Reverse Slipping, Found a check? ball
 

2000 model, 47re transmission.
It started with the rear case being cracked due to a bad driveshaft. Trans lost oil and was towed to mechanic. I got a core trans and he changed the cracked housing and had a new driveshaft made. When I picked it up, reverse was slipping badly. I needed the truck and since the forward gears and shifts seemed fine I thought I could just make a band adjustment and the trans oil with the correct PLUS 4 trans oil. When I dropped the pan, the rear band was very loose. About 3 turns to reach any resistance. There was some mud and metal in the pan and filter and a steel ball about 5/16" in diameter.

Does ayone have an idea where that check? ball may have come from? Could that be the cause of the reverse slippage?

Three turns on rear band is correct. 5/16 ball may be from shift detent. Other balls are 1/4 inch with a larger one in vb. Has to be disassembled to get to.
Rear slipage could easily be VB improper assembly during rebuild.

Thanks for the quick response. I am waiting on a aftermarket oil pan with a Drain Plug! And have to get a fresh oil filter. I will pull the VB off tomorrow and make sure it looks right. I have some experience with 727 and 914, but this is my first time inside a "4 speed".

It makes more sense that the ball be a detent, since it was loose in the bottom of the pan.

The 47RE is very similar in operation to the 727 only the overdrive section is added onto the 3 speed unit. Here's some good reading on the 727, http://www.allpar.com/mopar/transmis...-tom-hand.html

Slipping reverse has three possibilities. One is the front clutch and the other is the rear band and the third is the direct clutches in the OD unit.

The front clutch and the rear band are applied hydraulically to make reverse, the pressure is high, over 200 psi. The reason for this is the front clutch needs that much pressure to hold for reverse.

The OD unit is a little complicated. There's 2 clutches, direct (applied by a large spring) and overdrive. When a direct to OD shift takes place there is an overrunning clutch that continues to drive the vehicle forward while the direct clutches are disengaged and the overdrive clutch hasn't engaged yet, this prevents and RPM flare during the shift. When you are in reverse the overrunning clutch will allow the shaft to spin freely and not transmitt any torque to the rear, this is another reason why there is a spring loaded direct clutch in the OD section.

What section did the guy replace? The main case or the overdrive case?

I lost reverse several times on a 4 speed in one of my trucks, it was the front clutch every time, would pull fine forward in drive and overdrive, but wouldn't back up. They could never find the problem, I found it when I pulled the trans the last time to swap with one I had rebuilt. I took it apart very carefully and measured endplay and clearances as I took it apart, I found that the trans had too much overall unit endplay allowing the front clutch to ride off the sealing ring part way letting it leak pressurized oil away from the clutch allowing it to slip. The cause was a worn spacer ring on the back of the intermediate shaft that was never checked or replaced.