alignment, relation between driveshaft and pinion angle. Expert, chime in!
03-25-2016, 04:40 PM
#1
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alignment, relation between driveshaft and pinion angle. Expert, chime in!
hey guys, I am having a vibration issue lately with my jk. I found worn out LCA bushings, which almost fixed the vibration, but I'm still having a small one, around and above 80km/h. And I feel it right under my butt, in the seat.
Lets start by saying I am a Professional mechanic in a Chrysler (FCA) dealer, but hey, no one's perfect
I currently have around 4.25" of lift with a double cardan front driveshaft. According to an article found on Pirate 4x4, the pinion must be 2* above the driveshaft angle (at rest) so it drops equal when cruising (for the front end). I know I have to bring the jk to a specialist for an alignment, But I'm doing some try and errors before.
Tonight, in an attempt to get rid of that damn vibration, I have roughly brought my front pinion at the "same" angle of the driveshaft. The vibration seems to be better than before, but hell it drives almost like a food basket. I mean, If I look over the balljoints its like I have 0 degrees of caster, which is bad, if not on the positive side, which is worst.
As far as I know, the u-joints on my driveshaft are good, they are new from last fall, and have no more than 4000km's. This is a driveshaft I have rebuild, and to be sure I brought it to a truck shop where they build and rebuild this kind of stuff. so I believe it is welded straight and balanced properly (I hope anyway).
Next step would be to remove it and re re re test drive it without the front DS. Already did this before I find the LCA bushings, but I guess I'm gonna have to do it again.
If you had any experiences, good or bad, please share. this is a situation many of us, jeepers, will face someday. I think this could be a good info thread.
And this, made me wonder what are the alignment specs other lifted jeep have. If you have a data sheet, please snap a picture and post it on here.
AAAnd, I know the best solution for the richest guy in the place would be to drop a new dynatrac 44 unlimited under that jeep, buts its way out of my budget.
Lets start by saying I am a Professional mechanic in a Chrysler (FCA) dealer, but hey, no one's perfect
I currently have around 4.25" of lift with a double cardan front driveshaft. According to an article found on Pirate 4x4, the pinion must be 2* above the driveshaft angle (at rest) so it drops equal when cruising (for the front end). I know I have to bring the jk to a specialist for an alignment, But I'm doing some try and errors before.
Tonight, in an attempt to get rid of that damn vibration, I have roughly brought my front pinion at the "same" angle of the driveshaft. The vibration seems to be better than before, but hell it drives almost like a food basket. I mean, If I look over the balljoints its like I have 0 degrees of caster, which is bad, if not on the positive side, which is worst.
As far as I know, the u-joints on my driveshaft are good, they are new from last fall, and have no more than 4000km's. This is a driveshaft I have rebuild, and to be sure I brought it to a truck shop where they build and rebuild this kind of stuff. so I believe it is welded straight and balanced properly (I hope anyway).
Next step would be to remove it and re re re test drive it without the front DS. Already did this before I find the LCA bushings, but I guess I'm gonna have to do it again.
If you had any experiences, good or bad, please share. this is a situation many of us, jeepers, will face someday. I think this could be a good info thread.
And this, made me wonder what are the alignment specs other lifted jeep have. If you have a data sheet, please snap a picture and post it on here.
AAAnd, I know the best solution for the richest guy in the place would be to drop a new dynatrac 44 unlimited under that jeep, buts its way out of my budget.
Last edited by holeshot; 03-25-2016 at 05:33 PM.
03-25-2016, 05:31 PM
#3
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ho well, can't take you serious if you don't know Quebec is a french province.. Sorry for my mistake mate... lol
if you can't even reply with a smart answer about the thread, why don't you just go on another?
And by the way, I'm not that bad if you only found one mistake in such a big post loll
if you can't even reply with a smart answer about the thread, why don't you just go on another?
And by the way, I'm not that bad if you only found one mistake in such a big post loll
Last edited by holeshot; 03-25-2016 at 05:33 PM.
03-25-2016, 05:51 PM
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Caster at 5 degrees or so is a target many people shoot for after a lift. But as you found out, as you lift higher, you get into a trade-off between good caster and good pinion. It is individual preference to decide what caster you are comfortable with.
Some alternatives - As you noted, aftermarket housings are popular because of this. Another option might be lockout hubs (spyntec). Some people choose to cut the ends off and weld then back on, giving a similar setup as the extra-seperation housings. And some people just remove the front driveshaft, and reinstall when they get to the trail.
Some alternatives - As you noted, aftermarket housings are popular because of this. Another option might be lockout hubs (spyntec). Some people choose to cut the ends off and weld then back on, giving a similar setup as the extra-seperation housings. And some people just remove the front driveshaft, and reinstall when they get to the trail.
03-25-2016, 06:35 PM
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thanks for the reply.
JK's have 4 degree of caster with the pinion flange at 90* with the ground.
To cut-off the C's and rotate them to get better caster is an awefull job, I know a couple guys how did that, but not sure I wanna give it a try.
remove the driveshaft? hell no. I'm the kind of guy how want's his rig to wheel like new, even with 20 000$ invested. fully functionnal.
And. spyntec.. is that what you are talking about? not sure how this could affect the caster?
Jeep JK SpynTec Conversion - Spyntec Conversions - Spyntec Industries LLC.
JK's have 4 degree of caster with the pinion flange at 90* with the ground.
To cut-off the C's and rotate them to get better caster is an awefull job, I know a couple guys how did that, but not sure I wanna give it a try.
remove the driveshaft? hell no. I'm the kind of guy how want's his rig to wheel like new, even with 20 000$ invested. fully functionnal.
And. spyntec.. is that what you are talking about? not sure how this could affect the caster?
Jeep JK SpynTec Conversion - Spyntec Conversions - Spyntec Industries LLC.
03-25-2016, 06:59 PM
#6
Super Moderator
Spyntec would essentially disconnect your front driveshaft since the axle shafts aren't turning the diff that's turning the shaft.
If the shaft isn't turning then you won't feel the vibration you suspect is due to caster issues.
If the shaft isn't turning then you won't feel the vibration you suspect is due to caster issues.
03-25-2016, 07:11 PM
#7
JK Jedi
Good advise from Karl the spyntec would solve the issue but is expensive. Running that much lift without caster correcting the axle will be a trade off from vibration and pinion angle. Another thing to look at would be if the driveshaft is truly balanced. Some shops do a good job with balancing and some do a half assed job.
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03-25-2016, 07:34 PM
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never saw this one coming, totally true though! its on my wish list now.