Ron_H

That may be my next stop after I get all the looseness out of my system and the rack replaced. It certainly is more financially reasonable, and they assure me that they have done enough of them successfully. Of course I've heard that in the past.

959Lover

So I should drive the car for a week or so, then what?

I don't have a 959! It's my dream car. I have a VW though . And Arash, I wouldn't take the car to a VW mechanic. It's like telling a podiatrist to do work on your liver. Won't work out so well. And BTW, the odo no worky. Sorry for the bad news. And no, I didn't hit the reset while driving. It just stopped moving at 1/10 mile.

griffiths

Yes and no. On the 928 there is no "bushing" internally on the LH driver's side (gear side). In the LH side the rack shaft is held against the pinion gear by a shoe with piston, spring and shim; this controls the backlash of the gear set, we set EACH remanufactured rack's backlash from our facility and test each unit because the racks coming in many cases (given the age of these models) may have be rebuilt by either another rebuilder of the OE and in many cases the backlash is too loose.

Inside the rack is the inner tube seal assembly which helps to maintain the LH side of the shaft in center of the rack housing. We replace the OE "plastic" bushing with a "new" bronze bushing which has a tighter spec than the OE plastic bushing.

On the RH side of the rack (smooth side) there is a bushing assembly that maintains the rack shaft in the center of the casting and seal assembly.
This inner bushing assembly is compised of steel sleeve with a plastic guide insert. Frankly these seldom wear or cause "slop" on the RH side; meaning if you were to disassemble a "brandy new OE" unit and compare the dimenisons with respect to inner and outer diameter, wall thickness and concentricity of those found in units with 50k, 100k or even 100k miles of useage, you would not notice any excessive wear which would cause excessive shaft play or deflection on the RH side.

In otherwords the shaft "bushings" are seldom the cause for slop in a rack. However, after remanufacturing thousands of the 928 racks (for P when they were in Reno, for major WD distiributors, repair shops and retail) we can tell you this:
A) the bores in the RH side castings are seldom in true alignment with the center of the casting. In some cases you will see some shafts with equal spacing around the RH side of the shaft and casting and in some cases you will see a major difference. This is probably related to the early casting technology the OE used years ago.
B) The amount of slop or movement you see on the RH side of the shaft between the housing is greater on the 928 rack as opposed to other vehicles; as you extend the 928 rack shaft further and further outside of the RH side of its housing you will note the amount of slop or right to left or up to down movement increases the it extends out of the rack housing (the increase in movement is a trig function in terms of measuring it). This is simply the nature of the beast with this racks design and has nothing to do, normally, with the inner rack guide bushings whether they be new or old, it is just simply a "sloppy design". And the same holds true for hte LH or driver's side: you can twist the rack shaft to a greater degree and see lots of movement as compared to othe vehicles.


More common problems we find with the 928 steering, when a "problem is encountered and provided your rack is in good shape (whether original or rebuilt)" relate to: inner tie rod joints (frankly they take a beating), the 4 rack mounting bushings (by the way we replace them all with new and I have to laugh when P told us years ago that their rebuilder was not replacing them), the universal yoke joint or steering coupler (as these cars get older they fail).


Be warned that when taking a 928 to an alignment shop that has little or no experience with the 928, you are asking for trouble if they are not aware of the How's To's with respect to aligning or troubling shooting a shark.

I've owned three 928's: a 1978, a 1984s and 1989s4. I loved them all, and some more than others.

Garth S

Griffiths,
Thanks for the detail of the rack internals: the comments I made in post #18 are accurate.
I have strongly suspect that the rebuilder that refurbished that rack for me had left something out, for the RH side can be displaced easily, even when the rack is bolted solid to a bench and centered. From your description, it would suggest that the plastic guide insert in the steel sleeve went AWOL .... so I have a useless rack unless I have such an insert machined.

BTW, the cure was to install a Griffiths rebuilt - which worked out very well! .. but my 'spare' remains as a dry, leak free core .

