Lining up Parts for Tranmission/Transfer Case swap

Lining up Parts for Tranmission/Transfer Case swap


Plano, tx
1980 Jeep CJ7 Project. Currently 258,SR-4,Dana 300,AMC20,Dana 30. Soon to be 258 Rebuilt, T-18A, Dana 20, not sure on diffs but regeared for rock play.

Oh and a daily driver thats a 2011 Chrysler Wrangler JK Unlimited. With the number of issues since purchase on 1/15 I can't even bring myself to call it a Jeep.
I currently am doing a body off rebuild of a 1980 CJ7. While the body is off I am rebuilding the Engine, and want to swap the SR4 with a T18a and Dana 20, but I am not finding a lot of help (at least that I understand).

I can rebuild engines all day long, but I normally leave the rest to the shops, but this time I want to do some of the work myself.

I have a T-18a and Dana 20 plus drive shafts from another CJ7. I have no idea what year, but the Engine was a 304.

From what I have read, the Bell Housing will bold to my 258 fine, but after that is a bit unclear to me. The only clear difference I can find between a 304 mount vs a 258 mount is the bell housing adapter to the transmission. And references to the T18a possibly having a slight vibration in the drive shafts due to the angle to the differentials. And possibly the shifter needing heated and rebent.

Can anyone tell me what else I am in for?

My plans are to put a 4" suspention lift, and a 2-3" Body lift in, as well as to regear the differentials and install ARB Lockers. I'm going to do all this work while the body is off to make life a bit easier for me. I haven't totally decided on the differentials yet, I may be changing them out, not totally sure yet.

One thing is for sure though and that is that the SR-4 has to go.
This is a no brainer. I may be a little confused, it sounds like you want to swap the AMC 304 for a 258? If so this is still a no brainer. To do the 304 to 258 or vice versa the driver’s side motor mount stays the same but the passenger side relocates. You can reuse the original mount if you are carful while removing it from the frame. The fly wheels are not interchangeable as the 304 is externally balanced so if you don’t have the one off the 258 you will need to find one.

The CJ T18 was introduced as a factory option starting in 1972 thru 1979 so any of the T18 bell housings from 1972 to 1976 will work but all of the 1977 to 1979 bell housings are drilled for both the Ford and CJ T18s regardless of the original tranny. The clutch system is the same for the AMC I6 and V8. This all pertains to CJ not FSJ T18s as in the CJ there is no adaptor from the bell housing to the transmission. The Jeep T18 comes with a 1” adaptor to bolt to your 20 transfer case; in reality the adaptor is part of the transmission. If you are using a FSJ T18 then you have a different animal. There is a front adaptor and a longer shaft that uses the same bolt pattern as the T5. The adaptor lengths vary but generally are about 5”. This of course poses another issue with drive shafts and shifter placement. Try this links for more info:
I am keeping my i6, but wanting to install the T18a and the D20.

The T18 WAS bolted to the 304.

And the JeepTech site doesn't help me much because I know so little about tranmissions.
I am keeping my i6, but wanting to install the T18a and the D20.

The T18 WAS bolted to the 304.

And the JeepTech site doesn't help me much because I know so little about tranmissions.

If the T18 was bolted to an AMC 304, the 304 was only offered in CJs, and with a Dana 20 x-case; you should be good to use OEM, no adaptor, bolt together parts to do this swap with one possible exception, the D20 shift linkage when bolted to a T18 is longer to accommodate the longer 4 speed transmission in lieu of the shorter 3 speeds. There are a couple of fixes including twin sticking the shifter but if you can come up with the original x-case that was bolted to the T18 your problem is solved.

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