Swapping out 3 speed for a 4 speed

[Rippy]

Im wanting to swap out my 3 speed with a Dana 20 Transfer Case ,to a T-4 with a Dana 300 tranfer case, is this a pretty straight forward swap,or is there some tricks that I need to know about, The T-4 does not have the shift lever,does anyone know where I can get one at? And would it be a good idea to put the twin sticks on now while I have it out? Any help would be appreciated,thanks Rippy

 

[Torxhead]

Although the T-4 has a history of being a weak Transmission , probably due to the cast aluminum casing, if you could get one in fairly good condition, go for it. There might be some issues with the tranny spline count, pilot bushing size, and bolt hole location. These issues if any, can be easily resolved and the '79 style bell housing that was used in all the later CJs. Novak and Advance adapters should haven the info required on their websites. There will probably will be some driveshaft work needed also from a local shop and will probably require a later model skid plate. The shift lever should be an on-the-shelf item at any any of the big box suppliers. The twin stick is nice to get, but not a nesscessity. Getting an extra gear would be a great addition, plus the lower ratio Transfer Case , but will require a bit of research.

 

[Rippy]

thanks for the input,I might be waiting now,I talked to novak adapters they reccommended the T-18 ,so i might just wait a while and keep my eyes open for one,unless someone on here has one to part with,I am in the market for one,thanks again for your help Rippy

 

[Torxhead]

Good luck with locating any of the low first gear truck transmissions, like the NP435,SM420,T19,SM465,T-98 ,NV4500, and so on. The T-4 does have a 4.03 first gear and combined with the Dana 300 , with its 2.62 ratio, will give you far more lower gears than what you have now. The Dana 300 also has an aftermarket 4 to 1 gearset kit available, btw. The first gear on most of those transmissions are non-synchro anyway and too low for the street plus they are very heavy, but very good for rock crawling, if that is your style. Also if you didn't already know, there is another Transmission hole pattern on your bell housing that does require a drill & tap operation for mounting the heavier transmissions.

 

[BusaDave9]

What do you use your jeep for? Much off-roading?
The T-18 is a far cry from a T-4 . The T-18 is a heavy duty truck Transmission and it shifts as such. The T-4 is a light duty car Transmission and when it's working it shifts smooth, quick and easy.
The T-4 was the worst Transmission to go into a CJ. The first to go out on the T-4 is always the syncros. I had a '82 CJ7 with a T-5 and when it died I put in a Ford T-18 .
Since you now have a '79 a Jeep T-18 would be the easiest swap but they are hard to come by and there are several variations. If you find one from a CJ from the '70s (good luck) it would be the easiest. If it came out of a FSJ you would have to install a shorter input shaft. Check out this link: http://www.jeep-cj.com/forums/f105/manual-cj-transmissions-12112/#post97092

 

[Rippy]

I plan on very light off-road use,but would like it to be ready and strong enough for any occassion,i have found a few of the sm465's but no T-18 's,What mods would I have to do with the sm465,thanks

 

[Tin Medic]

Everyone has an opinion on on the SR4 , T-4 , and T-5 but if you look at what they are actually running most aren't running the SR4 , T-4 or T-5 because in the end they just weren't made for jeeps. I am still running the T-5 only because my T-18 hasn't made it from the floor of my garage to the cj. Personally I haven't had any problems with my T-5 but 5th gear is useless unless I am on a perfectly flat road. Busa is right that the T-4 /T-5 are fine if maintained and not abused but in the end most everyone swaps them out for something stronger. If you are going to a 4 speed make it a T-176 , leave the SR4 and T-4 alone, in the end they will be a waste of time. If you already have a T-4 and the parts needed to switch by all means use what you already have, I just wouldn't go shopping for a T-4 . Just my opinion.

 

[BusaDave9]

Your CJ has a Dana 20 TCase. It's much different than a Dana 300 in that the Dana 20 expects the Transmission to have a big gear on the output. This whole gear fits into the Dana 20 .
If you check out this link: http://www.jeep-cj.com/forums/f105/manual-cj-transmissions-12112/ you will notice all the transmissions that were mated to the Dana 20 have a gear on the output like this.

On the other hand any Transmission that mates up to the Dana 300 has an output shaft that fits into the TCase. Here is a Dana 300 . Notice that the input is only big enough for a shaft to fit into.

That's an important difference that will limit your choices. You mentioned getting a T-4 with the Dana 300 TCase. That's one resolution, to get a matched set. Then you only need to worry about mounting the tranny to the engine. The solution there is to get the bellhousing and clutch intended for the newer Transmission . If you get a Transmission from the '80s such as a T-4 , T-5 , SR4 or T-176 you will have trouble mating it to the Dana 20 since these were all mated to the Dana 300 .
All around you will have an easier time installing a Transmission from the '70s since these came with a Dana 20 . The CJs from the '70s had some good strong transmissions. Unfortunately a lot of them were 3 speeds such as what you already have.

 

[BusaDave9]

What mods would I have to do with the sm465,thanks

To install a SM465 you will need a bellhousing from a '80s CJ. Even then you will need to drill and tap the bellhousing. You would also need a clutch and clutch linkages from an '80s CJ. Check out this link for more info: Adapting the SM465 Transmission to AMC Jeep Engines

Then you will still need an adapter to install your Dana 20 TCase. Here is such an adapter: Adapting the SM465 to Dana 18 & 20 Transfer Cases

So the short answer is yes you can install a SM465 but it would be a lot of work.

Edit: I say your best solution is to look for a Transmission from the '70s. Going that route a T-18 from a CJ would be the only 4 speed that would be an easy swap. Then you would need to have the drive shaft lengths modified. There are lots of other options but they all require adapters.

 

[Saddle Tramp]

I assume your mission is to get some lower gearing as the Dana 300 has a lower low (2.62) than the 20 (2.03). With a 79 CJ the T-18 is a no brainer as the T-18 was a factory option in lieu of the stock T-150 . The T-150 has the Ford “butterfly” bolt pattern at the bell housing but the good news is that the 1977 to 1979 CJ bell housing is drilled and tapped for both the T-150 and the CJ T-18 giving you options.

The CJ T-18 has two basic gear ratios, the close ratio 4.02 granny low (1972 to sometime in 1976, exact date unknown) and the 6.32 wide ratio (sometime in 1976 but generally recognized as 1977 to 1979). Wide ratio is the most coveted for low gearing but don’t be confused between T18s as Jeep used around 18 different versions over time; the basic difference between them being shaft length. The FSJ have longer front shafts than the CJs to push the Transmission back to keep the shifter out of the dash. Replacement shafts can be had to retrofit a FSJ T-18 to be used in a CJ but there is no kit to retro fit a close ratio Transmission to a wide ratio.

I seem to find CJ T18s popping up more often than they use to as more CJs are being parted out (to me parting out a CJ is unconscionable but I suppose it’s like death and taxes…. ) and the Ford T18s can be had for as little as $50, of course work needs to be done but $50 is a cheap enough start. Follow these links; they have some great information on both the CJ and the Ford swap.

http://www.jeeptech.com/convtrans/cjt18/index.html
http://www.jeeptech.com/convtrans/fordt18/index.html

http://www.jeeptech.com/trans/t18.html
http://www.jeeptech.com/convtrans/ford/fordt18id.html