Stuck in Reverse with a Twist

[Walt Fricke]

Some understanding may help here. Reverse and 5th are engaged by a rod which has a finger sticking off to one side. In the main shift rod - the one which sticks into the passenger compartment - there is a slot. When the main shift rod is rotated to the 5th/reverse position, the finger engages the slot. At that point, moving the main rod forward or backward (and remember that the shift lever console reverses the direction of movement of the shift knob) moves this secondary rod. The secondary rod has a fork on it, which moves a sliding piece. This either engages the synchro and teeth of 5th when moved to the rear of the car/transmission, or physically moves gear teeth into mesh with the reverse gear.

What happens if a car is in reverse, and the driver yanks it out of reverse? Well, usually nothing bad, but it is possible for the finger to skip out of its slot before reverse is disengaged. If another gear is now engaged (1st, for instance), you are in two gears at once and going nowhere. Putting a transmission into two gears at once during a rebuild is one way of locking the shafts so that nuts can be tightened. Nothing much can turn at that point.

The backup light switch is a lightly spring loaded pin. Parts of the reverse gear system physically pusn on the end of this pin, and it closes a circuit in the switch, etc. But this means that the pin, if it gets shoved hard enough, can push the short shaft, and thus disengage reverse if pushed far enough.

This is not the only way troubles can happen in transmissions. But it is relatively common, as such woes go. Which is why you are being urged to try it - hard. You won't damage anything more than perhaps it already has been damaged, and you might undo the problem.

The slot in the main shift rod should have nice square, sharp edges. Over time, the edges can get worn, making this kind of thing more likely.

You might think, as I often have, that if a guy just put the car back into the reverse position on the shift lever end of things, the finger would plop back down into its slot, and all would be well again. As it can be if the backup light pin trick works. Doesn't seem to be the case, for reasons I don't understand.

it is much harder to get the tranny into any two gears when none involve reverse. Unless improperly assembled, there is a clever ball and spring interlock system such that when the 1/2 secondary shaft is in either of its engaged positions, the 3/4 shaft cannot move at all. Anv vice versa. However, if all else fails, and you decide to look farther before calling the flatbed truck to take the car to a shop, pulling the "inspection" plate (really the holder of the dongle fulcrum fork) will give you a view of sorts of the innards. You can see where the dongle end is, which of the two shift selectors is or is not engaged, and have a chance, if one of them is engaged, of disengaging it.

As you know, the shift rod has three rotational positions: 1/2, 3/4, and 5/R. In either of the first two, the ball end of the dongle (the thing the shift rod moves inside the main tranny housing, which you are staring at with the plate removed) should be in one of the secondary shift rod engagement slots, depending. When in the 5/R rotation, it has moved free of both of these engagement slots, and should be able to be freely rotated up and down through them. So it will be quite obvious if something is amiss in there.

Good luck

[Walt Fricke]

If you are only locked into one gear, depressing the clutch will allow the car to be pushed or winched. If locked into two, no. But the flatbed folks ought to be able to dolly it up. They usually have dealt with all kinds of problems.

[mrehrer]

Walt-

Thank you for your detailed and enlightening posts.

When I first started to experience the "stuck in two gears" symptoms I had already managed to back the car part way out of the garage. The temporary fix was to push it back in with the clutch depressed. If it is truly not possible to push the car with the "stuck in two gears" problem then perhaps I have another issue.

I am thinking the next step is to drain it, filter the oil for evidence and go from there. Assuming no obvious damage I'd open the bottom plate. Could a loose fork be causing my symptoms?

My question about pushing/towing an empty 915 was assuming a worst case scenario I'd not want to fill it again just to flatbed the car.

[wgirardot]

Originally Posted by mrehrer

Walt-

Thank you for your detailed and enlightening posts.

When I first started to experience the "stuck in two gears" symptoms I had already managed to back the car part way out of the garage. The temporary fix was to push it back in with the clutch depressed. If it is truly not possible to push the car with the "stuck in two gears" problem then perhaps I have another issue.

