Thrust Angle & Vibes

Offigojpn

Jeep Owner
I recently installed MetalCloak control arms on my 97 TJ 4.0 manual tranny to address my Caster angle, vibes and thrust angle. I then took to Axle boy 4x4 (reputable jeep shop) for their fancy alignment (control arm adj all wheels). I haven't picked it up yet but they say the vibes are still there and that I need a drop transfer case or SYE/DS for vibes and adj rear track bar for thrust angle.

I droppped it off with a 1/2" TC drop and based on the forum threads I really thought i would be good after the alignment. I have a zone 3" suspension, 1.25" BL and 1" MML. I will try a 1" TC drop but I am planning on a calling Adams Driveshaft next week for a SYE & DS. The drive shaft angle was just over 10 degrees from the pinions before i dropped it off. Is this too much and what is causing my vibes? They also did a road force balance of my wheels.

They said that I still have a positive thrust angle and that I need a rear adjustable track bar. I thought the control arms would fix this and the TB is just for centering the rear end. Are they correct or should have make another attempt at it. The alignment was expensive at $150. My rear end is not perfectly centered and off by a 1/2" The DS does look like it is slightly offset. Any comments and recommendations would be greatly appreciated.
 

timatoe

Jeep Fanatic
I'll start with the disclaimer that I have zero experience with TJ suspension, even though I have one it's basically stock....

Anyhow my thoughts are, I wouldn't mess with a t-case drop, just get the SYE and be done with it. You mention 10* pinion angle (I'm not an expert) I don't know if that's good or bad because I have no idea where that is in relation to the output on the t-case. If you're running a slip output to the drive shaft the pinion yoke should be basically parallel with the t-case output, with a SYE and double cardan shaft the pinion should point directly at the output then come down 1.5 to 3* (most people just go 2*) I wouldn't be able to even begin to tell you what the actual angle is at that point.

What rear is in there now and why is it not centered? The drive shaft itself doesn't need to be centered to run good.
 

Cloaked Willys

Jeep Fanatic
I recently installed MetalCloak control arms on my 97 TJ 4.0 manual tranny to address my Caster angle, vibes and thrust angle. I then took to Axle boy 4x4 (reputable jeep shop) for their fancy alignment (control arm adj all wheels). I haven't picked it up yet but they say the vibes are still there and that I need a drop transfer case or SYE/DS for vibes and adj rear track bar for thrust angle.

I droppped it off with a 1/2" TC drop and based on the forum threads I really thought i would be good after the alignment. I have a zone 3" suspension, 1.25" BL and 1" MML. I will try a 1" TC drop but I am planning on a calling Adams Driveshaft next week for a SYE & DS. The drive shaft angle was just over 10 degrees from the pinions before i dropped it off. Is this too much and what is causing my vibes? They also did a road force balance of my wheels.

They said that I still have a positive thrust angle and that I need a rear adjustable track bar. I thought the control arms would fix this and the TB is just for centering the rear end. Are they correct or should have make another attempt at it. The alignment was expensive at $150. My rear end is not perfectly centered and off by a 1/2" The DS does look like it is slightly offset. Any comments and recommendations would be greatly appreciated.
Thank you, Your current set up will work better with a SYE and removing the T-case drop. T-case drops always have a least a slight vibration because you can not get the angles lined up where they need to be on both ends.

They are correct that you may need an adjustable track bar to dial in the trust angle. If the axle is pulled to one side it will not allow the front and rear to be square to each other and cause it to dog track.
 

Offigojpn

Jeep Owner
Thanks cloaked. I just needed some unbiased opinions before spending more money.


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Offigojpn

Jeep Owner
I'll start with the disclaimer that I have zero experience with TJ suspension, even though I have one it's basically stock....

Anyhow my thoughts are, I wouldn't mess with a t-case drop, just get the SYE and be done with it. You mention 10* pinion angle (I'm not an expert) I don't know if that's good or bad because I have no idea where that is in relation to the output on the t-case. If you're running a slip output to the drive shaft the pinion yoke should be basically parallel with the t-case output, with a SYE and double cardan shaft the pinion should point directly at the output then come down 1.5 to 3* (most people just go 2*) I wouldn't be able to even begin to tell you what the actual angle is at that point.

What rear is in there now and why is it not centered? The drive shaft itself doesn't need to be centered to run good.
I got the Dana 35 rear. I know the transfer and differential pinion angles the same (parallel) but the drive shaft angle is greater than 10 degrees. It was actually 12degrees before I dropped it off at the shop. I have read it needs to be as close to the pinion angles as you can get it, which is easy to do with a small lift.
My Dana is not centered due to the factory track bar. I do have a relocation bracket.

