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Hi all,
Sorry if this is search-able, I may not be searching for the right terms but wasn?t able to come up with anything. Working on an 04 Grand Prix, sometimes it ?bangs? into 1st gear from a stop if it?s in D, but if I pull the shifter into 1 it never does this. I?d like to increase the base line pressure a bit in D but I can?t seem to find the right settings. What should I be looking for? (Besides a transmission rebuild, yeah I know?)
Thanks!
I resolved this issue on my wifes 2003 Monte Carlo SS. After repeatedly being told I needed a rebuild which I did not believe for a second. It simply didn't add up that a rebuild was the only way to resolve an issue that began at 30k miles and was very intermittent. By 150k miles it became rather frequent and the hotter the trans got the more likely it was to occur. This told me line pressure was part of the issue as the trans fluid warmed it got thinner. Putting the trans in 1st gear manually resolved it consistently. I did lots of reseach and determined that a new pressure solenoid and a SONNAX 4T65ELB1 line pressure booster would likely resolve the issue. The line booster installation required a separator plate that was $28 from a dealer only. The line booster slightly raises the line pressure and distributes the fluid over a broader area in teh valve body bore. I also bought a few gaskets for this job and it took me ~8hrs to complete, I'm slow due to severe arthritis. Anyway, the car has 180k miles now and not one single repeat instance of it not grabbing 1st gear or banging into 1st gear. Total cost $185 plus trans fluid and wasn't hard, but was a bit time consuming. You will likely need to realign the engine/trans cradle which I was able to do with a short section of 5/8" and 3/4" oak dowels.
I replaced the following:
Drivers side axle seal
Pressure control solenoid
Trans fluid temp sensor - just to be sure
Boost valve
Trans mount - since it was out
Trans side cover which included the valve body cover gasket(O-ring)
Separator plate - valve body to trans gasket basically and available from GM dealers only best I could tell
We like how the trans feels with the slightly increased line pressure so much that we're gonna do it to the 2002 Dale Earnhardt Edition Monte Carlo SS my wife bought, but I'm considering trying to raise the pressure via the PCM to see how that works out.
Thanks so much for the detailed reply. I resolved a similar 1st gear shudder in a ?98 3800 I had with a different tuner from before I had an HPTuner. I recall tables for line pressure in each gear position but I don?t remember exactly what they were called. In addition to the tuning I added a pressure gauge so I could see the pressure rise when pulling the shifter into 1st. Similar to yours, this ?04 trans has 170K on it and I know it will last many more years if I can just stop this slam into 1st. A rebuild is inevitable anyway but why in 1 year when it could be 5... It sounds like the solenoid you used is a good option if there is no way to do this via PCM programming. Another option for me is a recently rebuilt trans meant for another car, but I could add that solenoid before it goes in? but my real preference is to just raise the pressure a little with the computer!Quote:
Originally Posted by whtbronco
I believe the line pressure can be raised electronically to address this so long as the pressure solenoid is okay. I'd sure like to give this path a shot this time as well. Unlike the other trans this one has no current issues, heck it only has 9k miles on it. I have no info on the tables or the variables. Maybe someone will be able provide this info.
I can't believe that I unable to find the line pressure associated with D and 1st gear manually selected. I generally save notes on all my troubleshooting. I think it was something like 80-90psi in D and 120psi in 1st when manually selected, but that's going off memory.
So does anyone know if I can raise the line pressure with HPT? Did I imagine it? Replacing the solenoid seems extreme here when there is a solution with a simple adjustment in the program… ?
Thanks for any help here