Need help identifying non-FJ40 rear axle

[Guke34]

So I recently purchased a '74 FJ40 as a project vehicle and to hone my beginner level mechanics skills. The PO performed a front disc brake conversion (incorrectly I fear because I believe the bearings are already shot. That will likely be a future post). He also included the parts, minus a bracket, for a man-a-fre rear brake conversion. Being as the rainy season is here in Portland, I figured it was time to start working on it. I have read most of the threads and the FAQ section related to this swap. Yesterday, when I removed the wheel, it became immediately apparent that this is not a FJ40 rear axle. After doing some digging around, it appears to be a minitruck rear axle. Could anyone confirm this? If so, is there a way to tell what year it is? On a related topic, assuming that this is a minitruck axle, I will have a pile of drum parts in the near future if anyone is interested.

I will appreciate any help. Thanks.

 

[inkpot]

Does indeed appear to be a mini axle. Is the diff housing centered in the axle? None of the FJ 40-55 axles are centered.

 

[Guke34]

Thanks for the input. Yes, the diff housing is centered. Are there any drawbacks to the mini axle? Now this has me wondering about something else... Are the springs on a mini truck shorter than FJ40 springs? The rear tires sit noticeably forward of center in the wheel well and the rear shackles are almost vertical... Sorry, that was more thinking out loud than an actual question. My next question would be if I can re-use the rotors and brake calipers that I currently have and just order mini axle brackets. It looks like either kit uses chevy rotors and monte carlo calipers. Does this sound accurate?

 

[IFORDJC]

You might want to also take a look at the brake line length. From the picture it looks like the line near the right rear axle is pretty tight and wanting to snap. Good luck with the Cruiser.

 

[Guke34]

Thanks! Sadly the front ones are even worse

Almost all the brake lines are unsecured and just flopping around. I'm going to replace/fix them when I do the brake conversion.

 

[inkpot]

Thanks for the input. Yes, the diff housing is centered. Are there any drawbacks to the mini axle? Now this has me wondering about something else... Are the springs on a mini truck shorter than FJ40 springs? The rear tires sit noticeably forward of center in the wheel well and the rear shackles are almost vertical... Sorry, that was more thinking out loud than an actual question. My next question would be if I can re-use the rotors and brake calipers that I currently have and just order mini axle brackets. It looks like either kit uses chevy rotors and monte carlo calipers. Does this sound accurate?

Usually the mini axle is used to resolve drive shaft angle issues when using a non-stock transmission setup. Landcruisers have both driveshafts on the passenger side. Most domestic transfer cases, and mini trucks, have a centered rear output, so some rigs with v8 setups and domestic transmission/transfers use the mini axle to match position for the lineup. Biggest difference, other than being a centered diff, is that the mini ring gear is only 8", so not as strong. Your diff is kind of angled upwards, so I am guessing you are not running a stock driveline. Your leafsprings look like either minis or aftermarket also. John

 

[Guke34]

inkpot, it's amazing that you can deduce that by simply looking at a few photos. You just blew my mind! I have a chevy V8 w/ automatic transmission. I'm not planning on doing any serious off-roading so I don't think I'll worry too much about it.

 

[inkpot]

inkpot, it's amazing that you can deduce that by simply looking at a few photos. You just blew my mind! I have a chevy V8 w/ automatic transmission. I'm not planning on doing any serious off-roading so I don't think I'll worry too much about it.

I bought my first 40 in 1977. I put a 350 and MP 465 transmission in it within a few years. Been playing with them ever since. Last 6 months or so I have done nothing but build up custom 40's for other folks. Best part is taking them out for the TEST RUNS !!

Biggest concern for you will be the skinny pedal. Many others have had good luck with your setup, so don't loose a lot of sleep over it. It should hold up OK for normal driving and an occasional burst of entertainment. I have no personal experience with your setup, but I have considered it a few times.

 

[Living in the Past]

None of the FJ 40-55 axles are centered.

That's news to me. The early FJ40 had centered diff for the first couple of years. It does surprise no one wants them. Everybody gets stronger axle shafts made. Get three made and you have a spare. Convert the brakes to disc and you have a rear axle that bolts up and tougher than a mini truck axle.

 

[inkpot]

That's news to me. The early FJ40 had centered diff for the first couple of years. It does surprise no one wants them. Everybody gets stronger axle shafts made. Get three made and you have a spare. Convert the brakes to disc and you have a rear axle that bolts up and tougher than a mini truck axle.

My bad. I thought that was only on the FJ 25 models.

 

[Living in the Past]

My bad. I thought that was only on the FJ 25 models.

It should have been. All FJ40s had a offset rear output from the transfer case but it wasn't until sometime in 63 when the rear diff finally matched the transfer case output.

 

[inkpot]

It should have been. All FJ40s had a offset rear output from the transfer case but it wasn't until sometime in 63 when the rear diff finally matched the transfer case output.

Details! I missed that one. Duh? The older I get, the more I learn/forget/both.

 

[73tlcv8]

I'll start by saying I'm not familiar with the man-a fre rear axle brake conversion. I see they sell an Early - 7/80 FJ40 axle and an 8/80 + FJ60 axle conversion kit. Do you know which kit you have?

The first thing I noticed, the backing plate in the picture is rotated 90 degrees to the rear of the truck from the normal position. The round hole should be top center. The 8/80+ FJ40 and fj60 backing plate orientation is fixed by the four bolts on the axle end, two of which are wider apart than the other two. The backing plate can only be installed one way and cannot be rotated 90 or 180 degrees. You or someone else knowledgable can verify this is also true on the mini truck axle. If the mini truck axle bolt pattern is square such that the backing plates can be rotated as yours are, the 8/80 + man a fre bracket may not work. The E- 7/80 bracket will certainly not work since it went from a six bolt to 4 bolt flange.