Crack in Diff to Subframe area - Spot welds in the Boot?

[spurs fan in a coupe]

Hello all,

I have had a few issues recently (never sure where to post these things as my car is neither a roadster or an ///M).

Firstly a sub 5mph prang sees my car (finally) going in for some body work next Tuesday. Can't wait, bumper and bonnet re-sprayed, my car is (as has been since I bought it) covered in stone chips. It will transform the car.

Then - my exhaust started blowing, soundly like Colin McRae's old Subaru! Took it to Powerflow dealer in Slough, where I work. Naz said a rear silence cut out and stainless steel replacement pipe would be fine.... it is, sounds great and was cheap! I would recommend them!

Sadly - Whilst in the air the guys noticed the attached issue. The rear differential link to the subframe has cracked. I've been on here long enough to know that there are boot weld issues with Z3s so I have been studying some photos and I think I have the problem!

So ...... anyone know a sympathetic dealership near Surrey (Woking) who might be able to help me and fix these issues cheaply or free!

Thanks

(bad night for Spurs yesterday... you can try to be original but I think I heard it all today and then see my car hanging to pieces! not a good day!)



I know the photos aren't that clear but they just about show the exhaust back box on the left and then the crack in the mounting above slightly to the right

[pingu]

Looks like it was spotted just in time. You must have crouched down to get those pictures.

Forego any thoughts of getting it fixed four free unless you have a FBMWSH.

It takes about two days to do the job, and can be a real struggle.

Exhaust rear section off
Diff off
Plate and repair damage
I'd replace the diff mounting while it's off
Refit diff
Refit rear exhaust section

I did the job on mine last month.

On the football, I'm really on your side and hope Spurs give a good showing at White Hart Lane.

[spurs fan in a coupe]

Thanks Pingu,

I know it is going to be a big job!

I have even thought of selling up as a result but I just love my little Zed too much!

I think it was your video on youtube I was watching last night, gives me hope!

p.s. I've nearly recovered from Tuesday night and i'll be there on Wednesday to see us fight back! I'm a glutten for punishment!

[Adam]

Forego any thoughts of getting it fixed four free unless you have a FBMWSH.

You will be lucky full stop now to get anything off BMW regarding this issue. I have the FBMWSH and contacted dealers, customer service and had so much documentation on it all regarding the issue and previous cases (thanks to this forum) and I was told to basicly go take a running jump by BMW

[G2JRP]

I am in the same position as Adam, paperwork to die for and past cases that they have repaired, but BMW were not interested. Its over 10 years.

Hope you get it fixed though.

Thanks for the badges I am hoping to fit at the weekend.

[c_w]

If that's all that's gone then it isn't that big a job; the rear boxes from off easily to get some space round it (or maybe just the left box). From the looks of you won't need to remove the diff, just take the weight off it and re-weld the bracket back up.

I would recommend buying a new bracket though, but these can be adapted to double up over the exisiting bracket to provide a stronger fix, also worth strengthening elsewhere, but if it's just the bracket that's cracked then it would by an easyish fix.

[Gazza]

just take the weight off it and re-weld the bracket back up.

That's what I would do.

[pingu]

I'd take the diff off rather than trying to work around it. After you have learnt the technique it is not too bad a job. Not easy with the wrong technique, though. It is heavy (40 kg).

http://www.zroadster.net/forum/viewtopic.php?t=29172

[spurs fan in a coupe]

UPDATE!!!!

not good news

Photos tell the story but basically I got the car up in the air and once I took the exhaust heat shielding off the full extent of the damage could be seen.

My Dad is a mechanic but steers clear of the majority of welding and as the problems grew we have decided to leave it to the experts.

So I have stripped out the carpet etc. from the boot (took ages) then started to investigate the sound proofing only to realise you could see the outside world through the floor of my little Zed.

Not happy

I'll keep you all updated!


Diff bracket


Crack by N/S rear exhaust mounting


Heat shield off - OH DEAR!



Started to clean up the areas that need welding/patching


ARB (anti-roll bar) area is the worst affected


Most of the boot trim off


Boot floor doesn't look too bad!


Nut is the one that holds my tool kit in


Started to chisel off the stupid glue they smeared all over the floor


Rusty looking area is held together by glue


Two knackered welds under a bracket in the boot!


Oh well, I still know which one I would rather own!



Any comments very welcome, helpful ones please as I've had a bad day!

[Titan]

Any comments very welcome, helpful ones please as I've had a bad day!

