727 issue - Moves forward in all gears

[Marksman]

I'm trying to get the 70 charger ready for the Hot Rod Power Tour starting in a few days, and my buddy is trying to get his 68 satellite ready for it as well. Whoever turned his 440 crank screwed up, and we don't have time to have it fixed, so i loaned him a 383 i had lying around. Got it in and running good, but we have run into a transmission problem. When put into gear, it moves forward. When put into neutral and reverse, it does the same. It seems like it even wants to lunge in park. We only have a day or two to get the thing fixed, so we're trying to determine what the cause of the issue is quickly. This doesn't appear to be an uncommon problem, but the fix for the problem was never reported in the threads I read through.

The trans has been sitting for many years, so I assume something could be stuck. I would think it had a broken band, but that would just make reverse do nothing, not go forward. Maybe a stuck servo?

Just looking for any advice we can get! Hopefully someone around here has had a similar experience and could chime in. Really would like to avoid pulling and rebuilding the trans at all costs.

Thanks!

 

[383man]

Usually when that happens it can be the shifter is not working and not changing the gears or the rear clutches are welded together. When you put it in park does it seem like its in park ? In other words does it still try to move forward but it dont move because its in park ? It would be like power braking the car. And when you take it out of park does the car then move along as I assume it moves forward in any gear as you said but does park keep it from actually moving ? At least that would tell you the shifter is working. Could also be a part broken inside where the rooster tail in the trans is not moving but it would most likely be easier to shift the gears. Ron

 

[Darthomas]

Usually when that happens it can be the shifter is not working and not changing the gears or the rear clutches are welded together. When you put it in park does it seem like its in park ? In other words does it still try to move forward but it dont move because its in park ? It would be like power braking the car. And when you take it out of park does the car then move along as I assume it moves forward in any gear as you said but does park keep it from actually moving ? At least that would tell you the shifter is working. Could also be a part broken inside where the rooster tail in the trans is not moving but it would most likely be easier to shift the gears. Ron

 

[Darthomas]

What he said above, all true.

 

[66Satellite47]

Like above, or internal pressure leak in valve body. Really check that shifter linkage adjustment. Otherwise get another trans.

 

[hotroddinwillie]

Double check the band adjustment. I've seen bands adjusted too tight.

 

[66Satellite47]

I should have asked to be sure, it moves "forward" in Park?

 

[Darthomas]

If you push 'er backwards out of parking spots, I think you could use the car for the show. The dreaded stuck rear clutch problem. Maybe they're welded together, maybe not. Maybe they'll "free up ", maybe not.
Life's an adventure.
Torsion bars go bang and drop, water pumps decide to pee at the worst time.
Bring a tow strap and plan on having fun.
You aren't going to be alone, right?
God, I miss CB radios.

 

[747mopar]

Like above, or internal pressure leak in valve body. Really check that shifter linkage adjustment. Otherwise get another trans.

This would be my first step^^^^ What I like to do is unhook the likage at the tranny and put both the tranny and shifter in park and see if they line up then do the same in 1st. If they don't line up then you have an adjustment problem. Most problems outside of linkage adjustments aren't quick fixes other than changing the filter, adjusting bands or bumping up the line pressure.

 

[dvw]

If the linkage is moving the manual valve (which it should be if the neutral safety switch is hooked up) then my bet is the rear clutch is stuck together or damaged. If it is stuck, the low roller clutch holding the rear drum will cause forward movement without any pump pressure being applied.
Doug

 

[Marksman]

Sorry if I forget to acknowledge some of you. I'm on my phone so seeing all of them is difficult.

The car does not move in park, only because of the parking pall holding it. It does seem like it lurches forward though, and if you gas it, when the engine comes back to idle it seems as if the transmission is dragging the engine down to the point that it nearly dies for a second. Shifter adjustment is fine.

We'll check the band adjustment and change the valve body if we need to. I've have plenty of SB 727's lying around to pull parts from.

I'm leaning towards it being stuck or welded rear clutches. Maybe if we're hard on it they will come loose.

