Quote:
Originally Posted by BRG_N54
So it started having error codes 1k miles after the service job? Sounds like the service was less than ideal.
My experience is with ZFHP19's, and the fill/drain process is very specific. The fluid has to be in a certain temperature range to get the level correct. If it is allowed to get above 50C it will expand and cause an underfill condition. This scenario describes a bit of what you are seeing.
As mentioned above, the procedures are very specific, including accessing the EGS and resetting the fluid life counter when the service is complete. Again, it sounds like that step may have been missed in your case.
Just to reiterate, my experience is with ZF transmissions, GM may differ. However, I wanted to share what little I know about how they are made and how to service them. Just inside the fluid pan is the valve body, which is bolted to the transmission housing. High pressure hydraulic fluid is passed between these two elements and is contained by several rubber seals. The valve body also contains electrical solenoids, which handle the actual shifting of fluid as the car goes through the gears. This engages different clutches in the transmission housing itself.
The wear items are: 1) fluid 2) clutches 3) solenoids and 4) rubber seals. (There is a filter also, but in the ZF it's built into the pan.) When I did my cars, one was higher mileage and did not shift as well as the other. I did not have any issues like you describe, but it was a similar hesitation while coasting and then applying power. The "full service" would be the items mentioned above, minus the clutches, as they require complete removal and disassembly of the entire transmission.
The valve body was not replaced, but the solenoids were. It eliminated my issue, and now I can't really tell the difference between both cars, in terms of shift quality. Another important aspect that is often overlooked by generic repair shops is to clear the transmission adaptations when you replace parts. There are lots of arguments and urban myths about "adaptations" but my view is if the folks that made the transmission say to do it, then do it.
Anyhow, sorry to be long winded, but this quote:
Sounds like it could be related to the shift solenoids, not the valve body. The seals are cheap and should be replaced anytime you separate the valve body from the transmission housing, IMHO.
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Thanks for your reply.
My understanding, after doing some digging, is that it's possible with the GM transmission for the check valve which sits between the valve body plates to become worn, causing it to dislodge itself and become stuck between the plates.
My hope is that with a full valve body rebuild, this, along with solenoids would be taken care of.
It also seems as though a software reset and update would be advisable....