Snapped a bolt in the rearend

[Trueoo7]

Don't know how....since new, I have not pulled even one hole shot with it, not that I haven't been tempted but I somehow snapped the bolt that holds the rear axle carrier to the rearend. Half the bolt is still in there which should make for some fun trying to get it out.
I did change out the coil springs last year due to a production change and now I'm wondering if this had anything to do with it. Did all the bottoming out prior to the switch have an effect or is it the added tension caused from the new ones?

[Clois Harlan]

What linkage are your running? Upper and lower controll arms, three link, or something else? What grade of bolts are you using (Grade 5 or Grade 8)? I have seen that Backdraft launch at the drag strip with slicks and never have a problem.

To remove the bolt get a cut off tool and a center punch and jack up the rear of the car and remove some of the load on that point. After cutting off the head of the bolt try and drive the bolt out which ever side is most convient.


Clois

[trularin]

Is it possible you over tightened it? ARP claims I over tightened my flywheel bolts when I told them one broke.

Funny thing is, the Ford bolts work fine.

[vince911cobra]

If I remember correctly after talking to several BD owners when I was considering getting a BD, this has been an ongoing problem. Give Reg a call, I believe their may be an upgrade available now. I believe the bolt and threads are special to BMW if memory serves me correct.

[Nor Cal Al]

Clois, BDR runs the BMW complete rear carrier frame and suspension.

True007, I had my rearend out and there is only the one bolt going into the forward end just above the u-joint connection. There is just one bolt. They had said it was a hex head but mine turned out to be just a metric bolt. I do not recall the size. So maybe you will have to do the drill and easy-out trick on it. It probably has threadlok on it also. You need to contact Reg to get spec on that bolt. Maybe e-mail Tony at the factory re: breaking it because they race these cars a lot at the factory. Good luck..
AL

[DC COBRA]

True007

I believe that bolt may go allway thru with open end at rear on diff side, don't really remember, been a while since I changed my diff out. For some reason I don't think it was a blind hole. Don't know what the current fix is but it used to be that you drill the hole out and tapp it to the next size of american threads I think it is 1\2 or 9\16 or 5\8 not sure but you can replaced the bolt with a grade 8 quality or better and be thru with it. Might consider going with a solid diff mount while you repairing this problem, pretty sure Reg has them in stock. This used to be the fix for high horsepower cars.

DON

[Speedysnake]

Hey,

i was just looking at the diff. in my BDR. Which bolt are you speaking of? I see a single bolt on the front, right hand side of mine, with a socket head on the forward end. Is that it??

[Cashburn]

I am aware of the factory going to a larger bolt at some point in production. As others have suggested... call Reg and if you get him, tell him to call me back.

[DC COBRA]

SPEEDY

I believe you are looking at the correct bolt, is yours broken yet?

DON

[Speedysnake]

DON

Nah, mine looks good, in fact, it's an allenhead bolt, which I believe makes it a grade 8, I'm a little rusty on that stuff , but I figure it's something to keep an eye on when i'm inspecting "down under"

Thanks,

Paul, speedy

[Trueoo7]

Yes it is the bolt right next to and below and to the right of the driveshaft output plate that broke. (when looking from front to rear) I don't recall if it was a hex or allen head. At first I thought I could do the easy out trick but after thinking about it.... the bolt #17, according to this diagragm,

http://www.realoem.com/bmw/showparts...66&hg=33&fg=30

is not threaded all the way to the head. So if I try to drive the bolt the rest of the way through and out the back (which is open) it may get jammed up if it broke on the part of the bolt thats not threaded and if I try to back it out the way it came in and don't have the hole lined up with the bushing correctly it will jam too. Sooo..... it looks like I'm about to learn how to remove the diff in this car. Thats probably the best way at this point, I just don't look forward to dealing with the torx head bolts that attach the axles to the diff. Should I try to wrench them out by hand or hit them with an impact wrench? I damn sure don't want to strip them. Looks like if I remove the sway bar I should have enough room to manuver it out of there without dropping the gas tank.

DC Cobra What do you mean by a solid diff mount? Is that a type of differential or is it just a solid mounting point because it does look like there is some sort of rubber bushing that the bolt passes through now. (or should I say did) I would imagine its pressed in there and can be replaced if needed. At some point in the near future I will give Reg a call to see what he suggests. Hey Jay, I'll let him know he owes you a call and if this doesn't work I may have to pay you a visit with "car in tow".
Thanks guys I'll keep you posted.

[DC COBRA]

True007

That bushing will come out of there, you might be able to remove the other bolts at the back of the diff (2 of them), this will allow the diff to somewhat float maybe enough to get better access to the bolt, beats the heck out of pulling the diff. Although that is not that bad of a job. Pop that rubber bushing out of the front and knock the solid bushing in, put bolt in and it is a done deal.

DON

[Cashburn]

I got him, thanks.

Don't know when your next trip through town is but we have diffs out and in all the time. Changing joints and seals to ensure things are 100%. The solid bushing upgrade is pretty good, don't think you're making that much power to necessitate it, but it's a good little upgrade if you are in there anyway. We usually have the solid bushing on the shelf too.

[Rick Parker]

Parts list says it is a 12mm X 1.5mm thread pitch 80 mm long

[JayBar]

I had the same problem. Reg fixed it. I believe they drill out the borken bolt, then drill out the hole also. They then installed a grade "8" (it think) nut and bolt. What ever the grade of the replacement is is stronger than stock and now that it is not threaded into the housing if it brakes the replacement is much easier.

[Cashburn]

Kevin,
Expecting the bolt on Tuesday or so. Make sure you email your mailing address for the new bolt.

[Trueoo7]

Well I ended up removing the diff, not to bad of a job, about 2 hours. I don't think the bolt was tightened all the way because it had some play in it which is evidenced from the oblong hole it left in the bushing and the begining of the housing. Brought the diff up to Vintage Motorsports for there opinion and they said it should be fine. They drilled it out and retapped it for me, thanks again Jay and they're sending me the new bolt.
This is kind of interesting though, since I had the diff out I figured I'd change the gear oil in it because it doesn't get any easier when its out of the car. I removed the plugs and tipped it upside down over a drain pan and let it sit for about an hour. When I tipped it back over I found the head of a hex bolt with about 1/4" of thread left on it in the drain pan. Its a 10mm hex head. Part of the bolt went through the gears at some point which is evidenced from the jagged end. I removed the back cover to have a better look turned the gears all around but I don't see any obvious damage. Stuck a magnet all around inside but didn't find anything. Its the same size as the two bolts that hold the speedometer sensor in place (which were not missing). Don't know how it got in there but I guess I dodged another bullet with this car. Sure glad I decided to change that fluid.

BTW anybody know where I can order a new gasket for the back cover?

[Cashburn]

Kevin,
The bolt went out the other day, bet you have it Monday. As for the gasket, you are better off using rtv instead.

[Trueoo7]

Jay
I finally got the bolt on Wed. and it fits fine, thanks. Could you ask Brian if he has any specs for torquing the following:
Back cover on Diff
Axles to Diff
Diff into cradle
Driveshaft to Diff

Thanks
True