I suggested just pushing it out of spots (which is what I would do..) but he didn't like that idea.. He will be traveling alone (car wise) with his dad going to the Baytown stop. I'll be taking the charger from Austin to Wichita. He actually does have a CB for the car, oddly enough.

Thanks for the replies

 

[Darthomas]

I only once tried to go to the Mopar National meet in Columbus ,Oh in '86, and had my 71Dart in the body shop, so I planned on driving the 66 Belvedere II conv in the pic.
I was having the trans rebuilt, and it was to be done the Thursday before.
The man in the shop had fired all his R&R helpers for being less than helpful.
He took it on a test drive and it grenaded on him. I ended up going there in shame, in a '78 Pontiac Grand Prix, and I parked far away in shame. If only it had been something like not being able to back up, I would have taken that risk.

 

[mopar 3 B]

Time to drop the pan and see what is going on. One stuck clutch pack will not keep it going forwards in all gears nor will a stuck overrunning clutch.
With the valve body removed everything can be pressure checked. Time to get the FSM out and go to work.

 

[Marksman]

Checked the adjustment of the shifter again, pulled the pan, changed VB from his working SB trans that came out of the car and adjusted bands. Put it back together and nothing has changed. I hadn't seen the transmission driving in neutral or reverse in person, but I did tonight. With it in neutral, my foot hard on the brake, it drove over a 4x4 block with ease.

He has finally warmed up to the idea of driving it and pushing it into parking spots. Now if only the exhaust flanges for the magnum manifolds would come in the mail so he can have exhaust installed.

Mopar 3 B, we were working on the car when you replied and didn't check the thread in time to do what you suggested. We didn't have a pressure gauge or the correct size fitting either. If a stuck clutch can't cause the problem, do you have an idea of what might?

Thanks!

 

[Darthomas]

Time to drop the pan and see what is going on. One stuck clutch pack will not keep it going forwards in all gears nor will a stuck overrunning clutch.
With the valve body removed everything can be pressure checked. Time to get the FSM out and go to work.

If it ain't stuck, then it's welded together,
it's happened to me

Checked the adjustment of the shifter again, pulled the pan, changed VB from his working SB trans that came out of the car and adjusted bands. Put it back together and nothing has changed. I hadn't seen the transmission driving in neutral or reverse in person, but I did tonight. With it in neutral, my foot hard on the brake, it drove over a 4x4 block with ease.

He has finally warmed up to the idea of driving it and pushing it into parking spots. Now if only the exhaust flanges for the magnum manifolds would come in the mail so he can have exhaust installed.

Mopar 3 B, we were working on the car when you replied and didn't check the thread in time to do what you suggested. We didn't have a pressure gauge or the correct size fitting either. If a stuck clutch can't cause the problem, do you have an idea of what might?

Thanks!

Happened to me.
Bought junk 904 and didn't know an aftermarket mod valve body was in it, which kept pressure to the torque converter and all pressures higher in PARK. The spool valve was cut differently to do this.
Slight foward effort always in park.
No prob, until a 17 below day, when I warmed up the car for 20 minutes.
Got in, backed out just fine, put in drive and went home 20 miles.
Put it in reverse to parallel park, and still forward, all gears forward.
Rear clutch set was welded together the instant I put it in drive.

 

[Darthomas]

Should note, trans was fully rebuilt, and then this happened. I didn't put a junk trans in.

 

[Marksman]

Dang. I assume you had to rebuild the trans to fix it?

 

[Darthomas]

Yes, but the builder honored it, I paid R&R,
and he worked all weekend on it.

He's very well respected, to say the least.

 

[dvw]

Time to drop the pan and see what is going on. One stuck clutch pack will not keep it going forwards in all gears nor will a stuck overrunning clutch.
With the valve body removed everything can be pressure checked. Time to get the FSM out and go to work.

A stuck rear clutch could make it move in all forward gears. If the high clutch and KD band operate normally the trans would also have 2nd and 3rd gear.
Doug

 

[Darthomas]

A stuck rear clutch could make it move in all forward gears. If the high clutch and KD band operate normally the trans would also have 2nd and 3rd gear.
Doug

That's what I had, I drove it 60 miles to be rebuilt after that happened.
All forward gears, fine on the highway,
just....always forward.