By the way, a large percentage of 915 boxes have spun bearing race.

With such great response to my questions from such helpful and knowledgable people on this forum, I decided to tackle the job myself. Will start the teardown in the next couple of days. Finally and excuse to buy that engine stand.

My wife will not be pleased as I am supposed to start building a new set of Kitchen cupboards soon for a reno to our house she has planned for this winter. I guess that will give me a reason to get this tranny work completed in a timely manner. Being a chronic DIYer can be a real pain for those around you !

Is the spun race on the pinion bearing obvious when one gets in there ? Is that repair possible be any decent machine shop with some direction from the good folks on this forum ?

Ross

Oh, Kurt, the stories that I could tell you! I've done heavily damaged 915s with fewer than 50K miles, I've done 915s broken by valet parking "technicians," I've done a big number of synchro repairs on 915s with fewer than 80K miles. My shop had an active clientele of more than 1500 P-car owners, and 95% were 911s. A high percentage of those were from the 1972-1986 group fitted with 915s.

Please remember, I'm from L.A., where traffic congestion is the norm, and three shifts/minute is not unusual. I'm sure there are parts of the country where three shifts/thirty miles is more the norm. 915 life expectancy all comes down to driver technique and shifts/mile. When I write that 100,000 miles is my goal for every 915 that I repair, I'm writing from a Los Angeles point of view, not the mid-west countryside.

A loose pinion shaft bearing race will be very obvious. In extreme cases the race will pull loose from the diff housing as you pull out the pinion shaft. In milder cases you can put your fingertips inside the race, expand them like an umbrella, and turn the race.

I've only used one machine shop, a very diverse and talented group of guys, to do this repair, so I can't speak for other shops.

Point well made Peter! SmileWavy

I have good friends in MO, IN, and MN - it must be so much more fun to drive P-cars where you are than in L.A.

In summer, anyway!

My 915 with 75k on it had a spun race, needed most of the pinion and mainshaft bearings (badly pitted) and syncros and dogteeth on 1st, 2nd and 3rd. It wasn't worth the cost to even try to rebuild it at home. Just ended up getting another unit that had been rebuilt by someone who had the tools and experience.

gtihop,

What was your 915 like to drive before you replaced it?
Where did you get your rebuilt 915 ? And did it turn out to be a good one?

Also if you don't mind me asking , what does it cost for a properly rebuilt 915 ?

I know if I open mine up I will likely replace all of the parts recommended by Pete Zimmermann in his tutorial as I hate to do something twice.

I have a do it right or don't do it at all attitude to things like this which tends to cost me money.

I can always open it up do the inspection and make the final call but I believe in a tranny with 132K miles like mine, Pete Z. suggests all bearings , synchros, most dog teeth etc. be replaced for his 100K mile goal. In my reality I only put a few thousand miles per year on the car but I am planning on increasing the power down the road and will probably put more stress on the tranny once I get that work done.

The pinion race repair would likely put my cost way over the cost of a rebuilt unit so I may need to take a hard look at it when I get in that far.

I put together the engine stand last night so I am ready to mount the tranny and open her up this weekend.

Ross

Let me try to modify your thinking process just a little bit. You're saying that, based on repair cost, you would consider a "rebuilt" 915, rather than fixing yours by doing what's needed. That means, if I'm right, that you would consider paying less for a "rebuilt" than what you could fix yours for. Are you aware that "rebuilders" out there don't fix the loose pinion bearing, instead, they throw a little LocTite at it (or peen it) and hope for the best. Hope doesn't fix a 915 bearing race problem, and your new "rebuilt" might have a loose bearing after the first heat cycle you put the trans through. Not all rebuilders hide this type of "fix" (see below) where eyes can't see it, but some do. Often, a "rebuilt" 915 is cheaper for a reason...or reasons.

http://forums.pelicanparts.com/uploa...1284087549.jpg

http://forums.pelicanparts.com/uploa...1284087600.jpg

Thanks for the reminder Peter but if you read my posting closely, I note that price query on a properly rebuilt 915. I would only be considering one from a highly respected rebuilder with the reputation to back it up.

I suspect a properly rebuilt unit may be pretty costly but it would be nice to know this number if I find the problem.

With this pinion issue in the 915 being the only real weak point as you say, do you always make this repair regardless of the condition you find the pinion race in . I would think for the 100K mile goal you would have to address this regardless of the condition upon inspection. Maybe a new bearing will address the issue for another 100K if the race is in good shape ?

In your pics are the punch marks the rebuilders quick fix ?

This is the "after" condition of a repaired diff housing...note the steel ring that the new race has been pressed into.



http://forums.pelicanparts.com/uploa...1284091940.jpg

what Pete shows above is one of the proper way to fix this. A newly designed clamp plate by someone in San Carlos is another very good, permanent, and expensive way to fix the spun race.

There is a less expensive way that someone else on this board was able to provide. Knurling the race or plating the race and then pressing it back in. I know that a racer probably would not do that. It may or may not last 100K miles but the original did not last 100K miles either.

Thanks folks for the clarification on the proper repair technique.

The steel ring insert looks like a fairly straight forward repair. Is the ring and machining dimensional information commercially available for this repair so that it could be passed along to any quality machine shop to have executed.

