727 Hard to Roll backwards

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charger426

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Went to roll my big block powered dart today and it was VERY hard to move. I was able to push it forward no problem but the tires would squeal when backing up (smooth concrete floor old tires). Jacked the rear up and the tires would spin forward no problem but wont move AT ALL in reverse (just a metallic clang in the trans). Thought maybe the shift linkage was miss adjusted so I took off the part to the column, found neutral using the lever on the trans and still wont move backwards. Found the thread below and went down the rabbit hole of adjusting the bands and still no help.. I rebuilt the trans a couple years back, drove the car maybe 50 or so miles and then blew it apart to send it out for paint and body work. Other than leaking out the front (re-used the one time washers for the front pump because they "looked good") it shifted great and did everything I asked of it. Has a Cheetah Manual-Automatic Valve body, bolt in sprag, and "HEMI" clutch disks and steels, new bands as well.

Gut is telling me i'm pulling the trans again but want to ask before I go through all that crap.
 
Just noticed I forgot to link the thread I found on here with another person. I the same situation. Sounded like they had a washer that fell out while putting their transmission back together. Laptop I found that thread on is the in shop and I’m not going back out and seeing the gobs of work in front of me right before the car heads out for the final assembly (body shop left the front clip off to make re wiring and engine install easier).
 
Drop the driveshaft and prove the problem is NOT in the rearend.
A loose pinion, or pinion-nut will do exactly what you describe, as the pinion backs into the carrier and the helical gears jam up.

So will brake shoes adjusted too tight, or especially, if the parking brake is stuck partially on.
 
Agreed. Drop the driveshaft and make sure it's not something in the rear brakes that are out of whack.
Had a similar issue and it was a parking brake cable that was hanging up. Would roll one way and not the other.
Easiest thing first.
 
No brakes on the car and when I removed the driveshaft the rear spun fine and the trans was still only rotating one way.

Called A&A as that was the rebuild kit and bolt in sprag I bought when I did the transmission in 2019/2020. They said based on the transmission working great for the 25-50 miles I drove it before blowing the car apart and the transmission hasn’t been used since (read over 2 years) they want to hear back once I get the brakes on and use the motor to back it up. Thought being maybe sitting has some stuck and just simply using it will break if free. So that’s what I’m going to do, try it once I get the brakes and things done.
 
One last follow up before I parking lot this concern until after the brakes are on.

With the driveshaft still in the transmission but out of the rear I took a 2ish foot long prybar in the u-joint area on the driveshaft and was able to turn the transmission both ways (still really stiff in one direction). There is some dragging type sounds from the trans in the hard "reverse" direction (think brake pads on a rotor) but it did turn both ways. I think the "metallic" sounds I had hear before was just the backlash in the rear or something between the tail shaft and tires coming together when I tried to move the tires in reverse on the 2-post lift.
 
Just so you know, even on the bench, turning the output shaft backwards, always takes more energy than forwards, and indeed, it is the sprag forcing the planetaries to rotate the sunshell, and EVERYTHING inside there is turning in one direction or another; and the clutches and the bands are supposed to be slipping. Well, how well they slip will depend on how straight/flat they are, how much or little clearance they were set up at, and if there is any foreign substance on them.
 
Just so you know, even on the bench, turning the output shaft backwards, always takes more energy than forwards, and indeed, it is the sprag forcing the planetaries to rotate the sunshell, and EVERYTHING inside there is turning in one direction or another; and the clutches and the bands are supposed to be slipping. Well, how well they slip will depend on how straight/flat they are, how much or little clearance they were set up at, and if there is any foreign substance on them.
And thats what A&A said as well. Thats why they want to hear back once the car is back on the ground and under its own power. I figure the hardest part for me with the car is getting the transmission out, not so much worried about rebuild cost or time to do the rebuild, its having to remove all the oil coolers and other things to drop the k-member so i can get the trans out.
 
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