinders, and improved telescopes, since the current ones shot loose too!
There is also other tank related info.
The M3 75mm Gun – Though well-liked for infantry support and deemed to be reliable and durable, the using arms almost universally felt the German 75mm PAK 40 guns were much better anti-tank weapons, and a high-velocity 76mm gun was in demand.
75mm ammunition – these fixed rounds came unfixed, sometimes even in their travel packaging. They wanted this fixed. They wanted the WP shells ballistics to match the ballistics of the common HE shell.
Large caliber cartridge cases – Steel cases for the 75mm rounds for the M3 gun were well received and proved more durable. This was not the case for 105mm howitzer rounds.
105mm howitzer armed tanks – This was not a popular notion because the M7 105mm GMC was inaccurate when used for direct fire to support infantry assaults. The new weapons board did not agree, and plans for this vehicle were already in motion, and it would be well liked once issued.
Tank Officers – they wanted a tanker officer in the high-level headquarters to advise Division and higher level officers the best way to use tanks. AA and Tank destroyer officers were already an accepted part of these HQ staffs.
the 17-pdr gun – There was more interest in using this gun in M10s since the install was much simpler, the Sherman install was complicated and cramped and the Army was leary.
Tank Tracks – They show up again and the plain rubber block tracks could wear out in 250 miles in rocky terrain and lacked good off-road traction, and the using arm felt they were only good for training on roads. The T54E1 steel chevron type was preferred and much more durable, but the T48 rubber chevron would work in the MTO but wore out faster than steel types. The T49 bar cleat was also not good on sidehill terrain. The using arm wanted a wider center guided track in the MTO because the side guided tracks on the Sherman were prone to throwing on irregular and rocky side slopes. Extended end connectors were well received by the using arms.
Tank Suspension – Sherman suspension was found to be durable, with few volute springs failing. The biggest problem was the bogie wheels since the rubber tires had an erratic failure rate, and unlike the spring failures, usually sidelined the tank.
Ammunition stowage – They using arms were not interested in changes that reduced the number of ready rounds. The turret ready racks were very popular and crews did not like their removal with the ‘quick fix’ mods. They were willing to risk the higher fire chance, for the faster rate of fire the early storage setup allowed. The crews did not get their way on this one, at least until the M26 went into production.
The Radios – They wanted a better radio in the M32 recovery vehicles and better, more comfortable headphones for the armor crews.
The M10 GMC – This TD was very popular, and received high praise all around. The using arm did not require a replacement, just improved M10s. ♠ One thing to note, most M10 GMCs in MTO lacked the Azimuth indicator and range quadrant. Since the M10s get used as artillery a lot in the MTO, they would like replacements to have them.
Replacement gun tubes – The using arms were very annoyed, that all type of gun barrels from machine gun and mortar, to tank and artillery, were dispensed at a very miserly rate. The using arm argued replacement barrels should be bought at the rate that took into consideration how much ammunition for the same weapon was produced.
Improved fire control for all relevant vehicles – They wanted built-in rangefinders, or portable ones supplied. Better periscope and telescope sights and all vehicles that could be used for indirect fire to receive the full suite of tools to perform the task. I had never heard that some Shermans did not get these automatically. I’m not sure why some Shermans and TDs didn’t have the Azimuth indicator M19 and elevation quadrant M9. Maybe the crews dumped them to save space, maybe the tanks were rushed and built and approved without them I’ll try and find out. They mention 75% of the tanks in England had these items, but less 50% had them in the MTO. Tank units were much more commonly used for indirect fire in the MTO than they would be in the ETO.
Engines – The R975C-1 was getting around 200 hours before needing replacement. This was fine with the using arm, though they would like 60 to 100 more horsepower. The R975 needed little maintenance to reach the expected 200 hours and many run much longer. The lack of liquid cooling system has some advantages.
Powertrain – There was a higher than expected rate of clutch failure in the desert campaigns. The clutch system was also improved on the production like with improved leverage to lower the clutch pedal pressure. Many MTO units did not receive the improved clutches or linkages. The better clutches lead to better transmission life and better shifting, and even without the improved clutches, transmission life went up in Italy. The powertrain offered excellent service and generally outlived the engines by several overhauls if not damaged.
Crew comfort – the Driver and Co-drivers seats in the Sherman were found to be ok, but higher seat backs were requested along with deeper seat cushions. The Gunners seat was found to be ok but could use the same improvements as the driver’s seats but the Command and Loaders seats were deemed all but useless. These would be improved in the later models of the Sherman and various TDs. Crews do not use their seatbelts, fearing it complicating bailing out, and more padding inside was not wanted because the crews felt it was a fire hazard. The M4 and M4A1 tanks were praised for good ventilation. There was also some discussion about the value of turret baskets, and if they were needed at all.
