BMW Diff conversion...thoughts?

[wader3]

Hi, I'm wanting to change the diff and BMW seems the way to go. Does anyone have experience of this? There's a Monarch conversion where just the BMW diff is used (sounds easy and straight forward) and I think I've heard of a full conversion.

Anyone got any thoughts as to which is best?

[Guest]

Stagdad has a BMW conversion, he’s the man to talk to, he’ll be along soon I’m sure

[jpyke]

Stagdad has a BMW conversion

Me too, although mine was from another vendor, not Monarch. The conversion works very well, but I cannot advise you to consider the vendor I used, as I had a very bad experience - you'll work this out from forum searches, if not, drop me a PM.

Due to the problems I had with the vendor, I had to complete the conversion myself and I approach Alasdair at Classic Driving Developments to see if he could produce a variant of his CV drive shafts to suit the BMW diff, which he kindly did, and are now available for sale.

The conversion I have uses an E30 diff, which are getting harder to find these days, but not impossible I believe.

[Stagdad]

I have the complete bmw subframe mod and have spent many many hours redoing it as the symmetry and quality of engineering was appalling. The idea is good and basically I paid big money for an idea. When I get home on the pc I can show you some pics of the failed parts. The company I got mine from has now changed hands so I can't comment on the president offering. What I should have done is thrown it all back at them for a refund but the problems evolved as the insulation progressed and then I was too far gone.

On the plus side I have had a lot of welding practice.

The feel of the bmw parts even though they themselves are knocking on 30 years old are superb. Things like the double cv jointed driveshafts and the diffs feel very tough. And of course you get disc brakes.

[wader3]

Me too, although mine was from another vendor, not Monarch. The conversion works very well, but I cannot advise you to consider the vendor I used, as I had a very bad experience - you'll work this out from forum searches, if not, drop me a PM.

Due to the problems I had with the vendor, I had to complete the conversion myself and I approach Alasdair at Classic Driving Developments to see if he could produce a variant of his CV drive shafts to suit the BMW diff, which he kindly did, and are now available for sale.

The conversion I have uses an E30 diff, which are getting harder to find these days, but not impossible I believe.

Sounds like this is a good off the peg solution and if it means using all existing body mountings it should all line up ok. Seems Monarch do a drive shaft too. This could be the easier option...

[wader3]

I have the complete bmw subframe mod and have spent many many hours redoing it as the symmetry and quality of engineering was appalling. The idea is good and basically I paid big money for an idea. When I get home on the pc I can show you some pics of the failed parts. The company I got mine from has now changed hands so I can't comment on the president offering. What I should have done is thrown it all back at them for a refund but the problems evolved as the insulation progressed and then I was too far gone.

On the plus side I have had a lot of welding practice.

The feel of the bmw parts even though they themselves are knocking on 30 years old are superb. Things like the double cv jointed driveshafts and the diffs feel very tough. And of course you get disc brakes.

Like the idea of better brakes, but it does sound like a lot of potential for needing adjusting and re-work which I've had my fair share of already, so not sure I want to risk it! What diff does that use? E30's do look scarce...

[Stagdad]

Like the idea of better brakes, but it does sound like a lot of potential for needing adjusting and re-work which I've had my fair share of already, so not sure I want to risk it! What diff does that use? E30's do look scarce...

It is e30 medium case diff 188 crown wheel. I think later e39 are similar. When I did mine you could pick a diff up for £40 now they are more like £200 but still a lot cheaper than a stag diff. I have a spare in the shed.

[new to this]

Me too, although mine was from another vendor, not Monarch. The conversion works very well, but I cannot advise you to consider the vendor I used, as I had a very bad experience - you'll work this out from forum searches, if not, drop me a PM.

Due to the problems I had with the vendor, I had to complete the conversion myself and I approach Alasdair at Classic Driving Developments to see if he could produce a variant of his CV drive shafts to suit the BMW diff, which he kindly did, and are now available for sale.

The conversion I have uses an E30 diff, which are getting harder to find these days, but not impossible I believe.

The fool in the workshop next door to me broke an E30 last week,but before i could get to it,also broke an escort again before i had chance to get the sunroof

[Klaus Schlueter]

This chart shows that there is not much choice if you want a E30 diff with 3,7 ratio.
Klaus
e30 Differentiale.jpg

[Guest]

I converted to the bmw e30 diff last year. I converted the orignal diff bracket to suit the bmw diff. I left my half shafts as they are in good condition. Only other mod was shortening the drive shaft.l had a friend lathe the transition pieces to go from the bmw 6 stud pattern to the stag 4 stud pattern

[Stagdad]

This chart shows that there is not much choice if you want a E30 diff with 3,7 ratio.
Klaus
e30 Differentiale.jpg

3.7' we'e quite easy to get hold of when I did mine. Plenty floating about on eBay, I got one but sold it as the 3.64 seemed to work well. I also have a 3.46 in stock.

[djw113uk]

I fitted the BMW in Triumph diff to my MK2 saloon with some expected difficulty. I have just fitted the same kit to the stag.. and it isn't as straight forward as I expected. I was finally happy with boot clearance, propshaft etc, so fill it will oil and went to refit the exhaust... Is it just on my car, or will the standard stag intermediate rear pipe not fit around the BMW diff? Another delay that I don't need just before the RBRR on Friday!

[wader3]

I fitted the BMW in Triumph diff to my MK2 saloon with some expected difficulty. I have just fitted the same kit to the stag.. and it isn't as straight forward as I expected. I was finally happy with boot clearance, propshaft etc, so fill it will oil and went to refit the exhaust... Is it just on my car, or will the standard stag intermediate rear pipe not fit around the BMW diff? Another delay that I don't need just before the RBRR on Friday!

I'm yet to do mine, hopefully next year although the 3.73 diff is getting hard to find. An LSD one just fetched £726 on ebay. Did you fit the Monach kit? Picture's would be good!

[mike@thenook]

Do you need something with greater power handling ability like the BMW diff or just because you think its not possible to get a good recon/new stag unit?

If its the former I understand more but otherwise I'd stick with the Stag unit as for a standard car you definitely don't need discs on the rear and it is (as others say here) a very complicated job with not necessarily great outcomes.

The one particular company not mentioned here by name was the subject of a TV programme recently (Baliffs) and is Weslake - avoid at all costs!

[wader3]

I'm not fussed for the brakes, but I've had the diff apart twice to try and cure the leak from the quell shaft and also the the nasty whine at 65-75 mph. I've had professional consultation and set up as per factory. It's almost perfect going by the book, just slight wear in the planet gears. New top quality bearings and seals. But it still leaks badly and whines. I don't want to drop it again in the hope i could make things slightly better, I want a quiet dry diff and sadly the Triumph one will not deliver. I don't think from what I've been told, the Triumph diff was good even from new.