6T40 to 6T45 Transmission Swap

[Blue Moon Sonic]

Recently, I've been doing some digging on what the 6T40 transmission can handle and it seems a little bleak for adding more power mods. Listed are the differences between the 6T40 and the 6T45 trans specs

6T45 (mh7) specs
Maximum Engine power: 215 hp
Maximum engine torque: 232 lb-ft
Maximum gearbox torque: 314 lb-ft - All gears

6T40 (mh8) specs
Maximum Engine power: 180 hp
Maximum engine torque: 177 lb-ft
Maximum gearbox torque: 277 lb-ft- All gears

So here's the grand question. Is there a major difference between the 6T45 and the 6T40 transmission's bell housing and mounting points? I would also like to know if there would be issues with the tcm not working with the car's ecm. If The trans swap isn't possible I would also like to try and look into upgrading the 6t40 transmission's internals to handle more power before I start to consider buying a sonic RS and doing the MZ0 swap. I would still keep the one I already own now and use it as a daily driver.

 

[zbencur]

I am glad I am not the only one thinking about this issue! I plan on/ will have to do something after the MPFab turbo kit is put in. I have briefly spoke with zzp about upgrading the 6T40 and as expected it would be expensive and would take as long as 3-6 months to develop hard parts.

About the 6T45.. I would not waste my time throwing a stock 6T45 into my car if it fit because if you need a trans to hold more power than the 6T40 your likely thinking about MPFabs turbo kit. Unless it was a built 6T45.

I have searched for 6T40 parts and could not find anything, anywhere. If you find anything let me know because this is a big issue for automatic guys wanting more power. Perhaps with multiple people for something custom from zzp we could reduce costs.

 

[Sneakerfix]

When I go to storage I'll post pics of the Torque converter I had built for my 6t45.

 

[zbencur]

Besides the torque converter what else would have to be upgraded in either the 40 or 45 to make it reliable at lets say 300hp?

 

[Sneakerfix]

Besides the torque converter what else would have to be upgraded in either the 40 or 45 to make it reliable at lets say 300hp?

The wave plates are weak on the 6t45 GM updated them but I'm sure better ones could be made

 

[zbencur]

I am all for going the cheaper route without sacrificing reliability. I can't see having to buy a 6t45 and having it built, cheaper than just building a 6T40. Some expert opinion on which would be the best way to go would be great.

 

[Sneakerfix]

I am all for going the cheaper route without sacrificing reliability. I can't see having to buy a 6t45 and having it built, cheaper than just building a 6T40. Some expert opinion on which would be the best way to go would be great.

Depends on your power goals

 

[zbencur]

I guess that number would depend on MPFab's turbo kit dyno with some room to grow.

 

[Blue Moon Sonic]

MPfab's turbo kit will be a definite must have for the grand majority of everyone that is waiting for it to come into production and I know a lot of us auto guys are really wanting to install it with out any issues to the drivetrain. It will become an issue later on so we may as well address the issue now before it is too late. If anything we may as well go overkill for the transmission. Better too much than not enough.

I'm currently in the process of checking a couple transmission shops in the downtown madison area to see if they can get parts for the 6t40 transmission or get a direction of who can machine the hard parts for when it comes down to the rebuild. There is also a possibility that the mh7 and mh8 transmissions have interchangeable parts in them which would be a nice thought. At some point I'll have to make a trip to Kenosha and look for a couple transmission from a couple totaled sonic's and regal's carrying those variants and tear them apart. to see what the differences are.

I will agree with seeing about getting zzp on board with this as well. Definitely will make the parts cheaper and they already have a good history with GM's cars as is.

 

[zbencur]

Sounds good, hopefully some more auto guys will get on board. Let me know about your experience with the trans shops. Are you in Wisconsin by chance?

 

[Blue Moon Sonic]

Yes I am. Probably one of the few and possibly only modded sonic in the Madison area.

 

[Blue Moon Sonic]

I sent out an email to ZZP to see what they come up with for our transmissions. Still haven't heard back from the transmission shops yet to see if they have an answer for our issue. I'll head to Kenosha in a couple weeks to see if I can get a transmission from a salvages sonic to tear apart in case people need parts to be looked at.

 

[Maddmatts]

gmpowertrain.com lists some of the differences between the 2 transmissions.

"To enable greater torque capacity, the 6T45 features a 1.25-inch-wide output chain, versus a 1-inch-wide chain in the 6T40. The input gear set of the 6T45 uses five pinion gears, versus four pinions for the 6T40. The case of the 6T45 is slightly larger to accommodate the larger chain system and includes enhanced case ribbing for additional strength."

So the housing is likely going to be a little wider. Someone will have to put the two side by side or look at the blueprints to know for sure.

 

[christopher.s.terry]

Couldnt the 1.8's use the 6T45 as well? I have the 1.8 and im doin a turbo build on it but with the number im about to achieve the 6T45 might be the best route for me


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[laborsmith]

I think the 1.8s are using the 6T30.

Laborsmith

 

[Blue Moon Sonic]

They are. It's going to be difficult finding parts for these transmissions just because of the fact there is a small market for these transmisions.

 

[Sneakerfix]

Couldnt the 1.8's use the 6T45 as well? I have the 1.8 and im doin a turbo build on it but with the number im about to achieve the 6T45 might be the best route for me


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Not sure why it couldn't just comes down to the TCM mating. The 6t30 would be better on a turbo 1.8.

 

[Blue Moon Sonic]

The whole TCM mating issue is going to be a problem for both the 1.8 and the 1.4 if we decide to go to the 6t45 trans regardless. We still also don't know if it will bolt on directly or not for the family 0 engines.

 

[rodslinger]

Not sure if there is any value to this info but...

I just chatted with a friend of mine that works at American Driveline. They do high volume rebuilds for Aamco transmissions. He did say they use the same test controller for the 6T40 and 6T45. He indicated the pinout was the same and that they didn't make any changes to test either one. Basically indicating that electronically they are interchangeable.

Now this guy is in quality control. Not engineering or over the rebuild line so I don't know how accurate that info is.

So maybe if you can physically squeeze it in then it should plug up and go without freaking out the system.

 

[shorebreeze]

Isn't the 6T40 also used in the base model Buick Regal or something? It's used in quite a number of GM models, with the 6T45 oriented towards higher performance models with all-wheel drive. But the 6T40 is paired with models up to and including the 2.4 liter Ecotec. Certainly enough overhead there for a tune. Beyond that, yes, I'd want the 6T45. But it's nice to see the specs in this thread. It sure looks like there's more overhead with the 6T40 than on, say, the six-speed manual gearbox that comes with the 1.4 turbo.