I am thinking the next step is to drain it, filter the oil for evidence and go from there. Assuming no obvious damage I'd open the bottom plate. Could a loose fork be causing my symptoms?

My question about pushing/towing an empty 915 was assuming a worst case scenario I'd not want to fill it again just to flatbed the car.

push the pin in man, you have to push it hard

[Walt Fricke]

Sounds like you are only stuck in one gear, which is better than being stuck in two.

And that the one gear stuck is reverse.

Hence the exhortations about the pin.

Is your shift lever in neutral, or thereabouts?

[mrehrer]

If I was only stuck in reverse then it should not stall when I let the clutch out so there must be something else going on.

I have definitely tried pushing on the pin (though I see now I did not make that explicitly clear). I have not hit it with a hammer yet but I gather I don't have to worry about it being delicate.

Shift lever is in neutral near reverse. Trying to shift into any of the gears at this point has a large amount of resistance.

[schumicat]

what are you pushing it with, your finger? unless you're Dr. No, that won't work. you don't need a sledgehammer, but you need to give it a solid rap (like with a plastic face hammer and punch).

[mrehrer]

Some progress I hope!

Fiddled with the linkage shifting into and slowly back out of reverse seemed to leave the pin in a more protruding position. Whacked it with a small hammer using a long bolt as a punch. Buttoned it back up (even optimistically reattached the switch wiring).

Against my better judgement I fired it up on the jack stands because I wanted to be able to see rotation no matter what gear I was in (assuming I was in any one). Eased the clutch out and spinning rear tires!

I the shifter appears to be in neutral can I assume pushing the pin back put me in fifth? Or is that precisely impossible since whatever gear I'm in now can't be the opposite pair on the slider for reverse (5th).

Thanks all for the mechanical support group!

[Walt Fricke]

Up on stands, RPMs just a bit above idle, you should be able to see if tires are rotating forward or backward. And 5th would rotate rather fast, even at low RPMs, vs a lower gear.

You might try moving the shifter into 5th (I assume you have pulled the rubber boot around the shifter up so you can see what is going on there, as you want the hook on the shift lever over the tab on the shift tower to be sure you are in 5th).

Can we assume you have pulled back the rear passenger seat area tunnel upholstry, and removed the cover plate, so you can look at the shift coupler? The easiest thing to get a bit loose and go wrong with that coupler is for it to start sliding a bit where it attaches to the shaft coming to it from the shift lever. You put a whole lot more force on that clamped joint moving the lever forward and backward than side to side - you have to overcome synchro forces and so on, not just moving internal levers side to side. If pulling extra hard moved this joint backward, that might explain being in 5th but seeming to be in neutral (other than the fact that the lever would not feel like in neutral, just positioned as if it were).

The movement you saw of the pin sounds like pretty good evidence that you were able to move the 5/R shift fork rod. I don't know if the backup switch pin is long enough to force things into 5th - maybe it is. Getting neutral is usually enough for victory.

[mrehrer]

Shift boot is pulled up and yes the panel above the coupler is off. When this was originally problematic I expected to see that the coupler bushings in pieces as others have reported. Coupler bushings are intact but I will replace them, the cup and rod bushing as soon as I square this issue away. I don't think the coupler is loose but I will double check that.

It seems that what would normally be expected is that pushing the pin in would result in my being in neutral. Is there something else that I should do at this point to try to get into neutral?

[Walt Fricke]

If you conclude from watching how the wheels rotate you are most likely in 5th, try to move the shift lever there to see if it will re-engage.

[mrehrer]

Earlier input from Walt that may help others:

Originally Posted by Walt Fricke

You really don't have anything to lose by sticking a punch in and tapping it. Given the location, you couldn't hit the punch or whatever rod you can get in hard enough to hurt anything, right? Pretty limited room. If you have something long enough, you could try levering against your punch against the end of the floorpan or some nearby useful fulcrum, perhaps.

