Need some help diagnosing vibration on my bigger jeep
07-29-2014, 07:08 AM
#1
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Need some help diagnosing vibration on my bigger jeep
Symptom: I feel a pretty heavy vibration through the whole jeep, equally in the wheel my ass and pedal right around 38-40 kilometers per hour(sitting at 900-1000rpm). Only on; flat or slight uphills when im on the gas but maintaining speed (cruisin thought residential zones). Starts slow gets worse and worse till i let off the gas, dissapears when I hit the gas a bit harder or hit the brakes. Never gets debilitating, but definitely feels like im on some rough washboard.
Doesnt happen every single time I go through this rpm or speed range. But often enough
Jeep specs:
2008 4 door automatic.
33 inch nitto ats
Or 34 inch mtrs (happens with both)
4.88 gears
Stock rear ds
Coast 1310 front
Recently lifted from 3 inch zone to a 3.5 inch metalcloak. All arms left at the length they shipped them for install. After alignment rear was perfect all the way around, front had too much castor 7 or 8 degrees. Now sitting at 5.5 if my memory serves me right. I did notice a rougher ride between the two kits (stiffer on the bumps) but I cant say I noticed vibrations right away
Fast forward a few months and my Spider gears in the rear went on me so I regeared from 3.73s to 4.88 and did a true trac in the front d30. Elocker in the rear d44.
Started noticing the vibrations just after the end of the breakin period.
Tell me if I'm wrong but I Dont think its the gears, im leaning towards driveline vibes because of the fact that it only happens at a specific rpm.
So today I plan on dropping the castor a bit more to straighten out the pinion a bit and see if that helps
I do not have a way of measuring the pinion or castor here and dont feel like driving an hour to get something.
If this doesnt work ill be going back t the shop that did the alignment and the gears. Only reason I dont right away is they are an hour away and quite busy and this Is my only day off. I use the jeep for work till I can get a ladder rack on my little jeep.
Any tips or ideas to try would help me out a ton.
Stay muddy my friends
Doesnt happen every single time I go through this rpm or speed range. But often enough
Jeep specs:
2008 4 door automatic.
33 inch nitto ats
Or 34 inch mtrs (happens with both)
4.88 gears
Stock rear ds
Coast 1310 front
Recently lifted from 3 inch zone to a 3.5 inch metalcloak. All arms left at the length they shipped them for install. After alignment rear was perfect all the way around, front had too much castor 7 or 8 degrees. Now sitting at 5.5 if my memory serves me right. I did notice a rougher ride between the two kits (stiffer on the bumps) but I cant say I noticed vibrations right away
Fast forward a few months and my Spider gears in the rear went on me so I regeared from 3.73s to 4.88 and did a true trac in the front d30. Elocker in the rear d44.
Started noticing the vibrations just after the end of the breakin period.
Tell me if I'm wrong but I Dont think its the gears, im leaning towards driveline vibes because of the fact that it only happens at a specific rpm.
So today I plan on dropping the castor a bit more to straighten out the pinion a bit and see if that helps
I do not have a way of measuring the pinion or castor here and dont feel like driving an hour to get something.
If this doesnt work ill be going back t the shop that did the alignment and the gears. Only reason I dont right away is they are an hour away and quite busy and this Is my only day off. I use the jeep for work till I can get a ladder rack on my little jeep.
Any tips or ideas to try would help me out a ton.
Stay muddy my friends
07-29-2014, 11:02 AM
#3
JK Freak
Unfortunately I don't have any tips or tricks, but I'm interested to hear if you solve the problem. I recently regeared as well (4.88) and just passed my 500 mile break-in period. Inspected the gears and everything looked dandy. If you (or I) were having a bad vibration that was associated with the gears, I would expect to see some sort of unusual wear on them.
Anyway, point being, I'm having sort of the same situation. Recently regeared, but my lift didn't change at all. However I did upgrade to 37s around the same time as the regear. They have balancing beads in them, so I don't really think it is a tire balancing issue unless perhaps I don't have enough weight in them. But around 41-42 mph I get a pretty good vibe. As soon as I move off condition, either slow down or speed up, it seems to go away. I think I get a vibe around other speeds too but I don't remember what they are. So maybe it is RPM related, but I hadn't thought to look at that.
If you come up with an answer, keep us posted. Or at least me. Thanks! And good luck.
Anyway, point being, I'm having sort of the same situation. Recently regeared, but my lift didn't change at all. However I did upgrade to 37s around the same time as the regear. They have balancing beads in them, so I don't really think it is a tire balancing issue unless perhaps I don't have enough weight in them. But around 41-42 mph I get a pretty good vibe. As soon as I move off condition, either slow down or speed up, it seems to go away. I think I get a vibe around other speeds too but I don't remember what they are. So maybe it is RPM related, but I hadn't thought to look at that.
If you come up with an answer, keep us posted. Or at least me. Thanks! And good luck.
07-29-2014, 11:20 AM
#4
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Shortened the front lowers one full turn. See if that does anything. Maybe im smoking simething but the rear looks way off in the otger direction to me? Should I get this as straight as possible?
Stay muddy my friends
Stay muddy my friends
Last edited by Jade_Monkey07; 07-29-2014 at 11:27 AM.
