A/T in Reverse, rolls about a foot then wheels lock?

[TTait]

My automatic sat neglected for a dozen years before we rescued and resurrected it. For the first few thousand miles it needed help - it would shift hard. I replaced the fluid several times, replaced shift solenoids and filter, replaced shift computer and adjusted vacuum modulator.

It slowly started behaving better and better, and as of last weekend it ran GREAT. Shifted smoothly, etc. I was told by Toby et al that it might start functioning better by just driving it, and it did - I was very happy.

Then today a new problem came up... When I put it into reverse to back out of the garage, it drives back normally for 9" to a foot, then the transmission seems to lock up. If I just get it rolling slowly in reverse and immediately shift into neutral, it rolls back several feet before I stop it normally.

I had another car behind it in the driveway by the time I realized it would roll in neutral, so I've only rolled it back and forth a few feet. Frankly I would prefer to figure out what is going on before I roll it down the driveway and try to test it further.


This cannot be good... It really seems to be a transmission thing - not brakes etc. There is nothing on the garage floor blocking a wheel. I don't recall ever reading about a similar condition, and a search of the forum makes me feel all alone with this experience. So... How bad is it guys? Next steps in diagnosing without causing any (more) damage?

Tom

[Dangermouse]

I wonder if it is somehow slipping into P or the parking pawl is being engaged?

Does it operate normally in D?

[TTait]

It feels like its dropping into park for sure - I've been afraid to try to drive it further...

[Dangermouse]

Are you just pushing it forward after reversing or are you driving it?

I'm not sure that it matters but it may confirm the parking scenario.

I think this is one for Dave S or Ron.

[TTait]

It runs forward fine in drive after rolling back in neutral about 3-4'.

It also runs forward fine in drive after driving it back in reverse 1' and then the wheels lock.

All of this is basically within the confines of the garage before i start hitting slope (or another car) on the driveway.

[Ron]

You can eliminate the parking pawl by shutting off the engine and seeing if it will roll..

I'm not sure if there is a weird case where the governor could cause iut, but pulling fuse 13 should prevent it from energizing a solenoid, making it go into a forward gear at the same time. Other than that, I hate to say it don't sound good...no easy fix for the things I can think of that would cause it.

[Bitsyncmaster]

Are there shift stops with an auto gear shift? If so, maybe it's just a linkage adjustment.

[DMCMW Dave]

I've seen one where the parking pawl link pin bent and it did some strange things, locking inappropriately etc.). It can be accessed/repaired somewhat with the trans in the car by removing the pan. I'd just be sure that your linkage is just not slightly out of adjustment, i,e. hitting reverse and park at the same time. .

[David T]

I've seen one where the parking pawl link pin bent and it did some strange things, locking inappropriately etc.). It can be accessed/repaired somewhat with the trans in the car by removing the pan. I'd just be sure that your linkage is just not slightly out of adjustment, i,e. hitting reverse and park at the same time. .

I agree with Dave S, go over the gearshift cable adjustment to be sure you are completely in each gear. To see if it is a parking pawl problem you could remove it and see if the problem goes away. It may not be installed correctly or the link could be bent. There are detents in the gearshift AND the transmission. You must be in the same detented position in both the transmission AND the shifter. You could jack up both rear wheels and run the motor and shift the transmission to see what is going on.
David Teitelbaum

[TTait]

I agree with Dave S, go over the gearshift cable adjustment to be sure you are completely in each gear. To see if it is a parking pawl problem you could remove it and see if the problem goes away. It may not be installed correctly or the link could be bent. There are detents in the gearshift AND the transmission. You must be in the same detented position in both the transmission AND the shifter. You could jack up both rear wheels and run the motor and shift the transmission to see what is going on.
David Teitelbaum

I'd be thrilled if its just a linkage adjustment problem, happy if it is a pawl adjustment, and even satisfied if removing the pawl could fix it temporarily. I'll work on it Saturday and let you know what I find.

[TTait]

Fixed for $1.40

One of the caliper mounting bolts had backed out, allowing the rear caliper to shift. The bolt has been replaced and all 8 mounting bolts re-torqued.

I'm fortunate that it was not the other bolt, in this instance when the caliper shifted the car would be in reverse, had one caliper locked up on the freeway at 75mph it could have been a different story.

I had a little damage to one of the e brake pads, less than 5% of the total surface area is now chipped away, aside from that it seems to be good again.

Thanks for you help guys.

Tom

[Dangermouse]

So why was it OK in neutral but locked up in R?

[TTait]

It rolled a lot slower in neutral, as it picked up speed it torqued the caliper, the only way to go that slow in reverse was to use the brakes, which caused the same problem.

When I rolled it down the driveway in neutral this am it eventually built up enough speed to lock up in neutral as well. Previously I had only let ir toll a few feet to the top of the driveway.