It is the short secondary shift rod - the one with the shift fork which pushes and pulls things into 5th when pushed forward (from the perspective of you trying to tap it - it will be in that direction) and backward into reverse - whose end pushes against the backup light switch pin. That is a stout rod - a whole lot stronger than the pin you are pushing against it. So you aren't going to hurt the rod. The pin is the weak link, but part of it is in a housing so it won't bend. And if this does not work, you may be having the transmission out and at least that end piece off, at which time you could replace the pin if it gets damaged. Or leave it off if you don't care about backup lights.

Otherwise, these symptoms don't add up: With the clutch in, you can push (have someone push?) the car backwards and forwards? With the clutch in, you can start the car, and it stays put as it should. But even with some gas, as you let the clutch out the car doesn't start to move, and eventually you will stall the engine?

Other than having your brakes (or e-brake) tightly locked, this stalling ought only to happen if you are in two gears at once. But if that is so, pushing the clutch in ought not to make any difference. When in two gears at once, the two shafts - input and pinion - are locked together such that neither can move.

Depressing the clutch means the engine is not coupled to the imput shaft. The input shaft has first, 2d, and 5th and reverse gears fixed to it. In neutral (and in proper condition), with the engine running and clutch out, those four gears are rotating. Their counterparts on the pinion shaft (except for reverse) are also rotating, but they are not fixed to that shaft so nothing happens. They just spin on the shaft. In turn the pinion shaft has 3d, 4th fixed to it. But because the corresponding gears on the input shaft are spinning freely on that shaft, nothing happens.

Shifting involves locking a free spinning gear to the shaft on which it is spinning. This allows the spinning input shaft to transmit its motion to the output shaft, then the differential, and then the wheels.

All gears except reverse are constant mesh. The gear pairs are always meshed to eachother. It is something which slides on splines along the shafts between gears which contacts and locks into the ends of the free spinning gears which makes them no longer free spinning. The synchromesh system is part of this.

Reverse engagement involves moving an actual gear so its gear teeth slip into the teeth of another gear. Because you don't shift into that gear with the car moving.

If, somehow, the input shaft were frozen, then letting out the clutch would, indeed, stall the motor. Wouldn't matter what gear or gears you were or were not in. And I can imagine that as long as none of the free spinning gears on the input shaft were involved, and no gear was engaged, then the car could be pushed either direction. But that would NOT require you to depress the clutch. It would just mean that there was no connection, so to speak, between the pinion shaft (which turns when both wheels are turning the same direction) and the input shaft. Which is how things are in a normal neutral.

Anyway, if I understand the symptoms as you portray them, they don't really add up.

You sure if you just get out of the car and try to push it, it won't move either way? With the hood up, can you see if pushing it tries to turn the engine? You'd see the fan try to move. In reverse you can't really turn the engine over this way with just one guy pushing or tugging, but you might see some movement before the compression of several cylinders is too much to move that way.

Bottom line, again - whack that pin in as hard as you can. Or lever it. Even when things are in good shape, they have significant resistance to moving - think of all the leverage the shift lever gives.

Certainly helpful to me.

Originally Posted by Walt Fricke

If you conclude from watching how the wheels rotate you are most likely in 5th, try to move the shift lever there to see if it will re-engage.

Will give this a shot and report.

[mrehrer]

First and foremost thanks to all for the help and advice. I drove the car to work today to celebrate victory.

In the end fiddling a bit with the shift lever (just within the play of the neutral area) seemed to drop the transmission out of the remaining forward gear it was engaged in.

Once the car was no longer stuck in any gear I did note that both rear wheels spin in the same direction when I rotate them by hand. Perhaps there is still some life in my LSD after all.

Next steps will be to replace all shift linkage bushings, change gear oil and enjoy.

[pete3799]

When you drain the gear oil remove the cover on the bottom and check that the shift fork is bolted tight to the cover.