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Old 09-06-2006, 01:41 PM
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Steen Jensen
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Default torque tube bearings

I'm having a lot of trouble sourcing tt brgs for my 88 S4.

The spec is 6006 2Z C5 HT51

The C5 (looser tolerances) and HT51 (high temp grease) are causing the problems. Apparently unobtanium.

I have checked with Jager (sold out) and various brg suppliers with no luck.

I can live with a C3 spec (easier to get) but I think the HT grease is a must have. Anyone out there have experience with using a regular spec grease?

Better yet , anyone know where I can get the original spec bearings? This project is going nowhere fast...
Old 09-06-2006, 02:00 PM
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sublimate
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SKF shows a C5 version:
http://www.skf.com/skf/productcatalo...did=1050070006
Have you asked them?
Can't the HT grease be added to any bearing?
Old 09-06-2006, 02:36 PM
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dr bob
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Originally Posted by sublimate
...
Can't the HT grease be added to any bearing?
The bearings are shipped with various combinations of shields and seals. That's the 2Z designation I think. With the seals installed, there's no good way to replace the grease.

Hi-Temp grease is a good idea with the exhaust running so close to the tube.

----

I'm not familiar enough with the internal supports in the tube to write a bearing prescription. But-- The 6006 bearing is common, and the number defines the outer dimensions. There are various widths and other differences, like double-row vs single row, that might let another bearing do the job for you if you can stand the additional width. But, it's not like these bearings are seeing any serious radial load in service. In fact, the weight of the internal drivesfat is about all they should see if all is aligned properly. So the cause of failure is most likely a lubrication failure. If I was designing the bearing cartridges from scratch, the single-row bearings would sit in a steel outer sleeve, and have a mild press fit on the driveshaft. The steel sleeve would be a zero-clearance, zero-preload fit in the tube. There would be screws through the tube, threaded into the bearing outer sleeve. If this design was for a long life, zero-downtime application, there would be lube fittings accessible through the outer tube to periodically add new grease to the bearings while in service.

-------

6006 bearings are used extensively in electric motors. If your normal bearing supply folks can't get then for you easily, try an electric motor rebuilder. You might get lucky!

------

Some early Pontiac Tempest models, the ones with the engine in the front and the trans in the rear, used a driveshaft design somewhat similar to the 928. And you though that was a Porsche invention... GM tried several different designs in prototype, trying to place the bearings at the most prominent vibration nodes on the shafts. They finally decided that they could slightly offset the middle bearing in the tube, causing the shaft to be bent, and that that would keep the NVH problems away despite normal production differences in driveshaft materials and dimensions, and in assembly. The driveshaft is really a torsion spring, so offsetting the center bearing didn't shorten the life nearly as much as the reduction in resonant vibrations seemed to extend it.
Old 09-06-2006, 02:52 PM
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Old 09-06-2006, 03:46 PM
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Steen Jensen
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sublimate

I think the problem is that although they have a listing , skf has not done a production run in awhile so none are around.

I don't think they will gear up a prod run for my order of two...
Old 09-06-2006, 03:49 PM
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Steen Jensen
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dr bob

I may be forced to go with a C3 brg with regular grease (easy to get , 12 bucks) and hope for the best. I really don't want to have to do this job EVER again especially due to having to try inferior parts.
Old 09-07-2006, 12:24 AM
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While hunting for C5 plus high temp grease about year ago all I could find locally was C4 and high temp grease. Even those were only sold at minimum batch of 20.

Other lister located in France managed to get correct type when bearing supply company made set of C5's for him using regular C3's as base. That would be way I would try to approach the problem if I didn't already have these C4's on hand.
Old 09-07-2006, 12:27 PM
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Steen Jensen
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Vilhuer

Did you buy 20? If so do you have any extras that you would be willing to sell me?
Old 09-07-2006, 12:46 PM
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Unfortunately I don't have any extras left. We organized group buy locally and ordered 30. All were gone within week or two.
Old 09-07-2006, 09:05 PM
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PorKen gave us PIX and TEXT.

Wow, Ken. Thanks. Very interesting history - a two inch deflection in the TT!

I note an acknowledgement that Europe might have already had a front-engine rear-transaxle vehicle. Anybody know what it was?

My grandmother had one of those cars and I drove ot all over Pasadena, LA and down to SD without having any idea what it was. What I remember is that I had to replace the dimmer switch to stop a bunch of fuse blowing. Who knew I was driving the precursor of Detroit's product for the next two generations!?

ww
blissfully ignorant
Old 09-07-2006, 09:31 PM
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sublimate
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Originally Posted by Fogey1
I note an acknowledgement that Europe might have already had a front-engine rear-transaxle vehicle. Anybody know what it was?
The 1950-1958 Lancia Aurelia, also known as the first true GT (so the father of the 928 in more ways than one).

But the earliest car with a front-engine, rear-transaxle was the Stutz Bearcat (1914-1939).

Also note that the 1964-1968 Ferrari 275 (as well as it's more famous replacement, the 1968-1973 Daytona) and technically the Porsche 924 (1976-1988) all beat the 928 to market with this design.
Old 09-07-2006, 10:39 PM
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If the bearings are that hard to obtain how are the rebuilders rebuilding? With C3 or C4 bearings?
Old 09-08-2006, 12:14 AM
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Eric Buckley
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Have a look at MSC www.mscdirect.com their P/N 45666898 is SKF # 60062ZJEM the JEM specfication signifies C3 and HT51, this is an electric motor spec.. They show them as in stock. I used these when I rebuilt my TT and they have worked well. See also:
http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=45666898
http://www.nichols.nu/tip814.htm
Old 09-08-2006, 01:59 AM
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Steen Jensen
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Eric

I'll check them out tomorrow. Thanks.



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