Tips for replacing Hewland/Webster stub-axle seals?

[h00die]

I'm reviving an old FM gearbox - standard stuff with vw case, hewland guts and webster side covers, I think 400s (have bosses for inboard brakes).

The oil seals are cracked and I need to replace them...several questions...

1) It looks like you need to heat the side covers to drop the entire bearing/shim/seal stack out the back side of the cover? Any tips on doing this? Simple as just heating around the hole, and the lot just drops out the bottom or does it need to be persuaded out?

2) If 1 is true, then I assume the reverse is also true for putting it all back in with the new seals? If so, seems kinda scary to have a lot of heat around the rubber of the oil seals and sliding all that stuff back in before the side cover cools seems like it takes some technique. Again, any tips here?

3) Having done 1 & 2, assuming all the same shims go back in, just with a new seal underneath, do I need to worry about differential bearing pre-load or all is well assuming it goes back together with the same bits as came out?

Any advise here is welcomed...Thx!

Chris

[h00die]

Responding to myself - I'm halfway there.

1) I clamped the sideplate horizontally in a vice with the bearing stack facing *up*, so nothing falls out uncontrollably once the heat is applied. It will all come out the top.

2) Walked back and forth around the "hub" that was facing up with mapp gas until I was able to shift the bearing carrier shell. Then, with a little more heat and testing, I was able to simply individually lift out the carrier shell, the preload shims and the spacer from the top of the bore.

3) I then mounted the sideplate vertically, and heated the outer/opposite side of the "hub" around the axle bearing assembly until I was able to gently push it out by hand with a socket - acting as a drift.

4) Lastly I mounted the sideplate horizontally again (flipped orientation from step 1) and heated around the oil seal shell hoping I could get it to just push out. I'm not sure if there was rtv or something in there, but eventually I started cooking the rubber and gave up and gently drove it out with a screwdriver and hammer...seal was junk anyway.

While things cool off (including my nerves), I am thinking about how to put the new oil seal back in. I don't like the heat idea, but I also don't think the seal will like being pounded from the back...I don't know if the bore is that kind of press fit for the seal or a heat fit.

So, any wise words before I jump to the next phase...?

NOTE: I used a straight edge and a feeler gauge set to reference the gap between the edge of the protruding bearing carrier and the housing - so when it's all back together, I have some idea whether the carrier went back in at the right height and hopefully not mess with my preload.

[h00die]

Made a driver out of a piece of 2" PVC conduit to support the oil seal from the back side for installation. This is thick enough that it fully supports the face of the seal from the back (the part you would normally push on when installing from the front) without deforming the outer edge of the seal carrier or the inner seal and spring itself.

Thin coat of silicone sealant on the shell of the seal to help it slide in, and further seal up when dry.

Dropped the seal in the sidecover (cold), and used the driver and a mallet to drive the seal home from the back. Take your time, walk it around, and it will go home. I wanted to press it in, but I don't have enough throat in my vice and don't have a press.

Then apply heat around the "hub" (staying away from the seal as much as possible) to enable the bearing, spacer, shims, and diff carrier to drop back in. The bearing is easily canted, which will cause it to jam - a few gentle taps with a piece of wood and mallet can walk it straight and it will just drop in. If more than a few gentle taps are required, then it's probably too far out of square, so best to (quickly) pop the bearing out and try again.

The shim stack had some "spring" to it as there were several shims (some quite thin) and if left to it's own devices, the carrier would probably have sat too high without something to press the gaps closed. So, once the stack was back in and things were starting to cool, I sat the differential on top of the carrier to weigh the stack down and keep it all together while everything shrunk back to it's final resting place.

Re-checking with my straight edge and feelers, I'm within a thousandth or two of the previous gap so I'm calling it good enough.

Using the same driver that I installed the seal with, I then supported the bearing from behind, and pounded the axle stub back into the bearing from the front - lubing the stub seems to help, and also is a nice thing to do for that new oil seal.

Re-install the circlip - this took few tries as my axles fit very close to the housing, so I had to pound it in, try the circlip, pound it more, try it, until the circlip groove was clear of the bearing enough to seat the circlip cleanly. Actually, the circlip dropped itself into the groove on the last few whacks it took to get the axle in as far as it needed to go.

Again, hope this helps anyone who needs to do this themselves.