Top left & right sides move in opposite directions

[WhatAmIDoing]

Hi all,

Some time ago my top got stuck. I finally tracked it down to faulty gears. Disassembled all roof parts and had it in 'manual' mode while I was slowly fixing the transmission using replacement gears I got on eBay.

Finally, both transmissions are done and I'm now putting the top back together.

I practically finished, but when testing the roof I encountered a bizarre issue:
when pressing the top open/close buttons, the left side acts as expected (e.g. if I press Open then the left side transmission moves and starts opening the top). But for some reason, the right side does the opposite movement (e.g. I'll press open, and it will move in the closing direction).

Essentially, I have the left and right parts of the roof moving simultaneously but in opposite directions. How is it possible? I am trying to figure out where I messed up and I simply can't think what would cause that behavior.

Thank you!

[old911doc]

First, verify that you have not incorrectly installed the right side ‘banana arm’. If it is not properly positioned on the transmission, it can give improper moment of both the top frame and the clamshell cover (a.k.a. turtleneck). Second, make sure that both transmissions are in the same points in their range of travel when the drive cables are attached to the electric motor. The transmissions have a ‘timing mark’ on their bodies to aid in assembling them in the same points in their travel. If you need to drive one transmission forward or backward to match it to the other side, all you have to do is to detach the driveshaft / drive cable at the motor, and chuck it into your handy-dandy portable electric drill. Turning the cable manually, while possible, is not feasible because of the large number of turns of the cable made necessary by the extreme gear reduction ratio of the transmission.

[78F350]

Originally Posted by WhatAmIDoing

... using replacement gears I got on eBay....

Essentially, I have the left and right parts of the roof moving simultaneously but in opposite directions. How is it possible? ...

A couple years ago I bought some of the cheapest replacement gears I could find on eBay. I got what I paid for. One was good and the other moved backwards. The gears are supposed to be beveled differently for each side. The ones I received were both identical. Lucky for me I had an extra left side transmission to rebuild.

[WhatAmIDoing]

Originally Posted by old911doc

First, verify that you have not incorrectly installed the right side ‘banana arm’. If it is not properly positioned on the transmission, it can give improper moment of both the top frame and the clamshell cover (a.k.a. turtleneck). Second, make sure that both transmissions are in the same points in their range of travel when the drive cables are attached to the electric motor. The transmissions have a ‘timing mark’ on their bodies to aid in assembling them in the same points in their travel. If you need to drive one transmission forward or backward to match it to the other side, all you have to do is to detach the driveshaft / drive cable at the motor, and chuck it into your handy-dandy portable electric drill. Turning the cable manually, while possible, is not feasible because of the large number of turns of the cable made necessary by the extreme gear reduction ratio of the transmission.

This is interesting. I didn't pay much attention to the 'banana V arms', but now after checking, it appears that I installed them on the opposite sides. I don't have "before" photos of my car, but the direction of the "V" on the parts diagram as well as any video I find online seems to be opposite to my setup. I suspect this might be the issue.

I did align both transmissions using a drill before installation and they matched the marks perfectly. I now realize this is no longer the case (as I moved the roof a bit), so I'll just re-align them before re-installing the V arms.

What do you mean by "If you need to drive one transmission forward or backward to match it to the other side" - are you referring to having the right transmission "in the right place" (after the left transmission is already connected) to allow connecting the 2 arms to the clamshell and top?

Originally Posted by 78F350

A couple years ago I bought some of the cheapest replacement gears I could find on eBay. I got what I paid for. One was good and the other moved backwards. The gears are supposed to be beveled differently for each side. The ones I received were both identical. Lucky for me I had an extra left side transmission to rebuild.

So, the two gears I bought are not identical, their direction of gears is 'mirrored' if you put them next to each other. Sounds like the issue you experienced like isn't what I am dealing with, but can you confirm?

I was also pretty careful to compare them with the ones I took out of the car, and it seems each of them was identical to each of the original gears. The gear on the right transmission wasn't busted, just cracked, so I may put it back in to test but opening the transmission again is last on my list of things to try, because I do believe I did a decent job there.


Thank you so much for your replies! I feel like you certainly put me on the right track to finding and fixing the issue!

[old911doc]

Although you may assemble the right-side and left-side transmissions in exactly the same positions, when you fit the transmissions to your car you may find that one side binds a little, because the convertible top frame, or the turtleneck cover, isn’t perfectly straight (anymore). Sometimes it takes a little touchup on one side to get the top and the deck to fit and to move without binding. It should not take very much, if the transmissions are aligned, and the top or deck haven’t been bent.
While you’re at it, I suggest you clean and regrease the slider tracks, and replace the little rectangular sliders, to eliminate binding as the top moves. Dirt and grit accumulate heavily there.

[WhatAmIDoing]

old911doc - your note regarding V arms was spot on. Once reversed, the movement of both transmissions is in the correct direction.

I'm now having a new problem though, as aligning the left/right sides turned out to be harder than expected. Plus, the right cable is either busted or there's an issue with the right transmission. The top worked briefly and stopped while I was working on alignment.

It doesn't seem to be too big of an issue. I just hope nothing was bent or damaged. I'll check it and update.

Thanks again for the great information!

[dghii]

Originally Posted by WhatAmIDoing

old911doc - your note regarding V arms was spot on. Once reversed, the movement of both transmissions is in the correct direction.

I'm now having a new problem though, as aligning the left/right sides turned out to be harder than expected. Plus, the right cable is either busted or there's an issue with the right transmission. The top worked briefly and stopped while I was working on alignment.

It doesn't seem to be too big of an issue. I just hope nothing was bent or damaged. I'll check it and update.

Thanks again for the great information!

I'll pipe in here......Now is the time, given your effort to date, to replace BOTH cables from motor to transmissions. Once you have good cables, you should fine alignment to be pretty straight forward (although slow). I used a cordless drill to drive my cables to align both sides. Take your time and make small adjustments to both sides as you get closer. You got this!

[old911doc]

If one side abruptly stopped moving at all, I would suspect that the square end of the drive cable has slipped out of the square hole in the worm gear in the transmission, or at the other end, the square hole in the end of the motor shaft. The cable is free to be pushed back and forth through the outer cable, with nothing to limit its travel. I would check the transmission end first.

[WhatAmIDoing]

Hey all! I finally found the time to work on the car.

Ended up getting one cable despite various recommendations to get two. Primarily, because the left transmission was already connected and working.

After installation, everything is working fine. No errors on the dash. Movement is smooth - probably even smoother than it was before since I applied new grease to the entire mechanism.

The only leftover task, which I hope to get done next week, is alignment. When the top is open, one side of the shell is missing slightly 1cm/0.5in to be completely closed and even. I'm pretty confident it's just a matter of some manual fine-tuning.

Thanks everybody for your advice! It helped a lot!