1970 FJ40 Axle Identification and ARB Air Locker Model Selection Question

[BrownDog1]

Attached are photos of the front and rear axle/diff cover to help identify the axle year or year range so we can select the appropriate ARB Air Locker model. A couple of notes:

• The truck is a 1970 - I believe the rear axle is original based on the records I have, but could be mistaken.
• I believe the front axle is a used period correct replacement - I'm not 100% sure on that.
  • I measured the bolt studs on the steering knuckle and the measurements that I got off my truck indicate the front axle is a pre 1978. The link explaning these technique for identifying the axle year is below.
  • Steering Knuckle 101....(FAQ) - https://forum.ih8mud.com/threads/steering-knuckle-101-faq.117942/
• From what I've read and what ARB told me - stock axles for a 1970 FJ40 would require ARB Air Locker part numbers:
  • Rear - RD153, for a semi float
  • Front - RD142, for a full float
• However - as you can see in my photos - both of my diff covers are 10 bolt and the spec.s for both the RD153 & the RD142 indicate a 12 bolt....
• I believe the RD132 is for a 10 bolt but my understanding is that's not typically stock on the 1970 FJ40

So - I'm looking to identify if these axles are stock/period correct for the 1970 FJ40 AND the correct model # for both the rear and front ARB air lockers.
Any input would be greatly appreciated.

 

[franklin40]

can’t quite tell for sure but your pinion flange looks like the 69-74. this diagram might help. as you have a disc conversion is it possible the diff was also swapped or maybe the pinion flange was swapped out? do you have other driveline modifications? the only way to know for sure is to pull the diff as far as i know.

my 72 and 77 are both 10 bolt just fyi. not sure i’ve seen a 12 bolt on any of the axles i’ve had including my fj62. they all have interchangeable diffs.

here’s my 72 axle that i’ve dropped a 77 diff into (the pinion flanges are different however)

im guessing the 10 vs 12 bolt is actually the number of bolts on the ring gear not the diff housing but you’d have to confirm that with arb.