Builds Stretched 1-Ton FJ40 (4 Viewers)

[matzell]

We are talking bolt size. I am using 5/8 currently and I may stick with that instead of 3/4. I’ll make a decision this weekend.


You are helping the economy! I hadn’t even considered aluminum links until now. They must be solid aluminum? What size would you run? 2”?

I have 2.25" 7075 lowers in the rear and 2.50" 7075 in the front. Yes solid. I had them machine a hex on the ends so I can use a wrench to hold them. The other way is just have the put in wrench "flats" and use an adjustable.

You should be fine with 5/8 lower bolts and 9/16 uppers. You can also use .120 wall uppers to save weight but I used .250 because it is what I had and with the stress on the front 3 link I did not want to take a chance of it bending. I used .250 DOM for all my links and bent everyone of my lowers like banana's They I had to go out and buy alum lowers. Would have been cheaper to have started with alum lowers.

 

[Mike Shull]

Thanks again, @matzell and @DangerNoodle. It looks like I will be working at the chalkboard for part of the weekend.

 

[Mike Shull]

Before I order links, would you all mind having a look at these very rough specs and let me know if you see any major concerns with the geometry, please? I am running out of space to make it any tighter. I was aiming for around 90 anti-dive and 100 anti-squat without compromising the roll axis. It's tough!

On a sidenote, I didn't take any pictures but I am mocking this up with a piece of ABS pipe. Okay, now I need to snap a picture of this...

 

[Mike Shull]

Here are a couple snapshots of the appropriate position for the front upper link. I’m out of room on the right side so I’m going to try and stick it on the left side. I think that there is enough room for an exhaust pipe.

 

[matzell]

I would shorten up the uppers. Normally you want about 75% shorter uppers.

 

[EWheeler]

I would shorten up the uppers. Normally you want about 75% shorter uppers.

Is that primarily to control caster/pinion angle change?

 

[DangerNoodle]

Is that primarily to control caster/pinion angle change?

Yep, it's a good way to keep vibrations down at speed.

I second the 75% uppers. Your front roll axis looks a little high to me, I'd shoot for under 3*.

 

[Mike Shull]

You all are saying that the uppers should be 75% the length of the lowers, not shorter, right? In other words, the recommendation would be to make my uppers around 33” if my lowers are 44”? Does that seem a bit too drastic of a difference?

I was trying to improve my pinion angle when the axle drops but I wasn’t thinking about caster. Good thing I’m just messing around with ABS and cardboard At the moment. What if I did something more like 44” lowers and 38” uppers?

 

[matzell]

You all are saying that the uppers should be 75% the length of the lowers, not shorter, right? In other words, the recommendation would be to make my uppers around 33” if my lowers are 44”? Does that seem a bit too drastic of a difference?

I was trying to improve my pinion angle when the axle drops but I wasn’t thinking about caster. Good thing I’m just messing around with ABS and cardboard At the moment. What if I did something more like 44” lowers and 38” uppers?

It is not an exact science. the calculators are nice but it is also about packaging. If it does not fit than it does not matter. We used basic math on my race car but it was about were stuff fit. It handles good and I can run 18" chop at 50 mph with no problems. That is 18" up and 18" down! It works at speed but you will want to run at least a rear sway bar. I am running 14" shocks and a lot of HP so it will pull the front end up on hard accel but it does not bounce or hop when climbing and in the throttle. I do drive it on the road at times and it does fine at 45-55 mph. It is a different animal that what you are building but some of the same concepts.

 

[DangerNoodle]

You all are saying that the uppers should be 75% the length of the lowers, not shorter, right? In other words, the recommendation would be to make my uppers around 33” if my lowers are 44”? Does that seem a bit too drastic of a difference?

I was trying to improve my pinion angle when the axle drops but I wasn’t thinking about caster. Good thing I’m just messing around with ABS and cardboard At the moment. What if I did something more like 44” lowers and 38” uppers?

Those are pretty long links. I think I'm somewhere around 35" for my lowers, 25" ish for my upper. I mainly had to do that to clear my oil filter, but overall length isn't too important.

I would run between 70%-80% on your lowers. It helps keep a constant pinion angle which can be pretty helpful. If you aren't planning on roading this thing at all, and are just planning on going slow, 100% of the lower length can be good to get some better longevity out of the driveshaft joints, but that really isn't much of a problem.

 

[Mike Shull]

Yep, it's a good way to keep vibrations down at speed.

I second the 75% uppers. Your front roll axis looks a little high to me, I'd shoot for under 3*.

The roll axis has been a challenging one since I shortened my front axle to 63” WMS. I’ll mess around with the figures a bit more.

It is not an exact science. the calculators are nice but it is also about packaging. If it does not fit than it does not matter. We used basic math on my race car but it was about were stuff fit. It handles good and I can run 18" chop at 50 mph with no problems. That is 18" up and 18" down! It works at speed but you will want to run at least a rear sway bar. I am running 14" shocks and a lot of HP so it will pull the front end up on hard accel but it does not bounce or hop when climbing and in the throttle. I do drive it on the road at times and it does fine at 45-55 mph. It is a different animal that what you are building but some of the same concepts.

