i have a 97 blazer 4 door 4wd 4.3 vortec and i just installed a rebuilt tranny and new torque converter .it has about 250 miles on both . it was running great until yesterday when it shifted into overdrive on the highway , i was doing 65 and the rpms started jumping from 1500 to 2000 . it jumps back and forth when i am on the gas but when i get off the gas it doenst jump around . i checked the trans fluid and it is fine , i tried to let it cool down but its still doing it . it sucks because i spent all weekend changing this and im hopeing i wont have to switch it again . any help would be appreciated !!!!!

 

Sounds like the torque converter is unlocking... Who rebuilt the transmission? What kind of warranty do you have? Will tapping the brakes make it stay on 2000RPM for a bit?

 

there is a guy in my area i call the s10 guy he had someone rebuild it(he rebuilds all his trannys) ,he buys wrecked blazers and s10 and parts them out , i talked to him and he said to try to figure out if it was the tranny and if it was that he would make it right for me , nice guy and trustworthy . i will see if tapping the brakes work and ill let you know . thanks for the info

 

thanks for the info , i was on my way home from work and i was doing 55 when the tranny started acting up so with my foot on the accelerator i tapped the brakes and the rpms went up to 2000 for about 2-3 seconds then it started acting up again . so would the torque convertor be unlocking just because the tranny is bad or is there something else that could cause this?thanks again

 

my check engine light was on and it read p1870 manual transmission control is what it said i think . does anybody have a clue what that code is?thanks

 

If it smoothed out after you tapped your brakes, then started acting up again, your torque converter clutch is the cause of the jumping RPMs. It may not be the source of the problem, but the clutch locking/unlocking is what you are noticing. The problem could be the clutch in the torque converter or in the TCC solenoid on the valve body.

P1870 - Transmission Component Slipping

 

thanks i just actually saw the thread for that code . so if it is the solenoid i wouldnt need to change the valve body would i ? and how hard is that solenoid to change?

 

You may have to get the valve body reamed and get a larger valve (what the solenoid moves) to fit the larger bore.

 

can i just change the tcc solenoid by itself or will i have to get the valve body reamed??and how hard is it to change , i looked for a thread on how to change it but i couldnt find one .

 

It depends on the extent of the damage.

If you really want to attempt this work by yourself, I would suggest you buy the ATSG manuals for your transmission. You will need to remove the valve body to assess the damage.