Challenger will not back up please help in reverse or neutral

[delmarvarv]

Got a question. Went to back out the 71 challenger to go home from work and when I put it in reverse it would not move put it in drive and it was hard to move. Put it in neutral and you could push it forward but not backwards. Car was running and driving fine all day. A few hours before I ran out to lunch and stopped and filled the gas no problems at all. Car was a 318 car with slap stick auto now has 340 in it. Not sure what rear it has but it's sealed. We just got the car last week and have put about 100 miles on it since with no issues

[72cudamaan]

First thought is fluid level and condition? What do you mean "hard to move"? Like the engine
revs up but the car doesn't move? Or like brakes locking up hard to move?

[delmarvarv]

A first it would rev up and bogg. Down like the brakes were locked but when we put it in neutral it would roll free forward but would lock tight if we tried to roll it backwards

[72cudamaan]

Sounds like maybe it's a brake shoe/hardware problem. If hardware is bad, rolling backwards may make the shoes grab and
expand. When rolled forward the shoes release.

[delmarvarv]

Jacked the rear of the car up and you can turn the tires freely forward and the driveshaft also turns. You can turn the tires backwards but it is hard an the drive shaft does not move. When the car is in reverse it acts like it is in neutral. Could there be something in the trans that is keeping the car from moving backwards when in neutral?

[delmarvarv]

Thanks for the replies. Its off the the trans shop to get total rebuild.

[dutch]

You can turn the tires backwards but it is hard an the drive shaft does not move.

   sounds like a diff problem to me..?

[Kapteenikosmos]

Transmission fried and locked up? The "mechanical diode" (sprag?) would allow you to move the car forward while in neutral depending what has locked up? How are the forward gears?

[burdar]

Pull the drums off before you take the time to pull the trans.  Make sure a spring hasn't broken...making a shoe bind in the drum.  If that's OK, then pull the driveshaft and see if the rear end spins without binding.  You can also spin the driveshaft with it disconnected from the rear end and see if the output shaft spins.

[delmarvarv]

Reverse is gone in the trans for sure.  We jacke d it up and put it in reverse and it revved like it was in neutral. Put it in drive and it runs fine. I think it had a manual valve body in it also since it did not have power unless you shifted it. And the other day I shifted from 2nd to drive and it felt like I went to 1st and the nose dipped and the rims went up so I put it back to 2nd then back to drive and all was fine. Then the reverse went out the next day. We have only had the car for a few days and things have been modded. It's got a 340 in it and it has a aftermarket pistol grip shifter and the rear looks like a 8 3/4 and is sealed but it does not have open diff

[burdar]

Sounds like it has a reverse manual valve body in it.