Axle difference between 80 and early 70's

[cjgoode]

I am looking at a 1980 fj40 total rust bucket and disassemble. The chassis is still rolling but does not have front disk brakes. He beleives the previous owner put on axles from a 72 fj40.

What are the differences, strenght, size etc.. Any difference in axles, gear ratios etc. Any difference I would need to know if I have to order parts for them other then the brakes. Would the actual year of the axle be critical for getting parts.

Thanks Chris

 

[toomanytoyzz]

The gear ratios on the 79+ rears are 3.90's while the 78 under are 4.10's. Disc brakes were equipped on 76+ vehicles, but they still kept the 4.10's until 79. I know there are probably some other minor differences, but that's the main one I know of.

 

[numby]

As I remember the early '70s axles use a different style of inner axle bushing/seal from the disc brake ('76 and up) housings. I'm pretty certain that drum brake axles have different spindles from the disc '76+ and the '79+ axle assemblies use a different knuckle with a wider steering arm/bearing cap stud pattern and also have a stronger birfield that can be retrofit into the older assemblies with a little grinding inside the ball (think mini-truck disc brake swap). On top of that there are braking system differences that run from master cylinders and proportioning valves to brake lines (hard &soft) and the backing plates/connectors/fittings that are bolted to the housing but you didn't ask about that

This is all info I carried in my head 15-20 years ago so take it with a grain of salt.
Sounds like the PO swapped the newer axles onto his older, less rusty truck.

 

[vk7ybi]

The gear ratios on the 79+ rears are 3.90's while the 78 under are 4.10's. Disc brakes were equipped on 76+ vehicles, but they still kept the 4.10's until 79. I know there are probably some other minor differences, but that's the main one I know of.

I think you need to do more revision before you post gear ratio figures..

 

[cjgoode]

will the gear ration from the older axles help me or hurt me with bigger tires. It is running 33's now will likely keep them, but eventually might go 34 or 35's

 

[GarnerFJ40]

Older axles will be better for off-road, the newer ones are better for highway driving...

 

[toomanytoyzz]

I think you need to do more revision before you post gear ratio figures..

What's the right ratios for the years? I know it's 4.11's and not 4.10's for toyota (I'm a Ford guy), but I could have sworn the axle ratios for US built 40's 79+ were 3.90's. Maybe old age is catching up with me????

 

[schlaker]

What's the right ratios for the years? I know it's 4.11's and not 4.10's for toyota (I'm a Ford guy), but I could have sworn the axle ratios for US built 40's 79+ were 3.90's. Maybe old age is catching up with me????

Pretty sure it's 3.73

 

[Lake Rat]

Sorry for the interuption, but I have a '68 and 2 '78 fj40's, I believe that the spline count on the pinion gears are different too, the older the year, the more course the spline (fewer spline count), the newer ones have a finer spline(more splines). I also am just going by memory as I haven't taken my diffs apart in a while. But something to investigate, just in case you have two different year axles on your truck if you swap gears. The 4:10's in my 40's handle 33" tires no problem hwy or trail. I am currently running 35's on one of my '78's (4" lift sua) and the difference between those and 33's on the trail, power wise is negligible, hwy may be a little different, haven't tried that yet... too busy working on the other two......

 

[FJ40Jim]

78-earlier USA cruiser has 4.11111 diffs.
79-87 USA cruiser has 3.70000 diffs.

You don't want anything to do w/ 72 axles. Small CV joints, coarse spline front hubs, drum brakes, coarse spline pinions, small pinion flanges...

 

[cjgoode]

Unless I win the lottery will not have much choice for a long while.