Unusual ZF Steering rack... what is it??

[gereed75]

Refurbing the suspension on my early 1970 914-6. Pulled the steering rack to install turbo tie rods and decided to take a peek (while i'm in there).

This rack appears unusual in several ways:

1) I have never seen a picture of this particular rack any where on the net. There is a round cover with two bolts and a "star ribbed" pressure puck adjusting cover.

2) the pinion has no needle bearing. It has a ball bearing assembly at both ends.

3) Innards are totally disassembled and removed (including end seals) but I have been totally unable to get the rack out. It comes out 3/4 of the way (until one end is well down into the housing) then hits some definite resistance, almost like a stop.

Looks great inside, no discernable wear. It is filled with the most tenacious black grease ever and until I get to my parts washer, it will be tough to see clearly inside.

So.... do I have some un-obtainium rare 917 piece worth its weight in RS parts!?!?

Just want it apart, inspected, cleaned, repacked and re-assembled. Any help out there???

[gereed75]

More research looks like an early 911/912 rack. Anyone know why I can't get the rack out???

[pors1968]

65-68 swb stering rack.

[chris_seven]

If it is a very early rack it should have the steel pin to locate the steering damper fitted to the very early cars.

The diameter of the rack bar itself is also a clue.

Early racks have a base diameter for the rack bar of 30mm.

Later Racks use a 29mm rack bar and these mostly use the 'full complement' needle rollers on the pinion.

There is a 1969 - ish rack that uses the 29mm diameter rack bar with the early design of pinion bearing which is a sort of halfway model.

If you have removed the pinion and the pressure block the rack should come out.

It s possible that the pinion carrier may have moved slightly and is causing an obstruction.

I would check the pinion carrier hasn't rotated.

If it is a very early rack it is also slightly shorter that later models so I would just double check how many threads engage in the TREs to be certain that there isn't any issue in this area. The Turbo Tie Rod is designed for the later racks.

I think it is unlikely to be a problem as the difference is only a few millimetres but it is worth a look.

These early racks were lubricated with Liqui Moly LM47-L the recommended quantity being 40 gms.

These early racks were supported at their ends by rubber cased Steel Backed Bi-metallic bushes which have never been sold separately.

In the UK some rack re-builders use a Nylatron replacement which I am not entirely happy with using.

We have recently completed a small batch of the correct specification NBR Clad Bi-Metallic Bushes, we have also made new Delrin faced pressure blocks and gaskets.



We have new pressure springs, snap rings, Seeger Orbis retainers and deep groove ball bearings on order so we can carry out complete rebuilds or supply overhaul kits.

We will make similar parts for the later racks in the not too distant future.

[gereed75]

Thanks Chris, I suspect that this may be the "69ish halfway" model. I will check the rack diameter. It has the rubber encased bi-metallic end bushings and the pressure puck is remarkably wear free.

Not sure what you are calling the pinion carrier. Is it the lower bearing?? I too suspect that something is out of place and obstructing the rack. That lower bearing is all that is left inside the housing.

I will be traveling until next week and will not be able to verify all of this but I will certainly get back to you. Thanks for the help.

[chris_seven]

The early rack has a steel block with windows for the rack fitted inside the aluminium housing.

This block holds the lower deep grooved ball baring and can be removed once the rack is out.

If you are stuck I can dig one out and take photographs.

[gereed75]

Thanks again. I have not been able to access my parts washer yet to get that grease out of there to inspect further, but that makes much better sense now. Hopefully once cleaned out, I will be able to discern the carrier and get it properly aligned for rack removal.

Thanks again, the information exchange on this forum ROCKS!!

[group911@aol.co]

Looks like a 68 date stamp just below the ZF insignia

[chris_seven]

Originally Posted by group911@aol.co

Looks like a 68 date stamp just below the ZF insignia

Good spot but I think it is a 69

[gereed75]

Got back to work on this. Got the grease cleaned out and all apart. In deed the center carrier had rotated during dis-assembly and was obstructing the rack. Rotated it and the rack came out as advertised. Smooth bearings and no signs of play, all good.

Went back together with new lithium EP grease and seems very tight except that there is a slight "soft detent" on center. It was there before disassembly. Thought it might go away after "re-shuffling" the parts but it did not. The only wear I could see anywhere was the friction puck had polished a bright spot on the rack at center. I suspect that is what causes the detent feel.

I know you will never feel it assembled in the car because other frictions/momentum in the system (primarily tires on the road) will mask it.

Any thoughts Chris. Thanks again for the help.

[gereed75]

Yep, I see that distinction in greases now. The liquid moly is prescribed for "sliding" friction applications. Thought I had it covered using an EP rated CGLI #2 grease

It will stay together for now. I will await further expert comment and consider changing it at some point in the future. Thanks again Chris.

[Flieger]

I used an aluminum complex grease with MoS2 (126EP from Bel-Ray but I got the tube from McMaster-Carr).