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Re-geared, now I have a vibration above 50 mph

Mr. Bills

TJ Addict
Nov 24, 2017
1,314
Area Code 530
You can half way help. How is your rear setup?
If I understand your question -

2006 LJ Rubicon, 4 1/2" suspension lift, adjustable control arms, Tom Woods double cardan drive shaft. The pinion is 1-2 degree lower than the driveshaft angle, but I would have to re-measure to provide you with the actual numbers. No tummy tuck.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
8,651
NorCal
If I understand your question -

2006 LJ Rubicon, 4 1/2" suspension lift, adjustable control arms, Tom Woods double cardan drive shaft. The pinion is 1-2 degree lower than the driveshaft angle, but I would have to re-measure to provide you with the actual numbers. No tummy tuck.
That is exactly what I'm looking for. I want to know the relationship of the pinion to the drive shaft. I'm currently at dead set 0, meaning exactly parallel. I won't go into how many adjustments I've already made. 2003 Sport, 3" suspension lift, adjustable arms, Adams double cardan drive shaft, 1" raised tummy tuck. My front pinion angle is also dead set 0 (parallel).
 

ac_

zombicon
Supporting Member
Jun 15, 2017
4,211
AZ, United States
Honestly, Mine is smooth up to about 70 then I can feel a harmonic vibration on the freeway, but it is so slight, I can't tell you if it is just the aggressive tires. My pinion angles are all sorts of fubared. My rear is still set for a 2" lift but I now have a 4 inch lift. I don't know what the exact numbers are, but I will try and get out into the shop this weekend. The front is at +6 and the pinion angle is really low as I am tracking down a caster issue, that I can't seem to resolve. With the axle at +6 you can visually see the yoke is way low for the driveline. Both my front and rear are way off.

I honestly would be surprised if your pinion angle is the issue. I mean we already have a controversy. @Chris will tell you to be 1 or 2 degrees low where I believe @Jerry Bransford will tell you to be perfecltly 0 at the rear end. Right there tells me that they have played with their settings and found little to no difference for vibrations. I think I am about 5-7 degrees low in the rear end.

I am curious to see what happens when you get your new tires.
 

Jerry Bransford

TJ Guru
Supporting Member
Nov 9, 2015
10,625
Escondido California
1-2 degrees low is an age-old way of setting pinion angles due to how the pinion angle raises during acceleration... but it's more of an issue with leaf spring suspensions than our TJs with control arms. I've said 1-2 degrees low, at the most, several times though 0 degrees is probably what you want with a TJ. But if you can't get it precisely at 0 degrees, it's better to have it a degree too low than a degree too high.

AC_, your pinion angle shouldn't really change even for a 4" lift though the angles at the driveshaft u-joints would be so steep that they'd be vibrating like crazy... so you'd have to do something. I dunno if you have a SYE or not though.

What is your front axle's problem? Is your steering not stable/not returning to center after completing a turn? Or is it a vibration? Keep in mind that the front pinion angle always takes precedence over caster angle. You adjust the caster angle up until you get a vibration caused by an excessive pinion angle and then back off enough to get rid of the vibration. That gives you as much caster angle as you can get without major surgery on the axle by welding the knuckles into a different position. 6 degrees of caster angle is nice to have but it's likely more than you need which is dependent on tire size. The bigger the tire the less caster angle that is needed to have good steering traits.
 
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Mr. Bills

TJ Addict
Nov 24, 2017
1,314
Area Code 530
What is your caster angle?
Caster in the rear?????? I thought @bobthetj03 was asking about the rear driveshaft and pinion angles.


Bobthetj03 said:
. . . I want to know the relationship of the pinion to the drive shaft. I'm currently at dead set 0, meaning exactly parallel. . . .
During one of my telephone conversations with @mrblaine regarding vibrations after regearing to 5,38 gears , he described what he did with pinion angles to eliminate the vibrations, acknowledged that it was not always a complete success, and recommended that I experiment with front pinion angles greater than the driveshaft angle but that pinion angles lower than the driveshaft angle can be problematic. [I'm sure he will correct me if I am mis-stating the essence of what he said.]

When I was fussing with the front pinion angle, matching angles reduced the vibrations somewhat but at the expense of caster. When I raised the front pinion angle to 2 degrees above the front driveshaft angle the vibrations diminished a bit more but my steering was too slow to return to center so I returned to matched angles, called it a day, and embarked on my current project of converting to manual hubs.

With all due respect to Mr. Bransford, manual hubs render inaccurate his generalization that, "front pinion angle always takes precedence over caster angle" because in 2WD nothing in the front axle is turning nor is the driveshaft such that one can set caster for best handling and not worry about the difference between pinion and driveshaft angles unless the difference is extreme. Also, with manual hubs there is no need to re-position knuckles in search of more caster. I am surprised that Mr. Bransford didn't include that option considering he has had manual hubs on both of his TJ's.

