Build 1964-1984 FJ40 - "I got it one piece at a time..."

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

DangerNoodle said:
Not sure what size tire you are running, but I that the vertical link separation on the axle side seems small.

What class / team does he build for, purely out of curiosity?
Click to expand...
I think they are 35's that are currently on the Icon wheels I have. I will check.

He had three trucks in different classes competing this year and he was in the pit for one of the BF Goodrich teams in the Trophy Truck class.
 
rlong said:
Laughed out loud!! When I was working as a finsh carpenter at a fairly high level (comm/institutional work), we were building someting and the forman/boss was critically questioning another carpenters work, finally the other carpenter snapped at the boss "Just let me finish, then you can pick it apart!!!"

I think of this every time I am half-way through building something and am having self doubt..
Just let me finish and then you can pick it apart!!!
Click to expand...
I would honestly have it picked apart before I finish. Less rework.
 
Brian, my comments proceed from the assumption that we are looking at full droop mockup. I think in order to make the most relevant comments, it would be good to also see what full ‘stuff’ is anticipated to be, so that viewers can better judge the angularity of things like the axle locator bar (not sure of the technical term) and the drag link. I can readily see that the axle locator bar is in a very preliminary mockup. But I don’t understand why the upper drag link end drops in from the top on your pitman arm, when having it go in from the bottom is not only standard, but drastically reduces the angle of the link, which causes bump steer.

I’m also used to seeing hi-steer knuckle arms on rock crawler builds, so your arms seem out of place to me. I am again making an assumption that this was done purposefully because of some other anticipated use, like higher speed off road racing, where maintaining the stock Ackerman angle might be critical. Even my semi-modified FJ45 has hi steer to get the main tie rod further up out of harm’s way. I have bent two steering rods myself, and helped service two others on the trail.

Lastly, I think there is something wrong with how the pitman arm is attached to the steering box. There don’t appear to be enough threads on the end of the sector shaft. There should be enough threads for a heavy nut and split washer. Yours barely has enough for a nyloc.
 
Last edited:
65swb45 said:
Brian, my comments proceed from the assumption that we are looking at full droop mockup. I think in order to make the most relevant comments, it would be good to also see what full ‘stuff’ is anticipated to be, so that viewers can better judge the angularity of things like the axle locator bar (not sure of the technical term) and the drag link. I can readily see that the axle locator bar is in a very preliminary mockup. But I don’t understand why the upper drag link end drops in from the top on your pitman arm, when having it go in from the bottom is not only standard, but drastically reduces the angle of the link, which causes bump steer.

I’m also used to seeing hi-steer knuckle arms on rock crawler builds, so your arms seem out of place to me. I am again making an assumption that this was done purposefully because of some other anticipated use, like higher speed off road racing, where maintaining the stock Ackerman angle might be critical. Even my semi-modified FJ45 has hi steer to get the main tie rod further up out of harm’s way. I have bent two steering rods myself, and helped service two others on the trail.

Lastly, I think there is something wrong with how the pitman arm is attached to the steering box. There don’t appear to be enough threads on the end of the sector shaft. There should be enough threads for a heavy nut and split washer. Yours barely has enough for a nyloc.
Click to expand...
Thanks guys. Will let you know what I find out.
 
bmoonhajjar said:
Thanks guys. Will let you know what I find out.
Click to expand...
Thanks for the comments on the build. I talked to my fab guy and he plans on raising the top (third) link of the front 3 link up about 6", he just needs to check clearance. As for the pinion angle, I have brought it up twice and he says we are in good shape. The pitman arm was not on all the way in the pic, but there is ample room for a nut and washer. To address Mark's other concern about the knuckles being cut open. Those will get final weld, but for not they are plug welded to keep them where they are. I will try to post better pics.

Thanks to @65swb45 @EWheeler @DangerNoodle and others for keeping this build on the up and up.
 