07-29-2014, 11:39 AM
#5
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There is some info here:
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist (click both the 'JK' in the listing on the left side, and the 'tech info' at the top right)
How much actual height did you get from those MC 3.5" coils? The front will be a trade-off between good pinion and good caster. Unless you cut/turn or move to a caster corrected aftermarket housing, you may need to run lower caster (somewhere around stock numbers) to avoid the vibes. One easy way to check would be to just remove the front driveshaft and go for a drive. If the vibes are gone, then re-install, lower caster, and go for another drive.
For the rear, putting the pinion about 1 degree down from pointing at the tcase output is what I keep seeing for a double cardan. By the pic, yours looks to be a couple degrees too high?
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist (click both the 'JK' in the listing on the left side, and the 'tech info' at the top right)
How much actual height did you get from those MC 3.5" coils? The front will be a trade-off between good pinion and good caster. Unless you cut/turn or move to a caster corrected aftermarket housing, you may need to run lower caster (somewhere around stock numbers) to avoid the vibes. One easy way to check would be to just remove the front driveshaft and go for a drive. If the vibes are gone, then re-install, lower caster, and go for another drive.
For the rear, putting the pinion about 1 degree down from pointing at the tcase output is what I keep seeing for a double cardan. By the pic, yours looks to be a couple degrees too high?
Last edited by nthinuf; 07-29-2014 at 11:43 AM.
07-29-2014, 11:42 AM
#6
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There is some info here:
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist (click both the 'JK' in the listing on the left side, and the 'tech info' at the top right)
How much actual height did you get from those MC 3.5" coils? The front will be a trade-off between good pinion and good caster. Unless you cut/turn or move to a caster corrected aftermarket housing, you may need to run lower caster (somewhere around stock numbers) to avoid the vibes. One easy way to check would be to just remove the front driveshaft and go for a drive. If the vibes are gone, then re-install, lower caster, and go for another drive.
For the rear, putting the pinion about 1 degree down from pointing at the tcase output is what I keep seeing. By the pic, yours looks to be a couple degrees too high?
Tom Wood's Custom Drive Shafts - Tom Woods Custom Drive Shafts Custom Driveshafts Specialist (click both the 'JK' in the listing on the left side, and the 'tech info' at the top right)
How much actual height did you get from those MC 3.5" coils? The front will be a trade-off between good pinion and good caster. Unless you cut/turn or move to a caster corrected aftermarket housing, you may need to run lower caster (somewhere around stock numbers) to avoid the vibes. One easy way to check would be to just remove the front driveshaft and go for a drive. If the vibes are gone, then re-install, lower caster, and go for another drive.
For the rear, putting the pinion about 1 degree down from pointing at the tcase output is what I keep seeing. By the pic, yours looks to be a couple degrees too high?
Stay muddy my friends
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07-29-2014, 07:14 PM
#8
JK Enthusiast
Please, anyone, correct me if I am wrong here...
On your previous post about rear caster. There is no caster angle on the rear as caster only affects the steering geometry.
That rear pinion angle does look off by quite a bit. I can also see that the springs are at a significant angle as well. As I understand it, you should use the lower CA to position the axle properly forward or back and then use the upper CA to adjust it's angle. So, I would shorten the rear uppers to reduce the pinion angle so that the drive shaft is straight.
I am assuming that your lift includes all 8 control arms? On the right rear, is anything hitting the trackbar or it's mount? With that much angle, I would bet that there is very little clearance when the spring is fully compressed.
07-29-2014, 07:23 PM
#9
JK Enthusiast
Unfortunately I don't have any tips or tricks, but I'm interested to hear if you solve the problem. I recently regeared as well (4.88) and just passed my 500 mile break-in period. Inspected the gears and everything looked dandy. If you (or I) were having a bad vibration that was associated with the gears, I would expect to see some sort of unusual wear on them.
Anyway, point being, I'm having sort of the same situation. Recently regeared, but my lift didn't change at all. However I did upgrade to 37s around the same time as the regear. They have balancing beads in them, so I don't really think it is a tire balancing issue unless perhaps I don't have enough weight in them. But around 41-42 mph I get a pretty good vibe. As soon as I move off condition, either slow down or speed up, it seems to go away. I think I get a vibe around other speeds too but I don't remember what they are. So maybe it is RPM related, but I hadn't thought to look at that.
If you come up with an answer, keep us posted. Or at least me. Thanks! And good luck.
Anyway, point being, I'm having sort of the same situation. Recently regeared, but my lift didn't change at all. However I did upgrade to 37s around the same time as the regear. They have balancing beads in them, so I don't really think it is a tire balancing issue unless perhaps I don't have enough weight in them. But around 41-42 mph I get a pretty good vibe. As soon as I move off condition, either slow down or speed up, it seems to go away. I think I get a vibe around other speeds too but I don't remember what they are. So maybe it is RPM related, but I hadn't thought to look at that.
If you come up with an answer, keep us posted. Or at least me. Thanks! And good luck.
I have noticed, since I put Dynabeads in my 35's, that they cause some interesting tire balance phenomenon. I believe that I can feel the beads reposition themselves in the tire between 35 and 45 mph after being stopped. As I increase my speed it feels like the tire is out of balance and then it becomes balanced again. In my experience the ride is smooth from there up to around 70 when the balance goes to hell again.