I have a 383 SBC attached to a 4t60 in my 86 GT. Here is the issue, During a test drive I backed down my drive way, put the car in drive, drove back up the driveway, when I put the car back in reverse the trans shifted but wouldn't go. There was no pop, no thunk, no smell. It just wouldn't go. Forward gears work fine. I checked the fluid and it was red and not burned. Dipstick read a little low, so I added some to get it to full. I tried to back up again, still nothing...trans shifted, no movement. I'm thinking maybe a vac regulator or it is still low on fluid. we had to put in a new Torque Converter. It was filled up, but there may be air in the trans lines. The install only has a few miles on it ( maybe 50 miles if i'm lucky) and the trans worked fine. According to what I have described.....Any opinions on what could be wrong? I have friends working on the car on a different issue and I'd like to be able to point them in the right direction and maybe save some $$$ by not needing a new trans.

Thanks,
Jake

How did you build your selector? It is possible that it isn't going into reverse because the selector isn't hitting it right. You may have just got lucky the first time. Only way to be sure is pop the cable off, and have someone move it from park to reverse. Obviously you should have your foot on the brake to not run them over...

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-Brian

My 87 GT Poly Suspension Upgrade (all pics) thread
Removing the roof panel
My HUD install thread
Isn't it strange that after a bombing, everyone blames the bomber, his upbringing, his environment, his culture, his mental state but … after a shooting, the problem is the gun?

[This message has been edited by MulletproofMonk (edited 07-28-2013).]

quote Originally posted by MulletproofMonk: How did you build your selector? It is possible that it isn't going into reverse because the selector isn't hitting it right. You may have just got lucky the first time. Only way to be sure is pop the cable off, and have someone move it from park to reverse. Obviously you should have your foot on the brake to not run them over...

What! and take the danger out of it? I actually, tried that and nothing. The trans is definitely shifting into reverse. You can hear it shift, but nada. Wife had a 74 Javelin that had a trans dipstick tube seal issue. When it got low on fluid it would do the same thing, drop into gear and wouldn't move. It's like there isnt enough line pressure. LOL wow, I love brain storming......Maybe its the vac pressure regulator. IDK

Thanks,
Jake

Vacuum regulator/modulator should have little to no effect at low or no speed. It regulates shift pressure by pushing against a governor.
Lower the vacuum, the later and harder it shifts.
Some seem to have more system pressure in forward gears and partially plugged filter/loose fitting filter sump can screw up reverse.
Double check(if you can) if you have ALL forward gears. 4th/overdive may feel masked due to lockup converter. If you don't have 3 separate shifts could have bad sprague/oneway clutch. Clutch packs will engage, but internals just spin in reverse. There wouldn't be slipping in forward gears, just no engagement of one of them.