Hi I've just removed the diff from the car for bush change and while cleaning the rear plate I noticed a hairline crack through the casing through where the bush sits, just using the experience of you lads on here do you think it's worth welding or should I buy a new one, some people say that a weld is stronger that the existing alloy thanks in anticipation.
Diff back plate
- Thread starter Derick Mills
- Start date
I think that would depend if it's an LSD or not. LSD yes. Non-LSD probably not.
Hi Derick, do you have a photo ? I think I grasp where your on about and any crack there is no good.
A weld will be ok as long as it is veed out well to give a wider repair area Derek.
Tony.
Tony.
see here from my build thread:..
"The polybushed diff seemed to not have the best effect, and whilst 30 miles from home this happened:
the diff bracket snapped leaving the diff trailing on the floor.
Tarmac and aluminium dont agree and I ended up wearing the bottom of the diff cover away
I limped to a local Homebase and got some chain and shaclkes to get me home...
I had the diff cover welded whilst ordering a new cover. This was on a six week lead time, only to be told after 5 weeks that they are not making any more..... so I was refunded!
anyway the weld is holding up strong...
Poly bushers out there be aware....."
the LSD back plate is no longer available from BMW, and no one sells them separately when they can get premium price for the full LSD differential.
Weld is the only way.
"The polybushed diff seemed to not have the best effect, and whilst 30 miles from home this happened:
the diff bracket snapped leaving the diff trailing on the floor.
Tarmac and aluminium dont agree and I ended up wearing the bottom of the diff cover away
I limped to a local Homebase and got some chain and shaclkes to get me home...
I had the diff cover welded whilst ordering a new cover. This was on a six week lead time, only to be told after 5 weeks that they are not making any more..... so I was refunded!
anyway the weld is holding up strong...
Poly bushers out there be aware....."
the LSD back plate is no longer available from BMW, and no one sells them separately when they can get premium price for the full LSD differential.
Weld is the only way.
Attachments
That's exactly where mine has gone, what a p*** poor design
Also where does one get a gasket from , I used to make my own by taping round it with a hammer but maybe not on cast alli
Thanks for all your help so weld it is then.
Thanks for all your help so weld it is then.
Repair is the best option Derek. I have a gasket punch for tapping out the holes if you need it. I made it when I was an apprentice many years ago but I still have it, if you need it. You can make a gasket on alloy just the same, you just have to be gentle mate.
Tony.
Tony.
Thanks Tony don't suppose you know any good alloy welders local mate
Derick
Derick
I have the details of a very accomplished welder in South Wales if you want his details. He specialises in chassis restorations and is also a panel beater/fabricator including in alloy. PM me if you want the details. I expect he would accept it posted.
- Joined
- Oct 19, 2014
- Points
- 174
- Model of Z
- 2.2i Sport
Twenty year old car got problems? Not too bad, really.
Hi mate, when I was at work we used a company in Lincoln called Keyweld.
They're on Lincoln Fields just off A46
Tony.
Thanks all
Were you running the stock bush on this?
What mileage and what engine?
Can materials like this suffer from ‘casting’ defect when made that causes these problems?
Mine is 22yrs old with 135k miles, the last 5yrs with poly bush and it hasn’t cracked yet - gets used properly too.
When I was looking at uprated diffs I spoke to a place that builds diffs for race and rally BMW cars and they don’t worry about the single ear diff mount - his experience was if they haven’t broken yet they won’t so he has race and rally cars using that design. Seems to be something in the build process as likeThe boot for issue- some cars rip the boot floor out with light use and others never do even with ‘proper’ usage?
Something to muse over, aluminium work hardens. May be if the bush does not fully damp the vibrations the aluminium alloy casting will harden and go brittle ?
- Joined
- Oct 19, 2014
- Points
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- Model of Z
- 2.2i Sport
Maybe someone changed the bush in the past and nicked the casting with a hacksaw while cutting the outer ring? Or maybe it was owned by a ham-footed tw@ once upon a time.
This is quite common, see this on a few cars.
the crack looks too curved for an old hacksaw cut.
- Joined
- Oct 19, 2014
- Points
- 174
- Model of Z
- 2.2i Sport
Without having a good close-up look it would be impossible to tell, and even up close it may be difficult, but you'd only need a small nick in a stressed part like that for it to spread and eventually wind up looking like that, if not worse. A lot worse. That'll be why when I cut my bush out I did the cutting on the thickest part there was, very carefully. It's quite possibly nothing to do with any cutting, just a 20 year old bit of aluminium that's had a hard life. Welding should sort it, so long as there's someone competent around.