Fj40 axle upgrade recommendation (1 Viewer)

IslandJ

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New to fj40’s. Working on a project 1973, non purist budget build.
Not set on the driveline setup but the PO started a Chevy v8 swap but didn’t get too far. In our possession we essentially have the 73 body/frame/axles.
Talks of putting in a turbo charged 4.3 Chevy vortex engine and 4L60E transmission.
Goal, at the moment, is to upgrade the axles to something with at least disk brakes up front.
From what I’m reading so far is FJ60/62 axles would be the quickest and easiest for the upgrade, yeah?
Any other recommendations? I see the 80 series rear, 93+ would be a disk brake up grade in the rear.
We have a line on a set of 1985 mini truck axles but looks like besides the front disk brakes, it’s a downgrade in strength.
Pictures of the project

F5A74109-37FF-4860-966E-53B245A606CD.jpeg


9C4E140E-DA21-4DB6-9FF8-7B430CE7FCAB.jpeg
 
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76 40 series will bolt in with only mods to the hydraulic system. Early pickup would require using you current axle and knuckes out from the pickup. Land cruiser used slot rotors while pickup were solid. Land Cruiser have heavier brakes.
 
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I have the mini truck disc upgrade and recommend it. Pretty straight forward and you get fine spline birfields. Possibly aisin hubs. IFS mini truck calipers are bigger (as I recall) and adding vented rotors finishes the upgrades needed. It’s a messy job, but not terribly difficult.
As for the rear 80, I haven’t done it, but sounds like it has a few pros and cons.
Cons:
  1. Wider than a stock front axle, you’d want a wider front axle.
  2. Wrong offset differential- wonky driveline angles
  3. It’ll take some work to get all the coil brackets off and adding spring purches.
Pros:
  1. More stable due to width
  2. Stronger axle
  3. Elocker???
  4. Disc brakes
Personally, I’m running a mild SBC 350 with 35” BFG MT’s. Stock rear axle, stock front w/ aforementioned mini upgrade. I’m quite happy with the axles. If you wanted to do burn outs, you might think about stronger axles.
 
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Just out of curiosity- is that the stock turbo 4.3? Or have you lined up an aftermarket turbo? What kind of numbers will you expect?
 

IslandJ

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Thanks for the feedback guys.

Just out of curiosity- is that the stock turbo 4.3? Or have you lined up an aftermarket turbo? What kind of numbers will you expect?

I havent actually seen the engine yet. All word of mouth but supposedly its out of a 1993 GMC Typhoon with a stock turbo.
 

reddingcruiser

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60/62 axles are not a bolt in deal, but worth the effort if you want to go that route. Both require outboarding the springs.

FJ80 FF rear axle is a good choice, but again requires moving the spring perches.

High pinion FJ80 front axle is not a good choice as-is. Knuckle parts make a nice setup when paired with a Ruff Stuff or FJ62 housing.

Simplest is the late FJ40 front axle.
 
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Thanks for the feedback guys.



I havent actually seen the engine yet. All word of mouth but supposedly its out of a 1993 GMC Typhoon with a stock turbo.
So if it’s the factory tune, it’ll put out 250hp/350ftlb from the factory. Assuming it’s a little tired, less. You should be fine I’d think. Definitely, do the mini truck disc swap. Google it. It just the outer part of the axle you’re swapping.
****I did forget to mention you’ll need to figure out you steering arms to tie rod configuration. This’d be a good time to go to power steering(fj60).
 

lcwizard

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what will you do with the truck? Rock crawl, mostly street ? Is your idea of fun the John Bull trail in reverse, blindfolded or
more a take it fishing kind of guy?
 

IslandJ

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what will you do with the truck? Rock crawl, mostly street ? Is your idea of fun the John Bull trail in reverse, blindfolded or
more a take it fishing kind of guy?

Nothing extreme. Moderate off-road trails and just sun bathing while stuck in LA traffic. ;)
 

lcwizard

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Nothing extreme. Moderate off-road trails and just sun bathing while stuck in LA traffic. ;)

I'm sure you'll be fine with a knuckle swap from a 60 series/mini truck axle. A 60 rear is nice and requires minimal
effort. The brakes are better. You lose one cylinder on each side and the width gain ( 2 1/2ish ) gives you a little better
feel both on the highway in corners and on sidehills out wheeling. The perches need moving but that's pretty straightforward.
With a disc swap up front you'll be gaining 1 1/2" or so in width also. The front track is wider than the rear to start with. The
change to a 60 rear and disc front won't change that relationship by very much. The front will still be a bit wider.
An 80 rear is much wider, 8~10" off the top of my head. I've put them in a 40 but to match the front I had to widen a 60 series
front axle 6". This was a 80% trail, 20% street truck with 38" tires.
Not only is the width an issue but there's a load of brackets that need removing that supported the link suspension before
adding leaf spring perches
 
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I'm sure you'll be fine with a knuckle swap from a 60 series/mini truck axle. A 60 rear is nice and requires minimal
effort. The brakes are better. You lose one cylinder on each side and the width gain ( 2 1/2ish ) gives you a little better
feel both on the highway in corners and on sidehills out wheeling. The perches need moving but that's pretty straightforward.
With a disc swap up front you'll be gaining 1 1/2" or so in width also. The front track is wider than the rear to start with. The
change to a 60 rear and disc front won't change that relationship by very much. The front will still be a bit wider.
An 80 rear is much wider, 8~10" off the top of my head. I've put them in a 40 but to match the front I had to widen a 60 series
front axle 6". This was a 80% trail, 20% street truck with 38" tires.
Not only is the width an issue but there's a load of brackets that need removing that supported the link suspension before
adding leaf spring perches


Easier still to just add a 8/80+ short or mid wheel base 40 series. Same brakes as a 60 series but bolt right in. These also have hand brake. Want to add a E-locker just use a full floater. Personally like the narrower track. I'm sure you've cut a side wall or two in a narrow canyon here in AZ. I've had it happen out at P4W years ago.


Guess it depends on how you drive if you really need disc brakes. Still plenty of the fifty plus cruisers around with single circuit and eight wheel cylinder. Our DD for the Phoenix are are both from this century. Both have all the safety features including being able to drive down the highway 4WD. The 40 series is based off the 20 series from the mid fifties. Would take a lot more than disc brakes and power steering to feel comfortable driving I'm today's traffic.
 

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