Transmission compatible - JeepForum.com
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post #1 of 24 Old 04-08-2020, 06:50 PM Thread Starter
jwwhittle
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Transmission compatible

Well I suppose it's a good as time as any to change out the t 150 3spd to a 4 speed. I've looked at Novak's site and have a general idea of what I'm looking for. Currently I'm running a AMC 360 t150 as and a d20, now I know there is a T18 that will basically bolt in but don't know what it came in originally. Also a ford model that needs to have some adaption. Then there are the GM SM 420 seems to be a few of those around out of older Chevy pickups. What would be the easiest swap? What vehicles am I looking for that have these transmission?

Joe


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post #2 of 24 Old 04-08-2020, 07:28 PM
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Can't really answer your questions, but just wanted to say that from everything I've read over the years that a T18 or a SM420 are bullet proof transmissions... I've got a T18 behind my 351W. Can't say yet how it preforms as I don't quite have it running yet. But, you might also want to look at a T19... I think the only difference is that the T19 has a synchronized first gear where as the T18 does not... wish I knew that before I sunk money into the T18. If I'm wrong, someone can chime in and correct me.

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post #3 of 24 Old 04-08-2020, 08:00 PM
Tarneg
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first i must ask what are you trying to get out of the 4 speed swap? more middle gears, a taller end gear? what are you looking to gain over the 3 speed. and with the sm420 some of the numbers i found on your set up and knowing the chevy stuff you will need bellhousing , clutch disk. tailhousing adapter for tcase mounting, also some version of adapters to make the 420 output fit the d20 input gearing and im not sure how much shorter the cj5 is over a tj but this conversion will be longer and even my tj rear driver shaft is uber short and tight. i have not worked with a t18 so i got nothing on that one oh and the sm420 is in chevy trucks from like mid 60s (66 i think) and earlier and the first and reverse gear of it are square cut so they are stronger but cant be thrown into gear fast very easy
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post #4 of 24 Old 04-08-2020, 09:24 PM
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See following post.

The parts shop that stocks part for Skylab II will not have parts for our year/model of Jeep
We cannot accurately judge the trajectory of a speeding critter (cat, dog, sasquatch)
Record heat waves and floods only occur when we visit that area
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post #5 of 24 Old 04-08-2020, 09:28 PM
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Four Wheeler & JP Magazine did a shootout years ago https://www.fourwheeler.com/how-to/t...transmissions/ that was pretty comprehensive. Unfortunately I can't seem to get the photos to load on that page.
As for me I've got a Ford T-18 (6.32) languishing on my workbench. With that I puchased the TREMEC book that has the teardown information with excellent diagrams and exploded views. Jeep T-18's are very rare in these parts ever since Mac of Mac's Jeeparts went out of business after his passing (Godspeed Mac) so I found this up in Portland for a couple of hundred clams and although it's not a direct bolt in the Ford T-18's are highly adaptable. Mine has a bad reverse gear but mainly I want it up to snuff before I plunk down the kazooks for the Novak mainshaft.

The parts shop that stocks part for Skylab II will not have parts for our year/model of Jeep
We cannot accurately judge the trajectory of a speeding critter (cat, dog, sasquatch)
Record heat waves and floods only occur when we visit that area
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post #6 of 24 Old 04-08-2020, 09:33 PM
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...speaking of those rare Jeep T18's, a few years ago I spotted one with the Saturn Overdrive unit attached. Unfortunately it was out of state and the guy selling it knew what it was worth. $2000!
https://www.advanceadapters.com/prod...ransfer-cases/

The parts shop that stocks part for Skylab II will not have parts for our year/model of Jeep
We cannot accurately judge the trajectory of a speeding critter (cat, dog, sasquatch)
Record heat waves and floods only occur when we visit that area
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post #7 of 24 Old 04-08-2020, 11:24 PM
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Quote:
Well I suppose it's a good as time as any to change out the t 150 3spd to a 4 speed.
The first question that comes to mind is-----why?


High in virtually all the three and four speed transmissions is still 1 to 1. The truck transmissions (T18A, SM series, and NP435)have a first gear that is useless other than for slow speed wheeling. You really can't start out using that gear on the road, which means you will essentially have a three speed anyway. The T176 will give you a closer ratio between the gears due to to the added gear and is a direct swap.

