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

[mgphoto]

Hello,
I started collecting parts of this project 30 years ago and the last parts have fallen into place.

In this post I hope to clear up some confusion and convey some of what I found trying to complete this project.

First piece


purchased form PAR in Yonkers NY 1986 914.332.209.00 casting number 51D

The LSD found its way to me in 2013 from the venerable Cap'n Krusty



The diff needed some work as it was missing internal spring plates which are NLA.

Item number 4 in this factory illustration.
This part places tension on the clutch pack which is measured as drag.
The factory spec on this is 29 - 58 ft. lbs

This item can be replaced by what is now called a "cup" spring from and early 928
part no. 928.332.555.00

seen here as item number 10

As for the internal wear parts, the 914 parts are NLA but, get this they are replaced by mostly 917 parts! WAY COOL.

Just the beginning, stay tuned!
Mike

[mgphoto]

OK here is the list of internal parts and my measurements.
First I labeled the consumable parts, those consisted of 4 fiber coated disks (#6) and 8 metal disks with external splines (#5 and #4). #4 is the cup spring which is NLA and replaced with the newer style belleville washer 928.332.555.20.
Additionally there are 2 differential shafts (#11) with 4 spider gears (#10) with 2 thrust rings (#7) and 2 bevel shaft gears (#8) with 2 treaded pieces (#9) and 2 circlips (not seen in this diagram), these make up the center of the diff. These items with the cover (#2), LSD body (#12) and 2 thrust washers (#3) complete the unit. Additionally #1 in this diagram is the cover attachment screws (NLA) for the 914 part, substitute the 65-89 911 pan head screw part 900.119.002.00, they are yellow colored not black, so don't let the concourse guys look into your 901 box!



So 32 parts total make up this fascinating little gizmo!

I decided to make my measurements in SAE and metric.

Measurements of used parts

Outer spline A .0789 - 2.00 mm
Outer spline B .0785 - 1.99 mm
Outer spline C .0785 - 1.99 mm
Outer spline D .0780 - 1.98 mm
Outer spline E .0784 - 1.98 mm
Outer spline F .0785 - 1.99 mm
Outer spline G .0790 - 2.00 mm
Outer spline H .0795 - 2.02 mm

Fiber disk A .0765 - 1.94 mm
Fiber disk B .0750 - 1.91 mm
Fiber disk C .0775 - 1.96 mm
Fiber disk D .0775 - 1.96 mm


From here I will use SAE measurements, I will introduce metric measurements for illustration.

Than I set about measuring the body, cover and the thrust ring stack
Body internal 3.884 and the cover is .2440, the cover needs to be subtracted from the body because it fits inside so 3.640.
When assembled the thrust ring stack measures 2.682.

So we take inside of the LSD 3.640 and subtract the thrust ring stack 2.682 this leaves us with .958 space for the consumable parts.
There is a total of 12 disks, each group of 6 needs to take up .4790 or 12.17 mm

So there we have the used parts, next post I will measure the new parts.
Mike