Custom "FJ40" build Advice

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I'm hoping to get the collective advice from all the talented people building sweet rigs. Here are my plans:

  • FJ40 aluminum tub extended 18 inches by Aqualu
  • Primary use case is rock crawling with the ability to drive 4+ hours
  • Four Seasons (heat & AC) vehicle with modified extended Hard Top
  • Targeting wheelbase of 112 inches to 115 inches
  • 3-link front and double triangulated 4-link rear
  • Atlas 4 or 2 speed transfer case
  • Dana Ultimate D60 Front axle with with ARB Locker
    14-bolt Rear axle shaved with ARB Locker
  • Connect&Cruise LS motor with 6L80-E
  • 40 to 42 inch tires

Questions about the Atlas:
  • I was planning a 4 speed, but I was recommended to leverage a 2 speed due to the amount of power from the LS V8
    • Assuming the 2 speed is a better approach, which is 3.0:1 vs 3.8:1 ratios?
    • The gearing spread is capable 6.04 with the 6l80-E, with ratios in each gear as follows:
      • First: 4.02, Second: 2.36, Third: 1.53, Fourth: 1.15, Fifth: .085, Sixth: 0.67
    • Regarding the Axle gearing, I was thinking about 5:13 gears
      • Of course, 4:88 gears are another option.

Questions about Chassis:
  • Came across the Bustled Knuckle lower chassis and thought this might be a nice base to build from
    • This approach handles some of the suspension engineering required
    • Of course, would need to figure out how to mount the tub
    • Anything I'm missing going down this approach?

Examples from other Mud members of end results:
(apologizes for not @ mentioning the owner, only pulled pictures while researching):
1667249007468.png


1667249020355.png

1667249035638.png
 

EWheeler

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    • Anything I'm missing going down this approach?
If you have $100K cash lying around and lots of free time, you're not missing anything.

Joking aside, is this something you're planning to build, or are you paying a shop to build it?

There is a build nearly identical to your wish list called DoubleXL. The build thread has been linked here many times, the original thread is on Pirate 4x4. He doesn't have a hard or soft top, and he modified the tub for the stretch versus going with an Aqualu tub.

Also, check out @Mike Shull build here in hardcore section. He is building essentially the same truck you are after, except he is doing an NV4500 with 4speed atlas.
 

EWheeler

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I am going to get drug over the coals for this, but for your desired finished product, I think a Jeep is a better starting point. Buy a 2 or 4 door JK depending on your space needs. Then go to MotoBilt and spend about $10k-15k on link subframes, axle brackets, armor, steering and other neat stuff. This stuff is literally like an erector set to build a highly capable trail rig. Pretty cool the products they develop, I know they aren't the only ones doing this kind of thing, but I like their product.



Get rid of the front clip of the jeep and graft an FJ40 front end onto it, like this:



I'd also spend $25k on 74 weld portals and run nearly zero lift and have a ton of axle ground clearance:


Lots of resources for dropping the LS drivetrain with an atlas right into a Jeep frame, so all you have to do is buy the parts and drop them in. Harness integration is no problem and you don't have to build stuff from scratch.

Jeep - $20k
Fabrication items from Motobilt - $10-15k
Built 1 ton Axles - $10-15k
Portals - $25k
Coilover Shocks - $5k
Drivetrain (engine, trans, atlas, harness, plumbing, etc) - $15k
Other stuff - $10k

Build Cost - $105k

Even if you do start with a $5k FJ40, add in the cost of the Aqualu tub and you're still spending close to $100k.
 

GLTHFJ60

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:popcorn:

Lower case gears are better. With an auto, you can probably get away without a doubler (4-speed atlas) but you'll want as low a gear as you can get in that two speed case.
 
Joined
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Messages
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Location
Northern California
If you have $100K cash lying around and lots of free time, you're not missing anything.

Joking aside, is this something you're planning to build, or are you paying a shop to build it?

