Another Disc Brake Question

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Jan 25, 2006
I have gone through the tech links until my eyes hurt reading all the write ups on front disc brakes. Not to mention the write ups on trying to get a set of wheels to fit witout rubbing on the calipers. Here is my question. I have found a complete front axle assembly out of a '76 for a decent price. Will this bolt right into my '71? If so, sounds like the easiest way to go!
It will. I believe. Are you planning on using your diff or the new one. I believe the mounting holes on the flanges are different to some degree but I think it can be modified to work with your driveshaft. Then there is the issue of brake lines and brake master cylinder. You must remove the front residual valve from your system. A 71 drum brake FJ40 master cylinder should have this valve in both fittings....a 76+ drum/disc combo would only have one for the rear drum brakes.
I'm not a guru on coverting over but I'm sure someone will chime in. Other than that and maybe a new set of ubolts for safety your are good to go.
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76 is in the "funky" batch of axles, uses the small knuckle pattern and a longer birf. But if you don't really wheel hard, no big deal.
No, I don't plan on doing any serious off road stuff. I t being set up to be a DD.
You will need to swap the pinion flange from your old axle to the "new" one. Good time to replace the pinion seal, too. On my '66 there was a drop at each wheel in the front, but I don't know about the '71. At least you won't have to deal with the bastard-sized brakeline fittings. The '76 axle will have one drop on the passenger side, so whatever the difference is between what you have and that will need to be plumbed.
Are you going to replace the trunion bearings and seals? Good time to do that also.
New U-bolts are a necessity.

Good Luck,

I plan on throughly going through the differential and replacing all seals and bearings. I will also be installing new springs and shackles at the same time. Thanks for the info!

It is a bolt in swap. Plumbing the brakes will be the only real hitch, as your truck has the drop hose to the front axle on the driver side, and on the disc brake axle it will come in right by the front diff....

Easy enough to change....will probably need ne brake lines and hoses along with calipers and everything Ed was talking about.

Good luck!

Thanks for the reply. This assembly is complete. It includes calipers, rotors,etc. Should be a no brainer!
I put 77 disks on a 72, but I didn't change the whole axle, just the knuckles out. Would have saved plumbing it I guess, but the old lines were rusted/ dry rotted so I built all new ones. Also if you change the whole axle double check that they have the same gear ratio. I'd hate to hear you had 3.73s in the front and tested it in 4 low.
As busta said - it is an oddball size for birfs so while you've got it apart grind some material out of the interior of the knuckle so a later year birf will slide in. There is nothing wrong with the axle - just oddball compared to newer LC and mini

I couldn't find a definitive measurment on how much to grind out so I went with .025" and figured it would be close. If you don't plan on upgrading to Longfields or doing a trail repair with newer parts - forget this entirely.
Hi All:

I swapped a disc brake frontend from a '78 BJ40 under my '74 FJ40 some years ago.

Since I got the axle assembly completely dis-assembled, a friend helped me re-build (new seals, bearings, races, and so on) and re-assemble it.

To handle how the brake line drops down to the axle on a '78 on the right-side (versus on the left-side on a '74) I simply swapped the front axle hardline from the '74 drum brake frontend onto the '78 disc brake frontend.

Like has been mentioned before, remove the residual valve in the front circuit of the brake master cylinder (it is a little rubber "cup.")

Good luck with the project!


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