High RPM on highway 1999 4-cyl - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > TJ Wrangler Technical Forum > High RPM on highway 1999 4-cyl

TeraFlex Now at Rockridge 4WD! BEST DEALS around!Alloy usa heavy duty ball joint kitsENGO QUADLUX 6" to 54" LED AMBER AND WHITE MULTI

Reply
Unread 08-23-2014, 02:28 PM   #1
gjohns25
Registered User
 
Join Date: Aug 2014
Location: Chicago, IL
Posts: 2
High RPM on highway 1999 4-cyl

I recently bought a 1999 automatic Jeep Wrangler 4-cyl and while driving on the highway the RPM read around 4000-4500 going about 65-70mph. This seems high to me, but this is my first jeep. Is this normal? If not, what could be causing this?

gjohns25 is offline   Reply With Quote Quick reply to this message
Unread 08-23-2014, 02:57 PM   #2
Wheelin98TJ
JEEP FREAK
 
Wheelin98TJ's Avatar
1998 TJ Wrangler 
 
Join Date: Apr 2004
Location: , Southeast MI
Posts: 24,645
RPM should be closer to 3,400 at 70 MPH with stock size tires and stock axle gear ratios.

What size tires do you have?

Are you sure the speedo is accurate?
Wheelin98TJ is offline   Reply With Quote Quick reply to this message
Unread 08-23-2014, 03:02 PM   #3
gjohns25
Registered User
 
Join Date: Aug 2014
Location: Chicago, IL
Posts: 2
Quote:
Originally Posted by Wheelin98TJ View Post
RPM should be closer to 3,400 at 70 MPH with stock size tires and stock axle gear ratios.

What size tires do you have?

Are you sure the speedo is accurate?
Tires are 31x10.50-15
Not sure if those are stock sized
gjohns25 is offline   Reply With Quote Quick reply to this message
Unread 08-23-2014, 05:19 PM   #4
Wheelin98TJ
JEEP FREAK
 
Wheelin98TJ's Avatar
1998 TJ Wrangler 
 
Join Date: Apr 2004
Location: , Southeast MI
Posts: 24,645
31 x 10 50 is not the stock size. It is taller and wider.

The taller tires would drop your rpm at highway speeds.

You may have a different gear ratio in the axles.

Rotate your tires one complete revolution while counting driveshaft revolutions. That'll tell you the axle gear ratio. Or if you are due for a diff fluid change, open up the diff and find the ring and pinion tooth count stamped on the side of the ring gear. There is more info in the FAQ sticky thread on how to determine your gear ratio if I'm not being clear.
Wheelin98TJ is offline   Reply With Quote Quick reply to this message
Unread 09-01-2014, 04:38 PM   #5
chuck85225
Registered User
1998 TJ Wrangler 
 
Join Date: Jul 2014
Location: Chandler, AZ
Posts: 14
With the same tires you have I'm at 3000-3100 rpm at 70 with stock 3.73 in my 98
chuck85225 is offline   Reply With Quote Quick reply to this message
Unread 09-01-2014, 04:46 PM   #6
afusco1222
Registered User
2003 TJ Wrangler 
 
Join Date: Mar 2011
Location: Annapolis, Maryland
Posts: 966
Has the Jeep ever been lifted or have bigger tires on it? Sounds like the PO had upgrades on it, and took them off to sell the Jeep.
afusco1222 is online now   Reply With Quote Quick reply to this message
Unread 09-01-2014, 06:53 PM   #7
2jhanna
Web Wheeler
2002 TJ Wrangler 
 
Join Date: Jun 2007
Location: Denton County, TX
Posts: 5,761
Quote:
Originally Posted by afusco1222 View Post
Has the Jeep ever been lifted or have bigger tires on it? Sounds like the PO had upgrades on it, and took them off to sell the Jeep.
This was my thinking also. Maybe had bigger tires and lower gears. Then took the tires off to sale and left the lower gears in.
__________________
jhanna
denton county, tx
2jhanna is offline   Reply With Quote Quick reply to this message
Reply

Tags
4-cyl , rpm

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
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






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.