Ammo Storage – The early Sherman ready racks in the turret were well liked by the using arms, but they felt the sponson and hull ammo racks were no good and didn’t support the 75mm Shells enough. They would often separate and dump a bunch of gunpowder inside the tank making a deadly mess to clean. The using arm tends to stuff the tank with extra rounds, adding to the shell durability problems. These problems would be addressed in the second gen improved hull tanks.
General storage – The current storage space on the Sherman was deemed ok, but better, easier to access bins were requested. They also wanted any storage in the floor to be resistant to getting filled with dirt or water.
Machine guns – The bow machine gun saw a lot of use, but its usefulness would be improved by a sighting system. One was in the works, but not at the point of this report. The M1919 machine guns, both bow, and co-ax were reliable as long as the crew was careful with the ammo. Long road trips could vibrate rounds loose in the belts and cause problems, but under normal conditions, this was rarely a problem with well-trained crews. The crews wanted a better adjustment method for matching the co-ax gun to the gunner’s site, the current one was not very good. The .50 AA mount was not well liked or considered important. Requests were made for a better mount for ground targets.
Turret hatches – The current split hatch was deemed ok, but the crews like the looks of the new all around cupola and were also enthusiastic about a loader’s hatch on the new 76 armed tanks.
Armor – There does not seem to be a consensus on how much armor a tank should have by the using arms. Armored Force troops felt the current level on the Sherman was fine, but wouldn’t mind more as long as it did not negatively affect flotation, maneuverability, and speed. ♠The British generally wanted heavier armor than the US Army. ♠♠Combat in Italy showed the differential was taking more hits than anything, and another request was made for add-on armor for the area.
Sand Shields – The general consensus on these was they were useless in any theatre and needed to be redesigned. They needed to be easier to install, and designed to not trap mud.
Flotation – The using arms wanting tanks around 10 pounds per square inch. This was very optimistic since even the HVSS Shermans came in around 11 PSI, the basic 75 VVSS Sherman around 13. It seems the Germans flooded fields in Sicily and Italy when they retreated, and Shermans got bogged down most of the time. They offered the suggestion of just stretching the Sherman since more length would help, and the British M4A4 tanks, the longest production Shermans, had no maneuverability issues.
Maneuverability – In the US Army there was a desire across the board for more maneuverability, in tanks. One thing to keep in mind though is the tanks in the MTO were older and most had single anchor steering brakes, the double anchor made the tanks easier to maneuver requiring less lever pressure. The ability to skid turn was not something US troops seemed interested in.
Accessories – The troops had a lot of feedback here. ♠ The instruments and gauges in medium tanks were not good quality, if they worked they didn’t work long. Oil pressure gauges fail, and no one worries about the motor until both oil pressure gauges die and a low oil pressure light comes on. This seems to be US feedback, I don’t recall hearing complaints from the Brits about Gauge quality. I wonder if the different tank plants sourced gauges from different companies. ♠♠ The compasses on US tanks would not stay calibrated. This would be a very annoying problem but eventually solved on second gen Shermans. ♠♠♠ Armor for the air cleaners on the M4 and M4A1 comes up again. ♠♠♠♠ The Auxiliary giving good service, and are well liked, but the using arms would like the area around the fuel tank filler for the Aux motor to be waterproofed better. They also noted replacements were hard to come by.
Modifications – ♠ The jist on this one was, in many cases modifications can be seen by inspecting a vehicle, but in others, access panels or more might have to be removed to check. The using arms proposed a record imprinted on a brass plate, attached to the vehicle, listing all the modifications that had been applied. ♠♠ They also wanted to emphasize that they did not want any modifications that would not ‘materially increase the efficiency of the vehicles’
Development – The using arms were curious about the items in development, and finding out a large organization was working to improve almost everything was a morale booster. There was also interest in the T-20 series and if any test vehicles would be sent over for some for feedback like the M4A1 prototype has been.
Information and feedback on future equipment.
The M4E6 or pre-production M4A1 76w – ♠ This improved version was well liked by everyone who checked it out. The bigger turret was a big hit, though not much bigger, it seemed roomier. ♠♠ The improved fire control gear was very well liked and considered an ‘outstanding improvement’. The 76mm gun was well liked, and everyone seemed to agree needed. ♠♠♠ The only real concern was the less effective HE round, but it was hoped they would make a better one.
