Wierd 4l60 problem
Thread Starter
Launching!
Joined: Dec 2004
Posts: 242
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From: Cana, VA
Wierd 4l60 problem Ok ill start with a little background. Its a 94 Lt1 car has 60k on it, makes 500 RWHP on nitrous, 360rwhp on engine. the trans is a CPT trans that was supposed to hold like 600 RWHP. It has a vigilante 3200 stall. I bout the trans used with 10k miles on it. Before installation the converter was sent back to Precision for a rebuild/refresh, trans got a new filter and so on. 15k miles of driving it I flushed the fluid. now after 30k since I installed it and maby 10 nitrous hits, it started shifting real funny. It started out of the blue no warnings. Went for a drive it went to shift to 3rd and it wouldnt do it. I got nervous, I stopped took back off and it woked normally. Didnt even slip when I laid into it on engine. It kept doing it the rest of the drive sometimes it would shift and be normal sometimes it wouldnt. 90% if it wouldnt shift I could come to a complete stop take back off and it was fine. Even held a nitrous hit. Im thinking something electrical but I know the 3-4 stuff is the first to check out in these trannys. Any advice or opions?
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Joined: Aug 2010
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From: Ann Arbor, MI
The PCM completely controls the trans. Therefore if it is shifting at odd times (and not slipping), it is an electrical, PCM or sensor problem. Based on what you have said, I would suspect a sensor - MAF, TPS or VSS. If your speedometer seems accurate and not erratic, the VSS is probably OK.
Your could start by disconnecting the MAF to see that if solves your light/moderate shifting problems. I don't recommend going WOT without a MAF unless you are absolutely sure your PCM was properly tuned for speed-density mode (no MAF).
Also look for corrosion on the TPS connector.
Beyond this, a scanner needs to be hooked up to log the sensor values and then the PCM commands the shifts. A good trans shop can do that for you.
Your could start by disconnecting the MAF to see that if solves your light/moderate shifting problems. I don't recommend going WOT without a MAF unless you are absolutely sure your PCM was properly tuned for speed-density mode (no MAF).
Also look for corrosion on the TPS connector.
Beyond this, a scanner needs to be hooked up to log the sensor values and then the PCM commands the shifts. A good trans shop can do that for you.
Thread Starter
Launching!
Joined: Dec 2004
Posts: 242
Likes: 0
From: Cana, VA
When it trys to shift to 3rd it falls into like a neutral kind of sensation. but when it works it doesnt slip any even on nitrous. speedo seems correct. 94's doesnt have trans codes correct? I live right near a a fbody speed shop. will the tuning program show me the values I need to see? I mean it is trying to shift at the accurate time, but like I said it feels like it goes to neutral. I completly stop take off again and it shifts and works normally.
Thread Starter
Launching!
Joined: Dec 2004
Posts: 242
Likes: 0
From: Cana, VA
Update for future peeps that might have this problem.
So i changed the shift solenoids and flushed the fluid, still did it then the next day started slipping in 3rd. Pulled the trans and found the stator support shaft severly worn, teeth nearly gone. Also the reverse imput drum had blown completly past the snap ring. And of course the 3/4 clutchs were fried. Now remember when I pulled this trans every thing worked, just had a funny shifting into 3rd problem and then started to slip after the new filter and flush. Hope this helps someone in the future.
So i changed the shift solenoids and flushed the fluid, still did it then the next day started slipping in 3rd. Pulled the trans and found the stator support shaft severly worn, teeth nearly gone. Also the reverse imput drum had blown completly past the snap ring. And of course the 3/4 clutchs were fried. Now remember when I pulled this trans every thing worked, just had a funny shifting into 3rd problem and then started to slip after the new filter and flush. Hope this helps someone in the future.
