my transmission slips when cold. do i need a rebuild? on 2000 Oldsmobile Bravada

it also goes into overdrive instead of 3rd.

Asked by for the 2000 Oldsmobile Bravada
Possibly...or maybe the fluid is low...and why do you say it goes into overdrive instead of third? does the engine feel like it is lugged?
if i accellerate normally, it shifts from 2nd, to 3rd for a fraction of a second, then straight into o/d. unless i step on the pedal harder will it go into 3rd. the fluid level is good. thats why i am hoping it isnt the clutch plates ot torque convertor. if i step on the pedal hard, to pass and downshift, it might go into 2nd at high rpms and stay there till i release the pedal. then it will drop right into o/d. if i hit the pedal EXACTLY right on, it will go into 3rd so i can pass, but thats rare. anotherwords, it doesnt shift correctly anyway. this is before it started slipping. i dont dare try it now.
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is your engine light on if so what are the codes it could help us to give you a god answer
yes it is on. but i am barely surviving on disability and dont have the money to pay for someone to do that. i am currently trying to find a shop or government agency to pay for any repairs so i can get to and from my doctors and hospitals and shopping.
check your tran oil if level is good but I have saved tran before by changing the filter before but does not mean it will work