[DeTomaso] ZF Questions

[JDeRyke at aol.com]

In a message dated 3/04/07 6:45:32 AM, charlesbuthala at yahoo.com writes:

<< Assemble this way:
  1- Install Diff with out the ring gear, then install  the taper bearings.
  2-Install original shims behind the outer race.
  3-Bolt up assembly with the gaskets on flanges.
  4-Measure torque of diff.  re-shim if necessary to get proper torque.
  5-Assemble ring gear, and LH and RH flange assemblies.
  6-Reinstall flanges with all hardware and measure backlash.
  If necessary reconfigure shims behind LH and RH (no additions just swap) 
outer race to get proper backlash.
  7-Finish final assembly. >>

In place of steps 4-7, I find the following method of setting up any diff 
simpler and not requiring so many specialized tools:

Coat a few teeth on the ring gear with Dykem's Mechanic's Blue, let dry for a 
few minutes, then rotate the coated teeth past the pinion in the proper 
rotational direction while holding the input shaft with your other hand so as to 
'load' the ring gear slightly. Then slack off the load and closely observe the 
pattern of the gear teeth rubbed in the Dykem-blue lacquer. You'll get an 
elliptical rub-pattern representing the actual tooth contact. Do NOT go back and 
forth thru the coated teeth while doing this-it changes the pattern with the 
direction of rotation. 
If the elongated rubbed pattern is displaced to the bottom or the extreme tip 
of the ring gear teeth, the shim stack is wrong. Remove shims for too-deep 
ptterns and add shims for too-high patterns.  You should get a nice elliptical 
pattern more-or-less centered on the ring gear teeth. Most Ford or GM shop 
manual graphically show this pattern but their description of correction will 
obviously be wrong since they don't use shims.

And its far easier to add the required amount of lube while the access cover 
is off and the breather fitting is plugged. Remember that a totally 
disassembled ZF takes about 7.5 pints of lube, but you cannot drain that much out of an 
assembled tranny even if the thing is on its nose with the cover off 
overnight. There will ALWAYS be some lube caught in the rear gearcases, so refilling 
may be a two-step process. Slight over-filling is preferred to under-filling.
I add about 6-1/2 pints of 80W90 diff-lube for clutch-type positraction® 
limited-slips (which the ZF has), add the cover & torque to specs with the 
long-bolt shims correctly placed, flip the assembly over level, in position for use 
in the car, and go have a beer or a cuppa coffee for 30-60 minutes. Then from 
the normal fill plug, check the height of the lube inside & add a top-up 
amount. The distinctive odor of diff- lube will linger around you for only a couple 
of days or so, giving you high status among those few who've 'been there & 
done that'.... but repelling most females.  Good luck- J Deryke
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