3pt1lumina Posted June 1, 2011 Report Share Posted June 1, 2011 85k, trans shifts perfect, except for into 4th gear. I have yet to drive the car when it is cold. But after a 15 minute ride to my house it is at operating temperature, so I'll describe what it does. After a key cycle, drive past 45 mph and the car will shift into 4th (48-50mph) as it should, it will stay for maybe 10-15 seconds, then will shift back into 3rd and will not shift againinto 4th. No clunks or funny noises, shifts fine through the other gears, still has passing gear. If you stop, shut the car off, turn it back on and drive again, it will repeat above. I dont get it? Car was a little low on fluid (at the add line) so added some fluid, still acts the same. Any idea? Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted June 1, 2011 Report Share Posted June 1, 2011 sounds like its going into safe or limp mode Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted June 1, 2011 Report Share Posted June 1, 2011 (edited) Unfortunately, a common problem. Mine is in the transmission shop right now because of it. The TCC apply piston is STEEL, the valve body ALUMINUM. Over time, the differences in expansion gall the piston bore, and you lose TCC lock when the transmission gets above a certain temp...in my car, it was 179 degrees. When the transmission is cool, it works fine, but you lose TCC lockup when it's hot. The computer detects the excess slip, disables TCC lockup, and 4th gear (overdrive). You'll get it back "temporarily" if you shut down and restart...until the computer detects the lack of TCC lock, and the process starts all over. You'll also find a code set if you've got access to a scantool...P0740 on OBD 1.5 and up cars--like yours, and my '95 LQ1 Cutlass. I've dealt with and researched this for two years...and the only real solution is either a replacement valve body, or rebuild. Sonnax makes a kit to repair the TCC apply piston bore, called a "Sure Cure" kit, but it's not affordable for the casual (one-time use) user. Edited June 1, 2011 by Galaxie500XL Quote Link to comment Share on other sites More sharing options...
3pt1lumina Posted June 1, 2011 Author Report Share Posted June 1, 2011 (edited) This was more of what I was thinking. My 97 Lumina does this, gives me a P1770 (I think that's the code) from time to time, same exact issue as described here only OBD II. The only difference is on my 97 it wont "fix itself" when you re-cycle the key. I'd assume it needs to be rebuilt. Not that it's a big deal, 4T60E parts are plentiful, sometimes a good used trans is easier (and cheaper) too so might go that route. How did you find out that 179 was your temp for this to start acting up? Wishful thinking was that it was a TPS or some sort of another sensor, but I don't think we can get that lucky. Edited June 1, 2011 by 3pt1lumina Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted June 1, 2011 Report Share Posted June 1, 2011 I've got an old Actron CP-9110 scantool, works through '95. The transmission temp is part of the stuff the tool can read....not bad for a $50.00 Ebay deal.. BTW, TPS IS a possibility. If you have access to a scantool, it's definitely worth checking out. The ECM makes shift decisions based on information from the TPS...and a flaky one will create some strange behavior. Been there, done that, got the t-shirt... This was more of what I was thinking. My 97 Lumina does this, gives me a P1770 (I think that's the code) from time to time, same exact issue as described here only OBD II. The only difference is on my 97 it wont "fix itself" when you re-cycle the key. I'd assume it needs to be rebuilt. Not that it's a big deal, 4T60E parts are plentiful, sometimes a good used trans is easier (and cheaper) too so might go that route. How did you find out that 179 was your temp for this to start acting up? Wishful thinking was that it was a TPS or some sort of another sensor, but I don't think we can get that lucky. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 1, 2011 Report Share Posted June 1, 2011 possibility: the PCM is kicking you out of 4th gear due to the TCC slipping too much.... the PCM has a few variables coded into it to check for calculated TCC slip based on gear ratio, commanded gear and a few other things... but, if the PCM is commanding the TCC to be fully locked, and the amount of slip it calculates exceeds the threshold it will allow for a certain period of time, it will do the things you're describing. does the TCC still lock in 3rd? running significantly taller/shorter tires than stock? Quote Link to comment Share on other sites More sharing options...
