915 mag case guide tube

[kevingross]

I've got a 915 transmission on the bench that's a little different from ones I've worked on in the past. Magnesium case, given the s/n I think assembled in '73. What's different is that the clutch t/o bearing guide tube does not have the two ears that would fix it to the diff carrier by the usual countersunk M6 screws. It appears to be pressed into the case.



Porsche's parts diagram for '73 shows a "guide tube" on page 302-20, item 2, but without a part number -- lovely! The guide tube I have has some wear to its upper side, not horrible but also not ideal.

Is there a replacement part available from any source? Can the original guide tube be safely removed, for example using an internal puller and counterstay?

Happy new year to all! Cheers,

[Matt Monson]

Kevin,

CMS provides a replacement service. Check out there website and I suspect you can come up with your own fix. 72-73 were pressfit, and the seal needs to be installed from behind.

[kevingross]

Matt, thanks very much! The case parts are going to CMS, customer willing, to repair loose bores for both pinion bearings. Would be a good opp to have 'em address the guide tube as well.

Cheers,

[Matt Monson]

Perfect solution.

[Trackrash]

OK, I have a '72 915. I have access to a milling machine and know how to use it.

The question I have is this guide tube the correct one to buy when I am ready to upgrade my guide tube? Clutch Release Bearing Guide Tube - PORSCHE (1972-1983) 911 | 915 Transmission By Patrick Motorsports Porsche & Mid Engine Performance Specialists

[Matt Monson]

Does your gearbox leak or need to be rebuilt?

[Trackrash]

No, I recently rebuilt it. OK, that was 8 years ago, but for a '71 car that is relatively recent. I'm just looking to the future. At some point that seal will go out, just a matter of time. Perhaps I'm over thinking it, since the seal should last ten years, no?

[john walker's workshop]

Go to California motorsports dot net and click on 915. You can see a pic of the finished product, which does not use the one pictured above, due to no way to attach it.

[john walker's workshop]

Here's the picture. Being you have a mill and hopefully a lathe, shouldn't be too hard to figure out dimensions and fab the insert. The inside measurements would be the same as the later tube. Maybe you could even machine the flange off the later tube, leaving a small lip and cut the case to be a press fit. Maybe.

[kwikt 911]

^^ Agree too bad you didn't have a spare junk case to try!!

[Trackrash]

A friend of mine had CMS do that mod to his 915 case. Too bad I didn't take the time to carefully measure the insert and machine work at that time. Oh well.