There is a build nearly identical to your wish list called DoubleXL. The build thread has been linked here many times, the original thread is on Pirate 4x4. He doesn't have a hard or soft top, and he modified the tub for the stretch versus going with an Aqualu tub.

Also, check out @Mike Shull build here in hardcore section. He is building essentially the same truck you are after, except he is doing an NV4500 with 4speed atlas.
Thanks @EWheeler, I absolutely pulled inspiration from the DoubleXL build you mentioned. And I have been also following Mike's build here.

Yes, this is my dream build and will not cheap but planning to keep it forever!
 
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I am going to get drug over the coals for this, but for your desired finished product, I think a Jeep is a better starting point. Buy a 2 or 4 door JK depending on your space needs. Then go to MotoBilt and spend about $10k-15k on link subframes, axle brackets, armor, steering and other neat stuff. This stuff is literally like an erector set to build a highly capable trail rig. Pretty cool the products they develop, I know they aren't the only ones doing this kind of thing, but I like their product.



Get rid of the front clip of the jeep and graft an FJ40 front end onto it, like this:



I'd also spend $25k on 74 weld portals and run nearly zero lift and have a ton of axle ground clearance:


Lots of resources for dropping the LS drivetrain with an atlas right into a Jeep frame, so all you have to do is buy the parts and drop them in. Harness integration is no problem and you don't have to build stuff from scratch.

Jeep - $20k
Fabrication items from Motobilt - $10-15k
Built 1 ton Axles - $10-15k
Portals - $25k
Coilover Shocks - $5k
Drivetrain (engine, trans, atlas, harness, plumbing, etc) - $15k
Other stuff - $10k

Build Cost - $105k

Even if you do start with a $5k FJ40, add in the cost of the Aqualu tub and you're still spending close to $100k.
No doubt @EWheeler, the development on the Jeep platform would make this project more turn key. My challenge is how unreliable Jeeps are overall, I wheel with a bunch of Jeeps and constant problems on every trip. With that said, how much would really be left of the Jeep after the build is completed?!?! I appreciate the idea and approach and now you have me looking at Portals:) I wish there were more turn key options for FJs.
 
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Messages
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:popcorn:

Lower case gears are better. With an auto, you can probably get away without a doubler (4-speed atlas) but you'll want as low a gear as you can get in that two speed case.
Which is why I originally wanted 4-speed Atlas @GLTHFJ60 but if going with a 2 speed, sounds like you would recommend the 4:3:1. Do we think the 5.0:1 would be too extreme? I appreciate technical rock crawling at slow and controlled speeds the most.
 

GLTHFJ60

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I've never wheeled an automatic for any length of time. All the cars and trucks I've ever owned have been sticks. In my circumstance, a doubler is necessary.

My buddy @AJR has an 80 with low range gears in his case and 41s, and it does really well, but I'm sure he'd say he wants more gear than the 4ish:1 that he currently has.
 

EWheeler

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Which is why I originally wanted 4-speed Atlas @GLTHFJ60 but if going with a 2 speed, sounds like you would recommend the 4:3:1. Do we think the 5.0:1 would be too extreme? I appreciate technical rock crawling at slow and controlled speeds the most.
My crawler has a th350 and atlas II 3.8:1 with 4.56 diff gears. I've never once felt I needed more gearing. Moab, Johnson Valley, or Rubicon, never felt I was missing anything. It will idle/push through the brakes on steep downhills. I know that is more an issue with my brake system than final crawl ratio, but I really find it hard to believe you would NEED anything more than the 4.3:1 in the t-case for crawling with an auto and 5.xx diff gearing. I would think you would want the 4 speed options for those times you may want a bit more wheel speed, maybe some snow wheeling, or even just driving to/from the trail in some inclement weather? Having a 2:1 option and 3.8-4.3 option for crawling would be perfect, but I don't think you need anything more than 4.3 as your deepest gear set.

