differential / driveshaft decoupled

ajf

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Hi all,

Yesterday I was happily cruising down the highway in heavy traffic and was greeted by a whiney sound, which at first I thought was due to the grooving in the road at that stretch. The sound quickly seemed more ominous, and as I began to merge over to exit it became downright ugly -- occasional, but not constant, grinding, clanks, etc. I got to the exit and to a gas station within one block and parked the car.

Looking under the car it became clear that the differential was leaking, very heavily. I assumed a pinion seal or the like had gone very bad. Moving (pushing) the car it was clear it was A LOT (basically all) of the fluid that was/had leaked. I was 50 miles from home; called a tow truck (its own adventure). The odd thing at that point was that the car could be pushed in neutral backward but not forward. I had them load it on a flatbed without moving the rear wheels. It's now in the street a block from my house (I'm on a hill; impossible to get it into driveway). I have to get it out of there within 3 days.

I got under the car today and found the driveshaft separated from the differential where they connect: the bolts to the diff are all in solid and in place -- it is separated such that you can see the seal clearly. The rest of the driveshaft seems fine; the Giubo is good, the junction seems fine, the u-joints are solid and bolted, etc. The only issue seems to be the gaping hole at the diff/driveshaft. In the pics I've attached you can see it as I found it and also as separated more, which is easily done by sliding the shaft assembly by hand.

To my question: what the hell? Ok, my real question is whether the part that has become disconnected is ever supposed to? Are the two pieces integral or somehow bolted together somewhere I can't see? In other cars I've had this piece (gold color in the pics) bolts onto the diff itself via multiple through bolts but here it seems to be one unit? What holds the entire driveshaft assembly tight? Pardon my ignorance here but something is obviously wrong.

Of course I don't know what damage was done internally to the differential just yet, or if I'll be able to re-fit the shaft into the diff (maybe by jacking both rear wheels off the ground, rotating them, and hopefully finding the spot where it all fits back together; though this doesn't solve the underlying problem).

Thanks in advance for any ideas, knowledge, advice, etc. to get me back on the road, much appreciated.

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Gransin

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Maybe the nut that holds the flange (gold coloured piece) became loose/missing? I would start with removing the driveshaft to find out more.

The nut that holds the flange:

994foto4.jpg

Number 3:

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ajf

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Yes, almost has to be that, huh? That solves my mystery (thanks for the pics) of what holds the flange in place.
 

Wladek

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I also think nut was loosen and was gradually unscrewed by vibrations (probably no loctite).
 

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  • 33 11 011 - Replacement of shaft sealing ring for drive flange _ 33 - Rear Axle _ BMW 2.5CS - 3.pdf
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Honolulu

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The nut referenced above holds "the gold piece" to the input shaft of the diff. But the dshaft is bolted to the gold piece, so both have to turn, right? Yet I see no splines which would seem necessary... 33/10 parts diagram does not show a splined shaft in the gold piece, the pinion gear or other diff internals, so it's definitely not the whole story...

Not intimate with differentials, but suspect something darker is going on. At any rate unbolting the dshaft from the gold bit will be part of whatever you'll need, so let's get to it and see what is revealed.
 

Wladek

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The nut is bolted to the end of crowngear #1, so it is possible that drive flange with gasket came out after nut was unbolted and then oil flew out.
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Luis A.

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Take a look at the attached pic. The input pinion gear shaft is held in place by the two bevel roller bearings in their respective outer bearing races set in the diff case. So unless the bearings totally disintegrated and allowed the complete pinion shaft to slide out the more likely possibility is that the nut came loose and allowed the flange to disengage from the splines and very partial spline engagement/clashing is the racket you heard. But we don't have to guess! get down there and undo the driveshaft and we will all have an answer.

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ajf

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Thanks for all the great input and information. I'm getting the car to a place I can work on it today and will know more soon.
 

ajf

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Indeed, the collar nut was completely free from the pinion gear shaft, allowing the driveshaft to separate from the flange, just as folks here said was the likely culprit.

I drained what little remained of the diff oil and saw no bits of metal, etc. Also I'm able to turn it all properly by hand with no apparent ill effects, so I'm hopeful that it's merely a matter of tightening the collar nut properly, with (red) Loctite this time around as noted. Does anyone know the correct torque specification for the collar nut?

Thanks for all the input.
 

jmackro

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Indeed, the collar nut was completely free from the pinion gear shaft, allowing the driveshaft to separate from the flange...... just as folks here said was the likely culprit.I'm hopeful that it's merely a matter of tightening the collar nut properly, with (red) Loctite this time around as noted.

What is the condition of the male splines on the shaft and female splines in the flange? Those two parts clashing against each other were the noise that you heard/felt. Make sure that the flange can fully seat on the shaft. You don't want to tighten the nut to the proper torque (sorry, I don't know that value) but have the flange hung up on damaged splines, which would allow too much play in the bearings.
 

ajf

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Fortunately, it all looks good -- far better than the gruesome sound led me to expect:

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bavbob

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Should hve been a lock ring holding the collar nut. It fits over the nut and has a lip that fits into that groove at 3 oclock in your photo. When changing the seal, these are often trashed and then locktite is used. Assume your seal was changed and neither was used to hold it in place.
 

bluecoupe30!

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wow, you have been SO fortunate. Thank you for sharing this experience though, and especially for following up with the photos. Was wondering about lock ring too. Could happen to any of us. Quite the learning!
 

ajf

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I discovered the lock ring in the parts diagram too -- the part number is 23211490120. I'll be getting one and adding it back into the assembly; it looks like it can be used instead of loctite.

Anyone know the torque specs for the collar nut?

Thanks again to everyone.
 

sfdon

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Once you remove that nut you are supposed to replace the crush sleeve.
There is no set torque number really at the pinion nut- you are measuring for inch pounds of preload on the bearings by moving the gears. Tighten too much and gears will bind and then lock.

Get a new nut and seal.
Pinion bearings wear 3x faster- now is a good time to replace.
Take it to a good shop is a good idea.
 

Sven

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When refitting the lock ring use a cold chisel to bend the edge into the one recessed section in the flange. This should keep it in place and prevent it from turning.
 
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