Transmission (915) bearing race fix...anyone?

[Joe Bob]

The bottom race in the differential housing is loose....not a good thing. Has anyone come up with a succesfull fix short of replacing the differential housing?

For those unaware as to WHY this is an issue, it spins, it makes a bigger path, it allows slop in the shaft and things get cocked and things then explode.....

Typical weak spot in the 915, especially when a 3.6 is driving it.

[ChrisBennet]

Considering how few of these transmissions I've rebuilt it seems like I've seen a lot of loose races especially in mag 915's. I'd be interested to hear of any fixes as well.
-Chris

[Grady Clay]

Chris,

Actually this is more prevalent in the aluminum
casting 915. Porsche attempted a fix in ’85
actually about Dec 16, 1983 from:
915/67 02340
915/68 02192
915/69 10081
915/70 10217
and later

by changing the input shaft bearing from the larger
915 to the smaller 930. The intent was to increase
the material between the bearings. That probably
helped some. I’m not sure it solved the problem.

The dimension (red arrow) increased because of
the smaller bearing (#1).
"
"
(C) Dr. -Ing h.c. F. Posche A.G.



Call Roger Brown at Powerhaus II www.porschegears.com
303-442-4327. He has a solution.


Best,
Grady

[Jim Sims]

Loctite 660; one of it's intended purposes is to relock spun bearing races.


http://www.loctite.com/int_henkel/loctite_us/index.cfm?&pageid=369&layout=2

[ChrisBennet]

I've seen it in 3 Carrera 3.0 ('77?) 915's and one (maybe 2?) '84-86 Carrera 915s. The Carrera one had been "fixed" with Green Loctite but the bearing had come loose again.
-Chris

[Jim Sims]

Loctite 660 is not the "green wicking loctite"; it's more of a silver grey paste. To properly apply the 660 the bearing race should be removed and the bond area degreased.

[bazar01]

660 Quick Metal� Retaining Compound Press Fit Repair

A creamy, non-running adhesive/sealant. Repairs worn machine parts. Restores correct fit to mating assemblies. Fills gaps up to 0.020" diameter clearance.

Typical Applications
Worn shafts and housings, bearing spinouts, keyways, and splines.

[Joe Bob]

No problem with the removal....it fell out in my hand....%^(

[BReyes]

Grady. What do you think about about the guys say above?

Regards all,

[TerryH]

If it's aluminum it could be welded and re-machined. Other alternative is to use a hammer and punch and pound 3 rows of dimples completely around the bearing seating area. This will raise metal to create a press fit again. Then use a permanent type loctite.

I've never applied the above to any transmissions, but have on other heavy equipment.

[65rsr]

www.wevo.com

race case or bearing retainer

http://www.wevo.com/porscheproducts.htm

[ChrisBennet]

Jim, I looked up the 660 as soon as you posted it. Looks good. It sounds like something a friend told me about when I was looking for a solution to this problems a couple of years ago.

Terry, some friends of mine have a machine shop and I talked to them about doing this sort of repair. According to them, tolerances for the bearing race bore would require a special tool (customer borer?) and locating the bore in relationship to the other would be very important.
(These guys are sharp, they used to design the CNC lathes and milling machines at the place we both used to work.)
-Chris

[Grady Clay]

I’m not sure I can answer “what is best” yet. I want to measure the diameter, eccentricity of the bore (both easy) and the position of the centerline of the bore (very difficult) compared to original on a bunch of 915s.

While supporting new bearings is very important, the position of the pinion is more so. If those numbers are off Factory original, then any ring & pinion setting to spec is almost meaningless. If those are off, the transmission will destroy the R&P.

The goal is to extend the life of these transmissions. Porsche is manufacturing new ring & pinion gears for the 915 – at some US$7000 retail each! gulp

The guys at Powerhaus II have devised a way to electro-plate just the outside of the outer race, making it larger OD yet still concentric. If the bore is just larger ID and not offset or too eccentric, then this is a great fix.

For a race transmission or one you want to stay right, the Wevo fix is probably the best solution.

Terry, I think that welding would distort the dimensions too much. Yes, it can be done properly but it would probably be less expensive to buy a new Porsche part. You have to consider ALL the dimensions; differential, input shaft, pinion, shift rods and more. Not easy

I have successfully used Loctite (probably a predecessor of 660) on type 911 intermediate plate bearings. The difference is in a 915 this bearing locates the pinion radially with much greater loads.

Best,
Grady

[john walker's workshop]

some housings are so worn that the race can be moved side to side and you can see the movement. those are junk. the races that are still a slip fit with no discernable sideways movement, i believe can be loctited with a good chance of lasting a long time. the alternative is a new diff housing $$$$$$$$$$$$$$$$$$.

[ischmitz]

Mike, your bearing race moves visibly in the radial direction. It's not even a slight touch- fit anymore. I think Wevo is the only answer here.

BTW: Do you guys think the loos race has caused the second gear sprocket to grenade? Maybe the shaft was out of alignment or even vibrated leading to this failure mode.

[Joe Bob]

I'm thinking yes.....the second gear gave a low vibrating grumble when accelerating.....1st and 3rd, no noise beyond the usual......

[ischmitz]

Originally posted by mikez
I'm thinking....

how do you do that

[Joe Bob]

Took a shower and washed the grease outta my ears.....

[Flat Six, Inc.]

I use Permatex high temp sleeve retainer.....#64040

[Joe Bob]

Clean and shiny 3.6.....