Annnnd, if you do go portals, you leave the diffs at 4.10 and get an effective final drive in the axles of 5.0:1 or 3.73 with an effective final drive of 4.55 :)
 

EWheeler

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No doubt @EWheeler, the development on the Jeep platform would make this project more turn key. My challenge is how unreliable Jeeps are overall, I wheel with a bunch of Jeeps and constant problems on every trip. With that said, how much would really be left of the Jeep after the build is completed?!?! I appreciate the idea and approach and now you have me looking at Portals:) I wish there were more turn key options for FJs.
Yes, if you have the capital and don't need to spread the build out over many years to afford it, I think the jeep route is really the quickest path to "crusin". An even quicker route (and more fiscally responsible) would be just buying a built rig with the majority of components you are after and modifying it to suit your final vision. The only thing jeep would be the harness and interior really. Same as if you went cruiser based, only thing 40 series would be some sheet metal and some sections of the frame probably? Maybe some dash wiring, but you'll likely replace all that with fancy digital gauges and push button switches like a switch pro!
 
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You will be time and money ahead and out enjoying the trails if you just start with a decently built Jeep Rubicon .
 

Tank5

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There is a lot of good advice here and I don’t aim to contradict any of it but if you are going to spend the money being talked about here to build a Jeep or Land Cruiser build what you want. Spending 100k on a vehicle your heart is not in is a waste of time in my opinion and probably money too, since I would guess you would eventually sell it to go after what you want.

If you are building this rig purely for the experiences you hope to have with it and Jeep or LC doesn’t matter to you as long as it works most of the time,🤣, then going with the platform you can build the quickest most affordably would make sense.

If you are doing it for the experience of building your own rig with bloody knuckles, empty wallet, and constantly telling your wife you don’t have a girl on the side then build the Land Cruiser you want. Most of us who choose to build a Land Cruiser have gotten caught up in something that is sometimes hard to explain, you won’t be alone. Although you could get divorced and forget your kids names. I would encourage you to try and lure them into the garage with you to help. Sorry there is no technical help here, just words from your future support group.
 

Vossie

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There is a lot of good advice here and I don’t aim to contradict any of it but if you are going to spend the money being talked about here to build a Jeep or Land Cruiser build what you want. Spending 100k on a vehicle your heart is not in is a waste of time in my opinion and probably money too, since I would guess you would eventually sell it to go after what you want.

If you are building this rig purely for the experiences you hope to have with it and Jeep or LC doesn’t matter to you as long as it works most of the time,🤣, then going with the platform you can build the quickest most affordably would make sense.

If you are doing it for the experience of building your own rig with bloody knuckles, empty wallet, and constantly telling your wife you don’t have a girl on the side then build the Land Cruiser you want. Most of us who choose to build a Land Cruiser have gotten caught up in something that is sometimes hard to explain, you won’t be alone. Although you could get divorced and forget your kids names. I would encourage you to try and lure them into the garage with you to help. Sorry there is no technical help here, just words from your future support group.
This. This right here.

If your aim is to have built your own rig, the experiences that come with that, the pain and the joy, then it doesn't matter what the platform is. Although the fact that we are talking on a cruiser forum speaks volumes to which way most of us lean

What matters most is that you build what you want to build. again, the fact that we are currently in the hard core sections also speaks volumes as to how we feel about heavily modded vs stock.

Hell, I'm taking 3 completely different vehicles and frakensteining them into an abomination, but its an abomination that I want to build.

And for me, that's the essence of being a car guy. What's the point of driving around in the same metal box as everyone else? Make it your own. Make it yours. Best way to do that is to build it, to whatever extent you want, whether its a daily that looks like a hardcore 45, a civic with a laptop riding shotgun, a supra with 1000hp, or an extended 40 with an LS. whatever it is, just make it yours.