The M18 76mm GMC – The first and bad impression this vehicle lefts was it had no armor, and seemed very mechanically complicated. The fire control gear was well liked. When the vehicle was demonstrated, the tracks and unthrowable tracks also got a lot of attention. No one was sure if the speed would be useful, but the maneuverability was well liked. ♠ The same story with interest in deployment, not as a replacement vehicle, but fulling trained units from the ZI would be ok. ♠♠ This vehicle was not wanted by M10 units already deployed. Units equipped with it in the ZI then deployed were better received, the M10 was still more popular. An M10 with a 90mm gun was the preferred replacement.
M4A3 75W – Even though the Ford GAA was a big improvement, it was not enough of an improvement to take them on as replacement vehicles. They were fine for them to be brought with units already fully trained on them.
The M1 Dozer blade kit – This kit was an instant hit and would have many uses, including clearing rubble after heavy artillery reduced a strong point. Currently, this has to be done by an unarmored bulldozer and casualties were high. it was hoped they would work well enough to help tanks dig in or SPG prepare a position. ♠ Through testing, they found this kit could be installed on any Sherman tank type.
This report goes into detail in the appendixes listing all the items demonstrated, and where they were demonstrated. They also include data on how many of the various items demonstrated were ordered by the various theatres.
I think it’s pretty clear the MTO was a backwater. The general shortage of spare parts in the MTO and a shortage of personnel to staff the proper echelons of repair and salvage system are also indicators of this. As they got ready for the June of 44 landings, the troops in England would be getting top priority and supplies and spares.
There is a lot of info on other weapons like artillery and small arms, not directly Sherman related and therefore, uncovered here. The report is definitely worth a download and re through. I think it offers a good insight into the thinking involved on not swapping to 76mm armed Shermans before the Normandy landings.
The Sherman Motors: Why So Many, And Why The Weird Ones?
The Sherman had four different motors that made it into production tanks. The R975 radial, The GM 6046 ‘twin’ diesel, the A57 multibank, and the Ford GAA V8. There was also a Caterpillar motor they were trying out I cover in the Shermans of the Future section.
There are several reasons the US went with the radial aircraft engine instead of a dedicated tank power plant, and this was mostly due to lack of money to develop tanks and their drivetrains between wars. When the US got serious about tank motors, there were a limited number of choices and the R975 was the best one. Then they turned to the US auto industry for other motor ideas, but only after the war was clearly looming. The US Government went to General Motors, and Chrysler, and asked for a tank motor ASAP, they got motors ASAP, but they were lash-ups, but they ultimately worked well. In this case, desperation produced the weird motors, and American automotive know-how, made them reliable.
GM came up with their twin bus motor, the 6046 and it was well-liked right from the beginning. Then Chrysler came out with the nutty but fantastic A57. The US Army didn’t like either and didn’t want to even use them for training. If the British hadn’t been willing to take the A57 versions, the Army would have regulated them to training use only. It wouldn’t be until Ford figured out the bugs in the GAA V8 that the US Army would make the switch from the R975. R975 powered M4s and M4A1s would serve with the US Army until the end of the war in just about every unit that used Shermans though, and they would not be phased out until after the war.
Post-war many A4 tanks would have R975s put in them, or in much rarer cases, the 6046. Parts of the A57 became rare post-war, and people who knew how to keep them working were probably rarer. I’m pretty sure almost all A4s used post the 50s were converted to one or the other of these motors. Conversions to the Ford GAA were not done as far as I can tell, I think because the US Army was stingy with this model and spares for it, so they could keep them for their own use or close allies.
The Continental R975 C1/C4: The Motor the Sherman was designed around
The Continental R975 C1/C4: Type:9 cylinder, 4 cycle, radial Cooling system:Air Ignition: Magneto Displacement:973 CI Bore and stroke:5×5.5 inchesCompression Ratio:5.7:1 Net Horsepower: C1/C4 350/400 hp Gross Horsepower:C1/C4 400/460 hp Net Torque: C1/C4 800/ft-lb/940/ft-lbGross Torque: C1/C4 890ft-lb/1025ft-lb Weight:1137 lbs dryFuel:80 Octane gasolineEngine Oil Capacity:36 quarts
This motor was a license-built version of the Wright R-975 built by Continental for tank use. It had been around nearly ten years and used in civil aviation before the army started putting it in tanks, starting with the M2 medium in 1939, and would go on to produce more R-975s than Wright ever would, 53,000 motors total. The military version put out more horsepower than the civil version as well. This was a solid and reliable tank motor, but not ideal. It was a little underpowered and had to be revved up a lot to get the tank moving. The Army considered this a superior choice over the 6046 diesel and A57 motors, probably because it required a lot less maintenance than the other two motor choices. This motor would be swapped into M4A4 hulls by the French post-war, the French would use the A4, and A2 with the original motors during the war.