Manual hubs may not be the cheapest option in situations like mine, but it is an effective fix. When the hubs are installed I will set caster according to factory specs which will result in a lower front pinion angle than the front driveshaft angle, but it should not matter because nothing will be turning when I am in 2WD and in both 4WD high and low range I won't be going fast enough for the onset of the vibrations.

Bear in mind that my vibration/harmonic issue is directly related to the installation of 5.38 gears in combination with the NV241OR transfer case and 42RLE transmission. There was zero vibration prior to the re-gear from 4.88 to 5.38 and nothing else was changed. Since there are no vibrations at any speed with my front driveshaft removed, conversion to manual hubs should totally eliminate the issue.

I now have all the pieces except the long side inner chromoly 4340 axle shaft. [Amazon shipped a 27 spline shaft rather than the 30 spline shaft I ordered.] However, I should have everything on hand by New Year's Day and work will commence a few days later.

Stay tuned.
 
Last edited:

ac_

zombicon
Supporting Member
Jun 15, 2017
4,211
AZ, United States
1-2 degrees low is an age-old way of setting pinion angles due to how the pinion angle raises during acceleration... but it's more of an issue with leaf spring suspensions than our TJs with control arms. I've said 1-2 degrees low, at the most, several times though 0 degrees is probably what you want with a TJ. But if you can't get it precisely at 0 degrees, it's better to have it a degree too low than a degree too high.

AC_, your pinion angle shouldn't really change even for a 4" lift though the angles at the driveshaft u-joints would be so steep that they'd be vibrating like crazy... so you'd have to do something. I dunno if you have a SYE or not though.

What is your front axle's problem? Is your steering not stable/not returning to center after completing a turn? Or is it a vibration? Keep in mind that the front pinion angle always takes precedence over caster angle. You adjust the caster angle up until you get a vibration caused by an excessive pinion angle and then back off enough to get rid of the vibration. That gives you as much caster angle as you can get without major surgery on the axle by welding the knuckles into a different position. 6 degrees of caster angle is nice to have but it's likely more than you need which is dependent on tire size. The bigger the tire the less caster angle that is needed to have good steering traits.
Not to derail this thread too much, but I do have a SYE and a Ford 8.8 rear end, so I am low and to one side. I need to spend some time to get that straightened out but so far it is not causing any issues.

But the front, the steering does recenter, but taking off it kind of feels like an old 80s front wheel drive car. Remember those? When you gas it the front kind of walked back and forth. Mine does that but not to the extreme. I am not saying that is what is happening just what it feels like. then it is good till about 3rd gear and it kind of wanders again. then at 70+. Other than that it is drives straight as an arrow.

Here are my thoughts:
1) Caster angle not perfect or sweet spot
2) Anti-rock is causing too much body roll, so I am adjusting it with the steering
or
3) too much slop in the steering linkage from the box to the steering wheel maybe?

My specs are in my profile, but here is a quick rundown
Correctlink currie steering with currie front track bar brand new
Currie 4" lift brand new
rancho 5000x shocks brand new
anti rock brand new set to middle.
33 inch tires stt pros

I sometimes feel like others have stated like I am driving on ice. or it tracks straight but if there is road crown it will drift with the road crown but if I steer to conpensate the the steering goes back and forth. It is ever so slight though. I mean I am not changing lanes or anything. It is more annoying than dangerous.

The toe is right on the money.

Sorry @bobthetj03 for side bar, but I am up for any suggestions especially from people that know more about the coil spring suspensions than I do. And @Jerry Bransford asked. haha
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
8,651
NorCal
Thought I'd update the thread a little since some changes have been made, and as a result, some improvement made. A 1" TT was done, with a thicker skid. Pinion angles were re-adjusted. Net result was minor, but noticeable. Sent the front ds to Tom Woods to inspect. They balanced it a small amount better. Net result, another small improvement. Adjusted the front pinion angle to be 0.5* higher than ds. No improvement. Replaced my tires with some KO2's. This made the biggest improvement to date. I no longer have the harmonic from 50- 60 mph. Still have the vibe above 65. Most recent change was installing the rear lower arms with the last 2 MC arms to complete the set. Also adjusted the rear pinion lower just a tiny bit. This seemed to quiet down the 65+ vibes enough to notice a difference. The steering wheel still vibrates a little, but I can now do 65mph without it driving me bonkers. 70mph and above is still irritating, so I stay away from those speeds for now.
What's next? Well, I'm not sure. I still haven't replaced the TC input yoke, or the rear diff yoke. Have them on hand, but finding the time and ambition to tackle that job eludes me.
 

AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,474
Alabama
You know it may be the case in more of these situations that cumulative small improvements get you there.

I have the same tires and I have regeared and I have a very slight buzz above 65 that goes up and down.

