jpitman2

Dont know what nylatron is, but years ago I came across nylon rod impregnated with graphite at a bearing shop. This stuff is great for bushes under load, machines well, and is not very expensive...

jp 83 Euro S AT 50k, no steering problems...yet

Garth S

There are many types of nylatron , but many are MoS2 impregnated, and machine well.

GRTWHT

No.. There is no dead spot in the steering at all, only at speed.
I have taken the boots off the rack ends and moved the piston rods laterally side to side and found it moves at around 3/16" at least (engine off and car jacked). Normal??? not sure still looks wrong, although no leaks.

Glenn
'81 9-2-8

worf928

What's "it"? The rack? Or a steering rod (piston)? If the former then that sounds like rack bushings. If the latter - piston moving in the bore - then that sounds like internal rack wear.

GRTWHT

Yeh I would agree on the later...internal rack wear. The steering rack itself is solid - no movement - steering tie rods - no movement.

So I guess thats what I was really trying to find out ..... if this external 'quick fix' bushings reduce that movement. Rather than removing the rack for repairs/overhaul.

I hope that makes sense worf928.

Glenn
'81 9-2-8

worf928

The movement you describe seems different from what I described. So, I don't know if fitting custom-made bushings to the end of the rack bores will fix your issue. I also don't know how easy it is to mess with the bushings with the rack still mounted in the car. You'll have to ask Earl G or someone else that's made the bushings. If it was me, I'd probably look at a rack R&R.

Good luck.

Earl Gillstrom

Glenn wrote "So I guess thats what I was really trying to find out ..... if this external 'quick fix' bushings reduce that movement. Rather than removing the rack for repairs/overhaul."

You could probably make and install the bushings while the rack is still in the car, if you don't mind laying on your back. Machine the bushings with the correct inside diameter and rough outside diameter as big as the rack housing hole and about 1 inch long. Then sand the outside diameter to a taper that fits the housing hole. I used a bench mounted belt sander with very course sand paper. After installation, I drilled and taped a hole in the housing for the retainer screw, so the bushing would not fall out. Make the retainer screw long enough to go about half way through the bushing. Use a very smooth round head screw since the rack boot covers the screw head. I used delrin because my machineist recommended it, but other plastics could be better. Delrin has worked fine for me. Check back my earlier posts in this thread for more detail.

GRTWHT

Thanks Earl for your last post, I'm getting under her this weekend to get this done. I've read all your previous post on this subject and found them to be great info. Someone thinking outside the square if you like.
Once I get this done I'll post up some pics, before/after type.
Anyway good stuff.

Cheers,
Glenn '81 9-2-8

Chuck Schreiber

This thread is pretty interesting and very eye opening. I'm beginning to think that this is what's happening on the GTS. Just about all the "loose" and "vague" terms, apply to the steering on the car.
Did any "fixes" ever come from the ideas in this thread??

According to records I've got on the car. The rack was replaced back in 2004. Rack was inspected and found to be defective. Rack sent back to supplier, replacement sent out and installed. (No records of tie rods replaced) Rack was supplied by Vertex. To say the steering feels loose or sloppy is absolutely right on the money.

I replaced the rack in the 79 several years back (new tie rods as well) and the steering is sharp as a knife. That Rack was supplied by Griffiths.

Again, anyone having good luck with any of these fixes?? I'd just like to get the car to track, steer, and drive like it was designed to.

Landseer

I have the problem on an 84. All other steering parts are new, including aluminum rack mount sleeves.
Problem can be seen while underneath. No slop in other parts in the steering direction except as a result of shaft moving fore/aft where it exits rack.
Made a delrin insert. But made the hole a little bigger than the steering shaft. (didn't have a small enough drill bit)
It tightened the steering loosenes some, but not enough. (definitely in the right direction)
I think the only problem was this large center hole.
Need to redo as soon as I free-up some garage space.

jcorenman

The problem with the external bushings is what Earl discusses in post #8: you are trying to fit a bushing into an as-cast, un-machined bore. It can work but it will take a lot of hand-fitting.

There are, I think, three sources of steering vagueness: Worn tie-rod ball-joints, worn internal rack bushings, and loose rack mounting-bushings. With a helper it is pretty easy to figure out what is happening.

First, you need a precision measuring tool: your right index finger. Or left, you choose. Or two fingers, held together, for a larger sensing area.

