4.0 with T5 - issues with thinner flywheel - JeepForum.com
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 CJ Forum > 4.0 with T5 - issues with thinner flywheel

Rough Country Lift Kits and Parts!Ruffstuff 10 year saleSmittybilt XRC M.O.D Bumper and Brush Guard

Unread 06-06-2014, 02:43 PM   #1
Registered User
1984 CJ7 
Join Date: Oct 2009
Location: Shreveport, LA
Posts: 292
4.0 with T5 - issues with thinner flywheel

I've read a few things about the 4.0 flywheel being 1/4" thinner than a 258 flywheel, which could cause issues with clutch disengagement (clutch fork running out of room, along with the throwout bearing being close to coming off the fork because of the increased throw). I know Skerr went through an ordeal and had to drill, tap, and install an adjustable pivot (and weld trusses to strengthen that area around it).

With all of the 4.0 swaps that have been done, I haven't seen much published about these issues when used with the T5, T4, T176, etc. Does this commonly cause an issue with a 4.0 swap?

I'm trying to avoid any issues by making the necessary modifications before I put everything in - cuz once I do, I will not be taking it back out anytime soon (hopefully!)

So my question is what modifications, if any, do I need to do? The pivot mod like Skerr (if so, use a pivot from what vehicle?)? I've seen the adjustable throwout bearing that Novak sells, which would easily solve the issue. Problem is, they are still in production.

Not sure what I need to do for this.

1984 CJ7 Laredo
4.0 I-6 / T5 / D300 / D30 / D44
Black Diamond 3" lift, 33" tires, 4.11 gears
1984Laredo is offline   Reply With Quote Quick reply to this message
Unread 06-06-2014, 03:19 PM   #2
Registered User
1986 CJ7 
Join Date: Nov 2009
Location: California
Posts: 1,000
This exact discussion was recently had on another thread. Not sure what the resolution was, but there may be some helpful info there...

Good luck, and keep us posted on what you decide.
California 4.0 OBDII Engine Swap
SLO_Ken is offline   Reply With Quote Quick reply to this message
Unread 06-07-2014, 08:48 AM   #3
Mike Romain
Registered User
1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant, Nova Scotia, Canada
Posts: 18,090
The gent on the other thread had no issues. I used the 258 flywheel on my swap, so had no problems.

I haven't seen any threads where this was an issue. My YJ 258 now has the 4.0 with the 4.0 flywheel and its slave cylinder still reaches fine. It shifts great anyway.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
Mike Romain is offline   Reply With Quote Quick reply to this message
Unread 06-07-2014, 10:01 AM   #4
Registered User
1985 CJ7 
Join Date: Sep 2011
Location: Foresthill, CA
Posts: 2,430
I went from a 258 in front of an AX-15 to a 4.0 and did not notice a difference. I did not measure but the flywheels appear to be the same thickness.
RenoF250 is offline   Reply With Quote Quick reply to this message

Quick Reply

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:
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

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.