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90 GP SE Hard 2-3 Shift 4T60


redmetrix
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I picked up this 90 GP SE last fall. It had been sitting for 2 years before that. I have put about 9500 miles on the car since I got it. 109,000 miles on the original engine and trans. Anyhow, it does some things that are not normal when shifting from 2nd to 3rd. To me it seems like a "sticking" type of problem.

 

First of all, it has happened two times where I would drive off from a stop, it would shift from 1 to 2 just fine and then stick in second not going to 3rd. This has only happened twice in all the time I've had it. Putting it in neutral then back to O-Drive brings things back to normal.

 

And when you are rolling up to a stop sign comming down from highway speed, you can actually feel the downshift from 3 to 2 which I find interesting.

 

When I start the car in the morning and drive away, the 2-3 is smooth as can be, but every 2-3 shift after that is firm. The problem does not seem completely related to the temperature of the transmission because I can park the car after being fully warmed up, start it ten minutes later and drive away and the initial 2-3 shift is smooth and then every 2-3 shift after that is firm.

Edited by redmetrix
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Sounds a lot like a bad vacuum modulator. Without it functioning properly, line pressures will be a maximum, leading to very firm, unpleasant shifts. Check the vacuum connections, and then the modulator itself.

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I think that would affect more than just the 2-3 shift

 

That's what I was thinking since everything else is completly fine. I did go ahead and change the vacuum modulator yesterday, but the trans seems to shift exactly the same. The plunger on the old modulator was loose and would wiggle around though. I'm going to do some more driving and see if I notice any improvement.

 

In all honesty I suspect this car did a fair amount of city driving and it's simply wear in the trans that I am noticing. The car has been very very well maintained and all work done is documented. The trans fluid and filter were changed 12,000 miles ago.

 

On a side note, refering back to my 93 GTP, when I changed the upper and lower intake gaskets and put it all back together, that little black box about that's about 1 inch by 2 inches that attaches to the upper intake got cracked. This caused all the shifts to be hard, otherwise that was literally the smoothest 4T60E I had ever driven. Replaced that little black box with a different one and all was normal. I noticed the 3.1 on the 90 has it as well, but I do not suspect it to be the problem here.

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