Salisbury diff - easier than you'd think

[Snagger]

Being as suspicious as Bill was that the 3.54 diffs were a contributory factor in my gear box's failure, I have replaced the 3.54 diff in the 110 rear axle with a 4.71 diff from a 109 axle. The manuals make it sound terrifyingly complex, but it isn't. KAM Diffs' website states that the shims used for setting the pinion depth in the casing are to sort out the tolerances in the casing, the pinions being machined accurately enough that you can just use the existing shims even when changing pinions. My measurements of pinion depth in the old and new casings were within 0.02mm, and to be honest I don't think that was any more than measurement accuracy could manage.

The same is true of bearings - they are very accurately machined and can be replaced without shim adjustment.

As for the diff carrier, the 4.71 and 5.54 units were almost identical in overall width, including their bearing races, and didn't need any shim adjustment - the 4.71 slipped straight in (with the aid of the axle spreader) and the mesh was correct from the original shimming in its original casing. This matches up with the experiences of two others I found on the web who had fitted 3.54 diffs to their 109 axles, going the other way from what I did. I wouldn't be so certain that they can normally be transferred so easily, and may often need shims adding, removing or transferring from one side to the other, but a test fit to check for end float and free rotation with the spreader and pinion removed and a mesh check with engineers blue (or emulsion paint) will quickly tell you.

So, apart from the huge amount of torque needed to crush the collapsible spacer to set the pinion bearing preload, which would be OK with the flange lever tool and a breaker bar, it really isn't a difficult task, just heavy! I need to get the speedo calibrated again, though, but at least swapping the front diff is simple.

SO, It's back to the standard gearing, plus overdrive, which makes it a bit revvier, 10% thirstier and a lot noisier at 60mph, but it drives more nicely again.

Fitting non-standard ratios requires the use of 3.54 carriers and special gears. KAM say their gears are different thicknesses form standard, so the carrier bearings need shim adjustment for sure, and possibly some trimming of the housing with a grinder. Their non-standard ratio pinions are still a straight swap, though.

[Gremlin]

Well Done!

G