will not shift when warm
 

1998 blazer 4.3L 4x4 4dr 4L60e 250,000mls

has anybody had this problem? there doesnt seem to be an answer on the internet. so im wondering if anyone here has been through this.

my transmission will shift great when cold but a few minutes down the road it wont shift anymore.

if i cut the truck off and cut it right back on it will shift fine again for another couple of minutes, then it starts acting up again.

the coolant temp sensor was broke and corroded so i replaced it.

i replaced the tps and the maf.

its not showing a code for any solenoid just p1870.

the fluid looks and smells fine and its at the right level.

atf was leaking into the tcase. i didn't replace the seals yet but i did replace the vacuum plug on the tcase. i don't think atf is leaking anymore because the level has been the same for a while and atf doesn't come out of the upper fill hole on the tcase like it did the first time.

why would the transmission act up only when warm? and why when i cut the truck off and cut it right back on it works again for a few minutes?

the guy i bought it from used the truck to tow big equipment everyday. i dont know if thats related.

thanks

Even if the trans fluid looks & smells ok - when was the last time the fluid & filter were changed?
Shutting it off & on & then it's ok seems to be a electrical/BCM or solinoid issue but it may be fluid related because it's thinner when warmer.
Or when the trans is warm & the fluid is thinner it could mean the seals are toast.
Just my thoughts.

ok, ill change the fluid and filter.

in the mean time what seals are you talking about? the tcase seals i mentioned, or different seals?

and the reason i haven't tried solenoids is because theres no code for them just p1870. ive been told by mechs and read online that there would be a code for any soleniod.

by the way, there is no 'hard shift' just no shift and the engine revs as im pressing the gas. also the gas neddle will drop all the way down and the 'need fuel' light will come on - all this after its warmed up. all the other needles are fine.

ill change the fluid and filter and check out the bcm. thanks.

somebody suggested lucas transmission fix. is this a good idea? i dont really want to do that. id rather fix the actual problem.

this person had the same exact symptoms as i did and they put lucas in theirs and it fixed it. so what does lucas fix? i ask because id rather replace the part(s) that it fixes and not use that stuff.

thanks for replying.

The seals inside the transmission. Lucas mucas might help the seals but I agree that it's more of a bandage rather than a fix in the meantime anyway.

i just learned about a transmission control module.

where is that located on a 98 blazer?

it was the same symptoms i have and they said to check the ground wiring on the 'tcm'. but i dont know where it is or even how to check the ground wiring.

i googled it, but cant make heads or tails. i want to try that if someone could point me in the right direction. thanks.

1998 blazer LS 4dr 4x4 4.3L 4L60e