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theblue 08-26-2009 10:01 AM

output shaft / diff broken (pics)
so I was driving downtown to get a haircut and I hear a *bang* followed by my car refusing to engage in any gear. So I coasted/rolled to a safe spot and inspected the car.

This is what I found:
my 3.23 M3 diff (installed by me a few months back), broken mounting point

output shaft, with a few bolts backed out, others bent/stretched.

I think what happened was that a couple bolts on the output shaft backed out and then the rest get over stressed and forced their way out. Once the output shaft was disconnected, the diff tried to pull towards the other side and snapped the mounting point.

I did torque the bolts connecting the output shaft when I installed the diff a few months back, but I didn't locktite them.

the questions:

is my analyst reasonable / correct?

can I swap the guts of this diff into my factory non-LSD diff (or do I need a whole new LSD?)

what other damage might have been caused (drive shaft?)

if I remove the messed up bolts from the output shaft, it is safe to use again with new bolts?

theblue 08-26-2009 12:43 PM

I had somebody suggest just replacing the back of the diff if the internals are undamaged. that plus rebuild the output shaft and I might be back in business.

the gasket for the rear cover on the diff has the same part number for both the M3 and 328 diff.

The rear cover has a different part number for each. So I would speculate that I can use my 328 cover on my M diff as long as everything fits inside.

that leaves me with inspecting and possibly rebuilding the output shaft if needed.


T.Dot_E30 08-26-2009 02:49 PM

The diff is mounted securely without the need for the drivershalf or output shalf to be attached, they are not supporting any of the weight of the diff.

I find it every hard to believe your assessment. Although likely, i think it were more parts of failure and rather the driveshalf and outshalfs is a symptom not the source of the problem.

I would first check all other mounting points of the diff. If the diff wasn't properly mounted or a few of the bolts came off, the rear mount would be the only thing holding it and it would eventually break off.

I would also check all your rear subframe mounting points, they have a history to tear apart on e36s. If your rear sub-frame came apart and is loose enough I can see how that would put alot of pressure on the diff, snapping the mount.

Once you get that car on a hoist, it would be pretty easy to tell what happened.

theblue 08-26-2009 03:24 PM

imagine you only connected the driveshaft and one of the output shaft and then attempted to drive the car... this is basically what happened and would expect one of the mounts on the diff to let go, however in this case the diff cracked instead...

jeffrie 08-28-2009 02:37 PM

I snapped one CV axle bolt before in Nascar318is's car and with just one bolt gone on one axle it had a very noticable shake. If some backed out on you I'd think you would have noticed before it did that kind of dmg (I also think very unlikly a loose CV could do that).
Even if the diff was mouted loosly it would have the tendacy to feel like the car is taking off before it actualy is.. probably with some banging noise in the back too, search "front diff bolt snapped" none of theis guys had that happen even with just 2 back bolts holding it in.
Neither suggestions IMO wouild cause that.

My first geuss would be a small crack already their before your install. Dropped in shipping most likly and you just never noticed till now.

My 2 cents.

kruler 08-28-2009 10:52 PM

any 6 zyl E36 diff cover will fit on that diff, or would be a good excuse to get a nice Rogue or similar finned cover if you want to spend the money on one.

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