Adjustable rear control arm set up (1 Viewer)

[fjlau]

Recently installed a 3.5” dobinsin lift on my truck and was looking for some guidance on the control arm lengths and how to set up the arms to correct the pinion angle. I know the stock length for the LCA is 27.5” but have had a hard time finding any info for the UCA length. ( I do not have the original ones to reference at this time). After some research I was able to find out that the UCAs can stay the stock length and the adjustment would come from the LCAs however like I mentioned I don’t have the UCAs handy in order to get the adjustable ones to stock length.

 

[Rusty Marlin]

Not sure it matters as you have full adjustability. Use the lowers to set your axel pivot location so the wheel is centered in the arch, or so that the tire doesn't scrub at full stuff. Then set the pinion angle with the uppers. The pinion angle should be parallel to 1/2* low compared to the transfer case output (with stock shaft) at your most commonly loaded ride height.

 

[landtank]

if you plan on using your truck for anything more than a grocery getter I would throw those links in the trash. The threaded sections have been known to strip out making for a very dangerous situation. Mostly with the LCAs but a friend had both uppers fail simultaneously and the rear springs almost ejected out the back from the axle rotating backwards.

 

[Rusty Marlin]

Sounds like a good tool for setting the proper control arm lengths and then cutting and sleaving the originals to the new proper lengths required for the lift.

 

[SNLC]

if you plan on using your truck for anything more than a grocery getter I would throw those links in the trash. The threaded sections have been known to strip out making for a very dangerous situation. Mostly with the LCAs but a friend had both uppers fail simultaneously and the rear springs almost ejected out the back from the axle rotating backwards.

I don’t agree. Dobinsons would have MAJOR liability issues if that was the case. More likely installed incorrectly.

We fit them to all our builds with 600ftlbs of torque and have had zero issues.

Cheers

 

[landtank]

You are literally threading one end into a threaded tube and tightening a nut. How would that be done incorrectly?

And this isn’t some one off situation.

 

[rhc404]

You can use math/geometry to set the new length.

I set mine to what seemed right then took it to an alignment shop to dial it in. Any side-to-side variance will tweak the rear alignment.

 

[cruzinfj1]

I don’t agree. Dobinsons would have MAJOR liability issues if that was the case. More likely installed incorrectly.

We fit them to all our builds with 600ftlbs of torque and have had zero issues.

Cheers

Yep. Only time Ive seen failure is when the jam nuts werent tight and regularly checked.

These arms pictured above look like they are way to short. More threads in the tube, the better.

@fjlau I might have my stock upper arms laying in my scrap bin, if I do, Ill post up the length for you later this evening.

 

[baldilocks]

You are literally threading one end into a threaded tube and tightening a nut. How would that be done incorrectly?

And this isn’t some one off situation.

I’ve been beating the tar out of Metal Tech adjustable upper and lower links since 2014 with no catastrophes. Yes, if the OP will articulate the suspension hard the jamb nuts need to be rechecked. I found my uppers loose twice so I tack welded the nut. The lower have never come loose.

I do see that these Dobinson threaded shanks are smaller diameter than mine which I think are 1.25. I torque the snot out of the lower link jamb nuts then paint a tattle tale mark from nut to tube.

I believe I’ve also read a few hundred times here how it is suicidal to run wheel adapters/spacers. I did that too for several years and never a problem.

Living on the edge is my thing……

 

[fjlau]

thanks to everyone for the replies. haven't been able to get under it in a while as I had to travel for work. I think my best bet is going to be taking it to an alignment shop to have them dial everything in once I get the rims and tires I will be running. and as far ass the coming loose and failing tack welding this exam nuts seems like a good option for the time being.

 

[JoeCova]

What’s the issue with threaded links? 99.999% of links on Jeeps and Ultra 4 cars are threaded with no issues. Sounds like neglect to me. Here’s some 7075 with threaded heims I just triangulated. Minimum threads should be no less than the width of the shank.