Another reason the motor was not ideal was the shape, the R975 is wide and tall, and this dictated how large the rear hull of the tank had to be. The only motor larger was the A57, and it was huge. There are still a lot of Shermans still running with this motor, either in civilian collections, or museums that keep running tanks.
The General Motors 6046: The Motor GM Came Up With To Power The Sherman
The General Motors 6046: Type:12 cylinder, 2-cycle, twin in-line diesel Cooling system:LiquidIgnition: compression Displacement:850 ciBore and stroke:4.25×5 inchesCompression Ratio:16:1 Net Horsepower: 375 Gross Horsepower:410 Net Torque: 1000 ft-lbsGross Torque: 885-lb Weight:5110 lbs. dryFuel:40 cetane diesel oilEngine Oil Capacity:28 quarts
First used in the M3A3 and M3A5 and then in the M4A2. This motor tied two GM supercharged truck diesel together on a common crankcase. The motors could be run independently, so if one was damaged the other could be used to get the tank back to a repair depot, or to keep fighting. The engine weighed more than the R975 but had better torque characteristics, and the tanks with this motor handled low-speed operation better because of the superior torque.
This version was ruled out for use by the Army because they didn’t want to complicate the tank supply chain by adding another fuel to it. This motor was well-liked by its users, and the only version of the Sherman the Soviet Union would take via lend-lease were the ones powered by this motor. The Army testing of this motor found it was as reliable as or more so than the R975.
This motor would run and drive the tank if one of the diesels failed. It has also been reported the Russians would use the ability to only run half the motor to sneak the tanks closer to German lines without being heard. They were impressed with how quiet the Shermans tracks were.
The early drawbacks to this motor were tied to its air cleaner system for the motors; they would clog quickly and required a lot of maintenance. Getting the two clutches for the motors synchronized was difficult on early tanks with these motors as well and this made for short clutch life. There were some other teething troubles with the fuel injectors and other problems, but these would all be solved early in the M4A2 productions, including improved injectors, air cleaners, and clutch system.
The US Army hadn’t wanted to use tanks with this motor in combat, but they ended up doing so since this motor also powered the M10.
The Chrysler A57 Multibank: The Motor Chrysler Came Up With To Power Tanks, It Was Crazy, And It Worked!
The Chrysler A57 multibank: Type:30–cylinder, 4-cycle, multibank Cooling system:LiquidIgnition: Battery Displacement:1253 ciBore and stroke:4.37×4.5 inchesCompression Ratio:6.2:1 Net Horsepower: 370 Gross Horsepower:425 Net Torque: 1020 ft-lbsGross Torque: 1060 ft-lbs Weight:5400 lbs. dryFuel:80 octane gasolineEngine Oil Capacity:32 quarts
This motor was a bit of an orphan in US Service. It powered the M3A4 and M4A4. The Army used the motor for training and tried to pawn a few off on the Marines. That lasted about two months at the Marine Tank School. The ever-growing need for tanks by the British ultimately solved what to do with the tanks that ended up with this motor. They would end up taking nearly 8000 of them. Chrysler sent tech reps to England with these tanks and showed the maintenance crews how to keep them running. This worked well and the engines served their purpose with little trouble. Often powering the best pure AT version of the Sherman, the Sherman VC Firefly. This motor saw a lot of use, during the war, and after with many countries being given Firefly Shermans to help out their recovering militaries. Some even ended up in South America, but I’m not sure what versions. This is my favorite Sherman motor because it’s so absurdly complicated, it’s almost German, but it actually worked, so not German at all.
This motor was fairly robust and would continue to run and allow the tank to move with three of the five-cylinder banks not working. This would make the tank severely underpowered but would be useful to get it back to the repair yard or onto a dragon wagon. I’m sure it was much more common to have one of the five not operating right, and that level of power loss would be an annoyance, but wouldn’t keep the tank from fighting if it was really needed.