If you notice that BFGoodrich tire has a pretty aggressive sidewall... It might be that at high-speed that tire starts to stand up a little bit and possibly higher tire pressure move the vibration around a little...I say that and at the same time I know 26 PSI is a magic number.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
8,651
NorCal
You know it may be the case in more of these situations that cumulative small improvements get you there.

I have the same tires and I have regeared and I have a very slight buzz above 65 that goes up and down.

If you notice that BFGoodrich tire has a pretty aggressive sidewall... It might be that at high-speed that tire starts to stand up a little bit and possibly higher tire pressure move the vibration around a little...I say that and at the same time I know 26 PSI is a magic number.
I played around with that idea a little. When I had the tire shop mount/balance them, as is usual with tire shops, they aired them to 35psi. I was so excited to not have the 50-60 harmonic that I didn't think about the tire pressure at the time. Next day I lowered them to 30psi, then 28, and finally settled on 27psi cold. Vibes didn't change during those adjustments. I might revisit the tire pressure and go back up to 32psi and pay more attention to any change.
 
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bobthetj03

bobthetj03

vibrajeep
Supporting Member
Ride of the Month Winner
Feb 3, 2017
8,651
NorCal
I know your old tires were worn pretty good, any idea how much the rollout changed with the tire swap? Did you notice any decrease in RPM at the original speeds?
Yeah, they were down to 6/32's, so I'll bet I gained a little rollout. I didn't measure it, but it certainly could have slowed down the ds rpm's a little with more tire under there.
 

MarkAlan

Member
Jan 25, 2016
75
Alabama
I had the same issue, with my front shaft. I tried every pinion angle , etc. it would stop if I pulled the shaft. I could run 80 and it was as smooth as it could be. The only way I could fix it was to install a hub kit. I believe it was mrblaine that told me that on some TJ's this would happen. I don't remember it it was with a 32rh which mine has but it did fix the issue, and has been fine for the past 5 or so years. I was lucky to find a Warn kit.
 

AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,474
Alabama
What did everyone conclude is the best route as far as cost and equipment to put in manual hubs
 

jeepndogs

TJ Enthusiast
Mar 5, 2017
512
Crete, IL, United States
What did everyone conclude is the best route as far as cost and equipment to put in manual hubs
Well I spent well over 3k on replacing driveshafts (4), rebuilding transfer case, replacing motor mounts, replacing control arms, input shafts, re setting gears twice, two different sets of tires and rims, and I know I am forgetting some things. Realistically it was probably over 4K I spent trying to fix it, I would have saved a lot of $$ if I just did the hubs right off the bat. I ended up going with the Yukon 5x5.5 kit.
 
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AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,474
Alabama
Well I spent well over 3k on replacing driveshafts (4), rebuilding transfer case, replacing motor mounts, replacing control arms, input shafts, re setting gears twice, two different sets of tires and rims, and I know I am forgetting some things. Realistically it was probably over 4K I spent trying to fix it, I would have saved a lot of $$ if I just did the hubs right off the bat. I ended up going with the Yukon 5x5.5 kit.
Lord. You sound like a man on a mission...glad it worked out .

Do the hubs make it drive better, get better mileage or any notable difference?
 

ac_

zombicon
Supporting Member
Jun 15, 2017
4,211
AZ, United States
Well I spent well over 3k on replacing driveshafts (4), rebuilding transfer case, replacing motor mounts, replacing control arms, input shafts, re setting gears twice, two different sets of tires and rims, and I know I am forgetting some things. Realistically it was probably over 4K I spent trying to fix it, I would have saved a lot of $$ if I just did the hubs right off the bat. I ended up going with the Yukon 5x5.5 kit.
curious why a 5x5.5 kit over 5x4.5?

Did you run 5.5 in the front and 4.5 in the rear?
 

Mr. Bills

TJ Addict
Nov 24, 2017
1,314
Area Code 530
I also have the Yukon 5x5.5 manual hub conversion. I chose it over the Yukon 5x4.5 manual hub conversion kit for three reasons: 1) Bigger and stronger than the Ford style 5x4.5 hubs (although @mrblaine observed that in practice hub strength of the 5x4.5 kit isn't much of an issue); 2) I didn't like the idea of the 5x4.5 kit widening the front track 1.5" with no good way to match the rear track (although @mrblaine informed me that he actually prefers to set up jeeps that way rather than equal track front and rear); but most importantly (3) I was able to get a killer price on the 5x5.5 kit from Amazon that was $650 off retail and $400 less than the 5x4.5 kit. In the end I had to purchase $525 worth of new wheels with the 5x5.5 lug pattern, offset by the $400 I received for my old wheels, and it cost $75 to remount and re-balance my existing tires, so I really only saved $200 over the 5x4.5 kit.

Do I regret my choice to go with the 5x5.5 kit rather than the 5x4.5 kit? Absolutely not.

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