With the car on a lift or the front end on ramps (weight on the wheels), have a helper move the wheel back and forth repeatedly an inch or two, just enough to wiggle the wheels a bit.

Now go under the car and put your fingers between the rack housing and the cross-member cover-- can you feel any motion of the rack relative to the cross-member? Check both ends. If there is movement then the mounting bushings are loose-- the rubber breaks down with age and miles. They can be replaced, but keep checking.

Now pull back the boot on the driver's side. You will see the rod moving a little bit in and out of the housing. Put your finger(s) where the rod goes into the housing, touching both-- you can feel the in/out motion. Is there any side-to-side motion? If so, the internal rack bushings are worn. Have your help wiggle more, or less. If the rack is badly worn then they can wiggle the wheel an inch each way and the rod won't move in or out, just side-to-side (which doesn't steer the car).

Now pull the boot back farther and put your fingers where the tie-rod meets the ball joint. Any motion there?

Now check the passenger's side, same checks.

In my (limited) experience the most common problem is the internal rack bushing on the driver's side. This is not a bushing per se, but a "saddle" which pushes the rack teeth against the pinion gear and locates the rod radially (side-to-side, at right-angles to the axis of the rack rod). The pinion teeth are angled, and the tie-rods angle back a bit, so any radial looseness turns into steering error.

The other way to do these tests is to jack the front wheels off the ground, have a helper wiggle them in the 9-3 direction, and do the same checks. In-out (axial) motion of the rack rod is fine and what you expect, radial motion is not.

The "saddle" bushing (aka guide bushing, guide block, thrust block) can be accessed by removing the steel plate on the bottom, there is a convenient cutout in the cross-member for that purpose. Inside there is a spring (mostly useless), a shim-washer, and the back end of the guide-bushing. Remove it if you want, but the problem is either too much clearance in the bore (not easily fixed) or too much clearance under the plate (fixable, if you have some way to make new shims). The pass-side bushing is a simple plastic bushing, but requires disassembly of the rack and is unavailable to mortals (but easy to make with a lathe).

The simple fix is to get a new (i.e. rebuilt) rack. As pointed out earlier in this thread, a fresh rebuild is no guarantee of a tight rack, but I can report that Mark at 928 int'l is very good about taking care of any issues that come up. The problems that the rebuilders all face is a limited (and deteriorating) core pool, and difficulty sourcing parts.

You can also get a ZF-rebuilt rack for 2x the price (Roger can supply those), and racks from other rebuilders for half the price. It's good having choices, you decide.

And some folks have rebuilt their own racks, disassembly is easy and seal kits are available, but bushings will need to be made.

A 928 with a tight rack, proper alignment and tires that aren't worn funny is a thing of beauty. It becomes an extension of your mind that you can put anywhere you want, at any speed, on any pavement. It is certainly a worthy quest.

Cheers,

daveo90s4

Many many many supposedly reputable companies don't bother to peen the OEM rack bushes after fitting a new rack and new bushes. This failure then allows the rack to move vertically and results in lousy steering and excess tramlining.

I've read on rennlist previously that the aftermarket aluminium bushes - with no ability to peen and limit vertical movement - initially perform well but over time allow excess vertical movement.

The Delrin bushes that I am aware of likewise offer no facility to peen to limit vertical movement - but when tightened the are forced shorter and fatter so may stop the vertical movemement in the long term. Who knows?

I think that making sure this bush part of the system is properly limiting rack movement would have to be the 1st thing to address in any improvement program (especially if excess tramlining is being felt even WITH correct 65ET front wheels).

GlenL

This should be an aftermarket part.

I've seen this on racks and a lot of others have reported it as well. The wheels wiggle because the rack rod is moving radially in the housing.

Roger? Carl?

GlenL

Let's be sure to separate the rack bushings here:

There are four bushings that hold the entire rack to the crossmember.

There are two bushings that control the ends of the rod inside the housing.

You can tighten up the four bushings by getting large washers and clamping them behind the cover plate. Something like 1.75" OD and 1.15"ID and don't quote me.

Landseer

Exactly.

Rack movement is one thing.

Rod movement is another.

I was describing the bushing insert "fix" to the mechanic who was trying to align my 84. He said he does that fix on other foreign car racks.

Here's the (only) bad motion I'm getting.

Rough idea of what kind of insert apparently works. This one has too large an interior hole.