Suspension
@DangerNoodle @65swb45 @EWheeler 6" or closer to 8" separation? Obviously it will be boxed or gusseted for strength but wanted to get your input before finalizing.
78959510550__A98B4A41-75B2-47E2-BB4B-911B8AD657FA.webp
 
Last edited:
bmoonhajjar said:
@DangerNoodle @65swb45 @EWheeler 6" or closer to 8" separation? Obviously it will be boxed or gusseted for strength but wanted to get your input before finalizing.
View attachment 4063883
Click to expand...

The rule of thumb is usually around 25-30% of tire diameter, which is why I asked what size tires you were running. If you ever plan on going bigger, upsize it a bit.
 
As for me Brian, I am out of my depths when it comes to linked suspensions. I ‘learned’ (I use that term loosely) what little I know from being on the sidelines of Pirate 4x4 while guys like @Mace , @wngrog , @woody and others were hashing this stuff out 22 years ago like guys in a pitch black room trying to describe an elephant! In layman’s terms I would call myself an armchair quarterback when it comes to linked suspensions.

In my mind, which operates under the prime directive of ‘form follows function’ it just seems logical to me to make the angle of the link match the angle of the driveshaft in order to give the shaft half a chance to stay intact with the high degree of mobility it is expected to travel.

Since the link is probably longer than the driveshaft, it stands to reason that the angle of the driveshaft will get steeper faster than the angle of the link. Therefore, it would also seem logical that if there is to be a deviation from static-parallel, that the link should start a little lower than the driveshaft (a little more angle) so that they cross paths somewhere in the droop.

Hth
 
Last edited:
DangerNoodle said:
The rule of thumb is usually around 25-30% of tire diameter, which is why I asked what size tires you were running. If you ever plan on going bigger, upsize it a bit.
Click to expand...
35" tires.
65swb45 said:
Jeff, since you’re still in the framing phase of the bathroom…

I’ve always been a fan of pocket storage, dating all the way back to 1985, when I carefully sawed open the door on my K5 to make a handy storage spot for my nylon tow strap. When I remodeled the office 9 years ago, I put a pocket into the interior wall directly across from the commode to hold…an extra role of TP! It has literally saved my ash on more than one occasion.View attachment 4064117
Click to expand...
Mark, is this your way of telling me subliminally that my build is “s***ty”, or did you just post in the wrong thread?

Either way it made me laugh.
 
Have you cycled that front three link to see what the pinion angle does? I put the upper link on the passenger side to keep the pinion more stable through the axle travel (when crossed up).
 
bmoonhajjar said:
35" tires.

Mark, is this your way of telling me subliminally that my build is “s***ty”, or did you just post in the wrong thread?

Either way it made me laugh.
Click to expand...
Oops!
 
bmoonhajjar said:
35" tires.

Mark, is this your way of telling me subliminally that my build is “s***ty”, or did you just post in the wrong thread?

Either way it made me laugh.
Click to expand...

I'd shoot for 9" of vert seperation between upper and lower link bolts. That's just a rough guess, and I have no idea what numbers your guy is shooting for for antidive, your roll axis, or instant center, and all that can be played with a bit.

Are you planning on running a sway bar?
 
DangerNoodle said:
I'd shoot for 9" of vert seperation between upper and lower link bolts. That's just a rough guess, and I have no idea what numbers your guy is shooting for for antidive, your roll axis, or instant center, and all that can be played with a bit.

Are you planning on running a sway bar?
Click to expand...
Yes on the sway bar.
 
One of the nice things about additional vertical separation is that it reduces the forces on the links (from traction that is). I would be more worried about AD, roll axis and IC. Having a specific number on vert separation is not a huge deal IMHO. It's always a good idea to play with the numbers to see what the happy medium is. There is no such thing as "Perfect" when you are adding links to a truck. It's all a compromise somewhere. Just like the concept of hysteer and Ackerman angle that Mark brought up. What's more important to function and what can be modified to get there is the biggest thing.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom