i was driving down the interstate today and started goin up a hill so the tranny shifted down into 3rd gear to hold my speed and when i got to the top of the hill it shifted into third and then wouldnt shift into O/D. the truck has done this a few times. i've owned it almost 2 years and it has maybe done it 4 times. i drive it everyday. whenever it happens i just let the speed get below 55mph and it usually shifts into O/D and will be fine the rest of the time. its really weird. it only seems to do it when i've been driving it for a while and its kinda hot outside. anybody know what this could be? btw its the 46re in my 97 1500 4x4.

 

Did your OD Off light come on without your pushing the button? If so, the transmission is overheating and you should look into that straight away.

 

i didnt check the light. dang i wish i would have looked. my truck is a 97 so it doesnt show up on the instument panel the button is near the cupholders. i dont whats wrong with it.

 

Well shucks, that makes it difficult. If you've still got the anti-drainback check valve in the outbound cooler line, yank that sucker out and replace it with a chunk of transmission cooler line at least, a remote oil filter at best. It's lube failure that most often kills these transmissions, and that valve is very often the culprit.

After doing that, if it happens again, check that light. The way these critters work is that overdrive is disabled about five degrees (F) before the Trans Temp light comes on -- and when the light comes on, your ATF is cooked and must be replaced ASAP.

If it were my truck and the fluid/filter change and band adjustment hadn't been done in the last 30,000 miles, I'd go ahead and do them now along with installation of a remote filter in place of the check valve. And if the fluid coming out smells burnt, I'd do another fluid change a few hundred miles later, and maybe one more a few hundred miles after that. There's some slight risk that fresh fluid might break loose some cooked on crap that will plug a valve body passage or governor pressure solenoid, but if you've got that kind of cooked on crap in the first place the transmission's just looking for an excuse to leave you walking anyway.

Keeping my fingers crossed for you...

 

mine used to do that, and no light came on.
it just didn't want to shift into OD sometimes...
after changing the trans fluid and filter a couple of times it straightened out.

as unreg said, i'd do 2 filter changes about 2-3 weeks apart.
also do yourself a favor and install a drain plug. Advance has them for $3. search here and pavementsucks for lots of threads. watch where you place the plug and don't hit the stuff inside.