Reverse/No Forward

[Frank Mopar]

904 trans I traded for couple years ago. Itis supposed to be full race setup with Cheetah MVB. Been a running driving car.

Pulled into a parking lot and put it in 2nd. Made a bang, and it won’t go forward in any gear but reverse is fine.

Pulled the pan and it looks fine. Fluid is clean and no pieces are present.

Got the Tom Hand book out and its pointing to an internal pressure leak.

Bummer Mopar Day is Sunday and my daughter run this car. Thoughts? And thanks ahead of time

 

[voodoo340]

Stripped aluminum planetary gear would be my guess. Years ago I had to drive home backwards because of that (college years, too broke for a tow). Good luck with the repair, I hope it's not that and is a simple fix.

 

[Bobzilla]

904 trans I traded for couple years ago. Itis supposed to be full race setup with Cheetah MVB. Been a running driving car.

Pulled into a parking lot and put it in 2nd. Made a bang, and it won’t go forward in any gear but reverse is fine.

Pulled the pan and it looks fine. Fluid is clean and no pieces are present.

Got the Tom Hand book out and its pointing to an internal pressure leak.

Bummer Mopar Day is Sunday and my daughter run this car. Thoughts? And thanks ahead of time
View attachment 1715965833

Any loose parts in the trans pan, since you already have it off?
I would be leaning toward a planetary issue like mentioned in post 2 or a forward clutch pack or piston issue since it works in reverse. Forward clutch, the rear position with the input shaft attached to it, is applied in all forward gears but not in reverse.
And also take a good look at the low reverse servo in the rear of the trans case. Maybe post a picture of it as viewed with pan removed.

 

[Frank Mopar]

Any loose parts in the trans pan, since you already have it off?
I would be leaning toward a planetary issue like mentioned in post 2 or a forward clutch pack or piston issue since it works in reverse. Forward clutch, the rear position with the input shaft attached to it, is applied in all forward gears but not in reverse.
And also take a good look at the low reverse servo in the rear of the trans case. Maybe post a picture of it as viewed with pan removed.

No pieces in the pan. No grinding sound. It almost wants to move in all gears

 

[CudaFactHackJob]

Tell that guy to shave off his beard...and he can use your quarter panel to do it....Hey your tranny's bad....I bet you find little metal particles on top of the valve body.

 

[Cliff Ramsdell]

Well, let’s break it down. I’m doing this from memory so someone let me know if I missed something.

You have reverse so the front clutch drum works as does the low reverse band. The front drum is coupled to the sun gear and it spins the planetary gear set and drives the output shaft.

You said it’s a manual valve body, turbo action? A&A? I ask because TA doesn’t use a L/R band apply in 1st gear and A&A does. With the TA valve body the car launches on the rear clutch set and the over running clutch so if the O/R clutch took a dump and rolled over you would have no 1st gear.

How about starting the car forward in 2nd, will the car move or load the motor or does it sound the same as 1st gear? 2nd gear will be the K/D band applied to the front drum and the rear clutches applied.

A factory service manual and a gauge kit will help with diagnostics of a hydraulic issue. The fact you see nothing in the pan I wouldn’t think failed planetary because they would dump all kinds of stuff in the pan and sometimes lock the car up so you can’t roll it around.

My .02 worth,
Cliff Ramsdell

 

[Frank Mopar]

Well, let’s break it down. I’m doing this from memory so someone let me know if I missed something.

You have reverse so the front clutch drum works as does the low reverse band. The front drum is coupled to the sun gear and it spins the planetary gear set and drives the output shaft.

You said it’s a manual valve body, turbo action? A&A? I ask because TA doesn’t use a L/R band apply in 1st gear and A&A does. With the TA valve body the car launches on the rear clutch set and the over running clutch so if the O/R clutch took a dump and rolled over you would have no 1st gear.

How about starting the car forward in 2nd, will the car move or load the motor or does it sound the same as 1st gear? 2nd gear will be the K/D band applied to the front drum and the rear clutches applied.

A factory service manual and a gauge kit will help with diagnostics of a hydraulic issue. The fact you see nothing in the pan I wouldn’t think failed planetary because they would dump all kinds of stuff in the pan and sometimes lock the car up so you can’t roll it around.

My .02 worth,
Cliff Ramsdell

TA valve body. appreciate the info. Car won’t move in any forward gear and it should with the mvb. It acts as if it wants to. Just a little nudge is all.

 

[AJ/FormS]

Well then, time to drop it, strip it, and fix what's broke.
I agree about the forward clutch failure ......

 

[Bewy]

My guess is the rear clutch has gone. It is engaged [ supposed to be ] in all fwd gears, but not in rev. The bang you heard was probably the waved spring breaking in the rear clutch.

 

[Frank Mopar]

So far no parts or pieces of any kind. I fact it looks almost new.

Ais is coming out somewhere when I put air pressure to the clutch ports.

 

[CudaFactHackJob]

Put the pump in a vise and air test the drums with the clutches in them. And btw, that looks like too much direct clutch clearance; might give a spinup on the 2-3 and a harsh reverse.

 

[Frank Mopar]

Put the pump in a vise and air test the drums with the clutches in them. And btw, that looks like too much direct clutch clearance; might give a spinup on the 2-3 and a harsh reverse.

I did air test with the pump in and it shifts fine. No flare or slip

 

[lkopaska]

Take the snap.ring off the output shaft ,pull out front planetary and check splines inside planetary to shaft thy will be pulled out.
Bad front planetary, try to find a steel carrier to replace aluminum one.
Lon

 

[Frank Mopar]

A cracked rear ring gear is what i found so far. I don’t think thats why it won’t move. Ill pull the front section apart today.

 

[CudaFactHackJob]

Unusual is interesting.

 

[CudaFactHackJob]

You said air was coming out when you put pressure to the clutch ports. Are there unusual markings inside the sun gear shell?

 

[Frank Mopar]

You said air was coming out when you put pressure to the clutch ports. Are there unusual markings inside the sun gear shell?

Nothing unusual in the transmission period.

The rear clutch seemed to be losing air when I checked it in the case. Pulled it apart and there is nothing wrong. Put it back together and aired it through the pump along with front clutch and they work fine.

in the process broke a fiber washer that goes between the sections and I can’t even find that part. Wtf!

talked with Turbo Action as maybe its the valve Boyd. He’s puzzled too. He gave some thing to look at in the valve body.

 

[Frank Mopar]

Take the snap.ring off the output shaft ,pull out front planetary and check splines inside planetary to shaft thy will be pulled out.
Bad front planetary, try to find a steel carrier to replace aluminum one.
Lon

All steel

 

[Frank Mopar]

Problem solved!! I didn't realize that rear ring gear center is not supposed to be two pieces. Clean break which explains no crap in the pan

 

[Bobzilla]

Wow, that is interesting. How do all the teeth look on the planetary gears?

 

[Frank Mopar]

Wow, that is interesting. How do all the teeth look on the planetary gears?

Teeth all look fine. After it quit moving I didn’t keep trying it. That was a good thing.

 

[CudaFactHackJob]

That's very interesting. Thanks for posting pics. Check the end play. You can use a selective button on the front of the output shaft. Just under .040 is what I like.

 

[Frank Mopar]

Car is back together and back on the road. Thanks again to all the for the help.
Frank.

 

[MOPAROFFICIAL]

Stripped aluminum planetary gear would be my guess. Years ago I had to drive home backwards because of that (college years, too broke for a tow). Good luck with the repair, I hope it's not that and is a simple fix.

My 518 did it too. Only had reverse, planetary / sun were toasted o d was history.lol 2900 later with every update under the sun ...50k still going strong.