mguidry629

Car is new to me....Transmission won't shift from 2nd to 3rd at WOT (or even at 3/4ish). Have to take foot off pedal for it to shift as it just sticks to the rev limiter. Normal driving it shifts fine, nice and firm. Also, when cruising (at any speed really) it feels like the torque converter locks and unlocks. Does this in 3rd and 4th gear when trying to maintain speed.

Could it just be low on fluid? I looked under the car and it seems like there is a small trans fluid leak.

foggy

Checking the fluid level is always a good idea.. There is a specific procedure to do this on a C5.
You can find it here by searching or checking elsewhere.. Then go from there..
I wouldn't drive it until you at least check the fluid level

tblu92

This is 99% of the time simply a tuning issue-- Sounds like your trans is skipping over the shift point RPM at WOT and maybe finally hitting the "safety rev limiter" Where the engine stutters
If when you lift off the throttle the shifting changes from the WOT shift tables to the P/T shift tables -making it more likely to shift
Most often causes for this
1 Different sized rear tires than STOCK
2 Changed rear end gear ratio
3 addition of a Stall Converter
4 Poor tuning for engine mods that add HP which in return require trans re tuning
LOCKING / UNLOCKING of TQ converter
Normal causes
1 addition of a stall converter
2 Stall converters require special trans tuning
3 tire size change or rear gear change will upset the TCC operation if not correct
4 Failing transmision

PLEASE list all your mods and if your car has been tuned-- and if you know what softwre
Do you have or can get a copy of your tune file ?

mguidry629

I was thinking it may be the tune as well, like someone messed up the WOT shift point for 2/3 and set it higher than the rev limiter. I've had transmissions go out before and this one still feels strong. The engine and power train appear to be bone stock, including air filter and exhaust. Car has 103K miles. The stock wheels and tires were swapped out with a 18/19 set from a C6. I just bought all new tires (285/35/19 rear, 245/40/18 front which is stock size for c6). I ran a tire size calculator to figure out the difference and it was minimal going from stock c5 size to stock c6 size.

I will check the transmission fluid (I've read how-to's and watched a couple videos) and see if that helps. Then I will take it to a tuner.

Is there a way for a regular Joe like me to reset the tune back to factory?

Thanks!

tblu92

Tune File Depot had all the STOCK GM tunes however they are no longer availiable
However you can still find them here ----
https://www.dropbox.com/sh/4ydh5wltk...s4SRJ9NGa?dl=0
Just make sure you mave the same EXACT Operating system in your car as the one you attempt to load in
There are several different OS systems for all GM cars/trks they must be the same number---ALSO you need to copy and paste your VIN number into the tune file--

mguidry629

DRIVER456

What year c5 or did I miss that

mguidry629

DRIVER456

My trans use to do the the same thing i have a 97,i repinned my pcm to a 99-04 alot of 97-98 did that,you do have some miles on the car though,could be getting worn,chuck cow said there was a way around it but that was years ago.

0Chuck CoW

Paul is right..... Most likely a tuning problem......

Give me a call and let me know mose about it so maybe I can help you.

914-332-0049
Chuck CoW

Bluefire

Specifically in the tune it is likely one of two things:
1. Verify that your rev limiter is set to the appropriate RPM. If this is correct, the shift algorithm is seeing your car hit the Rev Limit before you have reached the target MPH. MPH has to be achieved before RPM limit to command a shift.
2. Lower the MPH for each shift point. 1>2, 2>3, 3>4