4.0 with T5 - issues with thinner flywheel - JeepForum.com
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post #1 of 4 Old 06-06-2014, 01:43 PM Thread Starter
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1984 CJ7 
Join Date: Oct 2009
Location: Shreveport, LA
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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
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post #2 of 4 Old 06-06-2014, 02:19 PM
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1986 CJ7 
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Location: California
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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
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post #3 of 4 Old 06-07-2014, 07:48 AM
Mike Romain
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1986 CJ7 
Join Date: Nov 2007
Location: Off the Grid in Chester Grant
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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.

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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #4 of 4 Old 06-07-2014, 09:01 AM
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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.
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