Any ideas would be greatly appreciated.here is the issue,

Tranny shifts into gear fine,reverse or forward and drives away. After driving for 15/20 minutes it ****s the bed, doesn't want to move at all or very slow and doesn't seem to make a lot of noise. The fluid and filter were changed and is at correct level.
Should I pull it apart for a rebuild( would be my first one) or just get a replacement?
Thanks

 

How many miles on transmission? When was filter and fluid changed? Was it working fine before filter and fluid changed? What type fluid did you use? And how did you check the fluid level?

 

there is about 120,000 km on it and the filter and fluid were changed recently. unsure of what kind was used as it is my sons truck and he put the fluid in it. level was checked with vehicle at operating temp and a level surface.

 

Type of fluid makes a difference. Needs ATF+4 only. If anything else was used, it needs to come out immediately and be re-filled with correct fluid.

Was fluid level checked while in Neutral (NOT in Park for these trannys)?

It sounds like it is low on fluid, but could be something else.

Was it acting up before the fluid change?