I bought my 02 Yukon 4.8 a couple months ago with 63K on it. It now has 66300. Two or three times in the couple months I have owned it, I have had a weird transmission problem. I will accelerate from a stop (always under light throttle) and the RPMS will jump from idle to 1500-2000 without the truck moving, then you can feel the transmission engage and the rpms come back down and the truck takes off. When it engages, its not harsh, just a little bump. No other symptoms. I pulled the service records and found this:

06/11/2004 252015 # K7285 - REACTION GEAR SET AND/OR REACTION SUN
SHELL - REPLACE 40016 miles

Could this be related, it feels more like a converter issue than the sun shell. I figured I would start with a fluid and filter change. Any help would be appreciated.

 

Sometimes the cause of this problem is low transmission fluid level. Have you checked it recently? I used to have a pickup that did this exact same thing, and it was a little low on fluid. When I brought the level back up to normal it quit.

 

I did check the fluid level after it did this about a month ago. It was a little low. I filled it up, no issues until today at lunch. It just did it again today at lunch. I haven't checked the fluid level since I filled it last. Guess I just figured it wasn't leaving puddles, must still be full. I will check it tonight.

 

I have had this problem many times and always wonderedc what it was. I know have it doing it all the time and my truck will bearly move in reverse. I would say get prepared for a rebuild because it is probably coming up soon IMO

 

I checked the fluid level, all is good there.

 

Eeesh... Might have more serious problems then...