|
Re: 02 suburban, tranny problems please help
With only the 325 V-8, I wouldn't bet on it being a 4L80. It might be, but it may also be a 4L60. That would depend as much upon the chassis as the engine.
I have an AWD with a high slip torque converter, and it will creep backward at idle on an incline against the torque converter. The truck has done that since it was delivered with 7 miles on it. It's completely normal, depending upon the grade and installed torque converter. With the smallish V-8 in a large/heavy truck, it's very likely that the converter has a K-Factor (GM-speak for stall RPM) of over 2,000. If that's the case, it's completely normal on a 3% or greater incline.
If you raise and hold the RPM just slightly off idle, does the rolling stop? If you have to raise the RPM considerably over idle speed (about 1,500 or more) then there may be a transmission problem. That could be a converter, but could also be low line pressure causing poor engagement of clutches (the PCM reflash Goodwrench mentioned could address that), or mechanically failing clutches, or actuation problems from varnish/sludge formation, so a trans oil pan drain and filter might help.
If it's a 4L80, it likely already has a trans pan drain plug. That would make the job easier for you. As previously cautioned by Goodwrench, DO NOT have the transmission flushed. Only drain the pan and change the filter.
One potential way to test for low line pressure is to manually place the selector in "1" or "L" range. This should bypass the PWM pressure control valve and force full line pressure to actuate the clutches and hydraulics. If the trans doesn't slip backward in this mode, the modulated line pressure may be too low, and a PCM reflash may be worth investigating. It could also indicate clutch plates sticking in the splines, but that would be inconsistent, whereas the pressure problem should be very repeatable.
|
