Knock on acceleration - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 02-16-2013, 04:44 PM   #1
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
Knock on acceleration

I have a knock that only happens right after acceleration from a stop. When I accelerate it knocks 4-5 times, sometimes followed by a quiet squeak from the front passenger tire area the best I can hear. It does not do it at any other speed or while braking. I checked the bolt tightness on all the steering components and they appeared to be tight. I checked the driveshaft ujoints and those appear to be good. Any ideas what it would be that it only knocks 4-5 times and only accelerating from a stop?

Godric is offline   Quote Quick Reply
Old 02-16-2013, 04:59 PM   #2
Jeeper
 
WaterDR's Avatar
 
Join Date: Feb 2011
Posts: 1,332
Check to make sure your transfer case rubber mount bolts are on tight.

I had a similar issue and that was my problem.if the bolts are lose the transfer case with want to move on take off.

WaterDR is offline   Quote Quick Reply
Old 02-18-2013, 04:10 PM   #3
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
I checked the transfer bolts and all those seem tight. Today I was testing it out and I can get it to do it for an extended period of time if I am driving and brake to maintain that slow speed. I can very slightly feel it in the steering wheel. It's not overly loud. I don't think it's an engine knock because I think it would change with RPM and always happen, and I think it would maybe trip the engine knock sensor. It is driving me crazy.
Godric is offline   Quote Quick Reply
Old 02-18-2013, 05:24 PM   #4
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
Also, it does not happen if it is in 4wd
Godric is offline   Quote Quick Reply
Old 02-18-2013, 06:07 PM   #5
Jeeper
 
UFOtestpilot's Avatar
 
Join Date: Nov 2012
Location: Portland, Oregon
Posts: 1,818
I have a very similar noise I've been hunting, sorta. It sounds like a popping-rattle on takeoff, like a bolt rolling in a truck bed or a small gear slipping on a cog or something. I'm down to front driveline ujoints or something with the transfer case I don't understand. Mine does it in 2wd and only on initial take-off. I'll let you know what I figure out, if anything, and I'll watch for you to find your issue in case it points to mine.
__________________
For some, it is easier to kill the light inside of themselves than it is to fight the darkness all around them.
UFOtestpilot is offline   Quote Quick Reply
Old 02-18-2013, 06:39 PM   #6
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
Will do. Mine is sort of a knock, maybe a loud wobble but only from a stop. I don't think it's anything damaging but it drives me crazy. I suspect the front Ujoint also even though it looks good.
Godric is offline   Quote Quick Reply
Old 03-03-2013, 05:58 PM   #7
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
With the axle ujoints and bearings replaced, still does it. I guess next ill give the driveshaft ujoints a try.
Godric is offline   Quote Quick Reply
Old 03-03-2013, 06:54 PM   #8
Jeeper
 
Shark_13's Avatar
 
Join Date: Dec 2012
Location: Idaho
Posts: 1,351
Quote:
Originally Posted by UFOtestpilot View Post
I have a very similar noise I've been hunting, sorta. It sounds like a popping-rattle on takeoff, like a bolt rolling in a truck bed or a small gear slipping on a cog or something. I'm down to front driveline ujoints or something with the transfer case I don't understand. Mine does it in 2wd and only on initial take-off. I'll let you know what I figure out, if anything, and I'll watch for you to find your issue in case it points to mine.
If it does it in 2wd , why would it be front driveshaft ujoints? Wouldn't it make more sense it's the rear drive shaft ujoints? Just thinking out loud here.
Shark_13 is offline   Quote Quick Reply
Old 03-03-2013, 06:56 PM   #9
Jeeper
 
UFOtestpilot's Avatar
 
Join Date: Nov 2012
Location: Portland, Oregon
Posts: 1,818
Quote:
Originally Posted by Shark_13 View Post

If it does it in 2wd , why would it be front driveshaft ujoints? Wouldn't it make more sense it's the rear drive shaft ujoints? Just thinking out loud here.
Because the front drive shaft still rotates in 2wd, and the stated noise is coming from the front of the vehicle.
__________________
For some, it is easier to kill the light inside of themselves than it is to fight the darkness all around them.
UFOtestpilot is offline   Quote Quick Reply
Old 03-04-2013, 09:36 AM   #10
Jeeper
 
zmallory's Avatar
 
Join Date: Sep 2012
Posts: 29
I have this same exact issue that I noticed this weekend, have not tried 4wd yet, but will now that I found this thread. Already did front axle ujoints, balljoints and also new trackbar, shocks, stabilizer, rotors and brakes recently. I will check my front driveshaft ujoint asap. Please keep us posted on your findings, as will I.


