The X5 has stayed leak and misfire free this past week so shes at the shop for a full front strut refresh, a vacuum bleed of the coolant system, some ride height tweaks with INPA (my version stopped working on my laptop), and correctly installed injector clips which my Indy says he can get on without pulling the harness…again. Unfortunately my diff shims from RacingDiffs hadn’t shown up in time for me to finish that job and toss it in the car, with the new bushings for him to install before I dropped it off. I don’t have easy access to a bushing tool so would have liked him to do that part.
The shims arrived all the way from Serbia on Thursday evening so yesterday I got to work. 10 snap ring shims from 3 to 4 mm, in .1mm increments.
The OE left shim (that locked the new diff up) was 3.6, so I went with the 3.4 on that side, and the OE 3.8 shim on the right. The fact that the diff would at least turn told me I was on the right track. The gear mesh pattern told me that the diff needed to shift to the right however…the drive side was too far to the heal side of the crown, and the coast was not engaged very much, and was too far to the toe side:
3.5 mm shim for the left and 3.7 for the right gave me what to my amateur eye looks like an OK mesh pattern…a tiny bit off, but I decided to stick with it due to fact that the shims were gettingdifficult to get in (and out if needed) with a race driver and punch as needed:
Next came the backlash measurement which came in right at .08mm, which is right in the acceptable range according to Quaife.
I may fiddle around with the backlash measure technique a bit more next week as I’m not 100% sure I have it right. A few more YouTube videos will get me squared away!
Next I gave the bearings, housing, etc a good clean and popped some OE BMW seals in each side with no drama. New circlips on the stub axles and in went the left side reasonably easy. The OE stub axles are a tight fit in the Quaife, but some antiseize in the bore and gear oil on the axle splines helped. A rubber mallet was needed to get it to bottom out in the inner grove.
The right sided however was real PITA. The Quaife has a grove milled into its output stub axle bore that kept catching the retaining clip on the stub axle and freezing it. I could not get the stub axle past this point and into the splined section of the Quaife. I finally had to pop it back out with a punch from the other side, which broke the snap ring. After locating the two pieces I put the original snap ring back on the axle stub and was able to work it past this point and down into the splined section and finally bottom it out with a rubber mallet.
The pic below shows the grove(arrow) which grabbed the snap ring on the output stub axle. The old snap ring was happily a bit more squashed and worn I guess:
All in all not a terrible project, so far. The Quaife was no where near correct with the OE shims, which could be the Quaife, or more likely is due to the new taper bearings being slightly different dimensions than the OE FAG units (which aren’t available any longer). The Quaife seems like a really tightly machined piece of gear.
The 188k medium differential is a pain in the sense that it uses snap ring shim rather than bolt on flanges with shims. They are not readily available, are a pain to work with ( broke 2 snap ring tools) and need some hammer and punch persuasion to get seated. The old races from the oe bearings were very helpful as spacers, something to tap on so I wasn’t tapping on the new races to get them in, and to get the output seals in.
Next up is to get it in the car. Time will tell if my decision not to pull the pinion was a good one. I will have a spare Diff though if I need to revisit something on the Quaife diff after it is in. Buyng the eBay diff for the Quaife was a good decision I think as I could take my time building it up, waiting for parts, etc.
Take everything above with a grain of salt, or 10. Nothing on this project was cosmic, but I relied on YouTube, Quaife’s instructions and forum reading. Bentley says nothing about rebuilding a diff unfortunately. I was amazed at how the diff is really not even as advanced as refrigerator technology, but the tolerances involved are very, very small.