SharkSkin

Thanks for that info, Charlie, it seems I was mis-informed. Or maybe not. You don't state whether you do anything to tighten up the RH side of the rack. For me this was a concern, since the play was excessive on the RH side of my rack. Inner/outer tie rod ends were tight, but with the boot pulled back on the RH side there was 2-3mm of play with the wheels straight ahead. This was a few months before the rack started leaking like a sieve out both ends. The replacement from 928I was very tight on both ends, <.25mm IIRC.

griffiths

Thank you for the positive post. It's very hard to bat a 1000 all the time.

griffiths

As we said: "On the RH side of the rack (smooth side) there is a bushing assembly that maintains the rack shaft in the center of the casting and seal assembly. This inner bushing assembly is comprised of steel sleeve with a plastic guide insert. Frankly these seldom wear or cause "slop" on the RH side;"
When we DO find an assembly that has a worn plastic guide sleeve we toss it out and replace the guide.

One thing you may or may not be aware of is shaft diameter.
When a rack shaft, typically the smooth section that slides through the seal system, is worn from pitting or rust (or from the idiot who used a pipe wrench or like claw device to hold the shaft from twisting when R&R the tie rods) the shaft must be "re-worked". I won't go into our process however it reduces the diameter of the shaft. If you go overboard with the refinishing process and make the shaft diameter too small.... naturally you will have excessive slop between the shaft and the bushing perse. There is a low limit we apply to our shaft diameters afterwhich the shaft if undersized is not serviceable in terms of sealing and slop... you toss it out (we know what the low limit is). Many retail clients think that the industry grinds down the diameter of the shaft, hard chrome plates them and then regrinds again. Years ago that was true but not today. Chrome processing is a very dirty business in the EPA's eyes, there are only a handful of companies left that do hard chrome plating (thick chrome) as opposed to "triple plate; copper, nickel and chrome flash which is cosmetic rather than structural. Then you have other issues with electro plating such as hydrogen embrittlement which leads to fracturing and failure.

So imagine some rebuilder or even a DIY who bought a seal kit on-line and they don't check the shaft diameter or they are naive with this issue, you could have a new bushing but undersized shaft and then you have your problem of slop. If you were to reduce the shaft diamter and put in an undersized sleeve or bushing you run into the problem of seal design matching the "set" (ID/OD's) and performance requirements (pressures/time). When you start modifying the component you run into product liability issues; and today most insurance carriers are staying away from any producer who modifies critical components.

There are some rebuilders out there, those who rebuild 10,000 rack per month (chevy, saab, porsche, toyota; they don't care as it is a numbers game), who don't know what happens at alignment only that it may or maynot have passed their leak test. I know of one extremly large rebuilder (names withheld naturally) which we purchased a rack from because it was an odd ball and not in the line which we specialize in. Anyway the rack was purchased as a "long" rack meaning with tie rod assemblies. We ran into a problem with it because the inner tie rods were completely shot (loose as a goose). When we talked to their "QC Manager" and asked why we did not get new tie rods he said straight out "because we (they) rebuild them". I said "Really? Tell me how you rebuild a ball socket and ball?" I was hoping they would refer me to some process alike joints for hips. What he said actually made me drop my coffee cup on the floor. And he said "Oh that's simple, we just squeeze them in a press" !!!!!
That is not a joke. That is a true story and I may still have the broken coffee cup hanging around to prove it.

SharkSkin

Thanks, it's nice to hear you explicitly state that you will replace the parts that keep the rack from wobbling in the housing if needed. Might be worth adding a note to your site. I was obviously misinformed, and couldn't find any info to the contrary.

griffiths

Dave,
I appreciate the positive feed back. At least no one is throwing tomatoes at us, yet, on this thread.

Regards,
Griff

SharkSkin

Griff, the only problem I've had with you is what I mentioned in post#6 in that other thread. I've been happy with the AC compressor I purchased from you. I understand many of the challenges of your business, especially selling to the public where often your customer knows nothing about the system they are repairing. Surely that can be frustrating at times. You may be one hell of a nice guy, but that doesn't come across over the phone. Obviously you have to try to protect your interests, but maybe this whole mess is a wake-up call to look at how you do so. Maybe not, It's none of my business really and I sure as hell don't have enough info to take sides. I have a lot of respect for Paul, and I have a lot of respect for you(setting aside the issue mentioned above). I'm not trying to slam you here, I'm trying to be constructive. I hope it works out well for all parties.

docmirror

My rack is being replaced this coming weekend. I will be doing my own non-Porsche approved broomstick alignment method. Now, I realize that I'm stuck in the '60s, with my Chevy pickup mentality. but I've found over a few years of living that my broomstick method is just as good on toe measurement as the $40k Hunter 4000DSP system. I've done the alignment, had my work poo-poohed then took it to a brand name shop where they couldn't get it any damn better than I did! Arghhh.

