MH7 vs MH8 Transmission – Differences & Swap
 

Hi everyone,
I have two cars (both 2011, 2.4L):
– Buick LaCrosse with MH7 transmission (6T45)
– Chevy Malibu with MH8 transmission (6T40)

What exactly is the difference between these two transmissions,
and is it possible to swap them between the cars?

Has anyone here done it before?

Thanks.

MH7 vs MH8 Transmission – Differences & Swap Question
 

Hi everyone,

I have two 2011 cars, both 2.4L:
• Buick LaCrosse with MH7 transmission (6T45)
• Chevy Malibu with MH8 transmission (6T40)

What is the actual difference between these two transmissions?
And is it possible to swap them between the cars?

Has anyone here done this swap before?

Thanks.

Merged duplicate threads. Post #2 is from duplicate thread that was at: https://www.gmforum.com/chevrolet-17...uestion-315595

The 6T45 is built heavier to withstand more torque input from the engine.

I have a Buick LaCrosse and the transmission doesn't work. I want to put a 6t40 transmission in it, will it work?

I don't think so. Besides, downgrading is a bad idea.

The two engines are different, and the Lacrosse engine has a bunch more torque across a wider RPM range because it is direct-injected. It would likely eat the Malibu transmission pretty quickly, even if driven conservatively.

2011 Buick Lacrosse 2.4L LAF
HP: 182 at 6,700RPM
TQ: 172 at 4,900RPM

2011 Chevrolet Malibu 2.4L LE5
HP: 169 at 6,400RPM
TQ: 160 at 4,500RPM

Does the broken transmission need to be replaced? What is wrong with it?

Thanks for the replies.

Here are the exact symptoms to better explain the failure:

The 6T45 in my 2011 LaCrosse failed while driving.
It started slipping, then after a key cycle it would move for about a minute,
then lose drive again. Within a few minutes it completely lost all movement.
At this point there is no forward and no reverse at all.

TEHCM has already been replaced and ruled out.
No change at all after replacement, so this does not appear to be electronic or solenoid-related.

From the behavior, this looks like a hydraulic failure:
either loss of line pressure from the pump,
or possibly a torque converter issue (pump drive / hub not driving the pump, or internal TC failure).

I do not have any loud mechanical noises, just total loss of drive.

I also have a complete 6T40 (MH8) from a 2011 Malibu available.
I understand this is a downgrade and not ideal long-term.

Main questions:
1. Based on these symptoms, does this point more toward pump failure vs torque converter failure on the 6T45?
2. Is there any common 6T45 failure that causes total loss of both forward and reverse like this?
3. As a temporary solution, is running the 6T40 with the LaCrosse differential and TEHCM mechanically acceptable?

I’m mainly trying to decide whether repairing the 6T45 (pump/TC)
or doing a temporary swap makes more sense.

Thanks.

I can't say for sure that it wouldn't work at all. What I can say is that direct-injection engines have a lot more torque at lower RPM than multiport engines. The shift strategies and pressures etc. are all mapped for this.

Here's are the two choices that I'm seeing:
- Pull the 6T45, install the 6T40, hope that it works at all, hope that it puts up with the shift map that applies lots of torque to it, repair/rebuild the 6T45, pull the 6T40, install the 6T45
- Pull the 6T45, repair/rebuild the 6T45, install the 6T45

Given these choices, I'd go with the second one every time.

It means a little more downtime in the middle, but the first choice doesn't assure me that there won't be downtime or other issues, both of which will draw time and attention away from repairing/rebuilding the 6T45, and that assumes that it even works at all.

That makes sense.

Based on the symptoms (sudden loss of both forward and reverse, TEHCM ruled out),
I’m leaning toward pump or torque converter failure rather than a full internal rebuild.

I’ll likely pull the 6T45 and inspect the pump and TC first,
and decide whether a targeted repair makes sense before considering any swap.

Thanks for the insight.

You're welcome!

Please let us know what you end up doing!