Sorry to see this news
But it's not been such a bad day - ManU lost after all
At least when it's fixed, you will know that the car is sound underneath as well as resplendent in its new top coat
And you can always trade it in for that white Roller

[pingu]

The more you can take off for access the better.

I would replace the diff mounting rather than repairing it. You will still need to weld in the new one, but I think it would be stronger.

You have quite a challenge ahead, but I've really got into welding and I would quite enjoy having a go.

[Gazza]

Andy, you are approaching this in the right way, well done

[Ian Kelly]

Look on the bright side, you're still in one piece and so is the rest of the car. It could have failed on you (big time) when being driven enthusiastically which could have been a disaster.

If you have access to a decent workshop space and can afford to spend some time on the car, then you'll end up with a strong repair and comfort in knowing that the rear end is sorted. The actual cost of the bits you need shouldn't be too much, just need access to a good welder.

Best of luck,

Ian

[TitanTim]

Sorry to see that hopefully it will get sorted and you can enjoy the Zed again

Seeing this has really put me off ever buying an M or even a 3.0L now unless the work has been done properly, maybe it will be a Z4 next time around

Tim.

[myredzed]

As you've got friends who are handy with welding it might be worth getting hold of a Randy Forbes repair kit for this. IIRC he ships these with an instruction sheet and offers lots of support online. You can contact him at randyforbes@aol.com

[Hard Top]

Ouch, and on a 2.8 !!

HT

[spurs fan in a coupe]

Yes HT - it hurts!

MyRedZed - thanks but the email I just sent him bounced right back, i'll google him later.

TT - mine is only a 2.8 but has done nearly 150K since 1998 so has faired pretty well.

Ian - thanks it will get done to a high standard so in the end it will be great, should make selling it one day easier to a Zed lover but explaining the work to a novice will be trickier (I suppose I could avoid the question by not mentioning it!)

Gary - long time no see - Surrey Meet? - I must admit to thinking about eBay when I first saw the damage when I got my exhaust mid section replaced. But I'm too honest to sell a wreck to someone.

Pingu - shame you're not in Woking as you would love my car at the mo!

Titan - my northern friend, indeed a newly welded rear and re-sprayed front end will cheer me up when I finally get out for a real blast!

Enjoy your Sunday guys and gals. BBQ time for me!

[spurs fan in a coupe]

DONE! ! !

Got my car back yesterday, a trip to White Hart Lane to watch one of the best games I've ever seen meant I haven't been far in her yet but the short journey I have made was wonderful!


Some photos of the work carried out.

Must say that Tony at Allwood Engineering, Woking Surrey

01483 740743

is a great guy and has done a terrific job, quickly and helpfully.

[Gazza]

Just need to colour math now and job done

Yep, we met at the Surrey meet at Newlands Corner

[pingu]

It all looks very familiar .

Nice job.

I used smooth blue hammerite to protect the bare metal (blue car). I'd suggest you get under there with some smooth red .

[Robin]

I've often thought 2.8's may well be susceptible to this as they have almost the same torque as M///'s.
I was fortunate my car was just under 10 years old when this happened so BMW paid for whole new boot floor pan & thicker diff mount. About £2.5k's worth with labour.
http://www.zroadster.net/forum/viewtopic.php?t=20157
It's one reason I'd be wary of ever buying an M/// that hadn't had this problem sorted with the beefing up etc.
So I'll be keeping mine long term.

[Robin]

Discovered today a recurrence of popped spot welds & torn chassis components. This after a complete new boot floor pan fitted by BMW about 4 years ago.

However the photo shows BMW didn't address the full problem in such a way to prevent a reccurence.

The only part that's not failed this time is the stronger diff arm bracket they fitted at the time.
viewtopic.php?t=20157

Clearly the OEM cross member & welding isn’t up to the job. What were BMW thinking both in the design stage & the repair stage!

The repair needs to be more than just re welding what's there if it's to last.

Does anyone know if there's a strengthening kit?

I think the Randy Forbes one mentioned is just for the diff arm bracket

Thanks

[Jonttt]

Ouch

I think Randy's kit includes the parts required to strengthen the boot floor cross member with the option being to fit a double eared diff bracket ie there are different options to his kit.

I read a post on bimmerforums a couple of days ago stating his server would be down for a while whilst he is moving house so it may be worth PMing him on there.

He has posted on here but not very often and not for a while.

