When I rebuilt my front suspension, I noticed that the steering box adjustment was pretty much all in. The adjustment screw was almost flush with the top of the lock nut. Since I have a right hand drive, I thought that I had better make a start in finding a replacement since they are no where near as common as left hand drive versions. The right hand drive steering box is a direct mirror image to the left hand drive. The machined worm gear spiral actually runs in the opposite direction as well - I can’t believe that BMW didn’t just arrange the same steering box on the opposite side of the car rather than get ZF to make an exact mirror copy.
After posting a ‘want to buy’ on the UK board and Australian Facebook, I struck lucky with a good box from the UK with lots of adjustment left and a smooth action. This was bought for a quite unreasonable sum (plus shipping) and sent to Adelaide. Unfortunately, I was in the middle of planning an interstate move and a 9 week tour with a camper trailer, so I had little choice but to pack the new steering box and ship it on to Sydney where we were moving to.
The (fast) drive from Adelaide to Sydney in my car reinforced to me the need to get the steering box changed out. While less noticeable when puttering about town, sweeping bends at 80mph we’re a bit unnerving as I waited for the steering to catch up with the input I had just given it. The rest of the suspension (all new) has performed well but the steering had some room for improvement.
I got a seal kit from Walloth & Nesch which also comes with a paper gasket, a new pitman arm nut and a tabbed lock washer. I know that I could get the seals individually for a lot cheaper from a bearing / seal supplier based on the dimensions on the seals but I saw the benefit of getting a complete kit. The pitman arm came off first, I used a puller and some judicious application of heat from a MAPP torch after spinning off the nut with my long breaker bar. The arm wound off with no dramas once the heat had expanded it and it lost its grip on the shaft. The box came apart easily, revealing the worm gear and sector rollers as perfect, no galling or obvious wear. The ball bearing cages were intact and no obvious wear on the races or balls. The shims were scrubbed clean with a scotchbrite pad. The housing was cleaned up and given a coat of ‘silver galv’ paint before the new seals were gently tapped into place with suitably sized sockets. The marks on the shaft were aligned with the marks on the case and then the box was reassembled. 300ml of clean SAE 90 oil was added and the box worked back and forth a bit to distribute around the bearings.
Removing the old box was relatively straightforward, though I did elect to remove the whole drag link and steering idler so that I could get the Pitman arm in the vice and give it a good whack with a BFH. I could have used a ball joint tool but I was conscious that I didn’t want to damage the rubber seal on the base of the ball joint so the ‘hard whack’ method was required. Removing the lot was the next logical step as I didn’t have enough room underneath the car for a good swing of the hammer.
I didn’t do anything to the steering idler apart from cleaning it up and topping up its oil. The RHD idler was common with NK and CS coupes (as are a number of RHD only parts). The unit is actually adjustable but I left mine alone as there was no appreciable play in any direction and yet it turned very smoothly. I am going to assume that is OK as I can’t find any instructions as to how it may be adjusted.
I renewed the flex joint after cleaning up the parts. The braided strap for the horn appears to have been working long term by just rubbing against the heat shield (RHD joints have a heat shield to protect the joint against the heat from the exhaust). I added a crimped loop of wire that I protected with heat shrink and installed within the heat shield to protect it.
The new flex joint is quite a bit smaller than the original (no date mark unfortunately, marked Jurid and SKF). I am hoping that there is no compromise in terms of strength longer term.
You can see the comparison between the old box and the replacement in terms of how much adjustment is available. I will give the replacement box a tweak once I have the car back on the road.
When I get a chance, I will tear down the old box and see what state it is in. It definitely felt a lot more rough than the replacement. I am hoping that the worm and roller are OK as I will get it rebuilt with new bearings if it is possible since they are getting pretty rare now. I will update this post with whatever I find.