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1979 to 1983 engine swapch

680 views 10 replies 7 participants last post by  CSP 
#1 ·
The 4.2L in my 1983 CJ7 locked up & needs to be replaced. I have a 1979 CJ7 that's in nowhere near as good of shape - except for the engine, which is a rebuild with 64k miles. The 79 has a newly rebuilt T150 3-speed tranny. I would like to put the engine from the 79 into the 83. Does that mean I have to also swap out the transmission (which than means I have to swap out the existing dana 300 transfer case for the older dana 20)? Or will that older engine work with the T5 5-speed? Help!
 
#2 ·
Hey neighbor !
I think you can still use it
 
#4 ·
I believe either will work as the bell housings have the same pattern, but they'll need to keep their respective transfer cases. I'm not certain but I don't think you can mate the 5 speed to the 20.

You have an interesting dilemma; do you go with the overdrive fifth gear, or the stronger 3 speed? Say what you will about the T150, but it is a rugged mutha.
 
#5 ·
The 79 will work with the T5 and Dana 300 but may need some plumbing changes to keep the 1983 systems..

You need to check the input shaft on the gearbox will work with the bearing in the middle of the flywheel. You may have to swap those over.
 
#6 ·
WindKnot said:
I believe either will work as the bell housings have the same pattern, but they'll need to keep their respective transfer cases. I'm not certain but I don't think you can mate the 5 speed to the 20. You have an interesting dilemma; do you go with the overdrive fifth gear, or the stronger 3 speed? Say what you will about the T150, but it is a rugged mutha.
You're right about the transfer cases having to match up. The T150 has a Texas bolt pattern the matches up to the Dana 20, but not to the 300. I just wasn't sure if the output shaft from the 79's engine would marry up to the T5. Thanks for getting back!

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#7 ·
I swapped a 79 258 into my 83 CJ in place of a later 258. Straight swap with no issues.
My 79 had the older 258 manifolds that bolt together. I swapped over the later 258 manifolds in place and left the all metal valve cover as it matched the older head. I extended the wire for the temp unit as it is up by the front of the head instead of the top rear.
The bell housing are the same and all that swaps so the transmission back is whatever you want but to make it easier try to match the transmission /and it mount to the bellypan and tunnel cover used. Also match the pilot bushing to your transmissions as the input shaft size is different (T150 is larger than the T5)

IN SHORT. You can just swap over the block/head/valvecover and dress it with all the 83 engine accessories.
The transmission is up to you, but you need to group the package as pilot bushing/transmission/tunnel cover/tcase/driveshafts.
 
#9 ·
only in a jeep cj said:
I swapped a 79 258 into my 83 CJ in place of a later 258. Straight swap with no issues. My 79 had the older 258 manifolds that bolt together. I swapped over the later 258 manifolds in place and left the all metal valve cover as it matched the older head. I extended the wire for the temp unit as it is up by the front of the head instead of the top rear. The bell housing are the same and all that swaps so the transmission back is whatever you want but to make it easier try to match the transmission /and it mount to the bellypan and tunnel cover used. Also match the pilot bushing to your transmissions as the input shaft size is different (T150 is larger than the T5) IN SHORT. You can just swap over the block/head/valvecover and dress it with all the 83 engine accessories. The transmission is up to you, but you need to group the package as pilot bushing/transmission/tunnel cover/tcase/driveshafts.
Thanks. That's really helpful. I'm not worried about dressing the accessories up, just really want a running Jeep-I was just lucky I had a backup on hand (a lady hit me with a Suburban in the 79 while on a cell phone). The engine in the older jeep was recently rebuilt as was the T150, so I'm good in any case. But I figure a 5-speed is better than a 3 overall, though the 3 got good mileage too.

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