02 suburban, tranny problems please help

[70camino]

I have an 02 Z71 Suburban with the 5.3 so I guess its got the 480Le , and I'm scared it's letting go. Often when shifting from park to drvie and I am facing up hill it rolls backwards quite freely, just as if it were in neutral. also many times when shifting into drive from park and hitting the gas it revs and takes a second or two to get in gear. Is my converter going out?

[silicon212]

Sounds like you've got slippage. I wouldn't be so sure on the 4L80e - it might still be a 4L60e. I wouldn't think of it so much being the converter as I would one of the clutches (forward clutch, input clutch etc). Check the condition of the fluid. If the level is low, this could cause slippage. If the fluid is dark and strong-smelling, this could indicate internal damage - especially if you see little sparkles in it under sunlight (metal particles). Is your engine light on? If so, have someone put a scanner on it and see if the resulting code is transmission related. Autozone and other parts places will perform this service for you, for free.

[EFGoodwrench]

Originally Posted by silicon212

Sounds like you've got slippage. I wouldn't be so sure on the 4L80e - it might still be a 4L60e. I wouldn't think of it so much being the converter as I would one of the clutches (forward clutch, input clutch etc). Check the condition of the fluid. If the level is low, this could cause slippage. If the fluid is dark and strong-smelling, this could indicate internal damage - especially if you see little sparkles in it under sunlight (metal particles). Is your engine light on? If so, have someone put a scanner on it and see if the resulting code is transmission related. Autozone and other parts places will perform this service for you, for free.

I dont think autozone can read transmission codes or all of them anyway. You need a tech 2 at the dealership whatever you do dont change the fluid if it is real dirty and black that crap in it is all that is enabling your clutches to grab. My truck is brand new and it rolls like a standard shift unless i am in 4wh lo. If it is burnt up real bad you will immediately recognize the horrible stench of burnt fluid

[EFGoodwrench]

I think there may even be a reprogram for the pcm on those

[Blue Bowtie]

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.

[70camino]

had it checked out at dealership and all is good, thans alot!