Random Harsh Shifting (electronics related?) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 03-27-2007, 05:29 AM   #1
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Default Random Harsh Shifting (electronics related?)

Around 20% of the time the 98 shifts harse at WOT at the 1-2 and 2-3 shifts, not a fast shift but a slower extremely firm banging shift. It will slam into gear so hard the hood will vibrate and the CD player will skip, every other time its fine. on a wet road the tires will break loose during the 1-2 shift. This happens on every shift when it wants to act up, every other time its fine and feels firmer/better than any other 4t65E car I've driven. Picture a 15 year old learning how to drive a stick for the first time..yep thats how it feels. Its like the drivetrain wants to jump out of the car.

What I know
- The shift buttons on the console do nothing, perform is identical to normal shift 100%, I've done about 20 runs on the same road with my scantool. there is no difference between perform shift and regular shift, the car shifs at 5900 rpm both ways.

- Its not a TPS problem, it has been replaced/swapped out with another one

- Its not a MAF problem, its been replaced/swapped out with another one

- Its not temperature related, the trans will get to 210* after heavy use but most of the time is around 170* on a 65* day like today.

- It only happens about 1 out of 5 times or 1 out of 10 times, it only happens at WOT

- Slower shifts around 4500RPM or 5000 RPM shift extremely firm and no vibrations, feels like a new transmission

- Fluid levle is normal, fluid looks very red and brand new identical to fresh fluid. I have a feeling the trans fluid was replaced recently.

- The fresh look of the fluid leads me to speculate that the trans may be from a different car..I will crawl underneath to verify the tag, is there anything I should look at to make sure its for a 98 SSEi, not a 98 park ave or something without the perform/normal shift buttons...or even a GTP trans with a different gear ratio?

- Trans mounts are brand new looking, they are perfect.

I took it to the local trans shop and we test drove it..oddly enough they said the trans feels like its brand new...it did not act up at all in the test drive and the temps ranged from 180 to 200. Trans shop say it shifts perfectly as if it has had a shift kit installed..We only drove it for 15 minutes though. Like mentioned it is random and will be fine for a while then act up for a few shifts then fine again. We did about 8 0-60 runs without any hard shifting.

Any ideas? I plan to swap out the trans for a rebuilt version before I run it at the track. I'm torn between what to throw in the trans.... This problem seems electrical though and I will admit I know NOTHING about these electronic transmissions.
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Old 03-27-2007, 10:32 AM   #2

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Have you checked your motor mounts? That would be a first reveiw. Next log the trans data and get 5-10 good and 5-10 bad runs, compare each point looking for any inconsistency. That would be the first place to begin
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