98 Lumina trans slip?

I have a 98 lumina when car is cold or been sitting for a while the trans will slip when first starting to go, in reverse or forward. Car revevs to about 2500 rpm before moving and acts like its slipping, than over revs until shifts. Seems to shift fine. After trans shifts to second everything operates normally the rest of the time your driving, until it sits for an hour or so.
Has anybody had such an issue or have any suggestions?

Thanx Bean

First and reverse are on the same clutch pack for intial engagement in a lotta trannies.

Sounds like that clutch pack is not being fully applied when cold, probably due to some bleed-off of hydraulic pressure through worn seals that leak until they warm up and soften a bit and begin to hold pressure.

If it's got high miles, and a teardown inspection is not an option, I'd do a pan drop filter change, add a can of KW TranSeal, and refill with new fluid, see if it improves.

Sometimes they'll be fine for a long time, sometimes they continue to deteriorate...just depends on the nature of the problem...

Does it shudder sometimes as it begins to move?

First and reverse are on the same clutch pack for intial engagement in a lotta trannies.

Sounds like that clutch pack is not being fully applied when cold, probably due to some bleed-off of hydraulic pressure through worn seals that leak until they warm up and soften a bit and begin to hold pressure.

If it's got high miles, and a teardown inspection is not an option, I'd do a pan drop filter change, add a can of KW TranSeal, and refill with new fluid, see if it improves.

Sometimes they'll be fine for a long time, sometimes they continue to deteriorate...just depends on the nature of the problem...

Does it shudder sometimes as it begins to move?
I get that shudder once inna' blue moon. Other than that, trans is mint. Was rebuilt b4 I got it ( Goodwrench tranny by FDNY) and has perfect fluid and an aftermarket external trans cooler. Other than that intermittent shudder, (no slip) it's fine. Torque converter maybe?

I know the shudder you are thinking of...it seems to be common, and usually in the 3.8's for some reason...I can't remember the cause...Corndog man had that issue, maybe PM him and see if he got it resolved.

I was just thinking of a more typical clutchpack shudder where it shudders and slips as you try to move initially...