[Robin]

Thanks John
I'll email him
Robin

[Deano1712]

Oh dear. That looks terrible. I remember seeing the pics of your repair - it looked extensive but was obviously badly executed. Any chance of bmw fixing it? You are probably better getting it made stronger via another route though. Its a worry for others who managed to get a free bmw fix done. Maybe free but not a permanent fix.

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[Robin]

I don't think it was badly executed so much as not an improved. They just replicated the way the car's are put together rather than strengthen anything, other than the diff arm bracket.

[c_w]

I would say it was badly executed if they were fixing a problem but ignoring the reason why it failed, so that it happened again. I'd take back to BMW looking like that! What a huge waste of labour taking the car back the bone at the back end and stitching in a new floorplan that was just as weak as the original!

[Robin]

I would say it was badly executed if they were fixing a problem but ignoring the reason why it failed, so that it happened again. I'd take back to BMW looking like that! What a huge waste of labour taking the car back the bone at the back end and stitching in a new floorplan that was just as weak as the original!

Couldn't agree more. Seems absurd for them to think the spot weld at the key point that's popped would ever be sufficient to transmit the immense force from the diff arm via the cross member to the floor pan!
I recall someone saying S54's are seam welded?
Would've been good for my repair.

Letter sent to Scotthall detailing the initial repair of the structural failure due to an inherent
weakness in the design has subsequently failed because initial cause not addressed.
Requesting it be rectified as the repair done under warranty is unsafe.

[Jays Zed]

Quite a disturbing post. Think I'll be having a good look at mine over the weekend. I'll certainly be keeping an eye on this topic and will be interested to see what BMW have to say about what is definately an inherrent design fault!!!!

[c_w]

I doubt any car is seam welded, but the S54 may have received more spot welds, but the gauge of the metal is too thin and really it needs plating on the left hand side.

[Jonttt]

Yep extra spot welds on the S54's and I think the thicker diff bracket (would have to check part numbers) plus extra sound deadening to hide the spot welds lol.

[c_w]

The replacement diff bracket I got for mine was microscopically thicker than my old one, still far too thin. You would have thought BMW would just think, "lets go OTT and make it beefy enough to handle anything", but they just went and increased it by about 0.5mm which probably according to their CAD increased torque duty by a fair amount but in reality it just too flimsy still.

[Robin]

The replacement diff bracket I got for mine was microscopically thicker than my old one, still far too thin. You would have thought BMW would just think, "lets go OTT and make it beefy enough to handle anything", but they just went and increased it by about 0.5mm which probably according to their CAD increased torque duty by a fair amount but in reality it just too flimsy still.

Penny wise & pound foolish. Possibly a case of engineers managed by bean counters.

[Deano1712]

I measured the diff bracket at just 0.2mm thicker than the original when I upgraded mine. I did some stress calcs though and found the hanger bracket was plenty strong enough. I think it only fails when the upper floor welds have failed and the cross member starts moving around - the diff hanger cracks as a secondary failure.

[Robin]

I measured the diff bracket at just 0.2mm thicker than the original when I upgraded mine. I did some stress calcs though and found the hanger bracket was plenty strong enough. I think it only fails when the upper floor welds have failed and the cross member starts moving around - the diff hanger cracks as a secondary failure.

That kind of makes sense. In which case they needed to beef up the cross member more than the diff hanger, but they didn't. Hence failure for the 2nd time.

[Damon]

Add another one to the list. Mine looks very similar to yours Robin (second time round). Getting mine sorted this week. Anyone else in Milton Keynes have the same problem? I can put you in touch with my garage (after they have practised on mine)

[Southernboy]

Here's my answer....


....and reweld the bootfloor to the crossmember with re-inforcing plates...

[Kornknarr]

Sorry to see your damage but you were lucky you did not have your diff and crossmember falling out wile driving. I would strongly suggest that you read up on this thread: http://forums.bimmerforums.com/forum/showthread.php?1979601-Subframe-trunk-floor-differential-mount-failure

To just patch it up is not OK I'd say. You need to take care of a lot of things with so extensive damage. I bought Randy Forbes kit and spent a few weeks this winter (because I only could work on the car intermittently) installing that and fixing up different things in the back of the car. With the amount of rust on yours that could be a good idea.

You can see what I did here: http://perkornhall.se/Per_Kornhall/Subframe.html

On Randy Forbes web page you can see how he has patched quite a few cars: http://www.spcarsplus.com/gallery3/index.php/

Again, it must be awful to discover, and I hope you get it sorted!