Just my $0.02.
 

bluehawk

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If you truly want to build a capable rig, just find a Jeep Jk frame and put your tub on that. Use what ever axles you want, engine, trans, ets.....
I can't keep anything stock.
Japanese Made American Modified....
Ian Johnson builds a lot of stuff mounted on a Jeep frame.
 

EWheeler

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Driving to the airport thinking on this. You may need a title and frame section from a pre ‘76 FJ40 to make this much much simpler to be exempt from CA smog laws :(

Maybe buy a troopy and shorten it? Or, import an FJ43 from south america that hasn’t been “shined up”. Personally i would modify a steel tub before i bought an aluminum one, but l im really a cheap ass.
 
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My crawler has a th350 and atlas II 3.8:1 with 4.56 diff gears. I've never once felt I needed more gearing. Moab, Johnson Valley, or Rubicon, never felt I was missing anything. It will idle/push through the brakes on steep downhills. I know that is more an issue with my brake system than final crawl ratio, but I really find it hard to believe you would NEED anything more than the 4.3:1 in the t-case for crawling with an auto and 5.xx diff gearing. I would think you would want the 4 speed options for those times you may want a bit more wheel speed, maybe some snow wheeling, or even just driving to/from the trail in some inclement weather? Having a 2:1 option and 3.8-4.3 option for crawling would be perfect, but I don't think you need anything more than 4.3 as your deepest gear set.

Annnnd, if you do go portals, you leave the diffs at 4.10 and get an effective final drive in the axles of 5.0:1 or 3.73 with an effective final drive of 4.55 :)

This is a great perspective @EWheeler, it seems the 3:8:1 would be a great overall approach. I agree the 4 speed would allow more flexibility and higher speeds in 4 wheel with the 2:1 option for incremental weather (less about crawling).
 
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This. This right here.

If your aim is to have built your own rig, the experiences that come with that, the pain and the joy, then it doesn't matter what the platform is. Although the fact that we are talking on a cruiser forum speaks volumes to which way most of us lean

What matters most is that you build what you want to build. again, the fact that we are currently in the hard core sections also speaks volumes as to how we feel about heavily modded vs stock.

Hell, I'm taking 3 completely different vehicles and frakensteining them into an abomination, but its an abomination that I want to build.

And for me, that's the essence of being a car guy. What's the point of driving around in the same metal box as everyone else? Make it your own. Make it yours. Best way to do that is to build it, to whatever extent you want, whether its a daily that looks like a hardcore 45, a civic with a laptop riding shotgun, a supra with 1000hp, or an extended 40 with an LS. whatever it is, just make it yours.

Just my $0.02.

This is 100% right and I realize this isn't the cheapest way to build a vehicle. I can't stand a stock vehicle either, I don't want to drive something that anyone can buy off the lot. Plus Jeeps are a dime a dozen, but a sweet customer FJ would be unique. I can't tell you how much fun it is to research and come up with my perfect build. The only thing that hurts are the expenses with this approach, but you only live once and I would rather build my dream rig now.
 
Joined
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Messages
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If you truly want to build a capable rig, just find a Jeep Jk frame and put your tub on that. Use what ever axles you want, engine, trans, ets.....
I can't keep anything stock.
Japanese Made American Modified....
Ian Johnson builds a lot of stuff mounted on a Jeep frame.
Yes, that is the cheaper/quicker path. I've been checking out those Ian Johnson builds and they are strong. Since I have access to a 80 series drive train, I can save a bunch by using those axles, transfer case with a blackbox doubler under the FJ40 tub and call it a day. The rig will be "ligher" than the 80 series and I can drop down to 38 inch tires to make sure I don't break the axles. Decisions, decisions....
 
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My race car has a 6L80 and a Np205 (1.96:1) and 5:38's. It does good at what it was built for (KOH), but sucks trail riding and technical stuff. It is not slow enough. I would think a 4:1 case would be better but if you have the room I would do a 4spd atlas all day long. I had a Black box-205 combo in my last rig. Never used the black box racing but did enjoy it trail riding on tech stuff.
 

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