Bent shift rod in transmission - how to repair?

[lespaul]

The PO bent the shift rod in the transmission. The thread below describes the problem. I thought that posting a new thread with a new title might attract those who have experience with replacing a bent rod.

I have done several searches about how to replace/repair the rod but came up dry. Is this a DIY? I don't have any desire to tear down the entire transmission -- just get the rod out and an repaired/new one back in as simply as possible. Any guidance will be much appreciated.

Shape of shifter hole opening???

[The cap'n]

Gotta take it apart ............................. You "might" be able to straighten iw while it's out, but that might be a long and tedious process.

The Cap'n

[john walker's workshop]

probably break the hard to find end cover if you try to just bend it back to shape.

trans out, end cover off, 5th and reverse stuff off, guide plate off, center housing and shift rod off together. reassemble in reverse order and be sure the internal detent in the center housing is all the way down before installing the housing.

[Peter Zimmermann]

Porsche Wiki

Please find my 9-part 915 Repair Tutorial at the above link. It'll show you what's inside your trans, and how to replace your shift rod.

[lespaul]

Thanks guys.

Thinking ahead a few steps ---

1. If I am only tearing down enough to pull the shift rod, which gaskets do I need to order now?

2. Once removed, should I take the bent rod to a machine shop and have them straighten it? Or, should I just buy a "new" used one that has proven to be straight?

Brad

[john walker's workshop]

a complete gasket set provides the shift rod seals, mainshaft seal and final drive seals you may need. post a pic of the rod when it's out. may help you decide whether it can be nicely straightened or if you need to round up a good used one.

[lespaul]

Ok. Gonna tear it down -- my first foray into a transmission in 36 years. Last time was a 1960 TR3A.

Wish me luck.

[poorsha]

Good luck

[Matt Monson]

I've seen them so bent you had to cut them in half to get it through the tail cone without breaking it.

[lespaul]

Thank goodness I am no where close to that.

[The cap'n]

If it's bent enough to be readily visible, there's a good chance it won't just slide back through the nose cover. It's a reasonably snug fit, and the tube is pretty long. If it were my car, and it shifted well (smoothly in and out of ALL the gears), I would probably run it. The critical motion is into 1, 3, and 5. That's why you push the shifter all the way forward into one of those gears before you disconnect the coupler when preparing to remove or install the transaxle.

The Cap'n

[911pcars]

If the shift shaft is causing the seal to leak gear oil, the only remedy is to replace it. As for those who support keeping the bent shaft, unless I'm missing something, how would one prevent the seal from leaking?

If it can be straightened, good, but replacing with a good used part is probably your best option.

Sherwood

[The cap'n]

Kinda depends how and where the shaft is bent.

The Cap'n

[911pcars]

Originally Posted by The cap'n

Kinda depends how and where the shaft is bent.

The Cap'n

For sure. However, refer to OP's photos at the top (to be confirmed upon removal and inspection).

Sherwood

[dtw]

Originally Posted by lespaul

Thank goodness I am no where close to that.

You may be surprised! You'll have some room to play with, but it may be that you can't get that nose cone off easily or at all. If it is between cutting the shaft, and risking cracking the nose housing, cut the shaft.

I've been watching your other thread with interest. For what it is worth, I have in the past bought two 911s with the ovoid seal area that you have. I was amazed that the nose cones were not cracked/broken on either car.

[The cap'n]

Originally Posted by 911pcars

For sure. However, refer to OP's photos at the top (to be confirmed upon removal and inspection).

Sherwood

I failed to note the pictures, which are in another thread. My bad, I guess. Can't spend all day chasing links ............. Yup, it's pretty bent, and it looks as if it's gonna need to be cut off.

[lespaul]

Lucky enough, I did not need to cut off the shifter rod. In fact, the nose cone just slipped right off. No problem. That said, the rod is bent. See pics below.

I have some irrational trepidation about taking gears, shims and spacers out of the transmission in order to be able to dig down to the guts so I can remove the shift rod and take it to a machine shop. I am really afraid that I will not be able to put it back together again correctly. Are my fears warranted or is this really an easy job? Are there pitfalls to be aware of such as making sure to mesh cog A with cog B before you do such and such .... and so on??

Alternatively, I am thinking that if I put the tranny horizontal on my bench resting on a foam pad and then support the two ends of the bent rod appropriately- but without lifting the transmission case -- and then cover the rod with a copper pipe to avoid marring it, a few taps with a ballpeen in the center of the bent portion should straighten that rod right up. After all, that is essentially how it was bent in the first place -- many taps on one end against the former round shifter tunnel hole beating it steadily into an ovoid. Or am I crazy to do this?

Finally, after the pics, there is a link to a drop box where I have a video of the play in the shifter rod as it now sits in the transmission. Is that play normal? It seems like the kind of play I have experienced just moving the shifter around in the car. If the play was somehow caused by the bending stress (some bushing has been stretched out), that would cement a decision to forgo the bench top self help and tear the transmission down further to extract the shift rod.












https://www.dropbox.com/s/l0086qlwjmf4id5/2014-08-20%2013.40.48.mp4

[stormcrow]

Brad

It is possible to straighten the shaft out if you heat it in the affected area where it's bent. But you need to know what your doing when you do this. What you need to do is heat the affected area until it's cherry red. I don't think the shaft has been heat treated because if it was it would have snapped.

When you start heating the affected area of the shaft, heat all around the shaft of the affected area - don't just heat one side- it will take some time doing this but you have to get the affected area evenly heated.

When you start heating the shaft it will turn brown then blue then start to get red. It is at that point that you need to pay attention to what you are doing and heat it only to the point where it is "cherry red". Do not under any circumstances heat the shaft to a "white " color - it is at that point it will start melting.

I would use "mapp gass" when heating the affected area on the shaft if you don't have access to a all position torch. Once you get the desired area heated (cherry red), you can use a tubing sleeve to straighten the shaft It will be really easy to straighten out so don't use excessive force.

Once finished let it cool down - under no circumstances do you want to blow air on it - doing that will make it brittle. Once it's cool, you should be good to go. One other thing - use a "heat sink" at the transmission to keep other parts in the transmission from heating up - wrap the shaft with wet rags or if you can get your hands on some "heat sink" paste which is used in the A/C industry it will work just as well.

[john walker's workshop]

i would think you could bend that back without heat or beating. invent some sort of clamp assembly on both sides of the bend that will pull it a bit past straight and not ding up the sufrace. you have to bend it past straight because it will spring back somewhat when released from the clamp. nuts and bolts, heavy steel plate and a couple of shims.
now if you could rig it up in a press, that would be much quicker. just need to support the trans at the proper height and stick the shaft under the press ram. (being that you don't want to disassemble any more). you're about 10 minutes away from getting the center housing off if you have the tools.

[javadog]

If it were mine, I'd remove it before fixing it. While there, I'd eyeball everything else in the gearbox, which is why I suggested having a shop do it. They would know what to look for and it would be a shame to get this car back on the road and find that you have a problem that could have been fixed while it was apart.

I'd fix it in a press with some v-blocks and a dial indicator. You need to support the shaft, so you don't just tweak it elsewhere. Whatever force you put on it has to be reacted somewhere, which is why I wouldn't just try to bend it in-situ. I wouldn't beat on it with a hammer, either. If I could staighten it cold, I'd do that before heating it.

Read this, you're almost there:

http://porsche.wikidot.com/how-to:915-repair-tutorial-part-ii

JR