FJ60 Diff in 1968 axle tube (1 Viewer)

[Alex Waddell]

I have a line on a set of front and rear 1987 FJ60 axles that I want to use for a disk brake conversion on my 68 fj40.
This gives me the option of swapping in the FJ60 third members that have 3.7 ring & pinions instead of my existing 4.11's
Does anyone know if a FJ60 differential would fit in my 68' FJ40 axle tube?
And I understand that the drivers side front inner axle on an FJ60 are longer than on an FJ40.
Does anyone know if an FJ40 inner axle will fit into a FJ60 birfield?
From what I see on line, they both seem to be 30 spline.
But I still need to verify that I don't have ball and claw's
Thanks!

 

[TundraTex]

I believe that the differential will fit without any issues into the housing. I think the axles will be an issue, as I believe the inner axle fine spline change on 40's occurred in '69. The pinon flange will also be different between a 60 and 40. I believe the 60 were round flanges being a little larger bolt arrangement and the 40 were square. And I don't believe you'll be able to swap the flanges as the pinon splines will be different as the 40 did not become fine splined until 78. A flange from a later model 40 would be needed. Cruiser Outfitters or some other vendor should be able to help you out with the flanges and axles. I believe you may also have to grind some metal from the inside of the knuckle for the later birf's. There's several posts about that around here.

I'm doing a similar thing myself with '72 axle housings because they're in great shape, but I'm swapping the diffs from a '80 for the 3.7 gearing. To make life easier on myself though I'm using the axles and hub from a '78, which shouldn't have the same complications as the hubs changed in '79 to the "beefier" fj60 style.

From what I've seen changes go something like this (experts may need to correct me here):
Earlier than '69: I believe there are some differences pre 68, but I'm not familiar with the early ones.
'69: change to fine inner axle spline to differential.
'73: rear axle seal and bearing change (seal is all rubber and no inner race on bearing)
'76: Disc brake change, fine spline inner and longer fine spline outer axles, but coarse pinon.
'78: Fine axle splines on both inner, outer and pinon.
'79: hub changes to the beefier 60 series equipment, birf is slightly larger, outer axle is slightly shorter, and gearing is changed to 3.7.
'81: rear axle flange changes to a 4 bolt flange and have parking brakes

I believe most can be "interchanged" with small modifications (except late model 4 bolt flange stuff). Only thing I don't know and I'm hoping someone will chime in (slight thread jack), is whether you can substitute and swap the early pre-'73 rear axle, seal and bearings with the later post-'73 rear axle, seal and bearings. I ask because I had originally planned to use the rear 1978 or 1980 housing I have and bought the full rebuild kit for it. But the rear 72 housing is in so much better shape that I want to use it, but I don't know if I can use the rebuild kit I have or if I'll have to buy a different one.

 

[Alex Waddell]

I believe that the differential will fit without any issues into the housing. I think the axles will be an issue, as I believe the inner axle fine spline change on 40's occurred in '69. The pinon flange will also be different between a 60 and 40. I believe the 60 were round flanges being a little larger bolt arrangement and the 40 were square. And I don't believe you'll be able to swap the flanges as the pinon splines will be different as the 40 did not become fine splined until 78. A flange from a later model 40 would be needed. Cruiser Outfitters or some other vendor should be able to help you out with the flanges and axles. I believe you may also have to grind some metal from the inside of the knuckle for the later birf's. There's several posts about that around here.

I'm doing a similar thing myself with '72 axle housings because they're in great shape, but I'm swapping the diffs from a '80 for the 3.7 gearing. To make life easier on myself though I'm using the axles and hub from a '78, which shouldn't have the same complications as the hubs changed in '79 to the "beefier" fj60 style.

From what I've seen changes go something like this (experts may need to correct me here):
Earlier than '69: I believe there are some differences pre 68, but I'm not familiar with the early ones.
'69: change to fine inner axle spline to differential.
'73: rear axle seal and bearing change (seal is all rubber and no inner race on bearing)
'76: Disc brake change, fine spline inner and longer fine spline outer axles, but coarse pinon.
'78: Fine axle splines on both inner, outer and pinon.
'79: hub changes to the beefier 60 series equipment, birf is slightly larger, outer axle is slightly shorter, and gearing is changed to 3.7.
'81: rear axle flange changes to a 4 bolt flange and have parking brakes

I believe most can be "interchanged" with small modifications (except late model 4 bolt flange stuff). Only thing I don't know and I'm hoping someone will chime in (slight thread jack), is whether you can substitute and swap the early pre-'73 rear axle, seal and bearings with the later post-'73 rear axle, seal and bearings. I ask because I had originally planned to use the rear 1978 or 1980 housing I have and bought the full rebuild kit for it. But the rear 72 housing is in so much better shape that I want to use it, but I don't know if I can use the rebuild kit I have or if I'll have to buy a different one.