Quote:
Originally Posted by Godric View Post
I have a knock that only happens right after acceleration from a stop. When I accelerate it knocks 4-5 times, sometimes followed by a quiet squeak from the front passenger tire area the best I can hear. It does not do it at any other speed or while braking. I checked the bolt tightness on all the steering components and they appeared to be tight. I checked the driveshaft ujoints and those appear to be good. Any ideas what it would be that it only knocks 4-5 times and only accelerating from a stop?
zmallory is offline   Quote Quick Reply
Old 03-04-2013, 10:19 AM   #11
Jeeper
 
Shark_13's Avatar
 
Join Date: Dec 2012
Location: Idaho
Posts: 1,351
Quote:
Originally Posted by UFOtestpilot View Post
Because the front drive shaft still rotates in 2wd, and the stated noise is coming from the front of the vehicle.
Gotcha, makes sense!
I was just thinking that it might be less likely to hear a knock from the front shaft unless it was under torque (ie in 4wd) not just spinning in 2wd.
Shark_13 is offline   Quote Quick Reply
Old 03-04-2013, 10:52 AM   #12
Jeeper
 
UFOtestpilot's Avatar
 
Join Date: Nov 2012
Location: Portland, Oregon
Posts: 1,818
Quote:
Originally Posted by Shark_13 View Post

Gotcha, makes sense!
I was just thinking that it might be less likely to hear a knock from the front shaft unless it was under torque (ie in 4wd) not just spinning in 2wd.
I'm still stumped on mine because I haven't taken any more time to get at it. I'm only thinking the front DS joints or a partial-part-time interference in the x-fer case, but I don't have any experience with x-fer cases so I don't know how well that theory would hold up under scrutiny. I've replaced and or thoroughly gone over nearly every other part that could be a possibility.

I read a post about a linkage bushing replacement kit that eliminates the knock from something against the tub, but it doesn't sound like the noise I'm hunting so I haven't looked into that further, yet.
__________________
For some, it is easier to kill the light inside of themselves than it is to fight the darkness all around them.
UFOtestpilot is offline   Quote Quick Reply
Old 03-16-2013, 12:57 PM   #13
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
So as I was crawling underneath getting situated to replace my driveshaft ujoints, I had an epiphany. I figured it out. The exhaust is knocking on acceleration. I grabbed the exhaust pipe near the driveshaft and wiggled it, sure enough, it knocks in the control arm area. To test I put a piece of wood in the gap and drove around the block a few times...no knock. Question is now, is there supposed to be mounts for the exhaust in the front that I am missing? Hopefully these pics can provide insight to a better solution than a block of wood on a hot exhaust pipe.
Attached Thumbnails
Click image for larger version

Name:	IMG_0455.jpg
Views:	40
Size:	222.0 KB
ID:	223332   Click image for larger version

Name:	IMG_0451.jpg
Views:	40
Size:	218.1 KB
ID:	223333  

Godric is offline   Quote Quick Reply
Old 03-16-2013, 09:29 PM   #14
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
I cant seem to even locate a spot where a bracket or hanger would be mounted to. I have read some suggestions about having it rerouted but that seems excessive. Might have to use some wire until I can figure out a more permanent solution.
Godric is offline   Quote Quick Reply
Old 03-16-2013, 10:03 PM   #15
Jeeper
 
UFOtestpilot's Avatar
 
Join Date: Nov 2012
Location: Portland, Oregon
Posts: 1,818
I bet the first mount you come to is dry rotted and weak. Maybe if you replaced the ones it has (I only recall the one at the back from when I glanced over it but there should be more) with new firm hangers it will tighten it up.
__________________
For some, it is easier to kill the light inside of themselves than it is to fight the darkness all around them.
UFOtestpilot is offline   Quote Quick Reply
Old 03-18-2013, 11:48 PM   #16
Jeeper
 
Godric's Avatar
 
Join Date: Feb 2013
Location: Urbandale, IA
Posts: 49
I have a feeling that the first mount I would come to is actually gone completely. Despite my best efforts I can't find anywhere on here, google, or my repair manual that says where the exhaust hangers/mounts are or should be located. Anyone have any idea where the first one should be?
Godric is offline   Quote Quick Reply
Old 03-18-2013, 11:55 PM   #17
Jeeper
 
mpbannon60's Avatar
 
Join Date: Jun 2011
Location: boothwyn pa
Posts: 101
One on the trans if memory serves me correct there should be one befor the gas tank and another right at the end
mpbannon60 is offline   Quote Quick Reply
Old 03-22-2013, 05:22 PM   #18
Jeeper
 
mpbannon60's Avatar
 
Join Date: Jun 2011
Location: boothwyn pa
Posts: 101
You ever check them hangars?

mpbannon60 is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 11:52 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC