differential repair question

deQuincey

deQuincey

Quousque tandem...?
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hi,

some months ago a set of drops started to fall in the floor of my garage under the rear part of the e9, in the diff area

now i am sure that the diff is leaking from the front side, in which the seal probably is worn

so i am now in the position of changing the shaft seal (ref. N. 5 in the following drawing)

diferencial.jpg


but one question arises: you might know that in a diff the part number 7 (clamping bush) has to be preloaded when the diff is mounted, that preload modifies the part geometry and it is said that if you need to repair the diff and if you dismantle it, you will always need a new clamping bush

the question then: if i intend only to change the shaft seal (green arrowed ref. 5) just undoing the nut number 3, remove parts 1, 4, and 5, and replace part 5 with a new one, do you think i will need to install a new clamping bush, preload it and so on ?

thanks for your answers

regards
 
DQ,

I can't help with your question but I, like others, I'm sure, am waiting for another trademark DQ step-by-step, beautifully photographed, deliciously clean, photo essay on taking the diff apart, servicing it to perfection and putting it back together. :)

I love those! Let's go!
 
I second Luis' comments :mrgreen: The manual says you can as long as you stop there, but it also says you have to have a device to measure "frictional value" so it takes the same amount of energy to turn the shaft after the replacement as it did before. Maybe this can be guesstimated without bad consequences later. There is a post in the 2002faq about this (maybe more by searching there):

http://www.bmw2002faq.com/component...ewtopic/t,288769/highlight,differential+seal/
 
torque value

Tighten the nut in small incrementsand keep checking the torque required to turn the input shaft, it should be no less than 22 inch pounds and no more than 25 inch pounds of torque. New bearings require 30 inch pounds, but thats part of a complete rebuild.
Good luck, Leroy
 
pinion torque

Ignore that previous post, that is the torque for the pinion with the ring gear removed. To do this properly in the car you will have to take out the axle stub shafts so that the wheel bearings, stub shafts, and brakes don't interfere with the torque values. Then after the new seal is installed, tighten the pinion nut in small increments until your torque value is approximately 45 to 50 inch pounds or the metric equivelent. Sorry for the first post, it was late last night when I read yopur post and I've always done complete rebuilds on all my diffs. Good luck, Leroy
 
I have done something like you are describing "in the field." I do not know what the long term consequences were because I did not have the car that long. The problem, as others have described, is the danger of over-torquing and metal deformation. I am sure there is some wiggle room. Similar to retorquing head bolts - using "torque-to-yield bolts." I suppose in theory you could reuse them, yet heat cycling, thread lubrication effects, and metal fatigue make this impractical and unwise except in an emergency.

Good luck:)
 
i have a solution

considering that the clamping bush is already deformed in its right geometry, here it comes my proposal

the position of the axle and nut is ok, so i mark it with a chisel:

IMG_4031_40.JPG


then i dismount the nut, i remove parts 1, 4, and replace part 5, assembly in reversal order and fix the nut until the exact position as marked with the chisel

opinions ?

regards
 
Hi, have you completed the oil seal replacement and how did it go? Also, what size socket is needed for the large nut marked #3? Thanks.
 
deQuincey said:
considering that the clamping bush is already deformed in its right geometry, here it comes my proposal

the position of the axle and nut is ok, so i mark it with a chisel:

IMG_4031_40.JPG


then i dismount the nut, i remove parts 1, 4, and replace part 5, assembly in reversal order and fix the nut until the exact position as marked with the chisel

opinions ?

regards
Click to expand...

If possible I would try to measure the torque as described by Leroy, since that's what the BMW Tecnicians would do.

However if that's not possible, I tend to support the "mark it and refit" approach. All that you are changing by replacing the oil seal is the frictional drag of old v new seal and possible small dimensional differences in seal thickness. These all seem relatively small changes to me compared to the changes the diff will experience through it's life with no maintenance.

Hopefully by fitting a new seal, you will remove any "slack"' which is what I encountered when I replaced my front seal. Using the above method, my diff spins freely and without slack, but has yet to be driven for final proof !
Rich
 
an alternative way to mitigate leaks in the diff

instead of repairing, i will swap to an LSD...

it has been a long way, i even had to make a Wood box to get it shipped, such a heavy piece, but you know i have to do things with my hands, so it was a pleasure





box traveled ona way and then back,...and here it is, thanks to A. who was so kind to do all the rest of the job...and it was indeed a lot of work, completely overhauled, bearings, seals,...






the mighty "S"



checking alignment is within 0,05mm :-)

 
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