258 to 4.0 flywheel question - 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 > General Technical Discussions > Advanced Jeep Tech > 258 to 4.0 flywheel question

FS: Wranger BRIGHT License Plate LED! Just $3! Great valueBlack Friday and Cyber Monday Sales at JeepHut.comThe Jeep Forum Discount is ON!

Unread 09-16-2013, 07:18 PM   #1
Registered User
1984 CJ7 
Join Date: Sep 2012
Location: Youngsville, Louisiana
Posts: 1
Cj 258 to 4.0 flywheel question

First time posting but been reading the forum for a while. I am getting ready to swapping in a 4.0 that I rebuilt to replace my worn out 258 in my 84 CJ7. I will be using the
Hesco CPS kit so the tone ring will not be needed. The question I have is that I have a fresh resurfaced 258 flywheel that was given to me but has a worn ring gear, I also have the 4.0 starter that I would like to use. Has anybody installed a 4.0 ring gear on a 258 flywheel? Or will there be a spacing issue with the 4.0 starter on the flywheel.

hfirmin is offline   Reply With Quote Quick reply to this message
Unread 10-19-2013, 09:38 PM   #2
only in a jeep cj
Registered User
1986 CJ7 
Join Date: Jun 2001
Location: Mobile, Alabama
Posts: 4,669
Either set up can be used but the spacing is different. The flywheel must match the starter and vise-verse. The cost of putting a new ring gear on the 258 flywheel vs resurfacing the 4.0 flywheel is kinda a wash. Do one of the two. How you wire the 4.0 should also play into the decision. If using the 4.0 distribution power block and relays would be easier with the 4.0 starter and flywheel.
1975 CJ-6 1983 CJ-8
1986 CJ-7 Laredo 1986 TJ-7 Trail Jeep
2003 Inca Gold TJ Rubicon
only in a jeep cj is online now   Reply With Quote Quick reply to this message
Unread 11-05-2013, 06:40 AM   #3
Registered User
1979 CJ7 
Join Date: Mar 2013
Location: Oregon Coast, OR
Posts: 792
I haven't done that swap on my jeep but I have swapped ring gears on several Harley Evo Motors, They come stock with about 110 teeth or 102 teeth on the ring gear 'Don't remember' The starter gear is about ten or eleven teeth. If you build 9.5-1 compression or higher teeth brake off. So I have used parts 'ring gears & starter gears' from older Shovel Heads Much fewer teeth per inch - larger teeth in the same space.
I went with this theory, If the OD of the ring gear is the same on the two ring gears 'and it was' and the OD on the starter gear teeth was the same in each case, 'and it was' it would work, And it does. I have done this conversion on some very fast machines and have had perfect success in doing so.
In your case the starter must fit check the travel or throw of the gear Is it the same? Then the ring gear must match ID and OD to the pressure plate exactly. The gear pitch is already established just consider diameters and distances to be critical.
Good Luck
RedNeckCorvette 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.