Another caster question

[mattfl]

2024 JLU with 4.5" Rock Krawler mid arm(8 adjustable control arms) lift running 40" mickey thompsons. Wanted to make sure my caster is set correctly and these are the readings I get

At the pumpkin

On the C

Look about right? Or should I adjust the pumpkin to 0?

Every so often, at higher speeds 65+ I'll get a slight vibration and I read somewhere that could be a combination of the FAD stuff(although mine came deleted) and a degree or two off on caster.

The Jeep doesn't feel super flightly on road and what I do feel is probably just because of the tires, but wanted to check and see if someone thinks some adjustment should be done.

thanks!

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[PT's19Rubi]

Caster is the angle at the pumpkin.

I'm not seeing track bar or steering arms in front of the diff. Is that the front diff?

 

[mattfl]

Caster is the angle at the pumpkin.

I'm not seeing track bar or steering arms in front of the diff. Is that the front diff?

yes front diff

 

[Old Dogger]

Adjust for 6° positive caster.

 

[yokramer]

0* on the pumpkin where you measured there should give you ~6* at the Cs which is about where you want it. I would bring that pumpkin measurement closer to 0

 

[mattfl]

0* on the pumpkin where you measured there should give you ~6* at the Cs which is about where you want it. I would bring that pumpkin measurement closer to 0

From other threads on the subject that's where I was landing at too. Just wanted some confirmation again.

Now, is it best to adjust using the lower or upper arms?

 

[yokramer]

From other threads on the subject that's where I was landing at too. Just wanted some confirmation again.

Now, is it best to adjust using the lower or upper arms?

Pretty sure its usually the lower arms where the adjustment happens

 

[mattfl]

Pretty sure its usually the lower arms where the adjustment happens

I have adjustable uppers too so it seems like I could adjust there as well.

 

[yokramer]

I have adjustable uppers too so it seems like I could adjust there as well.

There is some memory floating around in my brain that the uppers are to set pinion angle and the lowers to dial in caster. Like the uppers make bigger swings in adjustment than the lower but not sure why. Im sure someone else will chime in for the exact reasons.

 

[mattfl]

There is some memory floating around in my brain that the uppers are to set pinion angle and the lowers to dial in caster. Like the uppers make bigger swings in adjustment than the lower but not sure why. Im sure someone else will chime in for the exact reasons.

I found a post from clayton offroad on another forum where they stated adjust the uppers for caster and the bottoms for axle position/wheel base.

 

[Deke]

I've always used the lowers to set the wheel's position to be centered in the wheel well. Then I put a jack under the pinion and use it to adjust to the angle I want. Once the angle is set, I adjust the uppers length until the holes line up.

 

[Roky]

2024 JLU with 4.5" Rock Krawler mid arm(8 adjustable control arms) lift running 40" mickey thompsons. Wanted to make sure my caster is set correctly and these are the readings I get

At the pumpkin

On the C

Look about right? Or should I adjust the pumpkin to 0?

Every so often, at higher speeds 65+ I'll get a slight vibration and I read somewhere that could be a combination of the FAD stuff(although mine came deleted) and a degree or two off on caster.

The Jeep doesn't feel super flightly on road and what I do feel is probably just because of the tires, but wanted to check and see if someone thinks some adjustment should be done.

thanks!

The 1.3 is plus or minus from 6 degrees caster….so your caster is either 7.3 or 4.7. An easy way to to determine it is, with the finder on the diff flat, like in your pic, just rock it up to see if the number goes higher or lower…if the 1.3 goes down towards 0 then your caster is 4.7, if the 1.3 number goes up then your caster is 7.3…there’s other way to figure this out, but this is the easiest way for me…. I actually prefer an analog finder so I can tell automatically to add or subtract by the location of the needle, if it’s ahead of the 0 or behind the 90 or 0 (depending on how it’s on the diff)…. Here’s pic of mine, my caster is 5.9ish…

 

[mattfl]

The 1.3 is plus or minus from 6 degrees caster….so your caster is either 7.3 or 4.7. An easy way to to determine it is, with the finder on the diff flat, like in your pic, just rock it up to see if the number goes higher or lower…if the 1.3 goes down towards 0 then your caster is 4.7, if the 1.3 number goes up then your caster is 7.3…there’s other way to figure this out, but this is the easiest way for me…. I actually prefer an analog finder so I can tell automatically to add or subtract by the location of the needle, if it’s ahead of the 0 or behind the 90 or 0 (depending on how it’s on the diff)…. Here’s pic of mine, my caster is 5.9ish…

Ya, forgot I had one of those

 

[Roky]

Ya, forgot I had one of those

Without the FAD, that’s probably as much caster you can run or close to it… you can try and dial some more in but the vibration you’re feeling at +65 is likely the front DS…unfortunately, without the FAD, it’s a fine line between good pinion angle and as much caster you can get….

 

[mattfl]

Without the FAD, that’s probably as much caster you can run or close to it… you can try and dial some more in but the vibration you’re feeling at +65 is likely the front DS…unfortunately, without the FAD, it’s a fine line between good pinion angle and as much caster you can get….

Interesting observation this morning on the way to work. I usually have it it 4H but switched to 2H this morning and the vibration at 60+mph has disappeared. So I'm guessing this is what you were talking about with the front driveshaft.

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