I converted my 4A IRS to 240Z stub axles last year after having the stock
unit fail "at speed" at Willow Springs. (The ensuing tricycle ride through
the desert could be a story for another time.) Armed with the "theory" of the
conversion on Mordy's car, I located a talented machinist that helped me
noodle it out. Here's what we did:
Fabricated an "extension" that was press fit to the inside of TR hub to
accommodate the location of the Datsun inner bearings.
Machined the hub and extension to accept the Datsun bearings. I ended up
using sealed bearings (Datsun outer, I think) throughout and eliminated the
inner dust shield. The bearings used were SKF RLS 10-2RS1.
Bored the TR halfshaft outer U-joint to take the 240Z crosses. They are a
larger diameter and available as "high performance" sealed units (The
Driveline Co. #1-0029BF from Pep Boys).
Shortened the TR halfshaft by removing 1" on the male and 1 3/16" on the
female and rethreading for the retaining caps. (This removes about 1/2 of the
splined length that looks a little scary, but I've had no problems and even
moved to 4.1 rear end to get more grunt.)
I kept the Datsun metric studs and used the Datsun drums shaving the
inner edge a smidge for clearance with the TR backing plate.
I've had the unit in the car this year with no problems at all. The Datsun
stub axle is a much stouter unit and I don't want to relive that failure
again! I wished I'd gotten precise dimensions when we did this to relay in
detail, but I wanted to get the car together asap. With the Datsun stub axle
in hand though, you can determine the dimensions required for the ball races
and the necessary hub extension.
John Frymark (VARA EP #67)