Differential seal refurb question

[jerry]

looking over the factory OHM on the differential, it refers to this guage that measures the turning resistance (friction value) prior to removing anything. i'm not familiar with this tool.

what is the significance of this step? or alternatively, is it considered hack work to omit this step? apparently there's an adjustment required to return to original friction value upon reassembly.

anyone improvised this step?

is this tool still available in some form?

i'd like to ensure my differntial doesn't spew oil all over my newly cleaned and painted underbody.

thanks

[BillWilliams]

but removing the front seal and reinstalling it is best left to the pros with the correct tools. That front mechanism has to be set to the correct torque and has to be done with a special tool

With moderate skills, one can replace the seals on the output side, keep track of the shims and put them back on the sides they came from.

Jim at Metric Mechanic is good on the differentials.

[Emyers]

You do not want to remove the driveshaft differential input mount unless you have the crush spacer that goes in between the two bearings on the input quill. The torque/turn resistance measurement applied to the nut on re assembly actually applies "crush" to the aforementioned spacer to allow the proper amount of preload on the two bearings.

Earl Myers

74 2002Lux

02 M Roadster

72 Volvo 1800ES

[c.d.iesel]

[jimk]

The reason for checking the torque is to determine the run-in turning static torque of the tapered pinion shaft bearings. Turning Torque values in the manual are for setting the preload on new bearing sets. Once a tapered bearing set is run-in, applying the initial preload will make them wear more, and most likely wear-out.

So you record the resistance before you take it apart if you are reinstalling the existing bearings and set it to the same value while crushing the crush collar with brute strength and courage.

While crushing the collar the wrenching torque builds quickly then falls off as the collar buckles, so use caution. Once overtorqued (beyond the initial rolling torque value), you get to buy another collar and practice again!

Replaced noisy pinion bearings (photos of the race at home) on a $20 eBay 3.90 diff. Figured, what the hell, good practice. Am using the diff today.

[c.d.iesel]

...and to continue....PICTURE A FISH WEIGHING SCALE -

a hook with a string attached - winding the string up around the pinion shaft - nut end --- and draw the fish scale away from the pinion shaft at right angle - unwinding the string - measuring the torque to turn the pinion in it's bearing.

....AND

here is a special Saab tool, made by KENT-MOORE,

Saab # 83 90 130 ('DYNAMOMETER') for bearing pretension

when setting up drive pinion gear bearing / tightening torque.

the BMW Repair Manual spec for

"Friction rating of Pinion bearing without oil seal"

Ncm max 300 +/- 30 cmkp 30 +/- 3

"Friction rating of Pinion bearing with oil seal"

Ncm max 320 +/- 30 cmkp 32 +/- 3 ........(about 20 - 22 lbs.ft )pulling force with the 'fish' Dynamometer