Steering Rack Failure

[APKhaos]

Had an exciting day at Watkins Glen yesterday.
First run of the day, steering began to feel unusual mid-way through the run. As the laps progressed, I put this down to tire pressures/cold track, but then things started to get really strange - the front was extremely loose, and seemed to be dragging on corner entry. Shut it down and pulled into the pits. The Glen is a high speed track with no room for error - big walls everywhere!

On the pit road things got worse! The steering wheel had around 3" of play, and a loud clunk! Back in the pits, the diagnosis began.

The clunk and the play was from the driver's side tie rod area - back under the boot where the tie rod mates to the steering rack arm. Feeling around there, it seemed that the arm to tie rod joint had failed - I could push the rod and get it to move vertically and from side to side. Question was how the how was that possible, without the whole joint having broken and let go?

With the boot off, it took a minute to work out what had happened. There was a major gap between the steering rack casting and the actuating arm, which allowed the arm to flop around - it was not held concentric with the rack case. The bushing that located the arm in the rack had travelled out of the rack and up to the end of the arm! I could push it back into the rack, but once the arm was moved in and out again the bushing would move freely out of the rack casting and back down the arm.

Finally figured out a way to stake the bushing into the rack firmly enough for the six hour drive home. Made it safely!

This failure was dangerous, and could have been much worse, expecially on the track. I'm not sure what caused the bush to become so free that it could move out of the rack and down the actuating arm. I'm not sure how you could inspect a 911 rack to see if it was close to failing in this way. And thats the scary part.

I'll try to get a pic of this once I get back under the car to replace the rack. The bushing is a lot bigger than it appears in the diagram below - there is about 10mm of radial slack in the arm without the bushing in place.

[john walker's workshop]

happens a lot. if you look at the crappy retainer star clip, you can see why.

[Chuck Moreland]

Sounds like the same problem Fitzpatrick has been having. I think he's been through 3 racks in a couple months.

[APKhaos]

JW,
Is it possible to repair a rack that has failed this way?
I'm assuming the 'crappy star clip' retainer must have quit, allowing the bush to float out.
Is there an alternative to replacing the rack ??

[john walker's workshop]

search for ZF steering rack rebuilders on the net. i called griffiths and they were no help, but there are others. or pop one out of a junk rack at a wrecking yard, or see if pelican can pop one out of a core return.

[TRE Cup]

Just a little precaution: We've seen a few cars that did not have the rack stop washers in place after having turbo tie rod kits installed. This allowed the rack to extend too far on one side, with the other end crashing into the inner part of the tie rod. This will certainly cause premature rack failure and damage. Make sure the rack stops (large diameter washers on turbo tie rod kits/ large diameter washers that the inner side of the boot rides on in "regular" tie rods - #2 in your illustration) are in place

[APKhaos]

Chuck was right - exactly the same problem that Thom had, and had again, and had again. In fact, TreCup might have suggested the reason for serial rack failure like this. Have posted a pic from Thoms earlier post that shows the bits strung out on the actuating arm - not nicely tucked into the rack where they belong.
You can see the amount of slop that in introduced once the bush pops out the end of the rack. Nasty!

Soon as I get the chance, I'll check that the limit washers were replaced when the turbo tie rods were installed [I'm away from the car at present]. If not, I can see how that could cause this failure.

Thanks all for input on this - it was a scary moment or two, and my first loss of track time due to tech failure. Was royally pizzed!

[surflvr911sc]

Sorry to hear about the failure Tony but this Thread came just in time to save me from making a big mistake.
I installed Turbo tie rods last weekend. 101 Project (not quoting here) made it sound that if the threads of the turbo tie rod do not bottom out in the rack, you don’t really need the spacers. The way I interpret it anyway.
I tried using the spacers but I could not get the rubber boots on over them so I tried it with out them and they did not bottom out. So off they stayed.
Tonight I will be putting them back on. I’m glad I haven’t driven the car yet so the rack has not even come close to being over extended. Any tips on getting the rubber boot over the spacer? It’s a PIA, I know that much. Thanks for the advice TRECup.

[john walker's workshop]

once the rods are tightened to the rack, remove the tie rod end and slide the boot up to the rack. a liberal dose of spray silicone makes the boot easier to slip over things. the spacer shouldn't be a problem because it's quite small compared to the cast aluminum end of the rack that you have to work the boot over.

[surflvr911sc]

Thanks JW. I installed the inboard side of the boot on the rack, and then tried to get it over the spacer to attach it to the tie rod side after installing it. I'm glad the obvious doesn't bite. I would have been mauled a long time ago.

[widebody911]

My turbo tie rods didn't come with spacers, and I had been running without. I fabbed my own when I installed the last rebuilt rack, but it fix the problem. I nabbed a 914 rack at the junkyard ($20 + $2 admission!) and when I installed it, I used an even bigger spacer. I haven't been to the track yet, so time will tell.

I was running with my original rack, both in auto-x and on the track, for over a year with turbo tie rods and no spacers. I replaced the original rack because it was getting stiff - it turns out that water somehow got into it, and was rusting out the guts.

Here's my theory on the rebuilt racks: they paint them to make them look appropriately rebuilt. Then they assemble them. The originals were not painted - just bare metal. I think the clips don't get a good 'bite' on the painted surface, and thus slide out easier.

[KTL]

Did ZF realize at some point in time that these star retaining washers were not working under heavy use ? Reason I ask is because my 87's rack does not use these star washers. It uses circlips to keep the bushings in place:

The circlip is in the vise jaws to the left of the circlip pliers.

[widebody911]

The last rack I broke had the circlips. There isn't a groove for it to sit in, so it's still a half-a$$ed friction-fit.

Originally posted by KTL
Did ZF realize at some point in time that these star retaining washers were not working under heavy use ?

[KTL]

Originally posted by widebody911
The last rack I broke had the circlips. There isn't a groove for it to sit in, so it's still a half-a$$ed friction-fit.

I'm quite sure there's slots in my 87's rack housing where the circlips seat. But, I disassembled and relubed the rack last winter so I don't recall exactly. Sorry.

[CEO]

My rack just did this too. Any luck on getting the start clip washers?

[pete3799]

Send Juergen (autoban here on Pelican) a PM.
See this thread
Play in Steering Mechanism

[sugarwood]

Hey CEO, how did you know there was a problem? What were the symptoms?

[Reiver]

So if you've used the spacer/washer that came with the turbo tie rod kit (lemforder) you should be good to go?
One doesn't need to use the original larger spacer/washer that came with the original tie rod as in the diagram (#2) in the OP's post.

Got it when re reading...the spacers should do the trick

[Autoban]

As Pete pointed out, I had the same issue on mine. Tracked the part down and sourced it in Germany, but had to buy 250 of them I have some left, but running low by now. I mailed out 30 PCs a week ago and just had another Pelican PM me. Here is my thread: Play in Steering Mechanism

Juergen

[CEO]

Sugarwood, I had a very vague steering feel, lots of intermittent steering wheel play and the car seemed to dart in uneven pavement like something was pulling it in a diff direction.