Pirate 4x4 banner

381 - 400 of 401 Posts

·
Registered
Joined
·
37 Posts
Nice video but of the 17 minutes only a few had anything to do with link placing and adjusting. Practically nothing about 3 link systems. They could have put an hour into this topic easily. For instance I would like to know why factory systems seem to violate most of the rules of thumb. The dodge trucks I see with 4 link suspensions, well correction. 5 link suspensions seem to have plenty of angle on their links which we all know is going to lead to a ridiculous roll center and AD(anti-dive). My problems are getting the roll center to 0 and have any anti dive left on a 5 link. With the vehicle having only an 8 inch lift it is impossible to fit any triangulation into the front.
Such is the fun of a custom 4x4 Van :flipoff2:



 

·
Registered
Joined
·
1,244 Posts
I agree with what you are saying, although I like to think of increasing AS as increasing resistance to suspension compression not "increasing grab" as the normal force on the tires isn't changing under constant acceleration. Your explanation is basically my understanding of why the 70% rule. For the reasons you mentioned I think longer lowers generally makes for best AS change through travel. Although instead of 70% I generally shoot for 80% to help mitigate the pinion angle issue.

Additionally I've always built my own driveshafts and lately I've been using Dana 50 TTB axle shaft ends (1350 series) and I can get some rediculus angles out of them. Additionally I usually point the pinion up so it is pointing above the TC output at ride height. People have told me "you can't do that" for "blah blah blah vibe, u-joint wear, reasons, reasons" and I have yet to change a u joint in either of my DS. Additionally I challenge someone to get in my buggy and tell me what exactly is vibrating:flipoff2:

So anyhow pinion angle at full droop has only been an issue for me on my front axle, so I'm considering reworking the front 4 link or possibly making a new front DS out of Dana 60 axle shafts (1480 series). But when it comes to the front axle I wonder whats "the lesser of two evils" pinion angle change and poor DS angle or the castor angle change with travel that would be associated with using longer uppers than lowers.

Edit: Re read and changed top paragraph slightly.
Any chance you can post some tech on the Dana 50 TTB driveshafts? That would be awesome.

Also, have you come to a conclusion on the lesser of two evils regarding the long vs short upper link and driveshaft angle vs castor? I'm in that same boat right now.

Thanks!
 

·
Registered
Joined
·
1,390 Posts
Bumping this thread up. When linking front and rear axles how important is it to have the links similar lengths front and back to maintain equal driveshaft lengths?

Also I read you want your lower links as close as possible to the output shafts on tcase.

I have a divorce tcase and I can easily move it forward. Current driveshafts are 40" rear and 55" front
 

·
Registered
Joined
·
8,948 Posts
Also I read you want your lower links as close as possible to the output shafts on tcase.
Yes. You will get optimum droop angle out of you driveshaft U joint if the joint is exactly at your lower link mount point. Make them both move in unisun on the same plane.
 

·
Registered
Joined
·
3,245 Posts
Yes. You will get optimum droop angle out of you driveshaft U joint if the joint is exactly at your lower link mount point. Make them both move in unisun on the same plane.
If your goal is maximum flex, this is good advice. Your slip joint won't work as hard. As far as the drive shafts being the same length, There is not really any big advantage. Moving the t-case maybe good for drive shafts and links, but not for weight distribution. There's trade offs for everything.
 

·
Registered
Joined
·
1,037 Posts
The advantage is clear to having equal length shafts. One spare.

Imo, weight bias and gross weight are not concerns of the op. Check his build out. I believe what he is doing is eating the length of the intermediate shaft off the trans and swinging the balance of the long front shaft to the rear shaft.

In any other "buggy" app, equal length shafts ARE a result of BETTER weight bias and a midship is run on the front output.

