Transmission Problem I need help diagnosing

[DonMo]

I have a 1984 911 with a stock transmission and an elephant racing shift coupler. I recently was stranded where my car would not shift into any gear. Up until then, shifting was clean and precise. When it failed, I could not even move the shifter or find neutral. The clutch would disengage and engage the transmission but it appeared to be in a high gear.

Trying to figure out what my issue was, I changed the transmission fluid to see if it was a loose shift forks (didn't appear loose to my uneducated eye) and pushed the reverse pin back in. I now have shift movement but when I let the clutch out, it was in reverse when the shifter said I was in neutral. All other shifter movement resulted in what appears to be a high gear. I need help figuring this out.

Any words of wisdom on where to go next is appreciated.

[Tom '74 911]

Don,
The first things I would check are the shift coupler condition and adjustment (wasn't aware that Elephant Racing made a shift coupler) and the shift lever bushings condition. Both are easy & basically free to verify. If any of those parts & pieces are not in good condition or adjusted incorrectly, shifting will suffer. I'd start there (low hanging fruit) before getting to the more invasive options like what could be happening, or not happening, inside the gearbox itself.
Tom

[DonMo]

Thanks Tom, shift coupler is rock solid. Hadn’t thought about shifter. Fairly new with under 10k miles but as you say easy and cheap. I am convinced I will be opening the tranny access plate again so if any have pics of how it should be or diagnostic steps, I would appreciate.

[kevingross]

Check motor mounts.

[DonMo]

Thanks Kevin, wouldn’t have thought about mounts.

[911pcars]

Your issue could be internal (gearbox mechanism) or external (shift linkage).

Since you haven't described any catastrophic mechanical noises, the usual suspect is the shift linkage.

Remove the metal tunnel access plate behind the front seats.

Wiggle the shift lever and observe the shift tube between the shift housing and the gearbox. There should be corresponding movements between both.

If there's exccessive play/loss of motion, one or more of the plastic/nylon bushings have disintegrated (failed) or some mechanical part is loose or broken. New shift coupler? Check it anyway. What's left is a bushing at the end of the shift kever and a collar that supports the front end of the shift tube - historically common areas of wear. Could be a combination of both.

To inspect/replace either one requires removing the center console to access and remove the shift housing.

There's a ton of info and photos in the PP archives (and internet) on replacing these worn parts (maybe 15 fifteen bucks worth).

Let us know what you discover.

Sherwood

[76FJ55]

You mention several times the it seems to be in a high gear. What exactly are these symptoms?

I am going to jump to a lot of conclusions and suggest that the 5/R shift plane has shifted into R and the sift rod is in the 1/2 and 3/4 planes. can you actually move the shifter into the 5/R shift plane (I'm guessing not)? What I think is happening is that R is always engaged, so when you shift to N you are still in R. When you shift into anything else than N that would put you into 2 gears simultaneously and the trans is locked in position by the shafts trying to turn 2 speeds at the same time. With the clutch pedal up, I will guess that the car will not roll in any gear, and that with the clutch pedal depressed it will only roll in neutral.

If I'm guessing correctly you need to move the 5/R shift fork back to the neutral plane and I think you will be back to good shifting as before.

[DonMo]

Thanks, your description is right on target. Will drain and open it up again.

[DonMo]

Okay, I am back in the tranny via inspection plate. I found the shift rod in what appeared to be a stuck position. I freeded it up and now have the ability to move the shifter into all gears. The confusing part for me is that when I put the car in any gear and turn the wheel, the tires rotate. Doesn’t matter what gear, the wheels move. I was under the impression that when in gear, I could not turn the wheels. Am I mistaken?

Is the any wisdom as to what the internal tranny alignment should be when viewing thru the inspection port?

Any help is greatly appreciated.

[76FJ55]

I'm assuming the car is still up on Jack's? If so, this is normal for an open dif. With the car in gear and off the ground the wheel on the other side will rotate the opposite direction.

[DonMo]

I believe this is a good image to use for alignment. I just need adjust the shafts so the shift linkage can go into both smothly when in neutral. Correct me if I am wrong please. (thanks to Peter Z for pic)

[kevingross]

Better yet to look at all the pictures, read through the article at How-To: Porsche 915 Transmission Repair Tutorial Part 7 - Porsche Wiki

[DonMo]

Thanks Kevin, bookmarked Peter Z.’s Wiki. Good stuff.

[DonMo]

Ok, I am frustrated. I got the 1/2 and 3/4 shift linkage correct and declared success and buttoned upthe tranny, filled with gear oil and still no joy. I believe I missed the fix by not making sure the 5/R was in the neutral spot. Is the 5/R shift linkage visible through inspection plate, I didn’t see it but I admit I was focused on 1/2 and 3/4. Can someone share how to ID the 5/R linkage? Is it visible through inspection port or elsewhere? Pics would be nice. I am getting real efficient at draining and filling the tranny, a skill I really intend to master.

[Flat6pac]

There is 3 notches in the rotation at the plate. All have to line up to be out of gear.
Change the swivel in the back access.
Bruce

[DonMo]

My tranny is in reverse when it is in the neutral position and no gear at any other.

