Replace 1999 4.0 with 1998 4.0 -
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 > Models > Jeep Wrangler Forums > TJ Wrangler Technical Forum > Replace 1999 4.0 with 1998 4.0

FREE, FREE, FREE EVENT!! Save big on Lockers now till ApriJKS Grand Cherokee WJ, Adjustable Front Trackbar 1"-6Teraflex JK HD Hinged Carrier & Adjustable Spare Tire

Unread 07-27-2010, 11:06 PM   #1
Registered User
1999 TJ Wrangler 
Join Date: Jun 2010
Location: Utah
Posts: 69
Replace 1999 4.0 with 1998 4.0

I'm looking at very low mileage 1998 TJ 4.0 engine out of TJ to replace my very tired 1999 TJ engine. Not much available on the upgrades to the 1999 engine. A slight mod to the engine controller and added engine sensors is about all I've found. By checking some parts on the online parts stores I see that the head gaskets are different and the block part numbers are different. Motor Trend states that the 1998 had a 81mm stroke and the 99 has 86.7mm stroke yet the bore, displacement, hp and torque are all the same. I'm assuming that the head has been changed to maintain these specs. I suppose the HP and torque curves are flatter for a 99 but I'm not concerned enough with that to influence my decision, I just need to keep my Jeep on the trails for at least the next few years.
What I need to know is if I get a complete engine, harness, computer and all components for the right price ($600 tops) is there any reason to not do this switch?

TJMistress is offline   Reply With Quote Quick reply to this message

engine , swap , 4.0 , harness , wiring , advice , suggestion

Quick Reply

Register Now

In order to be able to post messages on the forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid e-mail 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

Suggested Threads

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