727 stuck in forward gear (not the shifter)

[BlooDSMeaR]

I have a 727 trans, that was supposedly rebuilt for drag racing. It has sat for 15 years but known good.
I just put a new motor in it.
I started it and was going to go for the first test drive. I put it in reverse and backed up with no problem. when shifted into the forward gear position it moved forward but like it was in 3rd.
when I got to the spot that I was going to back up, I moved the gear selector to reverse gave a little bit of gas but the car moved forward. I have checked that the shifter is moving like it should both at the gear shifter and down on the transmission. now in any selected gear position it only moves forward, even in the park position. I was not able to hear any sounds as it has open headers.
any ideas?? what do i look for??

 

[oldbee]

Certainly not an expert but sounds like vbody problem, rear clutch inop? Hope 'dvw' chimes in. You know for sure that shift arm coming off the case is not slipping on vbody. Still feel the detents when moving it?

 

[BlooDSMeaR]

The shifter linkage is working as it is supposed to. From the console to the trans, it has a problem inside.... But I need to know what to look for. This is the second time that a dodge trans has done this to me, once in my Durango rt, now this one. For the Durango, the transmission shop did a full rebuild. I don't have that kind of cash at the moment so I'm hoping it is done thing I can fix my self

 

[RT K_line]

Sounds like the valve body might be gummed up from sitting. Either the check balls or the shift valves themselves. You'll need to drop the VB and take it apart to clean and check valve movement. If you are comfortable dropping the VB but not opening it up just take it to a trans shop for them to clean. When I take them apart I use a small pick to move the valves against the springs and watch for them to pop back when you lift the pick. They are pretty straight forward. I bet there is a u tube post somewhere.

 

[1967coronet440]

@dvw probaly knows what’s going on

 

[miller]

There's plenty of VB photos that show them broken down, and where each part is located. Just find the right pic for your's, for reference.

Yep...valve body no worky!

 

[miller]

Also worth air checking the servos, to be sure their not hung. And, look for rusted parts, since it sat so long!

 

[moper]

There can be things that happen when a transmission sits for a long time. It can get water and crud in the pan if it's not a temperature controlled spot, seals can dry out, stuff can crawl into the input or output seals, etc. It's usually a good idea to pull the pan and look inside, pull the valve body to clean it out, and as noted sir test the clutch packs. You don't have to, but it's a good idea.
On your issues - reverse uses one band, and the rear sprag to work. 1st gear uses one clutch pack to work, unless the selector is on "1" in which case it uses the same band as reverse, plus the forward clutch pack too. All forward gears use that same forward clutch pack plus: a band (2nd uses the "kickdown band); and 3rd uses an additional clutch pack (high gear clutch pack). From what you describe, you have a variety of issues. Step one should be dropping the pan and inspecting the valve body, and the actual internal parts. Then air check the system. There are books available on doing this and you can probably find it online too. Ultimately, anything not valve body will require the transmission to come back out and get rebuilt.

 

[BlooDSMeaR]

I will be pulling the pan here in about an hour. I'll take pics and let you guys know what i found

 

[Steve Garner]

In the days that I did transmissions like these, I had never seen this issue come about as a result of a VB malfunction. In reverse the front clutch and the rear band are in use. That works okay. When you move to D the front clutch is supposed to release and the rear clutch applies. In high gear the front clutch and rear clutch are on together. Your front clutch is staying on. It drives in neutral because the front clutch is still on and the sprag is holding (always two elements on simultaneously to create movement). The most common cause, by far, of the clutch failing to release is a burnt clutch pack. Clutch plates burn up and warp and fuse the whole thing together.

 

[dvw]

Not the front clutch. Either the rear clutch is applied/stuck, a valve body issue, there is something sized in the planetary gear train, or it was assembled incorrectly. Since it is a new unit I doubt if a clutch has burned up and siezed. After removing the pan make sure the manual valve moves when the shifter is moved. If that's OK I'd air check the rear clutch. Do you hear it apply and release? If not it may have broken the belleville spring locking the clutch pack. If it sounds like the rear clutch applies you may want to substitute a known good valve body (a stock one would be fine to test) before going to all the trouble to remove the trans.
Doug

 

[BlooDSMeaR]

I dropped the pan, and I was not able to see any thing in the pan. No chunks of metal or glitter. Both bands have a little bit of play. I don't have compressed air to check the control systems.

 

[miller]

If it sounds like the rear clutch applies you may want to substitute a known good valve body (a stock one would be fine to test) before going to all the trouble to remove the trans.

Just as dvw says, your valve body could be the problem, since it controls all the shifting. The valves are a real close fit, doesn't take much to lock one up in it's bore. And, your's has probably been modified, so without knowing exactly what mods were done...if you take it apart, need to keep track of each valve/spring, and such, so it goes back together right.
As dvw says, changing to a stock valve body, will help narrow down where the problem is.

 

[Steve Garner]

Not the front clutch. Either the rear clutch is applied/stuck, a valve body issue, there is something sized in the planetary gear train, or it was assembled incorrectly. Since it is a new unit I doubt if a clutch has burned up and siezed. After removing the pan make sure the manual valve moves when the shifter is moved. If that's OK I'd air check the rear clutch. Do you hear it apply and release? If not it may have broken the belleville spring locking the clutch pack. If it sounds like the rear clutch applies you may want to substitute a known good valve body (a stock one would be fine to test) before going to all the trouble to remove the trans.
Doug

How did you figure rear clutch? OP says it backs up fine, meaning the front clutch and rear band are on. If the rear clutch were stuck, it would lock up when he selected rev; front clutch on, rear clutch on and rear band on. Too many components in play, everything locks up. Unless things changed, it's D1= rear clutch and sprag, D2 = rear clutch and frt band, D= frt and rear clutches, R= front clutch and rear band, 1=rear clutch and rear band (assisting the sprag) and 2= rear clutch and frt band. When he selects D (1) the rear clutch comes on, the front clutch is stuck on giving him high gear, which is what he says it feels like. We don't have a third element causing it to lock up because the 2nd element in D1 is the sprag (over running clutch), which simply over-runs in high gear and second.

Edit. Reread the orig post. I see he said that originally it backed up fine, but when he tried in reverse later it wanted to move ahead. Feeling like high gear in D1 is both clutches on, frt clutch carried over from Rev. Moving forward in rev is frt clutch not coming on, forward clutch coming on instead. Broken or damaged sealing rings on the shaft feed orifices causing cross feeds would be something to look at.

 

[mopar 3 B]

Sounds like a simple air test is in order. No compressor required juat a simple air tank, rubber tip nozzle and of course air.

 

[Fran Blacker]

If you don't have an air "tank" use a tire with 40 lbs of air in it. Put a tire nozzle to access air from tire. Put air nozzle on other end pressurize trans.

 

[mopar 3 B]

If you don't have an air "tank" use a tire with 40 lbs of air in it. Put a tire nozzle to access air from tire. Put air nozzle on other end pressurize trans.

I have airbrushed model cars that way.