4T65E Not Shifting 2002 Monte

[nhra78]

Vehicle is a 2002 Chevrolet Monte Carlo with 158K miles on the 3.4 liter. The car was given to me with known head gasket leak and possible transmission issues. I repaired the head gasket leak, now for the tranny. I take off in D and it has good acceleration with no slipping hesitation or surging it feels normal. It will never shift out of first gear even if I manually shift through the gears it stays in first. I went up to 4000-4500 rpm and no shift at that point if you let off the throttle and get back on it it acts like it is in neutral. Fluid is full not the best or worst I have seen as far as cleanliness but full.

I borrowed a Modis Edge from a buddy and I can see the solenoids 1 and 2 changing state on/off in the proper order to shift to 2nd and third but it never does.

There are no engine or transmission related codes.

I have spent hours searching and reading the net whenever I find a similar post it ends with no resolution.

My next plan of action is to pull the pan and see what I see.

Thanks.

[maxwedge]

https://www.gmforum.com/buick-172/04...-307190/page3/

[nhra78]

Originally Posted by maxwedge

https://www.gmforum.com/buick-172/04...-307190/page3/

Thanks for the info. I don't think it is stuck in limp mode because it has too much low end acceleration. I checked the connectors and they look fine. The speedometer is working and I get a speed readout on the scanner. Solenoids appear to be functioning based on the Modis scanner. Though they show they are turning on and off I can't say for sure that they are changing state mechanically. Before I drop the pan I plan to get a PCM over the weekend from the slavage yard and give that a try.

[Blue Bowtie]

Aside from exchanging the PCM it might be helpful to test line pressure:

https://www.youtube.com/watch?v=CNjDiPFcKuU

[nhra78]

Originally Posted by Blue Bowtie

Aside from exchanging the PCM it might be helpful to test line pressure:

https://www.youtube.com/watch?v=CNjDiPFcKuU

Thanks for the link on checking the pressure.

The pressure was a little high in park around 110psi and when I pulled the connector to put it in the high pressure loop it looked fine around 260 psi.

I talked to a mechanic friend and described the problem to him and he thinks it is a mechanical problem.

I did change the PCM with 2 different ones. It had a slightly different reaction. I drove the car with the scanner hooked up, when solenoid 1 turned off to attempt to shift to second gear I could feel a small hiccup in acceleration. When solenoid 2 turned off to shift into 3rd it was like it shifted to neutral. The original PCM would accelerate until I let off the throttle.

At this point I am convinced that it is a mechanical issue. I got a salvage yard tranny with 53k miles on it for 300 bones so unfortunately I will not have a root cause for the condition.

[nhra78]

Installed salvage yard transmission and the car is shifting fine, so the problem was internal to the transmission.