# 6T40 Transmission Specifications



## ECOmaniac (Mar 14, 2012)

Anyone have a good, hard data sheet that spells out the specifications for HP/TQ, talking maximum input/output tolerances/spefications, not gear ratios, for the 6T40 transmission that is in the A6? Again, not looking for engine crank specifications, I know what those are. I've found some literature on the 6T40 but the gear ratios don't line up with what I know ours are, not sure if the transmission was revised for the Cruze and kept the same 6T40 name with variations in P/Ns or what. Was hoping the 6T40 engineer would chime in...


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## 70AARCUDA (Nov 14, 2010)

...from the *GM-Powertrain* website:


*Hydra-Matic 6T40 (MH8)*
Type:
Six speed front-wheel-drive, electronically controlled, automatic overdrive transaxle with an electronically controlled torque converter clutch.
Maximum Engine power ( hp/kW )
180 hp ( 134 kW )
Maximum engine torque:
177 lb-ft (240 Nm)
Maximum gearbox torque:
277 lb-ft (375 Nm) - All gears
Gear ratios:
MH8
First
4.58
Second
2.96
Third:
1.91
Fourth:
1.45
Fifth
1.00
Sixth
0.75
Reverse:
2.94
Final Drive Ratio:
3.87
Maximum input speed:
Rev 4000 rpm
1-2 7000 rpm
2-3 7000 rpm
3-4 7000 rpm
4-5 7000 rpm
5-6 6000 rpm (corresponds to 4476 rpm in 6th after the shift is complete)
Maximum input speed in 6th:
4476 rpm
Maximum validated gross vehicle weight:
1996 kg (4400 lbs)
Shifter Posistions:
P, R, N, D, M
Case material:
die cast aluminum
Shift pattern:
Variable Flow Solenoids
Shift quality:
Variable Flow Solenoids
Torque converter clutch:
Variable Bleed Solenoid
Converter size:
236mm (reference) (diameter of torque converter turbine)
Fluid type:
DEXRON® VI
Transmission weight:
wet: 82 kg (180.4 lb)
Fluid capacity (approximate):
7.77L (6.56 kg)
Bottom pan removal:
NA
Pressure taps available:
Line Pressure
Transfer design:
Two-axis design, Output Chain
Assembly sites:
GMK (Korea), SGM (China), SLP (Mexico), TTO (Toledo).
Applications:
Chevrolet Malibu & Cruze, Buick Regal & Verano


...also see previous posting on this subject (midway down): http://www.cruzetalk.com/forum/34-1-4l-turbo/5888-manual-transmission-specs.html


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## OnlyTaurus (Mar 20, 2012)

I dont have much experience with the 40 series, but I completely disassembled and reassembled a FWD 6T75 and I was impressed on how relatively easy it was! No bands, servos, accumulators. Just clutches, pistons, and gears below the electonics! Heavy transmission, but I actually had fun tearing into one of those lol


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## Jim Frye (Mar 16, 2011)

From what I've been told by some folks that build them and from what I've read online, there are currently three generations of the 6T40 transaxle. 
First Gen: 2011 Cruze and Regal
Second Gen: 2012 Cruze and Regal new TCM, some bearing changes, and new software. 
Third Gen: Second Gen. but with a second TCM for the eAssist functions in the new Malibu and Verano. Not used in Cruze.


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## 70AARCUDA (Nov 14, 2010)

...there's basically three different versions (6T40, 6T45 and 6T50) under these RPO code applications: MH8, MH7, MHK, MHH, MHC, MHJ.


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## ECOmaniac (Mar 14, 2012)

Thanks for the info guys - more so concerned about the limitations when doing modifications. Doesn't look like there is much wiggle room here, wouldn't take a whole lot to hit those limits with all of the currently available bolt-ons and a tune, although I bet they add at least 20% overhead on that for ensured component reliability/longevity. 

Anyone know of hard part upgrades for this transmission yet? I've seen quite a few mods for the manual, doesn't seem to be much out there for the A6...


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## Jim Frye (Mar 16, 2011)

ECOmaniac said:


> Thanks for the info guys - more so concerned about the limitations when doing modifications. Doesn't look like there is much wiggle room here, wouldn't take a whole lot to hit those limits with all of the currently available bolt-ons and a tune, although I bet they add at least 20% overhead on that for ensured component reliability/longevity.


If you look at the specs. of the three models that Mr. Cuda listed, the basic differences are increased torque ratings as you progress through the models. Other than bearings and ratios, the big difference is the width of the drive chain from the output shaft of the gearsets to differential gears. The chain gets wider as you increase the torque load. Buick uses the 6T45 behind their 2.0L motors to handle the higher torque. Likewise the 6T50 resides with the V6 motors (IIRC). Yes, they are limited because each model of transaxle is designed for a specific power plant. I'd say we are a bit early in the product cycle for there to be aftermarket parts for these transaxles.


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## Higgs Boson (Mar 7, 2012)

Looks like the chart rating is at 4400 pounds..... I wonder if the power limit goes up at a more reasonable 3500 pounds w/driver?


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## nickameiss (Jul 18, 2014)

anyone know if the bellhousings are the same between the 6t30, 6t35, 6t40, 6t45 and 6t50? mostly looking to see what possibilities there are for a possible upgraded transmission. im not sure if the length of the transmission changes as the torque rating gets higher. anyone that could shed some light on it?


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## Jim Frye (Mar 16, 2011)

nickameiss said:


> anyone know if the bellhousings are the same between the 6t30, 6t35, 6t40, 6t45 and 6t50? mostly looking to see what possibilities there are for a possible upgraded transmission. im not sure if the length of the transmission changes as the torque rating gets higher. anyone that could shed some light on it?


You'd have to check part numbers for the different transmissions. Since they are used on different engines, the mate up may be different, so the only way to be sure is to compare part numbers for the different bell housings. Also, I know the 6T40 has undergone at least three design changes over the years, so there might be differences besides the internals. Likewise, the other transaxles in the family likely have undergone changes also, so there may be part numbers that are generation dependent. Also, the TCM of a particular 6Txx will be different and may not communicate with the ECM of any particular engine. Also, you'll need the appropriate service computer and firmware to update things. The firmware is VIN specific, so that's adds complexity to a swap scenario. Not like the old days.


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## nickameiss (Jul 18, 2014)

i can totally see that. just curious, ive tried to look up part numbers for the bellhousings for those transmissions, but it only gave me the entire assembly, while its nice to see that, the bellhousing, torque converter, and overall size is what im after. might have my buddy machine up an adapter plate, only problem with that is the torque converter clearance. thinking possibly take the flywheel and the torque converter from the 6t50 and see if i can figure out a way to make an adapter. ive been looking at tranmsissions out of wrecked veranos and its friggin expensive. if anyone on here either works at a wrecker yard or has access to the transmissions themselves, i could use some help trying to figure this out.


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## intrigued214 (Sep 8, 2018)

So what are these 6t40's actually holding up to hp/tq wise? I'm assuming the vendors and several members have some a6's putting down some numbers..


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## Aussie (Sep 16, 2012)

The Australian Cruse 1.6T and Diesel use the 6T45 transmission, here are the differences between them and the 6T40. 

*6T40/6T45 Differences*
To support the 6T45’s greater torque capacity, it features a 1.25-inch-wide output chain, versus a 1-inch-wide chain in the 6T40; and the input gear set of the 6T45 uses fivepinion gears, versus four pinions for the 6T40. The case of the 6T45 is slightly larger and includes a heavier ribbed case for additional strength.


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