Builds Stretched 1-Ton FJ40 (2 Viewers)

[Mike Shull]

It's the only one I would do in the rear, as for the front, you can only really do a 3 link unless you run full hydro.

Now I see why the big concern to do the rear while the body is off. I’ve got a bit of work to do back there, which should be a fun project.

I checked out a 3-link front on an FJ40 that is near my house and I can see why a 4-link front would not be preferable based on clearance to the oil pan. It’s hard to imagine what mine looked like with a drivetrain in it and my LS is a bit more bulky on the bottom end than my old 383. Can you tell me more about how full hydro would help create more space? It is simply because this setup would eliminate the tie rod from behind the axle?

I am just curious as I will most likely do a similar setup as described in the build mentioned a few posts above.

 

[DangerNoodle]

Now I see why the big concern to do the rear while the body is off. I’ve got a bit of work to do back there, which should be a fun project.

I checked out a 3-link front on an FJ40 that is near my house and I can see why a 4-link front would not be preferable based on clearance to the oil pan. It’s hard to imagine what mine looked like with a drivetrain in it and my LS is a bit more bulky on the bottom end than my old 383. Can you tell me more about how full hydro would help create more space? It is simply because this setup would eliminate the tie rod from behind the axle?

I am just curious as I will most likely do a similar setup as described in the build mentioned a few posts above.

It's not an issue of space, it's the problem with having a mechanical linkage, your drag link, wanting to move in an arc, while your suspension (if it is a 4 link) wants to move parallel to the frame. Whenever the suspension flexes or articulates in any way, the drag link must move the steering box to keep it moving parallel as well. You have massive bump steer issues with a 4 link + mechanical steering. Hydro is not mechanical, so it doesn't matter.

The problem with hydro is that 1. It is not DOT legal, and 2. If your engine ever dies, you pretty much lose steering capabilities, which is never good if something happens on the highway. I cannot recommend full hydro for a rig that is driven on the street a lot. Hyrdo assist is fine, as it keeps the mechanical connection to the axle from your steering wheel.

With a 3 link, the panhard keeps the axle moving in an arc, so the steering box is happy. That is why you need to match the angle, length, and relative height of the drag link to the panhard, to minimize bump steer.

 

[DangerNoodle]

All the buggy guys love dual triangulated 4 links in both ends, as there is no flex steer, since the dual triangulation keeps things very, very parallel. Single triangulation is ok, but you can get some flex steer since the axle can move laterally when articulating it. Would it really matter that much on something like this? Probably not, but if you have the space (which you should), you should use dual triangulation. There is no reason not to.

If you are planning on linking it, start figuring out what anti-squat / anti-dive numbers you are shooting for, and toss everything into a link calculator. It's all going to be a compromise, so whatever gets you the closest and fits well, is probably going to be your final design. I have about 110% anti-dive on my front links right now, and I am planning on dropping it to around 70% since it likes to unload a bunch during climbs. I've heard (from pretty experienced buggy guys), they like around 50%-70% on both ends for larger climbs, to limit the suspension from unloading. I'm sure other guys on here can chime in with their experience.

 

[Mike Shull]

Thank you for the wealth of knowledge, @DangerNoodle! It's been awhile since I've bothered with anti-dive and squat. When you mention that your suspension unloads on a climb, are you referring your front end extending while being more susceptible to lifting the wheels off of the ground during a climb? Shouldn't the higher percentage anti-dive figure prevent this transfer? In other words, wouldn't a lower anti-dive cause the front to be more susceptible to lifting under acceleration and/or steep climbs?

What are your anti-squat values?

When I first did my SOA conversion on factory FJ40 springs in 1999, my values were not optimal, especially after installing the 383 a few years later. Wheelies were common for me. I worked with Alcan Spring for a month while they fabricated leaf springs that would keep the front stuck to the ground while preventing the rear from compressing too much on an incline. They did this while maintaining a comfortable ride and I thought that this was done by raising my anti-dive/squat values, but this was nearly twenty years ago.

I've needed to refresh on suspension geometry and I am placing a few links below for future reference. I welcome any and all feedback to the credibility of the content:

4-Link Suspension Guide | Anti -Squat, Anti-Dirve, and Roll Center Explained

Crawlpedia is an off-road encyclopedia featuring a complete guide to 4-link and 3-link suspension characteristics.

www.crawlpedia.com

 

[DangerNoodle]

Thank you for the wealth of knowledge, @DangerNoodle! It's been awhile since I've bothered with anti-dive and squat. When you mention that your suspension unloads on a climb, are you referring your front end extending while being more susceptible to lifting the wheels off of the ground during a climb? Shouldn't the higher percentage anti-dive figure prevent this transfer? In other words, wouldn't a lower anti-dive cause the front to be more susceptible to lifting under acceleration and/or steep climbs?

