Adjusting rear with adjustable UCA

[IronScott]

I just installed a RK 3.5" lift that came with adjustable rear upper control arms, along with fixed front lower control arms, front and rear adjustable track bars. I got both axles centered and toe-in is a little less than 1/8". Front caster is about 5 degrees according to angle finder.

I'm confused about the rear, though. The instructions say this:

Recommended Alignment Specs are as follows;

3.5” Lift Height: 4.2 to 5.75 degrees of Caster with a .2 to .4 Cross Caster Split (.2 to .4 degrees more caster on the pass. side than the driver’s side.)

Tow: 0 to slightly towed in but within factory specifications

The rear pinion angle should be down 2 – 3 degrees from the driveshaft as shown below.

Using an angle finder I appear to be just a little over 2 degrees down on the rear pinion. Is this the only thing to be concerned with on the rear - that is, does this angle relationship handle rear caster as well? or is rear caster a separate thing or even exist at all?

I had planned on taking this to an alignment shop but I've heard that most shops won't adjust track bars or control arms. This is all new to me but if I'm good with my own measurements, I don't see the need in wasting time and money for a shop to check the toe.

The Jeep is riding really well.

Sponsored

 

[Roky]

I just installed a RK 3.5" lift that came with adjustable rear upper control arms, along with fixed front lower control arms, front and rear adjustable track bars. I got both axles centered and toe-in is a little less than 1/8". Front caster is about 5 degrees according to angle finder.

I'm confused about the rear, though. The instructions say this:

Recommended Alignment Specs are as follows;

3.5” Lift Height: 4.2 to 5.75 degrees of Caster with a .2 to .4 Cross Caster Split (.2 to .4 degrees more caster on the pass. side than the driver’s side.)

Tow: 0 to slightly towed in but within factory specifications

The rear pinion angle should be down 2 – 3 degrees from the driveshaft as shown below.

Using an angle finder I appear to be just a little over 2 degrees down on the rear pinion. Is this the only thing to be concerned with on the rear - that is, does this angle relationship handle rear caster as well? or is rear caster a separate thing or even exist at all?

I had planned on taking this to an alignment shop but I've heard that most shops won't adjust track bars or control arms. This is all new to me but if I'm good with my own measurements, I don't see the need in wasting time and money for a shop to check the toe.

The Jeep is riding really well.

No caster in the rear, arms for adjusting pinion angle. The higher caster on passenger side is to help with the crown in the road.

 

[IronScott]

No caster in the rear, arms for adjusting pinion angle. The higher caster on passenger side is to help with the crown in the road.

Ah. Thank you so much!

I thought that might be the case but it wasn’t clear to this n00b. I may go ahead and get adjustable front arms at some point to dial it in better. I work from home so don’t drive a lot of miles and most of what I do drive is in town and to the trails. I’ll drive it like this a while and see how I like it. Ready to test this new lift offroad.

 

[Roky]

Ah. Thank you so much!

I thought that might be the case but it wasn’t clear to this n00b. I may go ahead and get adjustable front arms at some point to dial it in better. I work from home so don’t drive a lot of miles and most of what I do drive is in town and to the trails. I’ll drive it like this a while and see how I like it. Ready to test this new lift offroad.

Sounds good.... you won’t be disappointed. I’m on the rk 3.5 xfactor, it’s awesome. You’ll notice a pretty significant improvement on handling when you get your adjustable lcas and get your caster up to 6 or over. It doesn’t sound like much, 1 to 1-1/2 degrees but it really makes a difference.

Sponsored