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post #8 of 24 Old 04-08-2020, 11:33 PM
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Joe, you are on the right track by looking at Novak’s site. Read a bit more and you’ll find the information on what model years (both Jeep and Ford) the T18 came in. Given that you are not swapping to a GM engine, I would encourage you to go the T18 route. Just make sure it’s got the low 6.32 ratio first gear. I transplanted a T18 from a ‘79 CJ (6.32 ratio) in my ‘74. Overall I am satisfied with it. I also did the 2.45:1 Bronco gear conversion in the Dana 20. IMO, if you can’t get a T18 with the 6.32 first gear, then it’s not worth the effort. My interest in the T18 was for going slow in low. If your interest is fuel economy and highway speeds faster than 55, then the T18 is not for you. Cheers!
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post #9 of 24 Old 04-09-2020, 12:28 AM Thread Starter
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I should have given more information earlier, sorry I get on one and figure every body can read my mind. I have a 81 Cj5 with a built 360, t150, d20 with d44s out of a scout with 4" lift cj springs outboard in front running open diff with 3.54 on 33". We live part time in Colorado part southern Calif. I call it the RUNT. It is strictly recreational but drives nice on the street. When I swapped the 44s in I ground off the outer Cs and rolled them back to a 6 caster, drives better than my pickup. The club I run with in Colo has bone stock rubies to badass crawlers, some of the trails are seriously black diamond. I attempted some with the 3 spd and that was a joke. I am looking for at least a 4 to 1 first with 4.88 gearing to get the crawl speed down low. I kept up for the most part at the cost of a clutch and a kidney. I came across a T18 out of a jeep of some kind guy wanted $350 and it was in a bucket. There are so many options with the muncie truck trannys 465, 435, 420 all bullet proof but expensive to adapt. I just want to find a bolt in out of a truck in some guys field for $100 bucks! I sure do miss the old days.

Joe
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post #10 of 24 Old 04-09-2020, 08:21 AM
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A couple of observations....
Sounds like you are, in fact, a candidate for a truck four speed, given your interest in a ultra low first gear.


Whichever transmission you choose, insure it has the gearing you want. While the SM's and NP's are stable, the T18 comes in a at least two first gear configurations. Insure you get the one you want.


Be wary. Some applications of the T18 can't be converted to a short shaft.



Do the transmission first, then drive it. I did a T18 swap and a lowered my gearing to 4.10 at the same time. I found first more than adequate and my highway driving suffered with the lower gears. In retrospect, I wished I had stayed with the stock 3.73's.

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post #11 of 24 Old 04-09-2020, 04:12 PM
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ah so looking at the 4 speed for the correct reason ! okie im in colorado so i know some of those trails and i do all of them up to an 8/10 (9 is skipped over and 10 are full buggy) is your bottom pic on little moab by the way- rainbow falls trail? now in my offroad monster i have a ancient 350 to a nv4500 to a np208 with 4.88 gears and 37 inch tires. those numbers in first gear low are 6.34 - 2.62 - 4.88 and i will say unless on the hardest parts of the hard trail i never use first gear and on most trails i use second and third gear unless climbing an obstacle. (second is 3.44 and third is 1.71) and i can say yes the 4.88s kill highway speeds and since your tires are smaller yours will have an even lower top end so i agree with do the trans first and see how you like it. and yes for ease on the wallet as much as im a muncie guy the t18 would be easier, if you are happy with your current first and second gear and can see using them and mainly just want a very low crawl id shoot for the wide ratio jeep t18 or get the ford t18 and make it work.

now the jeep we have runs a 4.00 first gear with 4.88 rear end with 37 inch tires. now he went the 4 to 1 tcase and its a pain as it is too low for trails 6/10 and down and he has to go back into high range, now with the bigger tires and axles it will do 65 or so not too bad but then it gets scary to drive cause how big it is BUT its cause it has an overdrive i think 4th gear ends around the 50-55 mph mark.

