FJ40 Axle Question (1 Viewer)

[Dave5863]

I'm looking to add disc brakes to my 72 FJ40 and have come across this front axle for sale. Can anyone tell me what year this is or is it impossible to tell just by looking? It has warn hubs. WoIuld there be any issues swapping this under my rig? I'm not too familiar with this stuff and any knowledge or advise would sure be appreciated. Thanks.

 

[Pura Vida]

You should be ok as long as it has the same gear ratio. I think 1979 and newer have 3.70 gears and pre 1979 have 4.10 gears.

Can anyone back me up on this? In 90% sure I’m right

 

[3_puppies]

you can measure the bolt pattern on the steering arm
small pattern would generally be early up to Dec 1978, 4:10 diff ratio
large pattern would generally be Jan 1979+ 3:70 diff ratio
Warn hubs could have been added versus drive flanges, so that doesn't help
maybe the diff flange bolt pattern but I can't remember when all those changes happened

not to say a PO could have changed the diff

either way I would want to go thru the entire assembly, to freshen it and get all clean fluids/greases and seals and bearings

 

[pb4ugo]

Steering Knuckle 101....(FAQ)

Here are pictures of the smaller bolt pattern knuckle using the 11MM diameter stud, found on USA drum brake Land Cruisers and disc brake axles until 12/78:

forum.ih8mud.com

This link should help you determine what frt end it is. If it has larger/better knuckles the diff ratio maybe different.
You'll be able to use the better knuckles and birfs. You will have to service the knuckles anyways. Either frt end will work for you. There should be numbers on the ring gear of the extra 3rd member to determine its ratio.

 

[jim land]

You should be ok as long as it has the same gear ratio. I think 1979 and newer have 3.70 gears and pre 1979 have 4.10 gears.

Can anyone back me up on this? In 90% sure I’m right

Yes but it is 4:11

 

[pb4ugo]

The extra 3rd is pretty rough.

 

[Dave5863]

Steering Knuckle 101....(FAQ)

Here are pictures of the smaller bolt pattern knuckle using the 11MM diameter stud, found on USA drum brake Land Cruisers and disc brake axles until 12/78:

forum.ih8mud.com

This link should help you determine what frt end it is. If it has larger/better knuckles the diff ratio maybe different.
You'll be able to use the better knuckles and birfs. You will have to service the knuckles anyways. Either frt end will work for you. There should be numbers on the ring gear of the extra 3rd member to determine its ratio.

So based on this I figure this is a 79 and up so I can either use the whole axle if I change the rear third member or just take the knuckles off of it and use on my current axle? Am I correct? What would be my options if the third is not servicable? Are they easy to source?

 

[pb4ugo]

Yes you are correct. Do you want to run 3.70 gears? You can install your 3rd into the disc housing and keep your 4.11's, if that's what your rear is. What yr is your 40? You can change your rear to 3.70 and use the 3.70 frt. It depends on what your going to do with your 40. If you do this you will probably have to get new pinion flanges to match your drive shafts. Frt 3rds usually have low miles on them. If you decide to change the rear you'll need ring and pinion, shims, bearing and a pinion yoke. I'd setup new. New pinions will most likely be fine spline, your 4.11 are not. Shims and bearings are usually sold as a kit. You could also try and find a used 3rd. Once you pull the frt axles and knuckles your just 10 or so nuts from pulling the 3rd. Or just adapt these knuckles on your housing. You'll have to slightly grind the inside of the ball so the late model birfs fit into the housing. Its No big deal. Like I said, you'll shouId service the knuckles anyways. This is probably the simplest.

 

[pb4ugo]

The 3.70 pinions will be fine spline. Around 1974 the driveshaft bolt patterns changed. There are vendors like Cruiser Outfitters will have everything you need and will guide you thru what you need, if you tell them what your doing.

 

[Dave5863]

Yes you are correct. Do you want to run 3.70 gears? You can install your 3rd into the disc housing and keep your 4.11's, if that's what your rear is. What yr is your 40? You can change your rear to 3.70 and use the 3.70 frt. It depends on what your going to do with your 40. If you do this you will probably have to get new pinion flanges to match your drive shafts. Frt 3rds usually have low miles on them. If you decide to change the rear you'll need ring and pinion, shims, bearing and a pinion yoke. I'd setup new. New pinions will most likely be fine spline, your 4.11 are not. Shims and bearings are usually sold as a kit. You could also try and find a used 3rd. Once you pull the frt axles and knuckles your just 10 or so nuts from pulling the 3rd. Or just adapt these knuckles on your housing. You'll have to slightly grind the inside of the ball so the late model birfs fit into the housing. Its No big deal. Like I said, you'll shouId service the knuckles anyways. This is probably the simplest.

Great info! I sure appreciate it. I have a 72 and use will be tooling around town and some light to moderate wheeling. I imagine the 3.70's would probably be best for this? Thanks again.

 

[pjohnson]

Swap out the third with your current diff.

 

[pb4ugo]

Then I'd try to find a good used 3.70 3rd or rebuild that extra 3rd in your pics for the rear and install the complete frt end. Then buy 2 fine spline pinion flanges that have the round mounting surfaces. They can be drilled for your driveshaft bolt patterns if the flanges arent already. Fyi, Driveshaft bolts are special and can be different diameters depending on trans. I'd keep your original 3rds untouched just in case you want to go back to 4.11s or possibly sell them. I just swapped 4.11 to 3.70 on my street 40 for mpgs. 350, nv4500 5speed. If your running the 3 speed you may want to go back to 4.11s for offroad.

 

[ToyotaMatt]

I'm looking to add disc brakes to my 72 FJ40 and have come across this front axle for sale. Can anyone tell me what year this is or is it impossible to tell just by looking? It has warn hubs. WoIuld there be any issues swapping this under my rig? I'm not too familiar with this stuff and any knowledge or advise would sure be appreciated. Thanks.View attachment 3238944View attachment 3238945View attachment 3238946View attachment 3238947

i would start by getting a real paper print media copy of the GREY chassis and BODY FSM repair manual


this will make your life free of guess work ....