Dana 30 Withe Stock Spring Height

I’m installing a Dana 30 in my 1971 Jeep CJ5. After reading all the posts, it sounds like 7 degrees is the caster number to shoot for.

All the posts that I read, were using shims with anything from 2” to 4” lifts. My question is; are shims needed if you are at stock ride height?

 

You never know. Use an angle finder to find out where you are at after installation.

 

Yes, the Dana 30 spring perch clocking to castor inclination is a bit different than the Dana 27...that's how I understand it.
I'm using 5-degree shims with a 2.5" lift in my '71. It's been fine for 10+ years.

 

I used a 3 degree shim and tried to measure caster near the nut for upper ball joint and it’s reading about 5 degrees. Not sure how accurate this is since the ball joint nut takes up most of the space.

im getting some wondering still so it sounds like I need to add more caster via a steeper swim?

 

Have you checked the toe-in?

 

This! You can not make an informed decision with no data. Digital angle finders are pretty cheap and you don't need a machine shop grade unit to do this. As much as I hate to admit, a HF version will likely suffice.
https://www.harborfreight.com/digit...MI6bCSmYLb-gIV1h6tBh3FhgwHEAQYASABEgKSVvD_BwE

Anything between 5 and 7 degrees should be good. Realize this is sort of a compromise. The more caster you put on it, the worse your pinion angle gets.

 

Have an angle finder, but having a tough time getting a proper flat surface to check with. I’m going to remove the castle nut for the ball joint and see if I can get a better reading.

 

the shop that rebuilt the motor said that they set it at around an eighth, I have not checked it personally. Maybe it needs more toe in?

 

1/8” toe in should be fine. You can use the bottom of the knuckle to check caster angle also.

 

thats great news, I think there is more flat space on the bottom knuckle.

 

This angle is driving me crazy. Using the bottom of the ball joint on both side, (seems flat) I’m getting 4 degrees on the right side and 2.5 on the drivers side. Any ideas why?

 

I didn't use any shims at all. Mine drives just fine.

 

I’ve been wondering about that not using shims. Every thread I’ve been reading have had lifts of some kind, then shims.

I’m in the process of ordering some springs (original ride height) and I asked their advice on caster shims. Their thoughts were about 1 degree per inch of lift for both caster and pinion. That got me thinking about no shims.

do you have a lift on yours?

 

3.5" Wrangler Springs.

 

x2

 

In addition to the castor issue, the shims can play a key role in aligning your pinion shaft and transfer case shaft.
The differential pinion shaft and transfer case output shafts should be as close to parallel as possible. This will increase longevity of your driveshaft U-joints.

 

Got a chance to work on the Jeep today. I removed the 3 degree caster shims and now, for the most part the Jeep goes straight down the road, much less wandering! The steering is still stiff and it doesn’t enter by itself after turning. Ended up with about 5 degrees caster.

Maybe once the new ball joints get some mile the steering won’t be so stiff

 

I agree in the tire wear and return to center but respectfully disagree that it won’t cause wandering. If excessive, toe in or toe out will cause wandering. The reason is instead of the tires rolling evenly and work together for directional control they fight each other and are dragging. When that happens whichever tire has more traction at the moment will cause the vehicle to want to go that way. As the tires drag it’s a constant battle back and forth which way the vehicle goes. Incorrect toe is one of the most common causes of tire wear and wandering because it’s the easiest to get out of specification.

 

I have to agree with everything Nick says above! Then I think about the original stock tie-rod arrangement with two short tie-rods meeting at the bell crank. The effective length of the “tie-rod” is ever-changing with suspension compressing/rebounding as you drive down the road, potentially changing from toe-in to toe-out. What were Willys engineers thinking?
-Donny