Hey Guys, I finally finished swapping out our TH125 for a 4T60. This site was an incredible resource! The transmission is awesome and shifts from 1st through 4th great and downshifts as it should. However, If I come to a stop after if has shifted to 2nd or higher, the transmission no longer pulls (like it is in neutral). A quick bump to neutral and back to drive and it's ready to go again. Any ideas of what may be causing this? Modulator valve? Should I just make shifting to neutral part of my new driving protocol? Thanks!

Contact Dave at www.tripleedgeperformance.com - he might have some insight. My friend used to have a 92 Lumina with a 4T60 that had this exact same problem. It had a ton of miles on it and I don't think we ever figured out what was causing it. He just drove the car like that until he did a 3800 SC swap and used a 4T60-E.

I do recall that while he had the 4T60, he always had to put it into neutral when coming to a stop and then shift it back into OD to get it to go back into gear when he had this problem. It never did leave him stranded though - he drove it for a long time with this issue.

-ryan

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Most likely a worn input clutch piston and or inner seal. OE is a short lip style. A lot of work to repair,but you can drive the way it is until you don't get a good apply.
Marc

Thanks guys. It's good to know that it should not leave me stranded! I'm hoping that something is just clogged from sitting in the junk yard, and that it will fix itself with some miles. I have an alignment scheduled for in the morning, so hopefully we can start driving it a lot. Thanks again!

FYI for others doing this swap. I found the answer to the problem with the downshifts. Turns out that where you tap into for the vacuum is important. It was hard to find guidance on this. I originally tapped into the brake booster line, resulting in the lack of downshift to 1st. Afterwards, I tapped into the EGR line, which resulted in the correct downshifts, but made the engine set code 32. After that, I found a reference in the space coast fieros article where he tapped into the small vacuum line on the manifold just above the distributor. Following this guidance, it works like a charm, though not when the engine is cold (I'm guessing the higher idle is creating too much vacuum). This is a very worthwhile swap!

Not sure if this is a stupid question but can I still use the vacuum from the manifold for the 4T60 even if I'm running a turbo?

Bump for an answer...

Yes. For safety,use a vacuum check valve teed in the vacuum line. Connect the valve so that it is closed under vacuum and open under boost. Just leave the other end of the valve open and let it vent to the atmosphere. I have one from GM for turbo aplications on mine. I looked for the P/N last night and could'nt find it. Quite sure it's been discontinued anyway. The tee deal works the same,its just not quite as compact as the OE one which has all three tits molded on the valve.
Marc