901 ZF LSD rebuild, 30 years of parts collecting pays off Options

[mgphoto]

Now for the measurements of some new parts.

Belleville washers new part # 928.332.555.00
A .078 - 1.98 mm
B .078 - 1.98 mm

These cup washers have a convex and concave side, we measure the thickness of the material not the thickness of it expanded.

Differential inner disc Fibre new part # 928.332.551.00
A .081 - 2.05 mm
B .081 - 2.05 mm
C .0805 - 2.05 mm
D .081 - 2.05 mm

Out spline new part # 917.332.552.12 Differential inner disc 2.1 mm
A .083 - 2.11 mm
B .0825 - 2.09 mm


At this point I seem to have enough parts for a number of different lock variations.



Now a closer look.
Where do these go wrong? Broken internals, severely wore parts and worn internal channels.






Here is a close up.



The ridges seen here need a bit of clean up with a small file





With no major problems time to proceed with figuring out a set up.
Stay tuned.
Mike

[0396]

Now for the measurements of some new parts.

Belleville washers new part # 928.332.555.00
A .078 - 1.98 mm
B .078 - 1.98 mm

These cup washers have a convex and concave side, we measure the thickness of the material not the thickness of it expanded.

Differential inner disc Fibre new part # 928.332.551.00
A .081 - 2.05 mm
B .081 - 2.05 mm
C .0805 - 2.05 mm
D .081 - 2.05 mm

Out spline new part # 917.332.552.12 Differential inner disc 2.1 mm
A .083 - 2.11 mm
B .0825 - 2.09 mm


At this point I seem to have enough parts for a number of different lock variations.



Now a closer look.
Where do these go wrong? Broken internals, severely wore parts and worn internal channels.






Here is a close up.



The ridges seen here need a bit of clean up with a small file





With no major problems time to proceed with figuring out a set up.
Stay tuned.
Mike

What sort of locking factor are you going to set the LSD up at?
Original 40 or pump it up to 60 or 80% ?

[jd74914]

The diff looks so similar to the BMW e30 LSDs. IIRC they also use 917 clutch plates which makes me wonder if they are similarly dimensioned. If they are it's be a much cheaper way to build an LSD since you can generally get them for ~$300.

If it's not too much trouble, would you mind getting rough measurements of the ring gear mounting flange OD and overall length?

[mgphoto]

The diff looks so similar to the BMW e30 LSDs. IIRC they also use 917 clutch plates which makes me wonder if they are similarly dimensioned. If they are it's be a much cheaper way to build an LSD since you can generally get them for ~$300.

If it's not too much trouble, would you mind getting rough measurements of the ring gear mounting flange OD and overall length?

All of the dimension are seen within this image at the samba.


ZF Diffs


ZF must have designed around what they already had.
Hopefully the need for these parts will keep supply up.

[jd74914]

Thank you! Now I just have to find my BMW model and compare...

[0396]

Now for the measurements of some new parts.

Belleville washers new part # 928.332.555.00
A .078 - 1.98 mm
B .078 - 1.98 mm

These cup washers have a convex and concave side, we measure the thickness of the material not the thickness of it expanded.

Differential inner disc Fibre new part # 928.332.551.00
A .081 - 2.05 mm
B .081 - 2.05 mm
C .0805 - 2.05 mm
D .081 - 2.05 mm

Out spline new part # 917.332.552.12 Differential inner disc 2.1 mm
A .083 - 2.11 mm
B .0825 - 2.09 mm


At this point I seem to have enough parts for a number of different lock variations.



Now a closer look.
Where do these go wrong? Broken internals, severely wore parts and worn internal channels.






Here is a close up.



The ridges seen here need a bit of clean up with a small file





With no major problems time to proceed with figuring out a set up.
Stay tuned.
Mike

What sort of locking factor are you going to set the LSD up at?
Original 40 or pump it up to 60 or 80% ?

Any thoughts on my question?

[r_towle]

You gave me hope.
I don't feel like such a procrastinator anymore.

[mgphoto]

Now for the measurements of some new parts.

Belleville washers new part # 928.332.555.00
A .078 - 1.98 mm
B .078 - 1.98 mm

These cup washers have a convex and concave side, we measure the thickness of the material not the thickness of it expanded.

Differential inner disc Fibre new part # 928.332.551.00
A .081 - 2.05 mm
B .081 - 2.05 mm
C .0805 - 2.05 mm
D .081 - 2.05 mm

Out spline new part # 917.332.552.12 Differential inner disc 2.1 mm
A .083 - 2.11 mm
B .0825 - 2.09 mm


At this point I seem to have enough parts for a number of different lock variations.



Now a closer look.
Where do these go wrong? Broken internals, severely wore parts and worn internal channels.






Here is a close up.



The ridges seen here need a bit of clean up with a small file





With no major problems time to proceed with figuring out a set up.
Stay tuned.
Mike

What sort of locking factor are you going to set the LSD up at?
Original 40 or pump it up to 60 or 80% ?

Any thoughts on my question?

Hey 0396
I did decide on 40% lock, going to use her on the street, no track time.
I used a bunch of index cards marked with the internal parts to mix and match to get the correct dimensions for my clutch packs.
I will update but I need to find the P-259 tool or fashion a replacement tool.
Stay tuned.
Mike

[mgphoto]

Another small step for me, one giant leap for my transmission!




P 259 by way of Meaney Racing, possibly used on the Daytona cars # 18 and #19.

A small ring, a few shims and the patience of a saint.

Mike

[rgalla9146]

Is it possible to test a LSD on the bench ?
Can you describe how it is done ?
I want to determine the condition my unit.

[mgphoto]

Is it possible to test a LSD on the bench ?
Can you describe how it is done ?
I want to determine the condition my unit.

Yes factory repair manual has the procedure, with pictures and self fabricated tools.

The ZF LSD unit assembled with drive flanges and two cv bolts are screwed into a flange and locked in a vice, the other flange is turned with a torque wrench and the breakaway point or torque is measured.
There is a specific torque that the factory uses but all bets are off as the orignal parts are NLA and I believe the "cup washers" have more pressure than the orignal "spring plates".
What is being measured is the "locking force" of the clutch packs, lower the breakaway point or torque, the lower the locking force.
Mike

[914forme]

Clamp one side in a vice.

Take a torque wrench, you will get a break away. 10-35 Nmeters is the specs that gets tossed about.

[jd74914]

Not sure that will truly give you a full assessment as to the health of the unit. In a "correctly" preloaded unit it would give some indication of clutch plate health, but you can shim it (or change springs) to increase preload. The extra clamping force would mask any issues with the friction surfaces.

[mgphoto]

Not sure that will truly give you a full assessment as to the health of the unit. In a "correctly" preloaded unit it would give some indication of clutch plate health, but you can shim it (or change springs) to increase preload. The extra clamping force would mask any issues with the friction surfaces.

Since I am using new friction plates, the unit will be as good as it can be.

[jd74914]

Since I am using new friction plates, the unit will be as good as it can be.

Sorry, didn't mean to imply yours won't be good as new. (IMG:style_emoticons/default/smile.gif) That was in reference to the above question about checking a used unit.