What are your anti-squat values?

When I first did my SOA conversion on factory FJ40 springs in 1999, my values were not optimal, especially after installing the 383 a few years later. Wheelies were common for me. I worked with Alcan Spring for a month while they fabricated leaf springs that would keep the front stuck to the ground while preventing the rear from compressing too much on an incline. They did this while maintaining a comfortable ride and I thought that this was done by raising my anti-dive/squat values, but this was nearly twenty years ago.

I've needed to refresh on suspension geometry and I am placing a few links below for future reference. I welcome any and all feedback to the credibility of the content:

4-Link Suspension Guide | Anti -Squat, Anti-Dirve, and Roll Center Explained

Crawlpedia is an off-road encyclopedia featuring a complete guide to 4-link and 3-link suspension characteristics.

www.crawlpedia.com

I don't really lift tires, the weight unloads towards the back, and it starts to get super light in the front. It doesn't lift, but I get no traction. More vertical separation on the frame side of the links would solve it, which should lower the % if I remember right.

I have no idea what my rear anti-squat is. Never did the math since I'm spring over.

 

[matzell]

It's the only one I would do in the rear, as for the front, you can only really do a 3 link unless you run full hydro.

You could do a 5 link like a jeep set up? a well designed 3 link will do ok but with a lot of travel it will walk on you.

 

[DangerNoodle]

You could do a 5 link like a jeep set up? a well designed 3 link will do ok but with a lot of travel it will walk on you.

I would think that the 5 link would do the same thing, it still has a panhard. I see it as just another bar to try and shove in there.

 

[Mike Shull]

 

[DangerNoodle]

No words are necessary…

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Nice box. I always wanted one.

 

[Mike Shull]

Sorry, @DangerNoodle, the box is no more.

 

[DangerNoodle]

Sorry, @DangerNoodle, the box is no more.

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[matzell]

Sorry, @DangerNoodle, the box is no more.

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View attachment 2874412Nice! is that the 5:4 case? 2:1 and 2.7:1

 

[Mike Shull]

@matzell, It is supposed to be but I just checked the ratios and it is actually a 5.74:1 with 2.11:1 main case ratio as noted on the case and 2.72:1 front case. The 2.11:1 ratio wasn’t an option so I’m not quite sure how that worked out but I am very happy with it.

 

[Mike Shull]

First test fit. The Atlas is about 1/2” away from the right frame rail when clocked at 7 degrees. @DangerNoodle, do you remember what angle that you clocked your Atlas? I will aim for the next notch tomorrow to see if I have better clearance.

Note that the angle meter shows 12 degrees when I took these pictures and this is because the engine slid down on the right side right before I took the picture. It is actually 7 degrees when the engine is level.

 

[DangerNoodle]

First test fit. The Atlas is about 1/2” away from the right frame rail when clocked at 7 degrees. @DangerNoodle, do you remember what angle that you clocked your Atlas? I will aim for the next notch tomorrow to see if I have better clearance.

Note that the angle meter shows 12 degrees when I took these pictures and this is because the engine slid down on the right side right before I took the picture. It is actually 7 degrees when the engine is level.

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I don't have an atlas, I have a toybox and splitcase. Honestly, I would clock it balancing the driveline angles and how much drop you are wanting for your skid.

 

[Mike Shull]

I don't have an atlas, I have a toybox and splitcase. Honestly, I would clock it balancing the driveline angles and how much drop you are wanting for your skid.

Oops, my bad. I need to remember to reference your signature line. I’ll experiment a bit more tomorrow.

 

[DangerNoodle]

Oops, my bad. I need to remember to reference your signature line. I’ll experiment a bit more tomorrow.

Ha, not a problem. Its all a game of balance.

 

[bluehawk]

Mike what fuel tank are you using? I'm looking for options

 

[Mike Shull]

Mike what fuel tank are you using? I'm looking for options

I’ve put my fuel system on hold. The tank that is in my Cruiser is from an early 90s 2-door S-10 Blazer. This tank might work for an axle in the stock configuration but it will not clear my axle as it is bigger and further back than stock. I’ve cut the tank to make a divot for the differential but I stopped shortly afterwards. I will most likely start over with flat sheet metal and build my own or have one built by a local fabricator.

 

[matzell]

I’ve put my fuel system on hold. The tank that is in my Cruiser is from an early 90s 2-door S-10 Blazer. This tank might work for an axle in the stock configuration but it will not clear my axle as it is bigger and further back than stock. I’ve cut the tank to make a divot for the differential but I stopped shortly afterwards. I will most likely start over with flat sheet metal and build my own or have one built by a local fabricator.

I am in the same boat but I bashed mine in with a dead blow hammer. I am looking at the in-take pump kit Mosley motors has and use stock tank.