I bought old S80 (1999) with B5244S motor. I was inspecting cam belt condition and found out that belt goes about 1 mm over pulleys edge in intake cams vvt-hub (1275362), it had about 2,5 mm axial play.
I found out that it’s quite common problem even with low mileages and only fix is new hub. Original hub cost almost same what I paid for whole car, not so great idea.
I found used hub from the scrap yard for 50 euro and though that I will check and probably repair it before installing.
I drilled rivets and opened it, I was bit surprised that there is no wear at all.
If someone is looking to buy used hub, that is not connected to cam shaft. About 2,7 mm free play (1275362) in inner shaft means hub is like new condition.
Chanced used but good hub to motor with new belt and stuff, works fine.
At same time I removed cams and chanced valve stem seals, those were totally busted. Used air pressure to cylinders method.
Now to the rebuilding part:
I opened old vvt-hub, that I removed from motor to see where it has 2,5 mm wear.
Inner shaft that is bolted to camshaft had most wear, like expected. Because it has only about 40% surface area that shim washer and outer race sliding surface have. See first picture.
They had to make sliding surface quite narrow, because of toothing of that integrated gear.
It might have too small surface area for the force (pressure/area)
=> oil film not so great between surfaces.
Shim washer and outer race sliding surface was also bit grooved, probably because metal chips in oil from inner shaft.
Turned outer race sliding surface clean.
Leaved shim washer out of the assembly, to get room for new solid sliding surface.
Turned inner shaft clean and made new shrink-fitted sliding ring of bearing bronze (CuSn12) to the shaft.
Used 0,03 mm interference and assembled with heat to inner shaft. Now there is about 60% bigger sliding surface area than original have.
Turned sliding surface clean in place and to correct diameter, 41,50 mm.
Then it was needed to determine right thickness for new sliding ring, so that it have small axial play when bolted to camshaft.
I put inner shaft to the planar surface (lathe way) and outer race to over it. Zeroed dial gauge to hubs outer edge, that is coming against cam end.
Then moved hub, so that I get reading from inner shaft end, it was something like -0,56 mm (I leaved about 0,6 mm for working allowance to the bronze ring).
Removed 0,6 mm from sliding ring thickness, to get something between 0,05-0,10 mm for axial play.
Outer race need small play for adjusting movement.
Ended up for 0,07 mm axial play.
Now inner shaft have same 2,7 mm free play that like new used one had, when not bolted to cam shaft.
Not installed this yet, probably in next belt chance…