Sorry if this has been discussed before - new user - but didn't see this problem after searching prior messages with "overdrive".

I inherited an '85 S10 Blazer 4WD 3-speed with overdrive, 2.8L V6, 68000 miles (that's right, sixty-eight thou). It's only had 5000 miles put on it in the last 16 years. It won't take off from a stop with the gearshift in OD - the engine just revs. You have to put it in D (3rd gear), and it shifts fine 1-2-3. When you get up to 40-45 mph, you can manually drop it into overdrive and it works just fine. Stomp the gas to downshift, or slow down enough to drop to a lower gear, and you'd better manually change to D again or the engine just revs. When I got the car in March, it was shifting OK but suddenly started doing this about 100 miles later.

I had the fluid and filter changed and the overdrive solenoid changed - made no difference. Old fluid wasn't burnt, no chunks, etc., and old solenoid was ok too. Is a tranny rebuild needed or could it be elsewhere, like the computer or electrical system? One mechanic said the OD bands were probably burned, but I doubt it - it was rarely driven fast enough to even go into OD, and works just fine if you manually drop it into OD.

This vehicle is cherry so I will be getting it fixed, I just want to know which direction to go next.

 

Probably gonna need a rebuild. If its not a highway truck just drive it in D. At my other job a lot of fords did this and they would run them not using overdrive for a few days til they could be fixed. Also I bought my 93 with the same issue 2.5 years later still driving the truck

 

Overdrive works (no slipping, no unusual noises, shifts smoothly), it just doesn't drop into overdrive or back into the "regular" gears automatically - you have to use the gearshift. One shop told me it was the overdrive solenoid so I had it replaced. Another said the bands were burned but they never took anything apart and they're trying to rip me off - they said it'd take 2 hours just to chisel off the undercoating but there isn't any undercoating on the tranny or bell housing.

I drive up to 300 miles a day so my ride has to be dependable. I can't trust this tranny until I pin down the problem and solution.

 

Yea that's a bit different. It wouldn't hurt to just have a complete rebuild. One less thing to worry about

 

Hi check out this forum for your tranny problems place to go.
I talk with Dana a couple times a month.
http://700r4l60e.com/forum/

 

This truck is running just fine except for not automatically shifting into/out of overdrive - I've driven it 500 miles this week with no problems. I'm thinking there's nothing wrong with the tranny itself - whatever tells it to shift into overdrive just ain't talkin'. There are a couple other electrical 'quirks' that make me wonder.

Overdrive is supposed to kick in around 40-45 mph, so what tells the solenoid to kick in? Is there a speed sensor somewhere that might be bad, and if so, where is it? Is there a fuse or fusible link somewhere in the line? All fuse block fuses are OK. Does the tranny sometimes need a ground wire to the frame to ensure a good ground?

One mechanic said the electrical quirks I've seen are sometimes caused by a bad ignition switch. Any reason to believe him (he's one that tried to rip me off)? Where can I get a wiring schematic for this truck?

I can live with manually shifting in/out of overdrive, but I'd rather to get it working right.