I suppose the trick to this repair is getting the housing alignment correct in the machining equipment so that the new ring and bearing is in correct alignment upon reinstallation. It is probably not easy to do that and probably where shop experienced in this particular repair is required.

Ross

The machine shop will have to know how to index the old bearing hole (to find its center), then they will have to machine the hole to its new OD. Then they will have to know what steel (for the new ring) to use, and how much press to aim for (heat the housing and press in the ring), followed by the appropriate press for the bearing race into the support ring. The job is done in a vertical mill.

If you do find a loose bearing you always have the option to ship the diff housing and new bearing race to Los Angeles. If you decide that's OK, pm me and I'll give you the shop info.

Spun Race
 

Opened things up today. Everything came apart quite easily. I used the " 2 gears at once" technique to lock the shaft. It seems pretty common so I thought I would do that to save the time to make or locate a proper shaft locking tool.

I believe I am the first one into this 915 as the gaskets looked original. There was nothing but the gaskets on the sealing surfaces.

I followed Peter's guide for the most part except for the shift fork removal part in intermediate housing. I kept those intact per the threads recommending this by John Walker to keep reassembly simple.

I will post some photos of the gears but I did not notice any broken or severely warn dog teeth. The very tips appear to be slightly rounded My PPI indicated a gearbox that was probably in pretty good shape except what is probably worn synchros. I do not know how to tell if the synchros are worn . I guess that will be determined later when I disassemble the shaft stacks .

Unfortunately the pinion race has spun as feared. It turned quite easily with greasy fingers . If you didn't know better one would think that the race was supposed to turn as it was so smooth in its oil film. I was able to remove the race with my fingers but it is not sloppy if that means anything.

I also see that there is some wear on what I think is the 1st gear (small gear). I have no idea how much wear is expected here.

http://forums.pelicanparts.com/uploa...1284250692.jpg
http://forums.pelicanparts.com/uploa...1284250790.jpg
http://forums.pelicanparts.com/uploa...1284251671.jpg
http://forums.pelicanparts.com/uploa...1284252056.jpg
http://forums.pelicanparts.com/uploa...1284252121.jpg

Now I need to sort where to go from here since I guess this is definitely not a good situation to be in. I am not sure what is a good or bad looking 915 when you open it up.

I know I want to fix it right. I want to close this thing up knowing I have a 915 that I don't have to be worried about for many years of spirited driving.

I took quite a few photos and can load them up for all to see.

I guess I should continue the dissassembly or should I put it back together and ship it off. I did not find it difficult to take it apart to this point but I know I am just starting the process.
Comments please .

Take it all apart. Inspect the gears and synchros (the synchros are measured in the installed positions). If they are shiny, then they are likely worn out. Inspect the dog teeth. Inspect the sliders. Send out the intermediate housing to fix the bearing. Inspect the bearings. Replace what is worn, and put them all back.

Thanks Yelcab1

I should have no trouble taking it apart it will just be the diagnosing if parts are worn and need repair. Hopefully posting photos of the gears will help.

Does anyone have an east cost machine shop recommendation to get the bearing race repaired?

The questions over the coming days may look pretty silly to the experienced on this forum as this is the first time I have ever had a gearbox apart before so I am pretty green when it comes to this repair.

I was hoping I would not have to open the differential housing but I guess I am just not going to get off easy on this one .


Ross

Be sure to check the bearing shell in the intermediate plate....

I have question about a step I forgot to do when I took the shaft assemblies out of the case.

I forgot to remove the shift rod detents first . Is this a problem . I suppose it just made my effort greater but the assemblies still came out ??

It is mentioned by all the experts so I wonder if it caused damage not removing it.


Ross

More Questions and Some more pictures:

The pinion shaft came apart with a few whacks per the John Walker technique - all except the pinion bearing. How do I get this off ? If I am to perform the spun race repair a new bearing may be on order and I need to be able to get that bearing off the shaft

http://forums.pelicanparts.com/uploa...1284428657.jpg


I still need to get the input shaft nut off and dissemble but so for I have these apart:

5th Gear:


http://forums.pelicanparts.com/uploa...1284429117.jpg
http://forums.pelicanparts.com/uploa...1284429134.jpg
http://forums.pelicanparts.com/uploa...1284429161.jpg

1st Gear:

http://forums.pelicanparts.com/uploa...1284429194.jpg
http://forums.pelicanparts.com/uploa...1284429234.jpg
http://forums.pelicanparts.com/uploa...1284429261.jpg

2nd Gear:

http://forums.pelicanparts.com/uploa...1284429298.jpg
http://forums.pelicanparts.com/uploa...1284429320.jpg
http://forums.pelicanparts.com/uploa...1284429343.jpg


So far I plan on replacing all synchro rings and the associated break bands as well as the 1-2, 3-4 sliders . I guess I should be replacing the 5-R slider as well what do you folks think ?

The bearing races for 5th and 1st appear fine to me - no pitting or lines so I was thinking about reusing most bearings to try and keep costs under control (unless I can find a more economical source-are the 915 bearings available for most bearing suppliers ?)

The dog teeth look much better than most I see pictured on this site under rebuild threads. Do these dog teeth warrant replacement due to wear or is it just recommended practice because I have the system opened up?

Comments ?