Questions about doing an FJ40 SOA with 80 axles (1 Viewer)

DangerNoodle

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Hey all, I'm looking for some information about doing a Spring Over Axle conversion for a 78' FJ40. I'm pretty new at all of this, and looking to help my dad switch from stock 40 axles to 80 axles. The axle conversion doesn't seem too hard to do, however, I am looking at doing a SOA conversion while everything is ripped out. The cruiser currently has a 4" lift with Old Man Emu Springs. The front has a shackle reversal. I'm planning on ripping out the 4" lift as people say that the SOA will add about 6" of lift. We would like to ultimately run 37"s at the end of this. Having about 8" of lift overall seems like it would be the best for running the larger tires, so I am looking at putting in Pro Comp 2.5" lift springs with the SOA.

Now, onto some questions. Does a SOA seem to be a good choice for something like this? I've been doing some research, and people say that they like the handling much better with the SOA conversion. Converting to a coil setup would be nice, however, my dad would like to run springs and it seems to be a lot more work to convert to coils from an 80. How much lift would be the best for running 37" tires and still keep good articulation? Would you need to have the 2.5" lift springs to comfortably flex without rubbing? If not, what springs would run well with this? The stock 40 springs seem to be a good choice, but are there any other springs that would work well with this? With the SOA conversion, what are the things to look out for? I've read that an improper conversion can really mess with the handling and make it an unworthy road vehicle. What shocks are recommended? We currently have Rancho 9000s on there now, and coupled with the OME springs, the ride is really stiff.

Any information is greatly appreciated.
Thanks!
 
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The front reverse cut high pinion 80 axle is a step down in terms of strength. You might consider a Dana 60 or a custom axle. Lots of people run 37s on a SOA 40 using the stock 40 springs. The main issue with 37s will be rubbing on the frame, fender or drag link.
 

DangerNoodle

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The front reverse cut high pinion 80 axle is a step down in terms of strength. You might consider a Dana 60 or a custom axle. Lots of people run 37s on a SOA 40 using the stock 40 springs. The main issue with 37s will be rubbing on the frame, fender or drag link.

Are the 80 fronts very prone to breaking under higher stress? For a 350 swap with a NV4500 and stock transfer case do you think that it will be that much of a problem? Is there any way to strengthen the axle at all?
 

reddingcruiser

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Hybrid 80/62 front axle. Took a back seat to other projects. Third is in, finishing is on the 'to-do' list for winter.
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Hey
 

DangerNoodle

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DangerNoodle

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You realize the 80’s are wider than the 40 axle right? Were you planning on shortening them or running wide?
I'm wanting to widen the footprint quite a bit, as there is a lot of pretty high off-camber situations where we live and would like to add some security. That's the big reason for wanting to go with the 80 axles. Dana 60s would be really nice, but those are really wide and would require a lot more modification to fit with the cruiser now.
 

reddingcruiser

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The upside of FJ80 axles - four-wheel disk brakes/MC/booster where the OEM components were meant to work together, and drive lines that bolt up with OEM stuff. Easier to find spares on the trail.
 

DangerNoodle

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The upside of FJ80 axles - four-wheel disk brakes/MC/booster where the OEM components were meant to work together, and drive lines that bolt up with OEM stuff. Easier to find spares on the trail.

One of the big reasons I'm wanting to go with the 80s. Is there any way to strengthen the front at all?
 
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The 80 front if I recall has a pretty short short side that will likely make it tough to fit leaf springs. I would do a fj60 front axle with 2 4plus axle housing spacers stacked on the short side of the housing. I definitely wouldn't do soa with 2.5" springs.
 

reddingcruiser

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FJ40 and 60/62 short side inner axles are the same at 17.25" Dave's spacer gets you to a 60 width on a 40 housing but requires a custom short side inner axle. This is the exact setup I currently have on my 40. The 80 short side inner is 17.75". When you consider the size of the axle bell, birfields and the size of knuckles, the short side of the 80 is longer. The benefit of the 4plus spacer is not having to outboard the springs. So, it is true that a hybrid 62/80 axle will NOT work without outboarding the springs.
 
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PO mentioned stability as a reason for the wider axles. When I swapped the 60 axles in my 40 I was amazed at how stable the rig became. although the axles are 1 1/2" wider than 40 axles, I believe the added stability came from outboarding the springs up front.
 

DangerNoodle

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PO mentioned stability as a reason for the wider axles. When I swapped the 60 axles in my 40 I was amazed at how stable the rig became. although the axles are 1 1/2" wider than 40 axles, I believe the added stability came from outboarding the springs up front.

What exactly is outboarding? Is it a difficult process?
 

reddingcruiser

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What exactly is outboarding? Is it a difficult process?
Easy peezi. Outboarding is simply moving the spring and shackle hangers 'outside' the frame rails. You can build your own brackets or Ruff Stuff has some really nice ones at a very reasonable price. If you are contemplating going to a longer spring (i.e.FJ60) this would be the time to do it.
 

DangerNoodle

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Easy peezi. Outboarding is simply moving the spring and shackle hangers 'outside' the frame rails. You can build your own brackets or Ruff Stuff has some really nice ones at a very reasonable price. If you are contemplating going to a longer spring (i.e.FJ60) this would be the time to do it.

Ok. That seems pretty straight forward. Thanks for the information!
 
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You need to add metal to the side of the frame where the springs will attach. the short side of 60 series and 40 series axles are the same and this puts the differential over the frame in the way of the stock spring location.
 

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