dustyinthedirt Posted May 7, 2019 Share Posted May 7, 2019 As I’m setting up the front three link I started noticing the top bar is going to be equal to/greater then the length of the bottom two. 3/4” to a 1” longer. I’ve never heard of anybody having the upper bar longer. But I’ve also never heard of anybody saying you can’t do that. I know on a equal length 3 link the pinion stays pretty constant in pointing at the Tcase. If the upper bar was longer wouldn’t it push the pinion up during full droop. And keep it relatively flat during full bump? Somebody please enlighten me on this. Before anybody states it, I am not following the 70% rule for the links. Link to comment Share on other sites More sharing options...
Smokeyyank Posted May 7, 2019 Share Posted May 7, 2019 Not my info but just something I have bookmarked about link set ups from people waaaayyyy smarter than me. Upper Links: The upper link in a 3 link suspension can be difficult. Regarding length, there are some old and new rules of thumb. In the past, it was recommended to make the length 75% of the lower link length. Yes, this will keep your suspension geometry consistent during travel, but it can also cause the pinion angle to aim downward as the suspension droops. Instead, making the upper link the same length as the lowers (or even slightly longer) will allow the pinion to roll up along with the droop. Overall, equal length keeps the driveshaft alive and is especially useful for rigs with short wheelbases and/or driveshafts, or for low-pinion front applications. It doesn't really matter if the upper arm is a little longer than the lower arms. I don't see it being 8" longer just because of the mounting place on the axle. The frame side mount should be further forward than the lower mounts, pretty easy to do if the upper mount is inside the frame. Put the arms where they fit the best, if they're as level as possible it will be fine. If you want to see how much pinion rotation you'll have with different arm lengths and placement, just draw it on the garage floor with chalk and use a couple pieces of string or something to draw arcs of movement with chalk, then mark vertical axle travel in inches and draw a line to the arc and you'll be able to see exactly what pinion rotation you'll have throughout you travel with a particular setup. After you do that, you'll find that it doesn't matter much, but you'll feel better, and feel smarter. Link to comment Share on other sites More sharing options...
dustyinthedirt Posted May 7, 2019 Author Share Posted May 7, 2019 thats pretty much exactly what I was looking for. I am gonna draw it out this evening and. Get better measurements. To try and see what happens with the pinion Link to comment Share on other sites More sharing options...
dustyinthedirt Posted May 7, 2019 Author Share Posted May 7, 2019 So I made up this little chart while at work. The top link is a little longer then the bottom. It’s sorta to scale... 1/4.5 Link to comment Share on other sites More sharing options...
Awinski Posted May 7, 2019 Share Posted May 7, 2019 so a lot of this being a good or bad thing depends on a few things. if youre a crawler, have a shorter drive shaft or have a large amount of droop it might be okay to have the upper longer. but if you want geometry to stay consistent at speed, have a good split travel (12" shock 6" up, 6"down), and have a nice long drive shaft that won't bind then having the upper a bit shorter is a good idea. if you're driving through whoops offroad or a back road at speed and you're getting constant caster and camber changes it's not going to be pretty. also if you're geometry changes through travel to be undesire-able this can be a huge minus if you ever change the ride height or something of the like. personally for me, i try to keep my uppers in the 80-90% length of the lowers, have 1/4" tire diameter separation at the axle, and 1-2" less at the frame, completely dependent on the desired setup. so in the end it's going to be whatever compromises you're comfortable with. Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 8, 2019 Share Posted May 8, 2019 Link to comment Share on other sites More sharing options...
dustyinthedirt Posted May 9, 2019 Author Share Posted May 9, 2019 thanks for the input! What about a good caster angle? I checked the the caster before pulling the stock axles off and they where around 6.8 didn’t match between the two. I have read that I wanna around that number to drive this on the highway. Which is the end game. Drive to the trail/park wheel the snot out of it and hopefully drive it home Link to comment Share on other sites More sharing options...
Smokeyyank Posted May 9, 2019 Share Posted May 9, 2019 OEM is about 7 and if you want to maintain on roadability then staying close to that will be ideal. A little more definitely helps. Additional castor beyond factory spec can help with wandering issues with larger tires and helps steering return to "center", but too much can results in heavier steering. If you're not running any type of assist I'd go for 8-10* Link to comment Share on other sites More sharing options...
Awinski Posted May 10, 2019 Share Posted May 10, 2019 23 hours ago, dustyinthedirt said: thanks for the input! What about a good caster angle? I checked the the caster before pulling the stock axles off and they where around 6.8 didn’t match between the two. I have read that I wanna around that number to drive this on the highway. Which is the end game. Drive to the trail/park wheel the snot out of it and hopefully drive it home solid axles i usually set up 7 or 8 for non steering assist, hydro assist 9-11 Link to comment Share on other sites More sharing options...
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