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Tim Hancock's Avatar
 
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SC Steering Rack DIY Bearing Replace

Since I got my '79 SC a year ago, it has had a very slight amount of play in the steering wheel and when on the lift it has always felt a little notchy. This past weekend, while finally getting around to installing my new turbo tie rods, I decided to remove the rack for inspection. After getting it removed, I noticed free play at the input shaft.

After disassembling (note: the innards in the rack in the Bentley book is not at all what my rack looked like inside), I found that the entire rack appeared to be lacking somewhat in the lubrication
and cleanliness departments. The lower ball bearing was wore to the point that it was allowing the rack pinion shaft to to move about an 1/16-1/8 in the axial direction, which was why I was experiencing free play.

The upper needle bearing was dry and crusty but this was not causing any of the free play issues.

I found both of the bearings in my MSC industrial catalog and took a picture below showing the standard bearing numbers to look for if anyone else ever needs this info.

I cleaned everything up and allthough the pinion gear teeth are not in "perfect" shape after greasing and installing a new ball bearing, my steering is tight and smooth again.

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Old 05-31-2005, 09:14 AM
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Tim, nice!

Is there a lash spec?
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Old 05-31-2005, 06:09 PM
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I think there is a lash speck in this post, which I used for my rack

Steering Rack "Rebuild" Procedure
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Old 05-31-2005, 06:57 PM
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I am about to rebuild my rack so this is perfect timing. Are the #1712 and #6202 the MSC, manufacturers or someone else's part numbers?
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Old 05-31-2005, 08:38 PM
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Those numbers are the industry standard bearing numbers. If you rattle off those numbers to any beaing supplier they will know what they are. As it was a weekend I actually got my ball bearing (#6202) from a local NAPA store for about $4.00!

I have driven the car a couple times since and it is very tight and smooth now. Like I said before the lower ball bearing was causing the play by allowing the rack pinion shaft to travel axially about an 1/8" before actually driving the rack back and forth. The overall play in the bearing and lack of lube was what was causing the notchy feel.

There were some shims located under each "cap", I just reinstalled as they were and the rack is indeed tight and smooth now.
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Old 06-01-2005, 03:59 AM
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What kind of lube did you use?
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Old 06-01-2005, 04:06 AM
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I just packed the center section where the bearings and pinion are, with wheel bearing grease and I applied a film of the same grease to the entire rack. The Bentley manual made it sound like there was some kind of "special lubricant" in there originally. What I found was remnants of what appeared to be grease. There did not appear to be any kind of gear type lube in there and furthermore the end rack guide bushings are round, yet the rack has flats top and bottom which would allow any liquid type lube to leak out the ends under cornering, so I am confident that grease is the proper lubricant to use.
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Old 06-01-2005, 05:33 AM
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Tim

I've always wondered if it is possible to remove the stamped steel cover from the rack while it is in the car to add some fresh grease to the rack without having parts fall out that make it necessary to remove and rebuild the whole assembly. Did your experience make this look feasible? Or are the lower ball bearings in the way of getting to the rack?

Thanks

Jim
Old 06-01-2005, 08:17 AM
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Quote:
Originally posted by beamonk
What kind of lube did you use?
The other posts regarding rack re-packs say use a good synthetic wheel bearing grease.
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Old 06-01-2005, 08:52 AM
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Tim, how did you figure out which bearings you needed? Did you thumb through a catalog or did you find the generic bearing numbers in a Porsche reference manual?
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Old 06-01-2005, 08:54 AM
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Bill, the bearing #s are etched into the outer race along with the particular manufacturer that made it. I just jotted down the numbers and found them in an industrial catalog. The needle bearing was a Fafnir if I remember correctly. Bearings with these numbers are going to be the same no matter the manufacturer.

Jim, if you remove the two stamped covers the rearward one will have a spring, shims and a puck (which will probably stay in place).

Removing the forward cover will reveal the end of the pinion shaft and the ball bearing. One could easily shoot some grease in between the bearing cage with a needle tip on the grease gun which would probably
end up depositing some on the pinion gear itself. The upper needle bearing is too far away to get any grease this way (both of my bearings were dry by the way). If you study the pictures above showing it disassembled, you will probably be able to see how all this works.
Just keep track of the shims and spring as you disassemble the caps!

I am sure "synthetic" grease is probably BEST, but I am not concerned in the least bit that the wheel bearing grease I used will hurt anything (there was basically no lubrication left in it when I tore it apart).
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Old 06-01-2005, 10:05 AM
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Good post Tim.

