catastrophic steering failure Qs....

zenwrenchpaul · 07-03-2006, 12:06 PM

Here's some info about the car:

1968/69 911 with fresh rebuilt ZF steering rack
while being used on track - steering began to bind - later locking up completely while loading on to the trailer (!) VERY scary!

new rubber dampener / coupling torn, bolts possibly broken inside the coupling, but I suspect an INTERNAL failure in the rack. Even with coupling nearly completely disconnected and shaft splines serarated - we were unable to turn wheels - even by pushing the tires, etc.....we had to disconnect tie rods to roll car straight.

Any one out there experienced this horror? Could the problem be due to installer error, or track abuse perhaps? - Rack DOES have aluminum spacers under it, and car is equipped with coil overs.

Would a steering limiter save future failure? Are there "common" mistakes made during installation that were missed?

Any info GREATLY appreciated - THANk YOU!!!!

Paul

Grady Clay · 07-03-2006, 01:10 PM

Paul,

From your image you have a ’69 – right? A SWB ’68 Model is a totally different front suspension.

Clearly something was is a bind in the front suspension/steering. A good procedure always to operate the suspension and steering throughout the combined ranges – without the springs (or torsion bars) in place. This allows you to confirm that everything is acting as expected. It is useful to measure the alignment at various points during this process.

My last test is always jumping up-‘n-down in the trunk and at the engine to confirm proper suspension travel, no binding or strange noises.

I will speculate that you have the yoke-type tie rods (not Turbo-type). It is possible for the big stop-nut to be loose and allow the yoke to rotate 90°. This puts the rack in a serious bind and can brake or seize parts.

If the steering shaft universal joints are installed wrong, similar issues (binding) can arise.

I would consider everything in the front end as suspicious condition. The obvious problem will be easy to find. There can be difficult to detect farther damage you need to find. If in doubt, replace it. What are your and others lives worth?

Nice looking engine!

Best,
Grady

zenwrenchpaul · 07-03-2006, 02:29 PM

Thanks for the tips Grady - I'm also of the opinion that safety is paramount. (I offer a lot of tech advice to vintage BMW guys - and often raise my fist at those trying to cut corners on safety items - it's among my pet peeves...people can be so dumb!)

I built the engine for the owner, and have laid a hand on nearly every part of this car - but the steering rack was somebody else's install. We string aligned it, corner balanced it - all nuts and bolts tight. tie rods nice and straight when weighted, etc...

The car handles like a dream - so I suspect it's something closer to the rack than any other portion of the suspension.

I like the idea of disconnecting the other stuff for a rack travel test. ALL of the suspension is brand new.....all of it. (that could be good or bad - if any one item is incorrectly installed. )

The car has what might be a 1968 VIN - but has a mysterious past - including some very old log books (it may have been a race car since it left the factory. Originally a 2.0 injected R motor - now it sports (...and I do mean "SPORTS") a 2.9 with 10.8 and sprint cams. We had to fabricate new larger dia. shock towers in the rear bulkhead for the coil overs - as it was such an early car.

This car has been the core focus of my life at the shop for the last 3 months. I truly love it as if it were my own - but it may send me to an early grave from stress! (and thank god the owner managed to get it - and HIMSELF into the paddock in one piece!)

All the Best! - Keep those ideas coming!

paul

Grady Clay · 07-03-2006, 03:13 PM

Paul,

I know the feeling – been there, done that on the prep; just never had an issue like this.

The two critical issues are to first find the root of the problem. This may be an improper install, a defective part, improper application or some other. The issue isn’t to ascribe blame but to find the problem, cause and prevent any reoccurrence.

The others are the engineering issues. While much of this was resolved in the ‘70s, there is still plenty of room for improvement. Was there something here that was solved many years ago? Until the ‘net-age’ too much was cloistered. That is no longer true.

Post every detail of the set-up and subject it to the critique of many skilled builders. There is real value in sharing this info; we get to beat the other marques in our (not lame) old age.

There is serious value in documenting the provenance of the 911. If it was a Factory race build, every detail should be researched. It doesn’t matter the degree of success; just the history is worth the effort.

Best,
Grady