I can move the shifter into each of the gear positions but my guess is that I am in reverse and the piece that moves the shift rods can't get into the slot to move the gear so I am between.

Looks like I will have to drain the tranny again and open up the inspection plate. I guess I will have to look closer to see the 5/R rod and move it to realign all three of the notches.

Fingers crossed.

[Flat6pac]

If your selections are all lined up and you’re still in reverse then it sounds like you’re problem is under the end cap with a loose selector.
Bruce

[Walt Fricke]

Don - what you call the inspection plate on the bottom of the transmission isn't really there for inspection. It is there to hold the fork, and the fork is there to be the pivot for the dongle, so when you push the shift lever forward, the ball end of the dongle moves forward, and vice versa.

But you can learn a bit by looking with the plate and its attached fork removed. For instance, if the transmission is in neutral, the sort of U shaped forgings on the two shift rods will be lined up, which they sort of look to be in the picture you posted (I know, that's not from your car). When they are lined up, the transmission should be in neutral, or 5th or reverse. And the dongle should rotate so that when in the 1st/2d gear position side to side (in neutral)its ball tip lines up with the closest (if memory has it right) shift rod. And in the other one for 3/4. And for 5/Rev the tip of the dongle should be all the way beyond both of these parts, which is what allows the separate 5/Rev shift rod to do its thing.

You can't see the 5/Rev stuff through this hole - it is all on the other side of the front bulkhead of the transmission case, under the nose piece where the shift coupler rod enters the transmission.

The 5/Rev system is less robust. Instead of the ball end of the substantial dongle lever, rotating the shift lever to the far right against the spring pressure rotates a slender finger into a shallow square sided groove ground into the 5/Rev internal shift rod. When it is there, pushing one way or the other on the shift lever moves this shift rod fore or aft, but in a direction opposite of the way you moved the shift lever (no pivot in this system). So the internal rod moves back to engage 5th, and forward to get reverse.

You can see through the "inspection" plate what is going on there, pretty much. You can use a suitable implement to pry on the two rods to select the four gears they control. If one or both of the brass yokes which are attached to these rods have gotten loose, you ought to be able to see this. Or to confirm that they aren't. Neutral for those four gears has the slider (operating sleeve, the thing the yokes engage) evenly spaced between the synchro rings of their respective gear pairs. Setting these just right is about the only tricky setting when rebuilding a transmission. Between a flash light, or a borescope (for $10 you can get one which will use your laptop or tablet as a screen), you should be able to verify if there is a problem with the operating sleeve alignment in neutral.

Another thing to try is to pull the two bolts which are one above the other on the right side of the transmission. These each hold a spring, which presses on a rod. These are part of a clever interlock system, so when shift rod 1 is in one of its two engaged positions, shift rod 2 is locked into its neutral position and can't be budged. Prevents the "in two gears at once" problem. For the kind of testing you might want to do, you should defeat the interlocks. If you end up prying into two gears at once, you should be able to pry both back to neutral.

The 5/Rev system is a bit trickier. It is possible for the finger, when it is rotated to select either of those gears, to pop out of its groove. I think pulling out of reverse while still rolling backward may help this to happen. Now stuck in reverse, and for some reason moving to 5th doesn't slip the finger back into the groove.

There is also an interlock system for the 5/Rev rod, I think, which then causes troubles when trying to select 1-4. Otherwise, one might think just moving the shift lever back and forth (against the friction of the finger pressing on the smooth part of the rod) would pop things back into place. But it seems it doesn't.

You can eliminate the shift lever/tower/long rod/coupler from the variables if you disconnect the coupler when trying to pry into and out of gears. But unless the plastic ball cup up front has completely disintegrated, or the big round bushing over the shift rod is missing, or the grub screw has backed off of the part which holds the ball cup, or something really obvious backed off or broke up there, I doubt that part of the system is the culprit.

You seen to know the pin trick with the backup light switch, which is a way of being able to push the rod backward out of reverse when the lever won't do the trick. I've never had to do that, but will the pin come out so you can use a longer rod? I forget how it is laid out. Not a whole lot of room there, either. Maybe if you pull the transmission mount you can drop the front of the transmission down enough to get some room?

Anyway, I think you should be able to narrow down the problem. An assistant to move the shift lever while you are under there looking would be pretty useful.

When you get it sorted out, put those two rods and their securing bolts back in. You don't need a new gasket for the "inspection" plate. You don't need a gasket at all - just use some orange Loctite case sealer like you'd use when reassembling the engine. Or any of the other sealants (not silicone) which guys use and work as well.

I assume that the fork attached to that plate was securely fastened - the nuts were nice and tight.

With the rear up in the air, you can make reasonable estimates as to what gear you are in (assuming not locked into two at once) by measuring how many degrees the wheels move when you crank the engine by hand one revolution. Unless you have a limited slip, you do this by jacking up just one side.

PM me and I'll send you a chart showing how many degrees a wheel should rotate in which gear. I may not have it quite right for an 84, but no matter - you can tell one gear from another. And without any chart you should be able to figure out if you are locked into reverse as opposed to forward with one side jacked up.

I don't have a better guess than some as to just what has led to this, so I won't guess.

[DonMo]

thanks Walt