Steering rack question

My 91 Testarossa and 92 Diablo have near identical steering racks made by TRW Italia.

The Diablo rack has about 10 degrees of free play when the wheels are straight. When turning the wheel it makes an audible clunk. Too much free play. The TR WSM details a process to shim the pinion gear to remove excess clearance and take out the free play, using thicker shims. There is no adjuster screw like on some other types of racks.

Anyone ever adjusted their rack in this way? Any suggestions on where these shims might still be found?

Thanks to all for any suggestions.

 

Most likely it is the right hand bushing. In Ferrari racks the bushing is plastic and comes apart. I have rebuild them and I machine a bushing from oil impregnated material. It does have shims for adjusting but I haven't seen that part wear to the point of clunking or needing adjustments. The Diablo is likely the same.

 

John, if your pax side bushing is indeed broken:

Image Unavailable, Please Login

I have designed a replacement that can slip on and lock into the original slot. It's milled in Nylon:

Image Unavailable, Please Login Image Unavailable, Please Login

If that busing is indeed your issue, send me message.

 

I had that right side plastic end bushing issue on my 91 Testarossa - it would clunk every time I went over a bump as the rack hit the case. I replaced it with a new rack from Superformance and got a bronze right side bushing to rebuild the old one with.

The Diablo issue is different, the clunk happens when I turn the wheel either way - even when parked - it seems to be too much clearance between the pinion and the rack. The wheel turns without moving the front wheels. I will check the end bushing as you suggest.

The great news is that a 92 Diablo and a 91 Testarossa use the identical TRW steering rack - and I have that original rack from my Testarossa that was professionally rebuilt (with the upgraded bushing) as a spare sitting on a shelf. I guess I know what I am doing next weekend…

 

Re the symptoms: I had such play in the pinion area once on my Mondial rack and it was due to water ingress from the top of the pinion axis, which lead to corrosion of the pinion bearings. "All" the rack needed was a very good clean, new pinion axis bearings, a new top seal and grease. We used the original shimming for the pressure slide piston.

 

That sounds like an easy fix(!)

Japanese Diablos see rain, so anything is possible. My daily driver cars see many times the mileage in all weather without issue, but the rack in the Diablo develops issues at 48,000 km. Hmmm.