Per

[Rocketman]

Damon,

I am in St Neots (near MK) and would be interested to hear where you get your boot floor sorted. I actually have the Randy Forbes mod kit waiting to be fitted but have not yet sourced the Diff cover required or a decent welder to do the job. I am currently monitoring the spot welds, not drastic yet but some have pulled.

Regards

Rocketman

[Damon]

I'd love to see a picture of the components that make up the Randy Forbes kit. I've seen so many pics I'm not sure what you'd get if you ordered one.
Also, I'm going to stick with the single ear type mount. Keeping everything as standard as possible has to make it easier for your welder to get it right.

Remember to check under the car too. Mine didn't look too bad until I looked at the underbelly.

[Rocketman]

Damon,

When I get a chance I'll unpack the Randy Forbes kit and take a picture of the component parts and post.

Regards

Rocketman

[Kornknarr]

What you get with Randy is:

1. Precision cut pieces to build what will be an I-beam inside the crossmember and it will be connected to a strengthened part of the body on the sides. Check out his pictures. You can chose between using one ear or a dual ear. He provides the parts for dual ear but you will have to buy a new cover. If you go one ear he suggests you use your old + weld on a new. He has images of how that is done also.

2. But, the other thing you get with mr Forbes is detailed instructions and very fast support via mail when you need it. Mr Forbes is a fellow enthusiast and a nice fellow!

I'd suggest you mail him (Erandyforbes@aol.com and get some answers from him. He has fixed 100+ of our cars.

Bite the bullet and you'll get a car you trust and that you can play with...

Per

[pingu]

I am currently monitoring the spot welds, not drastic yet but some have pulled.

Get it sorted. It will get worse.

[Damon]

I am currently monitoring the spot welds, not drastic yet but some have pulled.

Get it sorted. It will get worse.

What he said. Its probably already worse than you think. I wish I'd sorted mine sooner.

[Rocketman]

So can anyone recommend a reliable quality workshop in my area capable of carrying out this job then ?

St Neots, Cambridgeshire but could travel.

[Damon]

So can anyone recommend a reliable quality workshop in my area capable of carrying out this job then ?

St Neots, Cambridgeshire but could travel.

It's so hard recommending a workshop to someone. It's a welding job. You need to find someone with good metalwork and welding skills. They also need the facility to remove then replace the diff.. I know a couple of good welders, through my work, but they only weld and don't have workshops. I know good mechanics that aren't good welders. It's difficult. You have the Randy Forbes kit don't you.... I would print out a few pictures from Randy's site showing the work . Take them along with the kit and instructions to several places and pick the one you feel most comfortable with.
I pick mine up over the weekend. I'll let you know how it went. He wasn't fitting the RF kit though. I've had the slightly thicker diff mount fitted and everything seam welded with some strengthening on the near (lh as you look in the boot) side. My car no longer relys on spot welds. It was a full day just welding.


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[Rocketman]

Damon,

Would be very interested for feedback on the job you had done and where it was done. As you say I have the RF kit but this is not necessarily the method I will finally go for.

[petecossie]

Rocketman,

On the M3Cutters site there is company based in Bristol, Reddish Motorsport, who have been doing great work on the E46 M3 floor/rear subframe repairs. They may not have done a Z3 as yet but it might be worth contacting to see whether they could do a repair. They even have a menu of costs for the M3 so you know how much it work out provided no hidden suprises turn up. The write up on the repairs they have carried out makes excellent reading. You just wonder why BMW didn't come up with a stronger design in the first place on both M3 and Z3 axle location points. Ok it's 130 miles from you but the quality of their work plus the ability to cover all aspects of the repair would make it worthwhile.

Link from Cutters site

http://forums.m3cutters.co.uk/forumdisplay.php?f=78

[Rocketman]

petecossie,

Thanks for that. Great info. That's just the sort of place I would like to have do my repair. Couldn't see an e-mail address for them but I will phone them later and try and get one, then e-mail them the details of the Randy Forbes kit and the fitting instructions and see what they think. I was born in Bristol so maybe it's about time I went back for a visit!

Cheers

Rocketman

[Damon]

Well I've had mine done now and I'm very happy. I would certainly recommend them. The paint he used is even a really good match for Estoril blue. I've mentioned fitting the RF kit and he is up for it. He used to prep race cars in his younger days, including seam welding the chassis.

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