Transmission problem or fuel problem??

[mikemhp]

2004 yukon 350- 145,000 miles

past couple of weeks been having an issue accelerating. feels like it starts out in 3rd gear from dead stop. won't upshift when at highway speeds either. just hangs out at appx 2K rpm.
from standstill it will accelerate ok, but not like normal (first gear, 2nd gear, etc.) then sunday driving around, went back to normal. but all day today was having same issue.

after reading some posts on here, i'm leaning towards maybe a sensor issue being the culprit?

any advice is appreciated.
thanks!

 

[rockola1971]

A 350 in 2004 Yukon? GM stopped putting in truck/suv in 2000 and Express Van in 2002. You sure you dont have 5.3L or 6.0L?

Getting a check engine light, if so what are the codes? Color of transmission fluid? Does it smell burnt? Getting a reduced engine power message on your instrument cluster when Yukon wont accelerate correctly?

 

[Big Mama]

What happens if you manually shift? All of the questions Mike asked above would be next. Do you have access to a Tech2 or bidirectional scanner? If no lights are on it’ll still tell you what’s happening and where. Could be a wheel speed sensor or something electrical if the problem comes and goes.

 

[Blucas12]

Sounds like a shift solenoid issue in the trans making it stay in 3rd gear i think. The issue your describing sounds exactly like when i rebuilt my 4l60 in my silverado. Shift solenoid was making intermittent contact so sometimes it would shift normal and sometimes it would be in limp mode. If you read the codes and its the solenoid code it should be able to be replaced just by removing the trans pan