The lower length of the links front to rear doesn't really effect the drive shafts until the geometry, WB or vertical sep of yokes gets to extreme values. What I mean by this is you can have equal front and rear shafts but different link geometry front to rear. Only have to mind the capability of the u joints. Also the length of the lower links in the X plane (viewed from side) is altered by the horizontal separation of the links in the Y plane (viewed from above). This means you can have 40" links but the further they are triangulated in the Y plane might mean you have a 36.5" link distance in the X plane. 40" axle horizontal separation and 7" at the frame Those are the figures from my rear links. 40" lowers f&r and 25" f&r shaft measurement iirc. 1410 joints, non cv.

X2 what Stubs said
 

·
Registered
Joined
·
3,245 Posts
The advantage is clear to having equal length shafts. One spare.
I like the way you think. I've always thought it would be cool to build a rig with equal length links, driveshafts and have identical axles at both ends. If you really wanted to go to extremes, get center diffs.
 

·
Registered
Joined
·
1,037 Posts
Funny you mention the links. I fought hard with link placement, the "#"s and the steering so I could carry 1 spare link in the toolbox to get me home. Steering, panhard, front lowers and rear 4 link are all 40". For obvious reasons the tie rod and front top link are of different length but least likely to fail or suffer a damaging impact. Vetteboy built his TTB buggy around equal drive shafts. Think he only had a 1/2" variance in his design :grinpimp:
 

·
Registered
Joined
·
8,948 Posts
The advantage is clear to having equal length shafts. One spare.
Yep.

All my lowers are all the same length and so are my uppers. Uppers dont bend very often but I am using DOM for my lowers and expect them to bend over time.
 

·
Registered
Joined
·
1,390 Posts
Thanks for responses guys. I want the design to also help protect the shafts with the links. A carrier bearing could come into play in front as well. The rear I original had a 1350 cv shaft but after dropping a significant amount of lift for better stability I could just run 1350/1410 shaft probably but the rear truss was built anticipating rotating diff for cv. Gotta start crunching some #'s in a calculator
 

·
Registered
Joined
·
37 Posts
I always wondered why Ford angled the rear of the leaf up.
I always understood this had to do with keeping the axle centered under compression. What with the curvature of the leaf springs and all. The angle cancels out the extension of the leaf as it goes flat under compression. I guess this would pretty much take care of the roll steer.
 

·
Registered
Joined
·
3,245 Posts
I always understood this had to do with keeping the axle centered under compression. What with the curvature of the leaf springs and all. The angle cancels out the extension of the leaf as it goes flat under compression. I guess this would pretty much take care of the roll steer.
Strange you would bring this up now. You realize you are quoting me from 3 years ago. In that post, I went on to say that I figured it was for roll steer.
 

·
Registered
Joined
·
1,255 Posts
Perhaps I'm overthinking it, but I have a question / discussion for the big brains...

What (if any) ill-effects would you see with a setup having the instant center behind the rear drive axle? In other words, a negative IC x-axis.

Playing with it in the calc, doesn't seem to affect anything too greatly slipping from the parallel plane to a negative IC, and I can't come up with anything in my head that would cause any weird jacking in the suspension (assuming proper separation & geometry otherwise)
 

·
Registered
Joined
·
4,566 Posts
I need some help here boys, Im terrible at figuring out angles without putting them into action first and then re doing my work.

Im putting a buggy together that formerly had toy axles, now going to 1 tons. Suspension geometry was good and would like to keep everything as close to the same as possible. Im trying to figure out my lower lengths right now to run through the calculator and scratching my head. Here is the info I know from before

old Lowers-44
current spacing at frame-12 inches
former spacing at axle (toy) -35 inches (center to center)

New spacing at axle (dana 60) should be 40 (center to center)

to keep my heims straight and inline with the old frame tabs, how long do my lowers need to be? I bought 20* link mount brakets to angle them in as much as possible, but I'm afraid it won't be enough. Any help here? This is probably simple as shit but I just can't put it together tonight.
 
381 - 400 of 401 Posts
Top