Early Axle Housing Strength

[Tank5]

I have a centered rear axle housing from a 1963 FJ40 that I want to use to build a full float axle. I started a build thread in the hard core section if you want to know more. I am posting in this section because I have one question that I thought could be better answered here. Question is:

Is there a difference in the strenght of early pre 1965 axle housings compared to later housing? I have found references that they are weaker but nothing factual that backs that claim up. I know the diff. housing studs are smaller.

I searched a long time before creating this thread, so if this is answered somewhere please point me in the right direction.

 

[Tank5]

Bump to the first page

 

[Living in the Past]

I think it's the coarse spline axles shafts that are the weak point. The studs for the diff and back inspection plate are smaller but could be drilled and tapped to the larger size. Fill and drain plugs should also be replaced to something with a smaller head, particularly the drian plug. Believe the brake backing plate is the same pattern as the semi floater until 8/80 when the full floater and semi floater were the same. I have a early FJ40 that has custom hubs the allowed to do away with the C clips in the diff. It has a Torsen diff. It was in a FJ25 but because of the brakes I know it's out of a FJ40. Since your converting to a full floater I would start with a early FJ40 centered diff axle over a mini truck to get the larger diff.

 

[69LC]

I have a couple of questions:

Is the axle for a close to stock resto, just adding FF?

If its for a custom trail truck, why not leave a rare-early centered axle housing for someone's resto (if resto isn't your goal)?

From the centered rear diff threads I've seen here it doesn't look very difficult to use a 40 center and cut tubes melded with mini truck rear tubes and shafts.

 

[Tank5]

I have a couple of questions:

Is the axle for a close to stock resto, just adding FF?

If its for a custom trail truck, why not leave a rare-early centered axle housing for someone's resto (if resto isn't your goal)?

From the centered rear diff threads I've seen here it doesn't look very difficult to use a 40 center and cut tubes melded with mini truck rear tubes and shafts.

No it is not for a resto. I want to put in under my tacoma. I listed that purpose of the build in the other thread if you want more info on why I am considering this.

I think it's the coarse spline axles shafts that are the weak point. The studs for the diff and back inspection plate are smaller but could be drilled and tapped to the larger size. Fill and drain plugs should also be replaced to something with a smaller head, particularly the drian plug. Believe the brake backing plate is the same pattern as the semi floater until 8/80 when the full floater and semi floater were the same. I have a early FJ40 that has custom hubs the allowed to do away with the C clips in the diff. It has a Torsen diff. It was in a FJ25 but because of the brakes I know it's out of a FJ40. Since your converting to a full floater I would start with a early FJ40 centered diff axle over a mini truck to get the larger diff.

I think you are correct i did my own research listed in the thread and the housing doesn't really seem to be different. I a trying to upgrade t get the larger LC diff. for this project.

 

[Tank5]

Ok, I think I have answered my own question and have concluded that there really is no significant difference between housings between the old and new. This is not the most thorough comparison but it is enough for me. Here is what I did.

I compared 4 axle housings.

63 rear centered FJ40 housing
76 rear FJ40 housing
93 front FJ80 housing
2001 rear Tundra housing (almost same as 01 tacoma housing I want to replace)

I used a Dial Caliper and measured to the thousandth of an inch

The two measurements I compared are:

Differential mounting flange thickness
Outer diameter of housing tube between the backing plate and spring perch.

Results

63 centered FJ40 housing

• Diff. Flange Thickness .409 inch
• Housing Tube Diameter 3.139 inch

76 rear FJ40 housing

• Diff. Flange Thickness .400
• Housing Tube Diameter 3.170

93 Front FJ80 housing

• Diff. Flange Thickness .422
• Housing Tube Diameter 3.155

01 Tundra housing

• Diff. Flange Thickness .462
• Housing Tube Diameter 3.160

The 63 and 76 housing have pretty much the same shape around the the diff. The Tundra housing looked like the shape from the diff housing extend further down the housing tube but this could be deceiving because the diff is small 8" I think. The 80 series has a similar shape to the 63 and 76 housings but has some added gussets the extend from the diff part way down the tube.

I would love to be able to measure the thickness of each housing tube but cannot without cutting the ends off of each of them which I don't want to do. I am guessing that this measurement would be very similar and consistent since the outside measurements were.

I took several measurements with the calipers each time I measured to try and get a consistent measurement each time. Measuring to the thousandth of an inch leaves room for error if the caliper is not strait or canted slightly, so please accept these measurements as pretty darn close.

If you choose to accept that the welds are equal in strength being all factory and if the tube thickness is as consistent as the diameter of the housing tube then there is not much difference between these axles in terms of construction. The early 40 axle could be improved by adding a truss or extension half trusses like on the 80 series axle.

I am sure I missed something so please add what I have missed.

 

[Living in the Past]

Simplest way would be to cut down the long side of the 80 series full floater then have a custom inner axleade for that side. Would also have disc brake and hand drum brake. 63 would need a lot more work to make a full floater, disc brake and hand brake. Even if the rear is perfectly centered should be close enough. 61-63 Toyota ran a centered axle with a offset T case on a shorter wheel base.

 

[Tank5]

Simplest way would be to cut down the long side of the 80 series full floater then have a custom inner axleade for that side. Would also have disc brake and hand drum brake. 63 would need a lot more work to make a full floater, disc brake and hand brake. Even if the rear is perfectly centered should be close enough. 61-63 Toyota ran a centered axle with a offset T case on a shorter wheel base.

I agree it would be easier to use a FF 80 axle. I don't have one though and don't have the spare funds to buy one unless I found it cheap locally. I am only considering this project because I have the fj40 centered housing already and the FF 80 hubs. If anyone wanted to trade me my centered fj40 complete axle for a complete 80 series ff, I would be all about it. I do have some reservations about cutting up the old housing to do this, so I will likely think about it for a while. I don't have a timeline for the project at this point I was just trying to decide if the centered housing was worth using for this project. I think it is a good housing to use I just need to decide if I want to commit to it.