My manual tran. YJ Wrangler shakes under power, above 2k RPM... thanks - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > YJ Jeep Wrangler Forum > YJ Tech Forum

Join Wrangler Forum Today

Thread Tools

Please support our sponsors and let them know you heard about them on
Old 06-13-2014, 04:22 PM   #1
Join Date: May 2011
Location: Merritt Island, FL
Posts: 30
Images: 2
My manual tran. YJ Wrangler shakes under power, above 2k RPM... thanks

Hi everybody, thanks for looking and commenting.
I have a 1991 Wrangler 4.0 5spd that's pretty much stock. I've rebuilt a lot of its mechanicals and until this week it ran perfect. Three days ago the Jeep developed an infrequent noise that sounded like it was coming from the muffler. I crawled underneath and noticed what looks like the exhaust pipe to the muffler's front connection had worn loose and developed play in the connection. The following day the metal on metal chirping noise grew louder and more frequent. Not being a pay week I made the mistake of JB Welding the connection to quiet the Jeep, until payday. In case you're unaware JB Weld burns at high temperature. For my whole commute to work it gave off a very strong chemical smell. I rolled down the windows and knew it wouldn't be long before I could do a real repair.

BUT then yesterday I noticed THE REAL PROBLEM.
My commute is mostly highway miles where I drive around 55 mph. The Jeep developed a pronounced shake above 2k RPM, in all gears. As RPM increases so does the severity of the shake/vibration. While driving home I began to problem solve and these are some of the clues I hope you guys can use to help me solve my mystery.

When I'm driving above 2k rpm the Jeep shakes. If I push the clutch in the shake disappears. With the clutch in I rev the engine and the engine sounds normal and the Jeep doesn't shake. That pretty much illuminates the suspension, steering, or engine as the problem. I'm assuming the problem is something to do with the manual transmission. On a side note I've owned the Jeep for about 4 years and ever since I've had it, getting it into reverse has been a slight hassle. Sometimes it slips right in, and other times I have to give it a small amount of RPM and slightly let out the clutch to allow it to slip into gear. This only happens with reverse. Given the transmissions prior performance I just learned to live with this little quirk.

I've had automatic transmission cars my entire life so I'm kind of unfamiliar with the manual transmission found in the Jeep. I noticed there is one (loose) bolt fastened the transmission to the skid plate. Is this bolt supposed to be snug? ...or does it allow for transmission movement during shifting?

Any ideas or tests I could perform to help isolate the problem would be GREATLY APPRECIATED. I'm thinking about trying to replicate the problem while the Jeep is up on jackstands. My friend will slowly operate the Jeep while I crawl underneath to inspect.

Thanks again everybody.

JimsJeep321 is offline   Quote Quick Reply
Old 06-13-2014, 04:36 PM   #2
Pmryall's Avatar
Join Date: May 2014
Location: NW Ohio
Posts: 234
It should be snug, I agree it sounds like your transmission, enough fluid, maybe drain it and look for shavings. I had some shifting problems ahwhile back that went away when I changed over to synthetic, sorry I'm not a transmission guy so those are my humble thoughts.

Keep on jeepin' on.
Pmryall is online now   Quote Quick Reply
Old 06-13-2014, 06:17 PM   #3
c5wagner's Avatar
Join Date: Apr 2013
Location: Reno, Nevada
Posts: 1,212
Check your U-joints first, if those are fine, put your transfer case into neutral and try going into gear and get your engine up to 2000 rpms. since the transfer case should be in neutral you won't go anywhere. If the vibration isn't with the tranny, then the transfer case could be the problem.

The shake could also be a warped flywheel or your pressure plate/ clutch disc can be unbalanced .
1989 Base YJ, 4.2l, Borla exhaust, offy intake, Motorcraft 2150 carb, CRT HEI ignition, ax15, np231 JB conversions SYE, D30 ARB & Ford 8.8 ARB 4.56, 35x12.5r15 Goodyear MTR's, bds 3.5" springs, 1" body lift, and 1/2" Boom Shackles.
Build Thread:
c5wagner is offline   Quote Quick Reply
Old 06-13-2014, 06:44 PM   #4
173ABN VN's Avatar
Join Date: Jan 2013
Location: rural N.E. Kansas
Posts: 168
ditto on what C5wanger said,I'd check the U-joints...russ
173ABN VN is offline   Quote Quick Reply

1991 , shake , transmission

Quick Reply

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.
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


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 05:07 AM.

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