'71 Opel GT rearend

[blancojp]

Hi guys!
I have a '71 rear end that a few brackets need to be welded to the outside of the area where the axle bearing is located. Just wanted to know how thick that area is because I really do not want to take the axles out just to weld two 3" brackets.

[GTJIM]

Welding near bearings is a bit of a crap shoot - stray currents can waft through a bearing and leave nasty craters and lumps (bit like the erosion on a set of points!). Also the bearing housing can distort with too much heat on part of the circumference.
Best to remove the axles/bearings and fit some lumps of shafting turned to the outer bearing size which will act as heat sinks.
There is always a price to pay for quick-and-nasty ways of doing jobs like this. The outer bearing race has lots less mass than a chunk of 3" shafting closely fitted to the bearing housing and distortion will put the race out of round.
Removing the axle/bearing you can check for distortion when refitting it and scrape the high spots out of the housing - rather than 'hoping' everything is OK.

[blancojp]

We doit all of the time to Ford axles but they are quite hefty in comparison.
We also put heat absorbing compound, a putty type compound, around the areas which we are not touching. This is needle bearing rear end unit which I believe it is not as strong as the late '72 rear end.

Well no matter, just have to take the axles out and get it done right.
Thanks

[GTJIM]

Originally Posted by blancojp This is needle bearing rear end unit which I believe it is not as strong as the late '72 rear end.

It is not the strength of these earlier diff which is the problem but the fact that outer (wheel) bearings are no longer available and that the rollers run directly on the axles. The axles are also held in with the dreaded GM "C" clips so that the axles come out when the clips break. Also the axles have some in-out movement which makes them NBG for converting to disc brakes.
Far better to replace them with the later diff having conventional wheel bearings held on to the axle by a shrink sleeve.

The heat absorbent paste is good in limiting the effects of welding heat but it is the shrinkage of the weld itself which distorts the bearing housing bores waaay out of round. Just speaking from the experience of the poor mugg who gets to fix this sort of 'quickie' modification after the wheel bearings crap out in a few thousand miles ...... far better to bolt stuff on using the brake backing plate bolt holes! IMHO