I plan on removing the rear DS tonight and driving it from the front DS to confirm where the vibes are coming from. I believed now that my only resolution now is a SYE and DS. Thanks for commenting


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timatoe

Jeep Fanatic
Oh OK, I originally read that as pinion angle not driveshaft angle, sorry if there was confusion there. Also makes sense on the track bar pushing it offcenter.
 

Offigojpn

Jeep Owner
Ok so back from shop. $150 alignment which includes control arm adjustments to correct pinion angles, etc. then also got me for the $90 road force balance cause they talked me into it. Again this shop came highly recommended and 90% of what they do is jeeps mods. When I first drove It it almost vibrates more than when I took it in. I took measurements and removed the rear driveshaft. Then drive Without the rear DS and it drives smooth as butta.

Here are the pics of the drive shaft and my measurements. I am not liking what I see and will be calling them tomrrow. I am however still going to get the SYE and DS as I know this will need to happen eventually. Sorry for pic quality as it was dark and raining.
The worst part is the shop is over a hour each way and I have trailer jeep there.

Are these angles bad? Shouldn't the two pinion match? It's my understanding that they should or the diff pinion should be slightly less to compensate for drop during acceleration.
At what point does the difference of the driveshaft angle to pinion angle create vibrations.



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lindel

Jeep Owner
Yup, go straight for the JB Conversions Super Short SYE, and CV drive shaft. I should have, and will be going that route at a later date (I got the Rugged Ridge SYE, in an effort to save money. It works, but I'll have need of the JB unit when I get a tummy tuck). Get a good rear track bar (I wouldn't get anything other than Metalcloak or Currie), and a good front track bar wouldn't be a bad idea.

Lose the transfer case drop
 

Offigojpn

Jeep Owner
Thanks guys and hope your thanksgiving went well.
I ended up getting the adamssriveshaft package with the teraflex SSYE. I am sure JB is better but we won't be extreme off-roading.
I do have the metalcloak front and just took advantage of the free shipping today to buy a rear adj track bar.
Hopefully be installing by end of next week


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Offigojpn

Jeep Owner
I did last night and filled tc with fluid for test drive today. It drove very smooth except for a small vibration once I hit 60. The pic shows the pinion just a few degrees downward. I raised after first drive it to make more 180° to the driveshaft but it's still there. Going to remove front driveshaft tomrrow after work to rule out front caster. 0-60 it drives amazing! I do have a small stretch of interstate in way to work so need to fix.
Then I got to get my speedo working again. I guess i need to spend more money on some conversion box. Ugh!




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Pthorpe84

Moderator
Staff member
The money never stops flowing to these. The wobble could just be in the tires. I know mine has a slight vibration at 47-50 mph then it goes away. If it was the drive shaft, it would do it at certain RPM's


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Offigojpn

Jeep Owner
You are correct and to make it worse I also own a boat.
Tires were road force balanced so they are dead on.
I pulled the front drive shaft and it drives smooth as a caddi as fast as I can go. I have double adjustable metalcloak front uppers and steel single for the rest. Unfortunately the alignment shop either has super strength or used some blue thread locker cause I can't break the lock nuts on the uppers to adjust. My thought is that they got the caster just a shade too high. I will try some solvent and a little heat tomrrow when I have more time. I am certain I will get it at this point. It's just a matter of dialing in the front caster (pinion angle).


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Pthorpe84

Moderator
Staff member
You can break it loose....you just need to borrow one of their cheater bars....




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Offigojpn

Jeep Owner
[emoji23] I think I found a pipe wrench at work that may fit. I am bringing home a bigger crescent wrench and will get it done tonight.




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Offigojpn

Jeep Owner
Here is a quick update:
I did end up getting the majority of the vibes addressed. Just below 70 I get a very slight vibration which I am certain is in the transfer case.
The main vibe was due to the front pinion seal not being seated. With a very big cheater bar the pinion nut was tightened. I suspected this cause I was able to get slight lateral movement when I aggressively move the driveshaft back and forth. At the transfer case I have the same movement which sucks cause it wasn't there before I did the transfer case rebuild. I plan to open the transfer case after the holidays and replace some bearings and seals. I also have transfer case fluid leak at the main shaft. I bought the cheap rebuild kit from Novak and won't do that again. I will be calling JB Conversions.
I did get the Dakota digital box and speedometer works great.
As for front caster I will have to report later. I did get a alignment again after the pinion nut front and year were properly tightened. Adjustable rear track bar was installed and fixed the thrust angle. I will also gets some driveshaft angles too.
Jeep has been my daughters daily driver since she turned 16 (April 2nd) and drives very nice. If we take it ina long trip that includes interstate driving I will disconnect the front driveshaft and tie it to the frame and then reconnect if needed. I know not the best way to address but don't take long trips often and temporary.


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