Pinion angle/caster fine tuning

bOLsAK3

Jeep Newb
After installing my GC 4.5 to recommended spec the front driveshaft had vibration from 60mph and up. The front driveshaft was not stock and was replaced with a new MC double cardan at the time the lift was installed. The pinion angle at the time was @ 0 degrees and the driveshaft was coming into the pinion @ 10 degrees. In order to relieve the vibration I brought the pinion up to 4 degrees and pretty much stopped the vibration, however, the steering is now "flighty" and the Jeep likes to wonder. It's not horrible but it's not aces either. I know that this is a pretty common problem but was wondering what options I have to better improve the steering feel. I've seen some people prefer a 3 degree pinion as a good compromise but I was curious if any toe adjustment may help. As a reference as to what I'm running on my rig I have a 6 speed Unimited Rubi with the 4.5 game changer, 37x12.50r17 with 4.5-ish offset.
 

Cloaked Willys

Jeep Fanatic
What do you have the caster set at?
It is more important because it will affect driveability. The pinion angle should be in a range that you do not get vibration issues at that height.
 

bOLsAK3

Jeep Newb
Pretty sure caster is +2. Correct me if I'm wrong but caster and pinion cannot be adjusted separately, right? The factory caster is +6 degree and the pinion 0. If you adjust one the other goes with it. So currently @ 4 degree pinion I brought the caster angle to 2. The vibration from the driveshaft @ 0 dregee was enough to understand that if it continued the shaft or transfer case would eventually suffer damage. My adjustments were made focused on ending driveline vibe. Now I'm stuck with the steering problem and was looking for tuning options.
 

Cloaked Willys

Jeep Fanatic
Pretty sure caster is +2. Correct me if I'm wrong but caster and pinion cannot be adjusted separately, right? The factory caster is +6 degree and the pinion 0. If you adjust one the other goes with it. So currently @ 4 degree pinion I brought the caster angle to 2. The vibration from the driveshaft @ 0 dregee was enough to understand that if it continued the shaft or transfer case would eventually suffer damage. My adjustments were made focused on ending driveline vibe. Now I'm stuck with the steering problem and was looking for tuning options.
OK, your caster should be set to 4.5-5° to eliminate your flightiness. Pinion angle in the front is a byproduct and will fall within the range of what the caster allows. The lowest caster you really can run is about 4° but I have seen issues that low also. I know that we have 1 JK here with 5° and it does not have any vibes.
 

Kjeeper10

Jeep Fanatic
If you set pinion to +2 caster should be in range. Confirm with alignment off coarse.
2° pinion = 4° caster
1° pinion = 5° caster
0 pinion = 6° caster

Total 6° separation


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Kjeeper10

Jeep Fanatic
That is why i myself never recommend lifts over 4" unless you run a corrected axle housing.
I questioned MC's new 5-6" lift and Driveline concerns before.

Ive heard of people running 1-2° caster with a double carden that had vibes.
Another option is locking hubs but can be expensive.



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Cloaked Willys

Jeep Fanatic
If you set pinion to +2 caster should be in range. Confirm with alignment off coarse.
2° pinion = 4° caster
1° pinion = 5° caster
0 pinion = 6° caster

Total 6° separation
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Unfortunately the housings are not consistent enough to set them off the pinion. I have seen first hand 4°-8° of separation to the pinion. 6º is a guideline but not a hard number. It also depends what side you are referencing off of to account for cross caster.

That is why i myself never recommend lifts over 4" unless you run a corrected axle housing.
I questioned MC's new 5-6" lift and Driveline concerns before.

Ive heard of people running 1-2° caster with a double carden that had vibes.
Another option is locking hubs but can be expensive.

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We are currently running the 5.5" lifts on 2 of the in house jeeps. The 4 door does have locking hubs and the drivetrain has been heavily modified so we won't use it as a reference for vibes. Our 2 door is a stock Rubicon set up and drives great with no noticeable vibes. It has our drivelines front and rear with the caster about 4.5°. Doing an aftermarket housing with more separation is not a bad idea at all but we are running without one.
 

Kjeeper10

Jeep Fanatic
Unfortunately the housings are not consistent enough to set them off the pinion. I have seen first hand 4°-8° of separation to the pinion. 6º is a guideline but not a hard number. It also depends what side you are referencing off of to account for cross caster.



We are currently running the 5.5" lifts on 2 of the in house jeeps. The 4 door does have locking hubs and the drivetrain has been heavily modified so we won't use it as a reference for vibes. Our 2 door is a stock Rubicon set up and drives great with no noticeable vibes. It has our drivelines front and rear with the caster about 4.5°. Doing an aftermarket housing with more separation is not a bad idea at all but we are running without one.
I call luck on that one LOL

thats the first ive heard that about separation (more then 6°) that info is right on Dynatrac's site, not saying i disagree because ive only dealt with my jeep. I used the pinion flange for measurement.


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Pthorpe84

Moderator
Staff member
[/QUOTE]We are currently running the 5.5" lifts on 2 of the in house jeeps. The 4 door does have locking hubs and the drivetrain has been heavily modified so we won't use it as a reference for vibes. Our 2 door is a stock Rubicon set up and drives great with no noticeable vibes. It has our drivelines front and rear with the caster about 4.5°. Doing an aftermarket housing with more separation is not a bad idea at all but we are running without one.[/QUOTE]

Could you all get a write up on one of the shop builds? I'm sure I'm not the only one that would like to see the full install of a MC jeep. Pretty please!


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Cloaked Willys

Jeep Fanatic
Could you all get a write up on one of the shop builds? I'm sure I'm not the only one that would like to see the full install of a MC jeep. Pretty please!
We normally don't build them start to finish in any real order. Most of the time it is done as R&D and not stuff that we will normally put in public view
 

bOLsAK3

Jeep Newb
So here's the final outcome that works best for my 4.5" GC:

19 and 3/8 front upper
23 and 5/8 front lower

No vibe and good steering.
 
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