Looking for some help and advice here. I have a 91 Camaro RS with a 305 TBI and 700R4 Trans It does not shift into fourth gear (overdrive) as it should. At 70 mph it is running at right about 2500 rpm. What could be keeping it from shifting into overdrive? It is not shifting hard or at odd times from first into second or third it just won't go into fourth-any ideas
My 88 IROC Z has the same trans and at 70 mph it is running at just under 2000 rpm and gets much better gas mileage than my 91 RS with 305 TBI. All help and advice is appreciated.

Fivestar

 

Sounds like the lockup converter is not working right?

 

I'm having a similiar problem except mine is shifting into overdrive but it is at 3000 to 3200 rpms from 70 to 80 mph. I have the same engine and trans as you do and wish I was at 2500 rpms! So far some of the members are saying a bad tach is too blame but it sounds it like it is reving high with what the tach says.

 

Have ya'll tried to manually shift it and watch the tach? Still sounds like a lockup converter problem.

 

Yes try to manually shift the car into all gears. If it still doesnt want to go into fourth you may have disintegrated your 3-4 clutch pack. Thats what I did on my 700R4 that is in my truck so I took it to get rebuilt. The guy showed me how thin clutch packs are in 700R4s, its ridiculous I think paper is thicker.

 

fourth gear uses 2-4 band, forward clutches, and 3-4 clutches.
the band likes to cup the reverse input drum not allowing fourth gear.
the 3-4 clutches would cause no third also-having only first and second.
most likely cause is the 2-4 band.
in third the forward clutches are on, forward sprag and 3-4 clutches
make sense?-range reference chart shows apply elements in tranny books.

 

Be Prepared to buy a new tranny as a worst case scenario. Happen to my 89 rs. Then 3rd finaly went, then 2nd. Once in a great while it would finally drop into OD when i was trying to figure it out. But once 3rd went, i knew it was time to find its final resting spot.

Come to think of it, i wish i took that tranny apart and seen what caused it to fail, cuz we "the buddy i gave it to as a gift" put in another 700r4 and it worked perfect.


Not sure what would be cheaper, to fix yours, or buy another tranny. I see them all the time for 2-300$.

 

the 2-4 band is cheap separately. you would also need the reverse input drum that the band applies against (otherwise known as the band drum). you'd have to rebuild the reverse input drum because it houses the piston, seals and reverse input clutches. The 3-4 clutches are cheap separately also, but I wouldn't replace them unless the rubber on the pistons that applies them, and the sealing rings were replaced also. A paper and rubber kit should suffice with these repairs. a filter is a must when things burn up.