Someone mentioned that alignment stuff is just a matter of trig functions. since I passed(and teach) Trig, and can figure the relative Sin of a few Thetas, it's not a problem to determine the toe setting with a few good pieces of wood, a tape measure and paper and pencil. anyone wanting to check my work is welcome to look at the tires on the following cars I've done: 83 Ferrari Mondial, 2000 dodge Durango, 70 Lamborghini Espada(being done again next month), and 74 Matra Bagheera.

It's not rocket science. Look for worn parts. Replace worn parts, set camber using a bubble level(yes, it works), then get out the boards!

Flame suit on and helmet down......

Doc

Ron_H

You won't get any flames from this kid. I agree with you. What is so freaking difficult about three functions, given all parts are in good condition and heights are withing spec? Three times I have paid for an alignment and three times I have gotten the car back with worn or loose parts that should have been caught before even attempting to set alignment. Basta! I have never had such a poorly steering automobile as this 928 in my life. And now I found, or Dave Lomas found worn rack bushings unexpectedly, after I had thought that they had been checked the last alignment. My rack is coming out and pronto. And so are my wheel bearings. Then we'll see about alignment. In one case, following an alignment, I went out and shook the wheels and found play in the bearings. (walks off cussing and swearing !!!)

BC

The racks still move too much under nominal pressures applied for my perception. The ends, (as mentioned) when moved out to a high degree (a moderate speed corner, with opposite corrections, say, the bowl at SOW), move back and forth, thereby creating unknowns in the steering geometry. With this movement comes movement of the seals keeping things dry. A stiffer rack will be a longer lasting one it seems.

The rack on my Honda is Electric, somehow (I signed a contract with my wife to not take it apart), yet it is HUGE in diameter, as are the rack ends. It is bolted more solidly, and seems to be much stiffer by cursory glance then the ZF racks we have controlling a car nearly 1000 pounds heavier.

Thsi is OT now, but anything we can do to make these things BETTER then new will help us catch up the 25 years that have passed since they may have been "good" technology.

Back on topic, the inner tie rods can be deceiving in thier "usability"

Charles: How do I lessen the spring tension in the spool valve to lighten up the steering?

griffiths

I'm still wiping tomatoes off my monitor screen here and I've run out of windex ta boot. After I finish my Dale Carnegie Training course tonight I'll get back to you.

In the mean time my Sprint phone service is finally working and the wife called and left a message... apparently the four kids are up to no good, something about them negotiating with some stranger who stopped with an 89 S4 who wants to trade it for may supercharged 911.... and 1.5 hours I'm late for dinner.

In the mean time something to chew on:
1) I've owned three 928's and the inner tie rods fail too early.
2) The torsion bar in the spool valve starts to open at xx newtons or inch ounces of torque which provides the non disclosed power "curve" by the OE's OEM supplier. The question is how often is the driver in the curve? Is it just when we are doing a "K" turn or only during the course until the rolling force of the tires overcomes our personal steering effort? Questions I have yet to answer but let's think about.
3) And finally. I have taken all three of my 928's to various shops for alignment and every friggin one came out with a different geometry. I've had shops forget to check the wheel bearings, forget to tighten tie rods, forget to tighten every lousy wheel lug and others who billed me and forgot to do the work.
However they are all still my friends!

BC

I never let the alignment shop do anything but align. I bring them new suspension cars, bushings, rods, racks, shocks, ball joints. I say "Don't lift the car to do this, or I will have to come back,"

An aligned 928 with new suspension and steering bits drives 1000% different then an unaligned 928 with 50-200k miles bits and pieces.