BJ40 Coarse Spline to Fine Spline Axle Swap (1 Viewer)

Joined
Oct 23, 2020
Messages
2
Location
Philippines
I recently purchased a 75 BJ40. It is early 75 with the drum brakes and coarse 6 spline hubs. The previous owner removed the front carrier and inner axles and I am working to get them replaced. The consensus seems to be to swap all of the parts so that you get the disc brakes and the fine spline hubs. Unfortunately, I'm having a difficult time finding all of the parts to do the conversion here in the Philippines and shipping them from overseas is tough (you need a special permit to import used auto parts). I have found a 3rd and inner and outer axles, but the Birfields are the fine spline. Finding fine spline locking hubs is also no problem. I've found one post that seems to indicate that this swap is not a problem (retaining the spindles and drum brakes), but some others indicated that there may be some issues. I'm hoping that someone could help me sort it out so that I don't end up with the front axle torn apart and without the parts to finish it. The questions I have are:

  • Will the later fine spline axles / Birfields fit in the housing of an early 75 without issues?
  • Aside from the hubs, is there anything else I need to swap for it to work?
  • If this isn't possible, and my coarse spline Birfields check out ok, can I use the inner axles and 3rd that is available here with the coarse spline outer axles?

Thanks in advance. I tried reading all of the FAQ's, but I just couldn't get to 100% certainty from the info there, although I certainly might have missed something.
 

Hugh Heifer

Chasing the Beast
Joined
May 10, 2006
Messages
7,268
Location
Rome, GA
Welcome to Mud.
I lived in Makati for 3 years so I understand your issues with used parts. I think I have the right answers for you:
  • Will the later fine spline axles / Birfields fit in the housing of an early 75 without issues? Sort of. You will need to clearance the inside of the knuckle ball slightly with a grinder in order for the later birfields to fit. This is covered in the disc brake swap thread. Minitruck Disc Conversion - Land Cruiser Tech from IH8MUD.com and Minitruck Front Axle Disc Brake Conversion For Dummies (FAQ)
  • Aside from the hubs, is there anything else I need to swap for it to work? If you are going to fine spline birfs, you also need the complete knuckle assembly.
  • If this isn't possible, and my coarse spline Birfields check out ok, can I use the inner axles and 3rd that is available here with the coarse spline outer axles? Somebody eles needs to chime in but I think the answer is yes. When a disc brake swap is done, the inners do not need to be changed so based on that, it would seem that the later inners will fit early birfs as well. Then you could use all the outer parts you currently have to put the drums back on. Just be sure your two diffs have the same ratios.
If you can a wrecked/donor 60 series or 70 series you can use the outers (knuckle, birf, axle hub, discs and calipers) to do your swap.
 
Joined
Oct 23, 2020
Messages
2
Location
Philippines
Thanks for the input. I'll probably just bite the bullet and do the swap to front discs since it seems almost impossible to find the coarse spline birfs. I still haven't quite figured out the scrap yard / surplus dealer network here, so I guess that will be this weekends project. If anyone knows some good scrapyards to start the search at, I'd gladly take the advice.
 

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