2003 Denali, tranny slip/shift problems at higher RPM range

[wade]

I have a 2003 Denali. 130K miles. Tranny shifts great on normal driving conditions. But when in higher RPMs such as to pass a vehicle, etc... my trans slips and wont shift unless i back off the throttle and let it shift then presume my driving. So I would say over 4700RPM it does this.

I can say, I have NO idea when the trans fluid was replaced last. I purchased the truck at 78K miles and havnt replaced it since I have had it (I know I know)

Can old worn out fluid cause this?

 

[fire730]

Is the fluid full? That can cause more problems than the age of the fluid. If its low it can aerate and it basically loses pressure.

130k is fairly high miles but ive seen transmissions with that many miles and the fluid still looks pretty good. It's depends on what kind of live it's had. Such as towing and hard driving.

Check the fluid after driving for at least 20 minutes to make sure it's good and hot and make sure it's close to the top of the hot range on the dipstick.