727 poor reverse quality

[Remusa12]

My dad's superbee has an issue where it's not moving in reverse even at higher rpms but if you build pressure in neutral it'll move for a few seconds before needing repeating. It seems to work okay when it's warmed up. It's been sitting for a year with infrequent driving before this.

 

[beanhead]

Was it working okay before the sitting? That should rule out a major parts failure.
I'm not much help, but after verifying fluid level and quality I would check if the band is out of adjustment because it's easy and you're there, if okay then check the servo and seal carefully.
The servo seal would be my first suspect though. Sitting can wreak havok on seals especially if they're 50 years old..

 

[Moparnocar]

Converter drain back? If cold, and you put it into nuetral for 1 minute, does it work fine? More that likely needs to be "freshened up"

 

[1 Wild R/T]

Two components make reverse...

The front clutch which is also used for drive/3rd gear... That probably is fine or you'd have a complaint about slipping in high gear....

And the rear band which is also used for manual low... The only thing it does in manual low is cause the car to slow when you take your foot off the gas... Most people don't even notice that but if you test it you'll likely confirm it...

So pull the pan and look at the rear servo, debris in the pan, adjust the band & hope for the best....

You might get lucky & have a bad seal on the rear servo...

Replacing the rear band pretty much requires taking the trans completely apart...

 

[66Satellite47]

The difference between cold & warm sounds like low fluid level. Rear band adjustment or seal is very likely.

 

[440 Charger]

My dad's superbee has an issue where it's not moving in reverse even at higher rpms but if you build pressure in neutral it'll move for a few seconds before needing repeating. It seems to work okay when it's warmed up. It's been sitting for a year with infrequent driving before this.

Learn the 727 awsome transmission.

 

[440 Charger]

Two components make reverse...

The front clutch which is also used for drive/3rd gear... That probably is fine or you'd have a complaint about slipping in high gear....

And the rear band which is also used for manual low... The only thing it does in manual low is cause the car to slow when you take your foot off the gas... Most people don't even notice that but if you test it you'll likely confirm it...

So pull the pan and look at the rear servo, debris in the pan, adjust the band & hope for the best....

You might get lucky & have a bad seal on the rear servo...

Replacing the rear band pretty much requires taking the trans completely apart...



View attachment 1024607

Think isn't that fun?

 

[440 Charger]

Two components make reverse...

The front clutch which is also used for drive/3rd gear... That probably is fine or you'd have a complaint about slipping in high gear....

And the rear band which is also used for manual low... The only thing it does in manual low is cause the car to slow when you take your foot off the gas... Most people don't even notice that but if you test it you'll likely confirm it...

So pull the pan and look at the rear servo, debris in the pan, adjust the band & hope for the best....

You might get lucky & have a bad seal on the rear servo...

Replacing the rear band pretty much requires taking the trans completely apart...



View attachment 1024607

Have you ever built one?

 

[440 Charger]

The difference between cold & warm sounds like low fluid level. Rear band adjustment or seal is very likely.

Fluid is a key for this one.

 

[440 Charger]

Was it working okay before the sitting? That should rule out a major parts failure.
I'm not much help, but after verifying fluid level and quality I would check if the band is out of adjustment because it's easy and you're there, if okay then check the servo and seal carefully.
The servo seal would be my first suspect though. Sitting can wreak havok on seals especially if they're 50 years old..

Lol time is the Key.

 

[Curiousyellow71]

When its cold does it do the same thing in 1st gear. To have a internal leak causing it to slip in first and reverse would be much more common.

 

[Lefty71]

Not a trans expert, but we had this happen on a Merc once. Turned out the sealing rings (with the little locks) were bad ones from new on that particular car. It worked just fine once the trans was warmed up, but it seemed like you could wait forever for it to start going. 1wildRT is spot on regarding clutch behavior ON/OFF for reverse, but if you lose fluid pressure at the key time when you need that extra boost of pressure to hold the front clutch (which is how it does behave in reverse), then that could explain your slippage. An aftermarket valve body that does not boost reverse pressure as far as stock, is also a possibility that could compound you problem. I'd pull it down and check everything closely, or find someone who can, and give it a rebuild as well. HTH, Lefty

 

[Slap Stick]

When its cold does it do the same thing in 1st gear. To have a internal leak causing it to slip in first and reverse would be much more common.

This is what I was thinking. I blew reverse on a 72 or 73 Charger way back in the 70s (I think it was the 73) and the tech described to me what had happened.
He said low and reverse used the same band and had an "ear" on each end, shaped somewhat like this: Ω.
The "ear" on the reverse side broke off so the trans freewheeled in reverse.
It still worked in forward and I drove it to the shop.
Now...I don't know if that is true but he was an ATA instructor, etc and had a stellar rep.
Years later I had an Escort transmission act up and he hooked up pressure gauges to it and found the problem and fixed it at a reasonable price.
He's retired now.

 

[Lefty71]

This is what I was thinking. I blew reverse on a 72 or 73 Charger way back in the 70s (I think it was the 73) and the tech described to me what had happened.
He said low and reverse used the same band and had an "ear" on each end, shaped somewhat like this: Ω.

If you look at a troubleshooting guide for delayed reverse, etc, it does mention broken or very loose rear band as a possible cause, as well as servo probs, accumulator, fluid or filter, seal rings, linkage, etc.....

I would check the adjustment, if its ten miles off, or not possible, then you know where to go when you teardown.

 

[Dipstick]

The difference between cold & warm sounds like low fluid level. Rear band adjustment or seal is very likely.

Fluid temperature affects the rubber seals. When cold, shrunken seals will leak but when the fluid warms up, the seals expand and seal better. This is a case where an additive like Trans-X might help by rejuvenating the seals.

Can't see where band adjustment would change with temperature.

 

[66Satellite47]

Fluid temperature affects the rubber seals. When cold, shrunken seals will leak but when the fluid warms up, the seals expand and seal better. This is a case where an additive like Trans-X might help by rejuvenating the seals. Can't see where band adjustment would change with temperature.

Only explanation I have is the lip seal gets a little better & is able to tighten the band for a short time as the OP described. Or low fluid, or band material warms up & gives enough hold for a short time. I'd pull it apart & fix what's wrong, like I did with mine in '73.