ddombrowski

So awhile back I posted about how our steering rack in the chumpcar started binding after a spin at Sebring - it was very tough to turn, but still operated properly and the toe/handling was no effected.

I found a bunch of posts where people listed similar symptoms and offered no real resolution other than that they wear out.

Since we had a good spare from our parts car, I swapped the good rack into the race car and started taking the old rack apart. I don't know all of the posts I looked at on my phone while doing this, but I appreciate the few that show the disassembly of the rack, and thanks to the tip from Van about putting the steering link on the pinion to give yourself a surface to whack against to get the pinion out.



With the pinion out, the gears looked fine to me and the rack STILL didn't want to move. I had to hammer it out of the housing. Looking at the bushing in the end of the rack (which I had heard was rubber but is most definitely metal), it seemed to be intact. Looking at its construction, I could see a crimped ring in the rack casing that I suspected was the 'stop' the factory used when pressing in the bushing. Measuring against the good rack, the 'bad' rack's bushing was pressed in further, and thus, was pressed past the crimp. This will cause the bushing ID to shrink in size and make the fit too tight. Thus - binding.



If you only have one rack, I can't tell you how deep the bushing needs to sit, because I didn't measure, but the idea is it has to not be into the crimped region in the photo below.



As an aside, I think the reason this happened is because we were not using the 'stops' that go on the end of the inner tie rod. If you convert a late car to a manual rack, you either need to use the prohibitively expensive late tie rod ends, or, in our case, the VW fox tie rods. If you use the VW tie rods, there are no 'stops' to put on them. Most people don't have a problem with this, but if you turn the wheel sufficiently hard enough at full lock (or in our case, spin the car so the wheel whips around and hits full lock), the nut on the end of the rack can hit the bushing and press it in. I ordered some delrin rod and Im going to attempt to make some custom 'stops' for the VW fox tie rod ends.

I used the removed rack as a drift (not my smartest idea but I had already written this rack off as bad at this point), placed it in the casing on the backside of the bushing and gave it a few whacks with the hammer until I felt a pop. Now the metal bushing at the end measured the same distance as the good rack. I put the rack back through the bushing and it traveled smoothly with very little resistance.

The backside of the rack looked like it had a lot of wear in it from the spring-loaded tensioner. I am not sure if this is normal wear or if this was a result of 14 hours of wrenching the wheel against the bound bushing. Regardless, I sanded the tensioner with some 2000 grit sandpaper to smooth out the pits. You can see it in the background but I never took any closeup photos of it. I left the rack alone as the surface was smoother than the tensioner.




I put the whole thing back together and loaded it with some Mobil 1 synthetic grease. The assembly now turns smoothly and consistently, just like the replacement rack. So, now we have a spare manual rack we can swap in if we need to during a race.

In the background of this photo, you can see the polished rack/spring tensioner.

kevin12973

Nice write up. This will be very helpful to the community.

pfarah7

+1

Noahs944

THANK YOU. Incredible write up. Very helpful... as I've spent hours trying to diagnose stiff steering in Gramps the 78 '24.

Very gracious of you mate.

ddombrowski

Glad you all enjoyed it. I need to write up a separate post about the development of my 'manual-rack-conversion' steering stops which don't exist from Porsche, but here they are. I machined them out of delrin to the specs we measured and then trimmed them a bit to fit. I haven't reinstalled the tie rods into the rack yet, but the spacers fit on the tie rods well so I am hopeful the setup will work.

nicqcrenaud

Do you have any more of the delrin bushing? Or measurements? Putting together a manual rack over the winter and I found out about this stop ring issue. Although, looking through VW catalog it appears their manual racks, which share a very similar construction, don't use any stop ring at all...

Van

Cool idea with the spacers!