Transmission creeps in neutral

[mquinn66]

I replaced my transmission with a freshly built 727 with rvmvb and 3500 stall converter last year. It creeps backwards in neutral. I thought it might go away after it got broke in a little but 300 plus miles later it still creeps. Should I be concerned? Its not a powerful creep . ‍

 

[Aron Gleason]

Something is definitely wrong, it shouldn't creep backwards in neutral.

 

[Cranky]

if you pull the shifter more towards drive does it stop the creep? I'm thinking something's going on with the shifter valve if that's the right term for it....

 

[Geoff 2]

Sounds like leakage within the valve body....or linkage adjustment.

 

[1 Wild R/T]

Sounds like leakage within the valve body....or linkage adjustment.

As Cranky & Geoff both mentioned VB or linkage.... Or possibly the rear band adjustment is to tight...

 

[Lefty71]

Definately could be the valve body itself. Whos is it?? Was it advertised as "clean neutral"?

 

[mquinn66]

I think its an A&A valve body. And its a reverse manual not sure if that makes a difference. Im concerned because I think reverse and 1st run on a different drum?

 

[Cranky]

......Or possibly the rear band adjustment is to tight...

Years ago when I was more stupider than I am now..... I adjusted the rear band using a lift at a buddies shop and well, forgot to back it off the correct number of rounds once snugging it up. Buttoned it all back up and went for a test drive and when it shifted into 2nd, it locked up the rear wheels! Immediately pulled it into 1st gear and it kept on rolling and knew exactly what I did. Had to drive it home in first gear because my buddy already had another car on the lift and did the job right with it up on ramps. Don't recall it having any neutral creep though.

 

[Cranky]

I think its an A&A valve body. And its a reverse manual not sure if that makes a difference. Im concerned because I think reverse and 1st run on a different drum?

Well, the rear band is the low/reverse band....

 

[1 Wild R/T]

Years ago when I was more stupider than I am now..... I adjusted the rear band using a lift at a buddies shop and well, forgot to back it off the correct number of rounds once snugging it up. Buttoned it all back up and went for a test drive and when it shifted into 2nd, it locked up the rear wheels! Immediately pulled it into 1st gear and it kept on rolling and knew exactly what I did. Had to drive it home in first gear because my buddy already had another car on the lift and did the job right with it up on ramps. Don't recall it having any neutral creep though.

Each gear requires two elements be engaged in order to work... In the case of reverse those two components are the Low/Reverse (rear) band and the front clutch.. If the clutch clearance is set on the tight side creep is possible... The allowable range is pretty wide & rookie trans builders tend to set them on the tight side thinking it makes for a better trans.... DAMHIK!!! (Learned that in around 1975) So obviously your forward clutch had plenty of clearance.....

So what happens if you set the clutches on the tight end of the allowable range? Well, the piston that applies the clutch doesn't have to travel as far so it applies quicker... But the other gear still takes just as long to release so you wind up with two gears applied at the same time.... This is called "Shift Overlap" and what you experienced when you forgot to loosen the rear band is a severe example of that....

Typically shift overlap only lasts a few milliseconds but right at the shift the car will feel like its hesitated or slowed slightly... I've experienced such severe shift overlap that at the shift the rear tires briefly locked.. (Refer back to 1975)

In some cases a flow restrictor is used to reduce/eliminate the overlap... This is common when installing shift kits... But when the overlap is to severe you gotta go back and add more clearance.. (Again DAMHIK)

 

[dvw]

It would need both the high/rev clutch and the rear band to be applied to back up. Check the shift linkage first. If the clutch clearance is tight and the rear band is tight it maybe it could happen, but I've never seen it. You could pull the pan and check the rear band adjustment. But I'd call Rick at A&A first and talk to him about it. He's good to work with.
Doug

 

[Lefty71]

But I'd call Rick at A&A first and talk to him about it. He's good to work with.

This is exactly what I was gonna say.

 

[oldkimmer]

I bet the builder took the clearance out of the rear drum where the big concave spring is. They were designed to have clearance. Or possibly the manual valve is out of adjustment. Kim