Driveshaft or Tranny?
Thread Starter
JK Jedi
Joined: Feb 2007
Posts: 7,568
Likes: 3
From: Denver, CO
Driveshaft or Tranny?
I drive a lot for my job - this week is no exception. On the way home I noticed some bad vibes when I get up around 65-70mph.
I turned the radio off and really studied it for quite a long ways. I can really feel it when I press my right foot on the body over the tranny. I could also feel it in the steering wheel and shifter as well.
Although I couldn't hear it over the wind noise (I was heading into a stiff head wind), based on what I felt and thought I might be hearing it was like an oscillating grind. Again, it was only coming into play over about 65mph.
I'm thinking my pinion might be slightly off, and pulled over to check it - and it looks straight, but I need to remeasure it in the morning. If its not the rear driveshaft, anyone ever heard of or had a tranny make that type of vibe/noise?
I turned the radio off and really studied it for quite a long ways. I can really feel it when I press my right foot on the body over the tranny. I could also feel it in the steering wheel and shifter as well.
Although I couldn't hear it over the wind noise (I was heading into a stiff head wind), based on what I felt and thought I might be hearing it was like an oscillating grind. Again, it was only coming into play over about 65mph.
I'm thinking my pinion might be slightly off, and pulled over to check it - and it looks straight, but I need to remeasure it in the morning. If its not the rear driveshaft, anyone ever heard of or had a tranny make that type of vibe/noise?
JK Super Freak
Joined: Mar 2008
Posts: 1,176
Likes: 2
From: Springfield, MO
If you have a wrench and want to try a bit, here is where I would start troubleshooting. (assuming you are fairly certain the vibration is in the drivetrain and not just a typical wobble)
1. Disconnect the front drive shaft at both ends. Then go for a spin and see if the vibe still continues. (or gets better) You will essentially be driving in 2WD.
2. If you don't find it there, put the front back on and take it for a spin. (to make sure there is nothing new) Then you can remove the rear shaft and put it in 4Wheel High. (essentially making the JK a front wheel drive) I wouldn't want to drive this way for a long time, but it will allow you to try to isolate the problem. (and can get you home if you ever break the rear shaft on the trail)
If the vibration doesn't go away under either scenario, that likely means a problem with a wheel, alignment, or something other than drivetrain. Then you can start with the easy stuff - Torque everything down, especially the track bars. IF that doesn't take care of it, take a drive and pay special attention to the vibration first and then rotate the tires. You can usually tell if a bad tire moves from front to rear. If the problem doesn't follow the tires, hit the alignment shop...
If I was going to place a bet, one of your driveshafts will be out of balance and you will know it in step 1 or 2. Good luck!
ADDED: Also, you might pay attention to whether it happens while accelerating, decelerating, or both. Since you are only using the rear driveshaft to propel the JK when in 2WD, it will be impacted more when accelerating or decelerating, while the front driveshaft is pretty much freewheeling while in 2WD. If it seems to be more prevailent under acceleration or deceleration, this may give you a place to start from.
Another thought is that before you take off the driveshafts, you could pretty easily crawl under and visually inspect them for u-joint failure. Also, try to wiggle the shafts as that can also be a good heads-up.
1. Disconnect the front drive shaft at both ends. Then go for a spin and see if the vibe still continues. (or gets better) You will essentially be driving in 2WD.
2. If you don't find it there, put the front back on and take it for a spin. (to make sure there is nothing new) Then you can remove the rear shaft and put it in 4Wheel High. (essentially making the JK a front wheel drive) I wouldn't want to drive this way for a long time, but it will allow you to try to isolate the problem. (and can get you home if you ever break the rear shaft on the trail)
If the vibration doesn't go away under either scenario, that likely means a problem with a wheel, alignment, or something other than drivetrain. Then you can start with the easy stuff - Torque everything down, especially the track bars. IF that doesn't take care of it, take a drive and pay special attention to the vibration first and then rotate the tires. You can usually tell if a bad tire moves from front to rear. If the problem doesn't follow the tires, hit the alignment shop...
If I was going to place a bet, one of your driveshafts will be out of balance and you will know it in step 1 or 2. Good luck!
ADDED: Also, you might pay attention to whether it happens while accelerating, decelerating, or both. Since you are only using the rear driveshaft to propel the JK when in 2WD, it will be impacted more when accelerating or decelerating, while the front driveshaft is pretty much freewheeling while in 2WD. If it seems to be more prevailent under acceleration or deceleration, this may give you a place to start from.
Another thought is that before you take off the driveshafts, you could pretty easily crawl under and visually inspect them for u-joint failure. Also, try to wiggle the shafts as that can also be a good heads-up.
Last edited by MOWrangler; Feb 3, 2009 at 08:33 PM. Reason: Added comment
JK Enthusiast
Joined: Jul 2008
Posts: 436
Likes: 0
From: on the banks of the ocmulgee , GA
if I WAS TO PLACE A BET ON IT
I'd bet it ain't driveshaft related. More common is a tire with a belt that is separating or a wheel that slung a weight. It would be cheaper to fix too. Troubleshoot this one by removing any of ur tires that look like they might have structural problems. replace with ur spare take a test ride. Repeat until u find a problem. If u don't find a problem maybe u have a driveline problem. So follow the last guy's instructions.
JK Jedi
Joined: Feb 2008
Posts: 7,215
Likes: 10
From: Georgia
I drive a lot for my job - this week is no exception. On the way home I noticed some bad vibes when I get up around 65-70mph.
I turned the radio off and really studied it for quite a long ways. I can really feel it when I press my right foot on the body over the tranny. I could also feel it in the steering wheel and shifter as well.
