ISUcyclones3

On Saturday I rebuilt the 700r4 out of a 91 Z28 with a kit from Dana at Probuilt. Great kit, was working perfect as I backed it out of the stall and test drove down the road twice, checking fluid level between each trip. After driving the car home I parked it in the driveway and went to back it out later and had no reverse and in neutral it felt like it wanted to go forward. The transmission was air tested to make sure the seals were working properly and they all held. I pulled the pan off tonight to check the boost valve and it seems to be secured and the snap ring is in the right location. Fluid is not burnt and tv is adjusted properly. I have all forward gears, M1 doesnt feel like its slipping and the torque converter is locking up. Not sure if anyone has any suggestions before the transmission gets pulled apart for a second time.

paulo57509

I would drop the pan and check the boost valve again. The boost valve is not in the valve body, it's in the pump.

If the valve is positioned like the one in the photo, you're not going to have reverse. The valve needs to be seated further into the pump.



You don't need to drop the valve body to get to the boost valve. But you will need a third hand because you're having to work against gravity. Look thru this window:

ISUcyclones3

I apologize, I misspoke in my last post. I meant to say I dropped the pan, not the valvebody. Here is a pic of the boost valve:







It has about 1/8" play and the snap ring is definitely holding it in.

krrust

Thanks for this post it solved my reverse problem. I rebuilt one two years ago and just now got my vette going and no reverse. Checked the reverse boost valve and sure enough I didn't get the clip in far enough. Pushed it in another quarter of an inch and walla had reverse. Thanks again for this post.

Lou6t4gto

that was it ! must be a very common mistake, LOL. Thank You for the help