Thanks for your thorough and informative response.
I called Cruiser Outfitters and they were very helpful.
Let me know about the rear axle bearings.
I may need to change my rear axle to a newer one in order to use the FJ60 differential.
I hope your project turns out well and be sure to send pictures.

 

[TundraTex]

Looks like Cruiser Outfitters got business from both of us today! I called them with my question and they said that there was an actual difference, so the later bearings and seal would not work. So I went ahead and ordered an earlier set from them.

Your current rear axle should work fine for the fj60 diff. But I think you will need to find a set of 69-73 fine spline axles to use with your 68 housing and the later diffs. The pre-73 axles are basically straight at the end next to the flange where the inner race is pressed on, whereas the post 73 axles expand out slightly right at the end where they touch the bearing. I went out and took some pictures and attached to try and show the difference.

What is odd. And what I'll be interested in seeing when I get the 72 housings back from being sand-blasted, is what the difference is on inner part of the housing. I pulled out some calipers and took measurements of what I could right now, and the pressed on inner race is the same diameter as the expanded part of the Post-73 axle. the outer diameter of the Pre-73 and post-73 housings are the same, as is the length of the housing past the flange. I have the housing ends all taped up and sealed for blasting, so I couldn't get measurements of them. I would imagine that the inner diameters or something will be different, otherwise the seal would be common and the bearing would be the only thing different and dependent on the axle set used. But I'll report back when I get to that point.

Happy hunting!

 

[Alex Waddell]

Looks like Cruiser Outfitters got business from both of us today! I called them with my question and they said that there was an actual difference, so the later bearings and seal would not work. So I went ahead and ordered an earlier set from them.

Your current rear axle should work fine for the fj60 diff. But I think you will need to find a set of 69-73 fine spline axles to use with your 68 housing and the later diffs. The pre-73 axles are basically straight at the end next to the flange where the inner race is pressed on, whereas the post 73 axles expand out slightly right at the end where they touch the bearing. I went out and took some pictures and attached to try and show the difference.

What is odd. And what I'll be interested in seeing when I get the 72 housings back from being sand-blasted, is what the difference is on inner part of the housing. I pulled out some calipers and took measurements of what I could right now, and the pressed on inner race is the same diameter as the expanded part of the Post-73 axle. the outer diameter of the Pre-73 and post-73 housings are the same, as is the length of the housing past the flange. I have the housing ends all taped up and sealed for blasting, so I couldn't get measurements of them. I would imagine that the inner diameters or something will be different, otherwise the seal would be common and the bearing would be the only thing different and dependent on the axle set used. But I'll report back when I get to that point.

Happy hunting!

I guess I am committed now. I will be picking up the rolling frame this weekend.

However, I am hearing conflicting information on the front and rear axle shafts.

I am hearing from one guy, who has been in the business for many years, that the FJ60 third member will plug into my 68' FJ40 rear axle without changing shafts.

He is also saying that my inner front axle shafts will install into both the FJ60 birfields and FJ60 differential in my existing axle tube.

And I hear from you and Cruiser Outfitters that I will need to change out both the rear axle shafts and the front inner shafts to mate with the FJ60 birfields and differentials.

I guess some 68' FJ40's had ball and claw (course spline axle shafts?) and others have birfields (fine spline axle shafts?).

This may be why their is some confusion. I suppose I won't know until I start to pull it apart.

But until now I have been busy working on installing the 3F-E engine and haven't had the time yet.

But I have located several complete rear axles and an empty FJ40 disk brake front axle tube just in case.

 

[Alex Waddell]

Looks like Cruiser Outfitters got business from both of us today! I called them with my question and they said that there was an actual difference, so the later bearings and seal would not work. So I went ahead and ordered an earlier set from them.

Your current rear axle should work fine for the fj60 diff. But I think you will need to find a set of 69-73 fine spline axles to use with your 68 housing and the later diffs. The pre-73 axles are basically straight at the end next to the flange where the inner race is pressed on, whereas the post 73 axles expand out slightly right at the end where they touch the bearing. I went out and took some pictures and attached to try and show the difference.

What is odd. And what I'll be interested in seeing when I get the 72 housings back from being sand-blasted, is what the difference is on inner part of the housing. I pulled out some calipers and took measurements of what I could right now, and the pressed on inner race is the same diameter as the expanded part of the Post-73 axle. the outer diameter of the Pre-73 and post-73 housings are the same, as is the length of the housing past the flange. I have the housing ends all taped up and sealed for blasting, so I couldn't get measurements of them. I would imagine that the inner diameters or something will be different, otherwise the seal would be common and the bearing would be the only thing different and dependent on the axle set used. But I'll report back when I get to that point.

Happy hunting!

View attachment 2312104

View attachment 2312105

I could be wrong but it looks like the difference between the two axles is that the pre-73 axle has a sleeve pressed onto it and the the post-73 axle was made from a single piece. Is the OD the same on both? If so, are you sure that there is a functional difference?