During the war, Chrysler really went to bat to keep these motors working well. Since it was based on a motor already long in production, spare parts were readily available. I’m not sure how long support for the motor lasted after the war. I doubt it was very long, and American car parts were probably not easy to acquire to keep these motors running. Because of this, the M4A4, more than any other model seems to have its engine replaced in post-war service. I’ve read about the twin diesel and the R975 being swapped in. There are a few M4A4s around in Europe with running A57 motors, both fireflies if I recall right. You have to love anyone willing to keep one of these motors running.
Daily maintenance could be done with the motor in the tank, carburetor and timing adjustments, fluids and filters, and things like that. If anything major needed to be fixed, one of the motors had a bad piston or valve, or even something minor like a big vacuum leak on the intake of one of the motors, or even a leak in the cooling system, the whole motor would have to be pulled. Chrysler knew this and made getting the motor in and out as easy as possible, including huge lifting eyes built on the common block to help lift the motor out. The British probably had several depots set up to rebuild A57 power packs that were in need of major work, and Chrysler made a lot of spare motors and parts to support the motor.
To be fair, many serious problems with the other tank motors would require pulling the motor to fix them as well.
The Ford Motor Company GAA V8: The Best Sherman Motor
The Ford GAA: Type: 8 cylinders, 4-cycle, 60-degree V8 Cooling system:LiquidIgnition:Magneto Displacement: 1100 ciBore and stroke:5.4 x 6 inchesCompression Ratio:7.5:1 Net Horsepower:450 Gross Horsepower:500 Net Torque: 950 ft-lbs Gross Torque:1040 ft-lbs Weight:1560 lbs. dry Fuel:80 octane gasolineEngine Oil Capacity:32 quarts
The Ford GAA only made it into one Lee as a testbed. But it powered a lot of Shermans, both large and small hatch. It would go on to be the motor of choice for the US Army for the rest of the war, and in the next tank, the M26. Just look at the numbers above and compare them to the rest of the motors. The GAA is really a much better motor for a tank in the Shermans weight range. This tank was not lend-leased to the other allies in large numbers if at all. The USSR may have gotten one to evaluate, the UK too, but the Army wanted to switch over to this and stop using R975 powered tanks. After the war, the only Shermans they kept were M4A3 76 w tanks, and over time they converted as many of these to HVSS suspension as possible. They went as far as swapping T23 turrets from M4A1 76 W tanks onto M4A3 75 hulls. The army would produce several other gas-powered tank engines, but none would really shine like this one did in the Sherman.
The motor started life as a V12 Ford had designed to compete with the Rolls Royce Merlin, after a deal to produce the RR engine fell through. Ford was incensed that a deal could not be worked out and decided to build his own V12 aircraft motor. When he tried to sell it to the Army he was turned down, but later when the army needed tank motors he used the V12 as a basis for the V8, by removing 4 cylinders. As a tank motor, it was under very low stress putting out only 500 horsepower, and could have been really upped in horsepower with a few tweaks.
This motor does not get much credit for how advanced it was. The much talked about, and unreliable as hell, German Maybach HL 230 P30, the motor used to power the Tigers, and Panther tanks, was not nearly as advanced, or as reliable as this amazing V8. This V8 is apparently the largest gas-powered all-aluminum V8 ever produced. It has some very advanced features, even for a modern V8, like a one-piece cast aluminum block with dual overhead cams and four valves per cylinder a true, dual, overhead, cam, motor, or DOHC. It had a very innovative 8-way power drive system for its accessories, like the generators, fuel and water pumps, and two magnetos. The motor used no belts or chains, everything was gear and shaft driven.
This motor saw post-war use in civilian hands, from powering logging equipment, to use as stationary pump motors. The most interesting post-war use is in pro-tractor pulling and hotrod use. These installations in most cases just update the intake and exhaust using modern carbs, but in one crazy case down in Brazil they have updated a GAA with coil and spark plug and crank sensor` computerized ignition, fuel injection and twin turbos, and just 8 pounds of boost it makes 1500 hp, with a higher boost number the engine is capable of 3000 HP. For more info on these modifications and some pics, check out this link.
Sources: Sherman by Hunnicutt, The Sherman Minutia Site, Son of a Sherman by Stansell and Laughlin, M4 Sherman tank at war by Green, Tanks are a Might Fine Thing by Stout, TM9-731B M4A2, TM9-731G M10A1, TM9-745 GMC M36B2, TM9-748 GMC M36B1, TM9-750M3, TM9-752 M4A3, TM9-754 M4A4, TM9-759 M4A3, TM9-1725 R975 C4, TM9-1731B Ford motors(GAA, GAF, GAN), TM9-1750F A57 Multibank