Torque Tube Bearing Info for Rebuild
I am going to replace the bearings on the rattling tube I took apart last year, and found some interesting things when sourcing the SKF replacements.
The SKF part number I have for an 87 tube is 6006 2Z C5 HT51
This bearing is a Metric (6006) Double Metal "Z'" Shielded (2Z) Highest Clearance between the balls and race (C5) and Hi temp greased= HT51(-30 to +150 DegC).
Now the standard running clearance is CN to C3. The standard grease and clearance are good for quite a temperature range.
The C5 - which is a special and rarely specified, has excess clearance so when the bearing heats up it will not bind I suppose.
Clearance or play on the front bearing is what creates the tube rattle. The tube I took out was fine except for a lot of play. The tube I replaced it with (60K miles from an 87) had much less play, but still would rattle if the shaft was struck with a rubber mallet. I also let the front bearing soak up some synthetic grease before installation.
The converters operate at high temperature (~700 DegC), so I am wondering is the temperature inside the tube above 110DegC in normal operation?
Also a clearance spec of C3 would certainly reduce the tube rattle.
I thought this might be some help to 928 owners.The bearings in my torque tube were INA 6006-z-c4, but I had a lot of trouble trying to get these. In the end I spoke to a technical engineer at INA who told me the following:
Porsche's IF tolerances for the bearing is 10-35 microns
6006-zz-CN= 5-20 microns
I know that in the tip above, the author mentions the cn to c3, but I thought it might be useful to know the exact tolerances. I've ended up using c3 bearings as this is in Porsche's tolerances that INA had (original bearing supplier). He did go on to say that his blueprint was dated 1989 so this might explain why my bearing was a c4 (my car's an 87 s4 auto) and the bearing within the tolerances is the c3. Hope this helps fellow 928 owners
Thanks for the article. For your info, the torque tube bearings on my 89 S4 were type 6007.
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