Automatic Transmission - Trans is slipping only 3k miles after rebuild
07-27-2009, 11:18 PM
My trans was slipping in 3rd and 4th for a little while before I finally lost both of those gears completely last month (1 and 2 still worked ok). I took the trans in to a very highly recommended local shop for a full stock spec rebuild with new clutches, bands, servos, planetaries, converter, etc. The trans then performed flawlessly every time I drove it for about 3k miles until this morning when the slippage returned on the highway. It works just fine for about 10-13 miles before it seems to come unlocked, then it slips pretty bad to the point where it's revving over 3000-3500 RPM when I'm just trying to cruise at 60-65 (normally when it locks up it's at 1500). Then when I stop the car it seems to reset or something; it shifts and locks up just fine for another 10-13 miles, at which point the problem returns. It's the same set of symptoms it had right before 3 and 4 went completely out the last time. What could be happening here? Why doesn't it slip all the time and not just after 15 minutes of driving? Obviously it's something that was temporarily fixed in the rebuild.
07-27-2009, 11:33 PM
take it back to where it was built you either have a pressure issue as in to much clearnce in the pump or the 3-4 has gone out again
07-28-2009, 08:00 AM
If the 3-4 clutches have somehow gone out again, wouldn't it slip all the time and not just after being warmed up for several miles? Or would heat indeed be a factor? It does have a cooler on it.
07-28-2009, 10:01 AM
I would think yes if they were gone out again it would slip all the time. I would scan for codes sounds like you may be either going into limp mode. Or getting engine missfire causing the PCM to unlock the converter.
07-28-2009, 10:07 AM
The last time it was slipping I had it scanned in real time while driving by two different tuners; they didn't find any codes or anything else unusual being indicated by the PCM. I took it back to the trans shop this morning, hopefully they'll be able to find something. Thanks! :)
07-29-2009, 09:50 AM
So could this be related to heat, seeing how it only slips when it's been warmed up for a while? I do have a cooler on it.
07-29-2009, 10:05 AM
When I was having lockup clutch troubles on my
previous converter, it kind of acted this way. A
P1870 (component slipping) will set if the TCC does
not hold locked, an immature code will then make
it quit trying until next key-on cycle. I'd begin with
turning the TCC PWM duty limits to full-on, full time
so no stupid "slip learning" can starve the TCC of
pressure (varying w/ driving history). That may or
may not (didn't, for me) suffice because at light
cruise the PCM commands minimum line pressure and
TCC only gets that, or less (subregulated from main
line). You may have to bump General Pressure, TCC
Locked line adder if you have that in your OS, or
bring down the light-load mA numbers in the force
motor table until TCC slips no more.
Watch TCC Slip RPM and your input / output shaft
speeds and you can determine whether the TCC or
the main frictions are the slipping element. What to
do, depends on that.
07-29-2009, 12:03 PM
a full stock spec rebuild with new clutches, bands, servos, planetaries, converter, etc.
Problems--stock spec rebuild, running 12's, upgrading the planetaries and nothing said about electronics. Did they use the original electronics?
JMHO you wasted your money on the planetaries, should have left them stock and upgraded the clutches and replaced the electronics.
07-30-2009, 08:27 AM
Jimmy, I really doubt that it's the main friction elements because I just had it rebuilt and because it only does it on longer trips after a while of driving, not all the time. I guess I'll have a tuner check it out and maybe replace the TCC solenoid, I've read that a bad solenoid can cause this.
The trans shop replaced a manifold pressure switch in the VB and said that it should be ok now. I drove it home and nope, the slipping is still there on the highway.