One more topic to show people that these racks should be re-lubed as part of a long term maintenance plan. My rack was the same way- very dry inside. Warren (Early_S_Man) has said that the Bosch grease that was used to initially lube the rack is known to separate/dry up and leave you with next to nothing in there.

Tim,

Would you happen to have a closeup picture of the pressure block/piston? Looks like yours has a nice groove worn in the surface, just like mine. I rotated mine 90 deg. to make the rack ride on the higher, original surface.

I used a basic moly grease (actually 2 tbsp. of Dow-Corning Extreme Pressure BR2 wheel bearing grease) to repack mine. Like Tim said, anything is going to be better than the current dry conditions under which most people's racks are currently operating!

edit.................

Oh, I also put some RTV around the stamped steel covers for the rack. Some manuals have shown that these covers use gaskets. My rack did not have any gaskets. So a tiny bead of grey RTV will help prevent minor leakage. They do leak. The inside of the belly pan cover usually has a spot on it where the grease oil drips out.
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Last edited by KTL; 06-01-2005 at 10:17 AM..
Old 06-01-2005, 10:12 AM
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Kevin my puck did have wear, but reassembled like it was after debating about doing what you did. My pinion teeth were kind of nasty looking but like I said, it works smooth as silk now and I have absolutely no discernable play.

I would not discourage anyone from replacing their rack or paying to have it rebuilt, but I myself am very happy with the results of my $4.00 bearing replacement.
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Old 06-01-2005, 10:28 AM
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Agreed Tim.

I debated for a while on how to reinstall the puck. I figured what the hey, it'll be better than it was before.

I too am very happy with my breakdown and repack of the steering rack. Combined with new turbo tie rods and ball joints, my steering feels like new. Before the work the steering feel was really light and sloppy. Now it's firm and communicative. BIG improvement @ a little cost. It's a must-do for anybody refreshing the tie rods or front suspension.

Here's a topic that I put some scans of the rack assembly from a 914 Clymer manual

Steering Rack Rebuild Pages
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Old 06-01-2005, 10:34 AM
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Xlnt write-up.

There is also a thread by Zeke/Milt for those searching for info on this.

Can somebody post:

1. Any long-term maintenance that should be done on the rack (every 10, 20, .. years)?

2. How exactly one should check the for play in the rack.
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Old 06-01-2005, 10:40 AM
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Tim,
I am so happy to hear of your success. My wheel feels "hollow" and clunky at dead center and light in the rest of the travel. My hope is that new shocks, turbo rods, ball joints, wheel bearings, sway bushings and repacking the rack will bring her back to life.
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Old 06-01-2005, 10:43 AM
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Tim

Thanks for the excellent photos and the response. I'll be putting this on my list of things to do this summer.

Jim
Old 06-01-2005, 03:51 PM
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Randy, I do not know the official way to test, but my car when going down the road, had a barely noticable amount of free play that took me awhile to even notice. You cold move the wheel ever so slightly in each direction without any steering response. I kind of thought that my old original tie rods were to blame but when I lifted the car to change them, I had my daughter turn the wheel back and forth, while I watched for play. This did not really identify the problem so I lowered the wheels onto blocking and crawled under and had her repeat the jiggling with the front tires fully weighted. The free play could be felt, but the tie rods and rack ends were not moving, therefore the play had to be coming from the rack.

I do not know how common the bad bearing is, but on mine it definately allowed the pinion to screw itself in and out before it actually started driving the rack. My "guess" is that quite a few racks have been scrapped over the years due to being "wore out" that may actually have just been suffering from a sloppy $4.00 ball bearing!
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Old 06-01-2005, 04:27 PM
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I guess one would check on a flat road - wider tires tend to track and follow wear grooves from all those heavy trucks on the hwys., causing some 'wiggle.'

One thing I've done is to turn the wheel back & forth while watching the tire - thing is, sidewall flex can make you think there is wear when there isn't.

One thing is certain - these racks will go a long time but they can't go forever. I guess we should check them every 100,000 miles...
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Old 06-01-2005, 05:07 PM
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Mine had play in it also. After disassembly, cleaning, rotating the pinion 180 degrees, and relube with Castrol Pyroplex Blue, the play was gone, and the steering is real good.

I thought about putting some grease fittings on the housing for relube purposes, but discounted it because the grease will have nowhere to go except to fill the tie rod boots. Also, the Pyroplex may be too heavy duty, so I'll take it apart this winter and do it again with a synthetic wheel bearing grease. I'll see how it works out over the next few months.

I really think that the lubrication, or lack of it, is greatly overlooked.

Pat
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Old 06-01-2005, 05:21 PM
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