Although I couldn't hear it over the wind noise (I was heading into a stiff head wind), based on what I felt and thought I might be hearing it was like an oscillating grind. Again, it was only coming into play over about 65mph.
I'm thinking my pinion might be slightly off, and pulled over to check it - and it looks straight, but I need to remeasure it in the morning. If its not the rear driveshaft, anyone ever heard of or had a tranny make that type of vibe/noise?
I turned the radio off and really studied it for quite a long ways. I can really feel it when I press my right foot on the body over the tranny. I could also feel it in the steering wheel and shifter as well.
Although I couldn't hear it over the wind noise (I was heading into a stiff head wind), based on what I felt and thought I might be hearing it was like an oscillating grind. Again, it was only coming into play over about 65mph.
I'm thinking my pinion might be slightly off, and pulled over to check it - and it looks straight, but I need to remeasure it in the morning. If its not the rear driveshaft, anyone ever heard of or had a tranny make that type of vibe/noise?
They ain't cheap. 700 bucks will get you a decent one. I have one, but you're a little far off for a diagnosis.
Thread Starter
JK Jedi
Joined: Feb 2007
Posts: 7,568
Likes: 3
From: Denver, CO
I'd bet it ain't driveshaft related. More common is a tire with a belt that is separating or a wheel that slung a weight. It would be cheaper to fix too. Troubleshoot this one by removing any of ur tires that look like they might have structural problems. replace with ur spare take a test ride. Repeat until u find a problem. If u don't find a problem maybe u have a driveline problem. So follow the last guy's instructions.
If you have a wrench and want to try a bit, here is where I would start troubleshooting. (assuming you are fairly certain the vibration is in the drivetrain and not just a typical wobble)
1. Disconnect the front drive shaft at both ends. Then go for a spin and see if the vibe still continues. (or gets better) You will essentially be driving in 2WD.
2. If you don't find it there, put the front back on and take it for a spin. (to make sure there is nothing new) Then you can remove the rear shaft and put it in 4Wheel High. (essentially making the JK a front wheel drive) I wouldn't want to drive this way for a long time, but it will allow you to try to isolate the problem. (and can get you home if you ever break the rear shaft on the trail)
If the vibration doesn't go away under either scenario, that likely means a problem with a wheel, alignment, or something other than drivetrain. Then you can start with the easy stuff - Torque everything down, especially the track bars. IF that doesn't take care of it, take a drive and pay special attention to the vibration first and then rotate the tires. You can usually tell if a bad tire moves from front to rear. If the problem doesn't follow the tires, hit the alignment shop...
If I was going to place a bet, one of your driveshafts will be out of balance and you will know it in step 1 or 2. Good luck!
ADDED: Also, you might pay attention to whether it happens while accelerating, decelerating, or both. Since you are only using the rear driveshaft to propel the JK when in 2WD, it will be impacted more when accelerating or decelerating, while the front driveshaft is pretty much freewheeling while in 2WD. If it seems to be more prevailent under acceleration or deceleration, this may give you a place to start from.
Another thought is that before you take off the driveshafts, you could pretty easily crawl under and visually inspect them for u-joint failure. Also, try to wiggle the shafts as that can also be a good heads-up.
1. Disconnect the front drive shaft at both ends. Then go for a spin and see if the vibe still continues. (or gets better) You will essentially be driving in 2WD.
2. If you don't find it there, put the front back on and take it for a spin. (to make sure there is nothing new) Then you can remove the rear shaft and put it in 4Wheel High. (essentially making the JK a front wheel drive) I wouldn't want to drive this way for a long time, but it will allow you to try to isolate the problem. (and can get you home if you ever break the rear shaft on the trail)
If the vibration doesn't go away under either scenario, that likely means a problem with a wheel, alignment, or something other than drivetrain. Then you can start with the easy stuff - Torque everything down, especially the track bars. IF that doesn't take care of it, take a drive and pay special attention to the vibration first and then rotate the tires. You can usually tell if a bad tire moves from front to rear. If the problem doesn't follow the tires, hit the alignment shop...
If I was going to place a bet, one of your driveshafts will be out of balance and you will know it in step 1 or 2. Good luck!
ADDED: Also, you might pay attention to whether it happens while accelerating, decelerating, or both. Since you are only using the rear driveshaft to propel the JK when in 2WD, it will be impacted more when accelerating or decelerating, while the front driveshaft is pretty much freewheeling while in 2WD. If it seems to be more prevailent under acceleration or deceleration, this may give you a place to start from.
Another thought is that before you take off the driveshafts, you could pretty easily crawl under and visually inspect them for u-joint failure. Also, try to wiggle the shafts as that can also be a good heads-up.
You might go by your dealer and see if they have a Reed tachometer. See if one of the techs will ride with you and hold it on the dash. Depending on which section vibrates, will be where your problem is. A higher frequency vibration is drivetrain related, while a lower frequency is tire and wheel. Sometimes, when it's in the sweet spot where the lower and higher frequencies meet, it's hard to tell without a Reed tach. At that speed, it could well be tire and wheel related. Especially since you can feel it through the steering wheel. A Reed tach will look something like this:
They ain't cheap. 700 bucks will get you a decent one. I have one, but you're a little far off for a diagnosis.
They ain't cheap. 700 bucks will get you a decent one. I have one, but you're a little far off for a diagnosis.
JK Jedi
Joined: Feb 2008
Posts: 7,215
Likes: 10
From: Georgia
Anytime, Jack. Suspension, driveline and alignment were my specialties for a very long time. I wish we were a bit closer, I'd be glad to give you my 2 cents on it. Just from reading what you're describing, I'm bettin on tires and wheels. At that speed if it was driveshaft related, you would have more of a buzz than a vibration. It would sound and feel like a heard of pissed of bumble bees.