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2010 Chevrolet Malibu Transmission Pressure Control Solenoid Troubleshooting

5341 Views 4 Replies 4 Participants Last post by  Tonytootrill
2010 Chevrolet Malibu LT 4 Cylinders B 2.4L FI DOHC 146 CID
MH-8 6 speed automatic transmission-Reverse gear and 3rd gear doesn't engage-a check engine code showing one of the solenoids is stuck.
The pressure control solenoids were filthy from old fluid- I believe this is why it became stuck.
I've cleaned the solenoids well, but I've run into a problem. When I removed the solenoid assembly from the computer part, some of these yellow plastic pieces fell out of place. I have put them back in place, but I am left with this concern about some O-rings.

In the image you are looking at one side of the solenoid assembly-
It has these little O-Rings with a strange reddish membrane, on 3 of them. 1 of them has no membrane. It was either lost or that one by design doesn't have one-either way I do not know.

I imagine the 4th one is supposed to have the same red membrane. If so, where can I find a replacement?

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Those membranes are actually valves. I've read about them on another site. Shop manual would show positions, they may be part of a rebuild kit or maybe available separately, I'm not sure myself.
I've found this kit that will allow you to service and repair most, if not all, of those valves and update the valve body to correct the issue, preventing reoccurrence. It includes new diaphragms and O-rings.

This will be going in my transmission.
Take a look at the documentation and see if these symptoms compare. This is evidently a common point of failure on 6T40's. (MH8)
This guide has disassembly directions (included with the kit as well) if you want to try servicing it yourself with parts sourced from elsewhere.
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