Need some thoughts on how to proceed

Making some major changes on the Demon, new motor built and dyno'd. I rebuilt a good core 904 with all the hot rod parts to go behind it, and got a used Griner RMVB non-LBA. New 8" PTC converter and Cheetah shifter. After having to pull the engine once to fix an oiling problem, it's back in and running. New to a converter with this much stall. Only got a couple quick blasts around the block and now have no reverse, and it wants to creep forward in the neutral position. Never seen anything like that, so swap valve bodies or am I pulling the trans?

I'm thinking something with rear band or reverse servo if you have 3rd gear. The front clutch and rear band apply to give rev.The front clutch is also applied in 3rd. The creeping in neutral maybe caused by a lack of clearance in the rear clutch.If you have 3rd I'd wanna pull the pan and check the reverse band&servo. I don't know If I'd condemn the valve body until I looked. If you do decide to change the VB check the rear band application by air checking it.

maybe the shift linkage came out of adjustment?

Does this Griner have a trans brake?

No Reverse and creeps forward in Neutral is a rear clutch that's not releasing.

Not uncommon with high line pressure valve bodies, typically the Belleville in the clutch fails and allows the piston to pop out of its bore and jam the clutch pack.

Depends on if it free revs in reverse or if it feels like it is in gear but locked up. This could be hard to tell though with a very loose converter.

No brake. Clearances are on the tight end, but within the specs. Shifter should not be out of adjustment as I'm using the factory NSS and it starts in gear and the neutral position. It seems to free rev in reverse, but hard to tell since the converter doesn't even start to let the car move until about 1700rpm.

Well, that doesn't sound good. Everything was air tested when it was put together, and sounded like it engaged and released correctly. I'm guessing I can drop the VB and check again with air? Any upgrade solutions to the Belleville?

A dragging direct clutch will not inhibit reverse. If high gear functions you have a low/reverse band issue. Pull pan and and valve body to air check. Does the band function? If it does you have a valve body issue. If not repair the band apply.
Doug

If the rear clutch was locked up it would drive in neutral and would lock up in reverse. I also believe you have a rear band apply problem if high gear is working ok.

Reverse was working correctly prior to the run around the block. All the forward gears seemed to work as well, but really haven't got to shake down any problems. I'll pull the VB and air test everything as well as check band apply and adjustment.

Pan off now.

Fluid is burned, fair amount of clutch/band material in the pan. Air test shows the bands were working correctly, but sounds like the forward clutch is leaking by. Guess it's coming out after less than a mile of drive time.

Figuring everything was air tested and working before, does this point to the valve body being no good? Apparently Griner is pretty well out of working on Mopar valve bodies, what's the best option to determine if this was the failure point?

Call Keith Long. 219/718-3542

He knows Griner valve bodies well.

Out and apart, forward clutch/steels/pressure plate totally smoked. So far everything else looks good. Belleville is not broken, piston seems fine in bore. Didn't have my snap ring pliers so that's as far as I could get it apart today. Really suspect the VB since everything was checked and re-checked before it went together. Every tolerance was set to the tighter end.

If you heard air escaping from the rear clutch with the VB removed, why suspect the VB? Check the fit of the rear clutch sealing rings.

It's the only used part in the trans. Everything else was new. I checked correct operation prior to installing in the car, stacked on the pump and in the case. I'm not a pro rebuilder by any means but I've also done more than one.

The rear clutch doesn't function in reverse. Is it the front or rear clutch (physical position in the trans) that is damaged? The small steel rings on the input shaft seal the feed circuit to the rear position clutch (applied in 1,2,3). The large rings on the stator support (back of the pump) seal the forward position clutch (applied in 3,R). Check the rings and where the surface they ride on. Was the rear clutch/input assy swapped from another trans or was it the front position drum, if so is it the correct part. The inner or outer rubber clutch piston seals may be torn as well. If the rear band is OK thenthe forward clutch has to be the culprit for no reverse. Shouldn't have had 3rd either. Should be easy to figure out.
Doug

Rear position, the forward clutch pack. Not the direct clutch pack located to the front position.

I put all new seals, and sealing rings in when it was apart. Any part that was replaced was with an identical one. Everything looks to be correct. And it was air tested several times. I suppose some of the parts could not be correct for the core, but seems pretty unlikely. I should have it all apart tomorrow.

does this have a 5 disc front clutch, if so make sure you have the correct front pump

It may have rolled a lip seal on the rear clutch piston, it's easy to do. Also if you were air checking it at full shop air pressure that can push a lip seal out as well. I seriously doubt this is a valve body issue but you can always check the pressure that is applied to it when it's back together with a pressure gauge.

4 clutch drum. I'll get it apart and look at that seal.