My 04Chevy's trans started slipping after extended down time. Slips in drive and reverse. Will catch sometimes but not enough drive it. Trans fluid is full and clean! Thanx!

How many miles? Slipping but functioning otherwise is usually friction plates worn. Got a check engine light? Might have a code stored. My first suggestion would be to change the fluid twice after driving a while in between. That gets most of the fluid replaced. Old worn out fluid can cause slipping too.

If the transmission needs replacement....how handy are you?

If it's 2WD, it may be a pretty easy job if you're willing to wrench, learn and save a few bucks.

Is it a truck of FWD?

An auto transmission begins to slip for two reasons. One is from low fluid pressure (several causes) and the result is inability of "clutch apply" force to be sufficient to clamp the clutch pack(s), the second is failure of the clutch discs surface (frictions and steels) to "hold" even with sufficient pressure.

Low fluid, obstruction to passages, foam (leaking pick up, or blocked filter) or failed torque converter internals resulting in metal entering the pump and wiping the pump (and ability to make sufficient pressure) are contributors to number one, and will always result in the number two failure of clutches.

And the failure of clutches can be simply loss of friction material from time/mileage or fluid breakdown, overheating or any slipping as a result of the low pressure or damage from improper operation. Once slipping starts it is done. Continuing will only burn up friction discs and steels, and can start taking out bearings, bushings, seals and eventually hard parts. (same with drum(s)/band(s) slipping, once it starts, it is pretty much over for the band, and if continues to be operated, will destroy the drum).

There is no "fix", anything you do will be temporary at best, very short lived and at worst, destroy hard parts.

4L60 or 4L80e?

4L80e
Drive and Reverse use the low/reverse band. Can you move it forward in any manually selected position other than Drive , Low or Reverse? (without slipping)

Had my wife's 2003 Chevy Trailblazer done last summer cost was 2k, it was slipping bad. 135k on the clock. Funny thing I always changed the fluid and filter every 50k at the Chevy dealer and we never towed anything.

Thanks for all the feedback.This was a good running truck .4X4 low miles,frame is not good. Put up for sale after buying a 2013 Suburban. Of course it STB now!! I think I will sell as is and cut my losses.Cost more to fix than I want for the truck!!