3pt1lumina Posted June 1, 2011 Author Report Share Posted June 1, 2011 Stock size tires, I have yet to see the TCC kick on, even after it shifts into 4th. Definitely no TCC in 3rd either. The only reason I thought TPS is because the car sat for a long time, and it idles a little high on start up but then comes down (say 1500 on a warm start up, but goes down immediately). And once it goes down it is not super even. Not misfiring or anything, just not super even. I'll test the TPS and start there, still have a fear it's a TCC issue and the trans is going to need some work. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 1, 2011 Report Share Posted June 1, 2011 hmm.... i wonder if the PCM is commanding the TCC on but it's not reacting, and since the PCM assumes it's on and RPMs are significantly higher than expected, sets the TCC slip code and disables 4th gear.... Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted June 1, 2011 Report Share Posted June 1, 2011 (edited) That's pretty much what's happening to mine...the PCM commands the TCC ON, but due to the sticking apply piston, there is insufficient hydraulic pressure/volume to the TCC to achieve a positive lock. The PCM detects the excessive TCC slip, disables the TCC apply, and overdrive, to preserve transmission parts. One significant difference, though between mine and his, if I understood him correctly. I have TCC lock and 4th gear as normal, as long as the trans temp is below a certain threshold. It sounds as if in his case, there is NO TCC lock under any circumstances. Edited June 1, 2011 by Galaxie500XL Quote Link to comment Share on other sites More sharing options...
3pt1lumina Posted June 2, 2011 Author Report Share Posted June 2, 2011 Update: Last night I put a new TPS on and cleaned the IAC. Car idles 10x better and is more responsive. Also, was able to drive it cold. Shifts perfect including 4th and the TCC is engaging as well. Drive the car about 40-50 miles and then you lose 4th and no TCC, so it's definitely as you all suspected and what I was thinking as well. This car (which my dad will be posting soon) won't see DD use so for what we are going to do with it I'll address it when we put the car away in the fall. Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted June 2, 2011 Report Share Posted June 2, 2011 Good news, though...since the ECM disables TCC lock when it detects the problem, the only thing really harmed when driving it is fuel mileage. I drove mine two years daily with this issue, with no real problems. The transmission shop decided instead of going further with my transmission to replace the transmission with another. Since they're doing it under their warranty, I'm good with that--as long as it solves the problem. Since I do drive my Cutlass convertible daily, the reduced fuel mileage is an issue for me, though in my case, since the transmission has to get hot for the problem to occur, most days it works perfectly fine==that is, it doesn't usually get hot enough to disable the lock on my typical commute, unless there's a traffic jam. Quote Link to comment Share on other sites More sharing options...
3pt1lumina Posted June 2, 2011 Author Report Share Posted June 2, 2011 4T60E's are easy to get, so a replacement is not a problem (or scary) to me. Would you recommend rebuilding or replacing? Quote Link to comment Share on other sites More sharing options...
urbex Posted June 2, 2011 Report Share Posted June 2, 2011 It's just what would suck is if you replace or rebuild the trans, and it doesn't fix the problem...which doesn't seem to be a tranny issue very often. Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted June 2, 2011 Report Share Posted June 2, 2011 My take is since it's a fairly common problem with 4T60E's, it's kind of a 50/50 thing, unless the donor car is drivable, and you can know in advance things are good. The transmission shop I'm dealing with says 2-3 times a year, he comes across one that he can't completely resolve, though I suspect the reason he's replacing the transmission is he doesn't want to replace the $250.00 valve body, and still possibly have the problem. Since he's paying for the new trans under warranty, and assuming a rebuild shop you deal with would do the same, it's worth it to me to spend the extra for the rebuild ($1200.00, in my case)...after all, if it's STILL not fixed, he's made it plain to me he's not giving up until it's good. Your mileage, as they say, may vary. In my experience, it's unsusal to find a transmission shop that actually does what they say they will. Quote Link to comment Share on other sites More sharing options...
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