18” of travel in BOTH directions! that Is a ton of travel. I’ll put the measuring tape down and start welding again. I mostly just cannot wait to drive it again.

 

[Mike Shull]

Those are pretty long links. I think I'm somewhere around 35" for my lowers, 25" ish for my upper. I mainly had to do that to clear my oil filter, but overall length isn't too important.

I would run between 70%-80% on your lowers. It helps keep a constant pinion angle which can be pretty helpful. If you aren't planning on roading this thing at all, and are just planning on going slow, 100% of the lower length can be good to get some better longevity out of the driveshaft joints, but that really isn't much of a problem.

I admit that my initial figures were a bit ambitious. Ha! I will reconfigure it next weekend. The rear may need to be a bit longer than the front clear the drive shaft. More to come.

Thanks for the tips.

 

[matzell]

The roll axis has been a challenging one since I shortened my front axle to 63” WMS. I’ll mess around with the figures a bit more.

18” of travel in BOTH directions! that Is a ton of travel. I’ll put the measuring tape down and start welding again. I mostly just cannot wait to drive it again.

No, sorry it does not travel 18" in both directions. I meant the swells at 18". may have about 20 of up and down travel and more when flexing out. That is not important. Figure out the links and how much travel you have then decide on shock length and get some limit straps and set them to about 1" short of max shock extension They stretch. I really think you will be fine with 10-12" travel shocks.

 

[DangerNoodle]

No, sorry it does not travel 18" in both directions. I meant the swells at 18". may have about 20 of up and down travel and more when flexing out. That is not important. Figure out the links and how much travel you have then decide on shock length and get some limit straps and set them to about 1" short of max shock extension They stretch. I really think you will be fine with 10-12" travel shocks.

I'd have to agree with the length of shocks there. I'd go 14" max. At some point, a ton of downtravel becomes pointless and wobbly.

 

[matzell]

Neapco makes a 30 deg CV with 1410 joints. Plenty strong and a lot of flex. Their 1410 slipe yoke also has a lot of angle to it.

Spicer stuff does not have the angle, I found out the hard way and had to grind the heck out of the yoke to clear.

 

[Mike Shull]

Thanks for the clarification, @matzell, I’d be very curious to see what 36” of travel looked like but I’m not interested for my setup. I’d need a bigger tire and lift for sure.

I had 10” of travel before and it was good. My tires would lift occasionally but it didn’t happen often. I can do 12-14” of travel with the shock towers that I purchased, and I have a torch to cut them down if needed. I was leaning towards 14” travel shocks with 1 to 1-1/2 reduced travel from the limit straps. You all have more experience with this setup in a Cruiser so if 14” is still too tall, I can easily weld the towers lower and install 12” shocks. I welcome some more chatter on the pros and cons.

I honestly don’t think that I would really care either way unless the taller route didn’t handle very well at higher speeds. We are only talking 2” though. Can it make that much of a difference?

 

[Mike Shull]

Neapco makes a 30 deg CV with 1410 joints. Plenty strong and a lot of flex. Their 1410 slipe yoke also has a lot of angle to it.

Spicer stuff does not have the angle, I found out the hard way and had to grind the heck out of the yoke to clear.

We are jumping ahead a bit and I like it! I’ll look into the Neapco joint when the time comes. I can’t wait to start talking about the A/C and body.

 

[Mike Shull]

@matzell, @DangerNoodle and others, please have a look at the revised front 3-link calculations below and let me know your thoughts about the lengths of my upper and lower links. I am hoping that they are not too short. I am trying to create enough room for the exhaust. I'm thinking that this should flex fine with a 14" shock as the lower links are still 5-7" longer than where my current shackle sits.

Also revised is the inboard of the lower links at the frame. If I inboard them by 4", I will lower my roll by 3 degrees. Are there any concerns with placing my lower links inward from the frame? Does this even matter in your opinion?

 

[DangerNoodle]

@matzell, @DangerNoodle and others, please have a look at the revised front 3-link calculations below and let me know your thoughts about the lengths of my upper and lower links. I am hoping that they are not too short. I am trying to create enough room for the exhaust. I'm thinking that this should flex fine with a 14" shock as the lower links are still 5-7" longer than where my current shackle sits.

Also revised is the inboard of the lower links at the frame. If I inboard them by 4", I will lower my roll by 3 degrees. Are there any concerns with placing my lower links inward from the frame? Does this even matter in your opinion?

View attachment 2938562

I can recomend not inboarding the lowers. It's a mistake I made, and it has made it much harder to run exhaust. With your current roll axis, I wouldn't bother.

 

[Mike Shull]

I can recomend not inboarding the lowers. It's a mistake I made, and it has made it much harder to run exhaust. With your current roll axis, I wouldn't bother.

How long are your lowers from eye to eye?