ps let me know if i need to clarify something i kinda info dumped numbers here
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post #12 of 24 Old 04-09-2020, 07:00 PM
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I have a 1980 CJ5 with a 258, I put in a NOVAK built T19. It is an Excellent trans! It shifts smoothly, and the shift into first is short compared to a T18. Meaning the T18 has a spur/ straight cut gear which makes the shifter move further forward in first gear than a T19.
Mine has the 5:1 first, and it is mated to a Scout dana 20 TC. It is smooth and quiet, I LOVE IT.
For how i use my CJ, I really would rather have the 4:1 first gear (the close ratio version) it would keep the ol 258 in the best overall rpm range. I also put in a '73 Commando Dana 44 rear axle with a Tom Woods double cardan driveshaft. The T19's with 5:1 usually come from mid 80's 4x4 ford trucks.
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post #13 of 24 Old 04-09-2020, 10:08 PM Thread Starter
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Originally Posted by Tarneg View Post
ah so looking at the 4 speed for the correct reason ! okie im in colorado so i know some of those trails and i do all of them up to an 8/10 (9 is skipped over and 10 are full buggy) is your bottom pic on little moab by the way- rainbow falls trail? now in my offroad monster i have a ancient 350 to a nv4500 to a np208 with 4.88 gears and 37 inch tires. those numbers in first gear low are 6.34 - 2.62 - 4.88 and i will say unless on the hardest parts of the hard trail i never use first gear and on most trails i use second and third gear unless climbing an obstacle. (second is 3.44 and third is 1.71) and i can say yes the 4.88s kill highway speeds and since your tires are smaller yours will have an even lower top end so i agree with do the trans first and see how you like it. and yes for ease on the wallet as much as im a muncie guy the t18 would be easier, if you are happy with your current first and second gear and can see using them and mainly just want a very low crawl id shoot for the wide ratio jeep t18 or get the ford t18 and make it work.

now the jeep we have runs a 4.00 first gear with 4.88 rear end with 37 inch tires. now he went the 4 to 1 tcase and its a pain as it is too low for trails 6/10 and down and he has to go back into high range, now with the bigger tires and axles it will do 65 or so not too bad but then it gets scary to drive cause how big it is BUT its cause it has an overdrive i think 4th gear ends around the 50-55 mph mark.

ps let me know if i need to clarify something i kinda info dumped numbers here
You are right my friend actually both pics are from mini moab the first is after I made the right approach. Right now we are in San Diego and I don't know many people here so I've yet to find the stash of parts.

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post #14 of 24 Old 04-09-2020, 10:14 PM Thread Starter
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Originally Posted by Rondawg80 View Post
I have a 1980 CJ5 with a 258, I put in a NOVAK built T19. It is an Excellent trans! It shifts smoothly, and the shift into first is short compared to a T18. Meaning the T18 has a spur/ straight cut gear which makes the shifter move further forward in first gear than a T19.
Mine has the 5:1 first, and it is mated to a Scout dana 20 TC. It is smooth and quiet, I LOVE IT.
For how i use my CJ, I really would rather have the 4:1 first gear (the close ratio version) it would keep the ol 258 in the best overall rpm range. I also put in a '73 Commando Dana 44 rear axle with a Tom Woods double cardan driveshaft. The T19's with 5:1 usually come from mid 80's 4x4 ford trucks.
That's what I was looking for, what truck to look for! Do you know if the T19 needs an adapter for the AMC bell housing and D20?

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post #15 of 24 Old 04-09-2020, 10:23 PM Thread Starter
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Originally Posted by jeepdaddy2000 View Post
A couple of observations....
Sounds like you are, in fact, a candidate for a truck four speed, given your interest in a ultra low first gear.


Whichever transmission you choose, insure it has the gearing you want. While the SM's and NP's are stable, the T18 comes in a at least two first gear configurations. Insure you get the one you want.


Be wary. Some applications of the T18 can't be converted to a short shaft.



Do the transmission first, then drive it. I did a T18 swap and a lowered my gearing to 4.10 at the same time. I found first more than adequate and my highway driving suffered with the lower gears. In retrospect, I wished I had stayed with the stock 3.73's.
Do you know which Jeep comes with a T18? I very rarely take it on the highway if we go far I flat tow with my motorhome.

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