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[polilara]

So, my turn to report about this. After 23 years the back plate is in such condition, should last longer I think. I am lucky as I have a spare back plate (new). I am just wondering:

1. Do I get troubles when trying to open those four screws holding the plate after this 23 years. Are the bolts going to somewhere where I can spray CRC etc. I cannot see the other end of three of them.
2. If the bolts can be opened I need to change the bearing as well? I remember that when removing the hub the bearing inner part separates somehow. I changed this side bearing about two years ago. I also heard that someone had made a cut to new back plate to install it without removing the hub and then welded the plate afterwards, any experinece?

[TheBoy]

When mine got (almost) like that, I swapped over the entire subframe from a donor, so its not a job I've done myself....

[Nick W]

The only way to fit the backing plate in one piece is to remove the hub. That's quite a lot of work, and as you say, will require extra work and expense to replace the damaged bearing.


I would cut out the section of plate that aligns with the brake caliper, so that it can be fitted around the upright. Once in place, I'd tack weld the removed piece back in. It's probably needed to retain the brake shoes and to keep dirt etc out of the mechanism, but doesn't need to be particularly robust.


The screws are accessible through holes in the hub, but the drive flange on the back means you can't get to them there. Thoroughly clean the bolt heads before you try to loosen them, use a well fitting tool and consider a hammer-type impact driver.

[polilara]

Thanks for comments, looking for suitable XZN-bit, 8 is loose, 10 is too big, is it 9 or 3/8?

[Enceladus]

It's a long M10 triple square splined bit; aka XZN. To the best of my knowledge it's the only XZN on the car.

[polilara]

Thanks Enceladus, 10mm does not fit, really not, I test tomorrow 9, where did you get this 10. How about inches as GM product, 3/8 is about 9.5.

[Nick W]

Thanks Enceladus, 10mm does not fit, really not, I test tomorrow 9, where did you get this 10. How about inches as GM product, 3/8 is about 9.5.

Why would a German designed, engineered and built car have 4 random, spline drive, inch spec fasteners?


From your picture there's a really good chance that rust has deformed your bolt heads, which will make undoing them interesting

[LC0112G]

If you remove the stub axle first you get better access to the heads of the bolts, rather than trying to undo them through the holes in the stub axle. Removing the stub axle will wreck the bearing though.

IIRC two of the bolts are in blind holes, so they don't rust from the 'wrong end' and are relatively easy to get out. The other two bolts are in open ended holes, so these do rust from the 'wrong end' - which makes getting them out very difficult. I've always had to use an angle grinder on them to cut a slot, and then hammer and chisel them round. Obviously this means you'll need new bolts to re-fit.

As Nick says, you'll need a very good snug XYZ bit to shift them. The heads are made of cheese, and once stripped you're doomed to the angle grinder, chisel and lump hammer approach.

Good luck - it's one of those jobs I pray never to have to do again.

[Enceladus]

Thanks Enceladus, 10mm does not fit, really not, I test tomorrow 9, where did you get this 10. How about inches as GM product, 3/8 is about 9.5.

The XZN triple square splines are mainly used on German manufactured / designed cars so I suspect that there is no such thing as an XZN spline in SAE inch sizes. The size on the backplates is definitely M10 unless maybe the bolts were substituted in the past. You may need to clean out crud and rust from the recess on the bolt heads, or maybe you are trying to use a standard spline bit.

The XZN has 12 x 90° points and a standard spline has 12 x 60° points. If you don't have the correct sized properly fitting bit then you will likely strip the splines out of the bolt heads.

I've got one similar (not a Facom) to this one here. You might get a bigger selection on ebay.de, so that might be better for you. EG something like this Expensive on the postage though.

[polilara]

Thanks Nick W, LC0112G and Enceladus, it's nice to get tips & opinions when doing something first time.

Bolt seem to be 10*1.25 and BOXO XZN which fits is marked M9, I bought a long 140mm version. As yesterday informed 8 is loose and 10 too large. I succeeded to remove three of the bolts, upper front is somehow destroyed, perhaps I did it last time when pulling the hub out with long wheel bolts. That one I have to drill out. Most important are the lower ones I believe, they take the braking force so I try to repair the thread of front upper after drilling.

Access was improved by removing the Back Plate first and then opening the bolts...

I did not know that there are two different spline angles, XZN fit was good and I could use happer type impact driver as proposed here. I already ordered new SKF bearing, I think that while I am there I can re-change the bearing and keep the back plate in one piece. Furthermore, I am not good welder and the plastic gas tank is pretty close.

[polilara]

Still working with this, only part missing is O-ring 24428129 between Back Plate and arm. Difficult to find. Does anybody know the size of it.

[Doctor Gollum]

Do you mean the hub rear seal?

[polilara]

Don't know, it is behind the back plate. If you check fig  acc to spare number you see. I cannot here enclose pic.

[Enceladus]

It's GM part# 24428129 for the newer backplates. The Opel KAT# seems to vary between 54-33-302 and 5-43-302.

I've no clue as to the size.

[polilara]

Driven so far without hand brake, MOT by Dec 2. so started to do something. Now new everything.., lower back plate bolts are original GM with "Low Cap", upper ones are normal Allen Screw. GM package contained 5pc of screws so now I have spares for the left side, too. Hard work in this age just in floor level...