Anything to be done to 915 while out?

GT2BH · 11-02-2014, 09:02 PM

While rebuilding the engine and generally refreshing the car, is there anything I should update/upgrade in my 915 transmission(while its out) which I can do myself? I already plan on replacing the shifter bushings.

sc_rufctr · 11-02-2014, 09:20 PM

Oil change?

You could replace the shift rod seal but it would mean taking the nose cone off.
Easy job but if it's not leaking I wouldn't mess with it. Even a slight weap is pretty normal.

I'd also take the opertunity give it a really good clean especially inside were the clutch lives.

yelcab1 · 11-03-2014, 12:55 AM

unless it is leaking, or grinding, or hard to shift, I would clean the outside, do an oil change, and leave it alone.

74-911 · 11-03-2014, 03:19 AM

Quote:

Originally Posted by sc_rufctr

You could replace the shift rod seal but it would mean taking the nose cone off.
Easy job but if it's not leaking I wouldn't mess with it. Even a slight weap is pretty normal.

I'd also take the opertunity give it a really good clean especially inside were the clutch lives.

I would take this opportunity to change the shift rod seal. MUCH easier to do with the tranny out of the car. Unless we (sc rufctr) and I are talking about a different seal, you just pull the old seal out and seat the new one, not necessary to remove the nose cone or anything else??

Over the years my slight weep turned into drips of transmission fluid on the garage floor.

kodioneill · kodioneill's Garage

How many miles on the car/trans? If over 140,000 I'd take it apart and check the pinion bearing race in the case.

GT2BH · 11-03-2014, 03:50 AM

I had a little grinding when shifting into first and sometimes I cant find third. The car has 115k miles and I have zero history on the tranny. I cleaned it already and I don't see any leaks anywhere. I already have a new 915 mainshaft seal (999-113-327-40-M30), is that the one you are referring to?

Discseven · Discseven's Garage

GT... my 2 cents:

Replace shift rod seal...

Replace throw out shaft o-rings (seals)...

Check wear on throw out shaft. If needed, rotate 180 degrees...

Clean and lube input shaft. Might be disagreement on what to use. Here, high pressure grease applied at "A." Antiseize at "B."

Cable retainer gone so drilled small holes towards outside of vanes for zip ties...

Replaced shifter coupling...

If filling from top... breather points away from flywheel.

Jcslocum · 11-03-2014, 10:49 AM

Not to hijack, but we have a 100K 915 that we have never driven. I supposed to be fine according to the PO but maybe while it's gonna be out a while, there is a more in depth look/check we should do?

KTL · 11-03-2014, 11:01 AM

While you have it out of the car, I agree the shift rod seal and the input shaft seal should be looked at closely.

Since its out of the car you can take off the tail case and look at 5th & reverse gear. If 5th gear has a worn synchro band (the friction band that does a lot of work to match speeds when you downshift) and blunted dog teeth, then I would be willing to bet you'll only find worse things if you go inside the main case. If curiosity gets the best of you, it's not difficult to remove the 5th & reverse assembly to get the main case off and look at the more important 1st-4th gears.

Peter Zimmerman's wiki how-to is a FANTASTIC resource to have in hand.

Porsche Wiki

Alan Lindquist · 11-03-2014, 12:03 PM

Because I had one crack and deform, I'm sensitive to the release bearing fork. When it goes, gotta pull the motor. And for $130 (I think) it seems to be a reasonable cost to replace and not have to worry for the next decade.

But if there's time, is there a reasonable way to do NDT on this part?

KTL · 11-03-2014, 12:09 PM

Quote:

Originally Posted by Alan Lindquist

Because I had one crack and deform, I'm sensitive to the release bearing fork. When it goes, gotta pull the motor. And for $130 (I think) it seems to be a reasonable cost to replace and not have to worry for the next decade.

But if there's time, is there a reasonable way to do NDT on this part?

Good suggestion. The release fork is indeed prone to cracking. Happens more and more as these cars continue to age. Can have a machine shop crack check/magnaflux it or have it x-rayed.

Bob Kontak · Bob Kontak's Garage

On my '81 915, I pulled the plate off of the side of the trans before sending it off for rebuild to inspect. Two of the three nuts that hold the Fork (#6) to the Shift Cover (#5) were loose. Not big loose but at least one revolution backed off and they were not applying torque.

I though that was causing the buzz saw noise when shifting into third but Mayo, the re-builder, said no. Pretty sure Peter Zimmerman, in another post where I mentioned this, mirrored what Mayo said. I had seen a post where someone said if the fork was loose it can cause strange and scary noises but appears it was not with our 915's. Plus mine was definitely wrong but not officially loose.

Still worth a look when trans is empty. Not sure why the two came loose to begin with but my trans had been worked on before Mayo worked on it. May have just been an oversight - several were brought to my attention during the rebuild.

KTL · 11-05-2014, 06:35 AM

Bob brings up another good point. That shift rod guide fork is prone to coming loose from the plate. A "racing trick" is to drill the fork mounting holes all the way thru the plate which allows you to nut & bolt the fork. Also recommended to loctite those fork nuts. They do indeed come loose more often than most people realize.