i have a 86 z28 305 tpi. The 700r4 will shift from 1st to 2nd. but wont go into third but in d from stop it will move and it will move in od. at 4500 rpms it will catch in od when im going 50mph but it will redline and do nothing. im not **** what is wrong i think its ether 3/4 clutch or a stuck valve i have no idea where to start with this issue.

 

You are most likely losing the 3-4 clutch pack, which is very common. The very least it will need the 3-4 clutch pack. What do you want to do here? Just replace what is wrong with it, or go through the transmission completely?

 

If you're confident enough in your skill level, you need to pull the trans and perform a complete rebuild. If not. Purchase a rebuilt trans and install it with a new stall converter. Don't forget to flush the lines and the tranny cooler.

 

My 1995 Corvette with 4L60E (same trans, but electronic) lost 3-4 at around 153,000 miles. I rebuilt the trans myself, took about a year for me to do it here and there. I replaced the gaskets and clutch packs (friction discs and steels).
I did not replace any bearings or the torque convertor. The car now has 254,000 miles. Over 100,000 miles on the rebuild.

My 1986 Z28 Qjet LG4 had 336,000 miles when it was stolen and the punks blew a seal or two and the 700R4 leaks too bad to drive, but changes all four gears. Nothing major had been done to the engine or trans for the 336,000 miles.

 

im buying another 700r4 from a friend he took from an s10 with a 305 im hoping it bolts right up it has 35,000 miles on it since the rebuild soon as the weather breaks im swaping them

 

you will need to swap the tail shaft housing, unless it was from an f-body before the s-10