DIFFERENTIAL REBUILDING.....HELP!!!

[vlados2002]

I want to install a used 3.91 differential (from 1982 BMW E21) in my 2002 so I took it apart to renew all the seals. However,I did not record the torque required to move the main shaft input flange . So my question is: HOW CAN I NOW SET THE BIG 30mm INPUT FLANGE NUT TO THE CORRECT TORQUE? I am hoping that those who have done this project before can offer a helping hand. Oh, I forgot to mention, I also did not mark the position of the mainshaft input flange relative to the pinion gear prior to disassembly (as the repair manual states I should). Is this a big deal?

thanks to all

[Emyers]

You can't unless you get a new crush collar that fits between the input shaft/pinion bearings. You can not reuse the old, it is designed to crush as the torque is applied to the nut to limit the preload on the bearings.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

[vlados2002]

You can't unless you get a new crush collar that fits between the input shaft/pinion bearings. You can not reuse the old, it is designed to crush as the torque is applied to the nut to limit the preload on the bearings.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

Thanks for you input. I do have a new crush collar and I will not reuse the old crush collar. My question was: what torque should I set the 30mm nut to when reassembling? The repair manual says that prior to disassembling a test should be done with a length of cord and springing device to determine the torque it takes to move the main input shaft flange . Than, upon reassembly, that figure should be used as a guide to set the torque on the 30mm nut. The problem is: I did not perform that test prior to disassembling...

[Emyers]

Got it. I have a blue manual and would be more than happy to see if it gives a value if you do not have access.

Earl

[vlados2002]

Got it. I have a blue manual and would be more than happy to see if it gives a value if you do not have access.

Earl

I don't have the blue manual so that would be great. Thanx

[Emyers]

Vladimir,

Unfortunately the blue book pretty much describes the procedure as you described. At this juncture all I can offer is give one of the shops a call that rebuild these things an a regular basis, i.e. Metric Mech, Korman etc and see if they can help you out of your hole. Also maybe someone on the FAQ can help, but diff repair is pretty specialized and most folks caution against pulling the pinion unless you absolutely know what you are doing. Good luck.

Earl

[02for2]

The Haynes manual lists the torque on the Pinion nut at 108 ft. lbs. minimum.

It states: " Fit a new collaspible collar and reasasemble the pinion to the bearings and driving flange making sure the latter is aligned correctly by mating the marks made before dismantling.

Hold the driving flange quite still, tighten the pinion nut to 108 ft. lbs. and using a cord and spring balance, check the turning torque of the pinion. This should be the figure recorded before dismantling plus 25% to offset the drag of the new oil seal. Where the correct pre-load is not reached, tighten the pinion nut to a fractionally higher torque wrench setting and recheck. Remember that if the preload of the pinion bearings is set too high, it cannot be reduced by backing off the pinion nut. In this case, the collapsible spacer will have to be renewed for the second time and the adjustment procedure carried out again."

So, if you did not record the turning torque of the pinion nut prior to disassembly, you have no reference for resetting it.

Several smarter 2002 people than I cautioned against doing this procedure saying it is one best left to the pros. Get it wrong, and you'll destroy your diff in a few thousand miles.

With most of the work already complete, I strongly suggest bringing it to an experienced 2002 mechanic to have this set properly, it should not cost very much. Don't try to save a buck here, it would be foolish.

Cheers!

[Cameron]

FWIW - every american car/truck axle I have rebuilt, the turning torque with new pinion bearings was around 25 inch pounds. You need a dial inch pound torque wrench, a clicker type will not work

[c.d.iesel]

adnthen ther's the problem of your ring & pinion gear teeth

alignment (you might be fuched!) but another photo from the repair manual show all the different gear teeth meshing patterns

and tells you what needs to be adjusted to correct for

proper teeth alignment. Not done properly and you have

a HOWLING diff wearing out gears in short time.

[vlados2002]

Well, I figure if c.d.iesel doesn't have a definite answer, basically I am faqued!

I guess I'll have to reassemble it to the best of my abilites, drive the car and see what happens....

[c.d.iesel]

if your re assembling it with all the same shims in the same places

as original - and all your changing is the NEW CRUSH SPACER,

then you should be good as you can be - careful tightening

of the input nut crushing the new spacer - measuring the turning resistance.......... you should be alright

[vlados2002]

if your re assembling it with all the same shims in the same places

as original - and all your changing is the NEW CRUSH SPACER,

then you should be good as you can be - careful tightening

of the input nut crushing the new spacer - measuring the turning resistance.......... you should be alright

Yeah, all I am changing is the CRUSH SPACER and 3 seals. Everything else stays the same. I will be carefull and tighten the nut slow, very slow...thanx

thn

[TobyB]

CD (spam man) Deesel actually DID give you the number-

it was just buried in amongst about 20000 other useless ones.

15- 29 inch- lbs.

That''s the free- turning torque of the preloaded pinion.

Here''s what you do- you tighten the nut carefully until all play is out of the pinion assembly, but it moves freely.

Then you measure it. Should be just a couple of inch- lbs for the seal.

Then you tighten about 10 degrees and measure again...

Probably 4 inch- lbs.

Then you tighten another 5, measure again.

Maybe 6. Then you tighten another 5, and discover you''re at 20.

If you''re unlucky you''re at 40, and get to take it all apart again and redo it.

It''s a really odd process, not unlike ''torque to yield'' head bolts- it feels wrong to be tightning that pinion nut like that, but once you do a few, you get a feel for what the pinion wants for preload- there''s a funny ''tight but free'' feeling to the bearings.

As to torque on the nut, it''s ''a fuckload''. No, a METRIC fuckload. I do it with a 24" breaker bar and a 36" bar on the flange, and, having done 2 in the last week, I have bruises on my chest from pulling the breaker with 2 hands and holding the flange bar against my chest.

Cleanliness is next to Godliness in this process- any grit in the bearings at all will ruin your hopes of getting an accurate number.

If you''re careful, you''ll be fine with this. The 2002 manual doesn''t have all the conditions that the 320 one does- and 2002 diffs, if anything, last longer than 320 ones do. Despite having smaller nose bearings.

t'

[vlados2002]

Does this Youtube video pretty much sum it up?

THANKS TO ALL!

[Zorac]

double post