So my 99 1500 has started automatically kicking out of overdrive if i'm taking it up a steep incline, like heading over a pass on the highway...and it would kick out of overdrive then a minute later my trans temp light would come on...i took it to a shop and got the tranny serviced thinking it might be a plugged filter...didn't fix it...took it back in and put on a brand new, bigger tranny cooler and now my tranny's not overheating but it will still kick out of overdrive...any ideas?

 

a bad TPS will cause it to not hold OD when it should.
a bad brake light switch can also cause it.

 

i replaced the tps about 2 years ago along with my iac motor because my rpms were fluttering on the highway and it fixed it...so that's still fairly new...and how could the brake light switch effect it?

 

You're not supposed to leave it in overdrive on a steep incline in the first place! So just stop doing that and the problem will go away all by itself.

 

i think it has something to do with when you push the brake it should kick out of lockup or out of OD and if its messed up its turning on the brake lights witch kicks it out. not real sure but maybe my response will get us a for sure anser.

 

My dad's 99 started doing the exact same thing as yours is doing.... It turned out to be that the OD unit in the trans had let go, and it required a rebuild....

 

ya, that's kinda what i'm leaning towards...do u recall how much it was to rebuild?

 

It cost me about 3000 a year and a half ago for a rebuilt.

 

$3000??? Canadian or American?

If that's American, I sure hope you got some upgrades in that package and not just a standard rebuild.

 

ya 3 grand is a LOT for a tranny rebuild unless it was beefed up!


I think his was around $1600 or so... He told me exactly what let go in it but I forget now, but it was something in the OD unit on the tail of the trans... It broke and put pieces through the trans, so they rebuilt it, flushed the lines, and installed a new cooler