3b lower gear options

[tow_hook]

to ask the question, i have to tell you first were i'm at..

i have a cj 3b the stock gears at as follows 1st 2:79 4 lo 2:43 diff 5:38 total 36 to 1... i'm upping my input shaft, and gear cluster to get 1st up to 3:44. i want to do a tera 3.15 gear set in the dana 18 with the diffs 5:38 that take me to 58.29 to 1 pretty much were i wanta be.. for teh trails i'm looking to do..

the problem is i have the smaller 3 1/8" hole, and need the bigger 4" hole dana 18 to make the gear set work. will that 4" hole work with my t-90 3" out put bearing? i have not scene a 4" out put bearing to convert this over so i can run the new t-case with the lower gears... i wanta have answers before i buy the newer 4" hole dana 18 case...


thanks

 

[Saddle Tramp]

It is unclear if the large hole 18 was ever used with the 134 I4/T90 combo and is generally believed not. After CJ3B SN 54-12506 the intermediate shaft was changed to an 1-1/4” with a 26 tooth input gear. The big hole 18 was used with the Dauntless V6. The big hole 18 case and the 20 case are the same case and I do not remember ever seeing a T90/D20 combo as the Dauntless V6 typically came with a T84 or T14. However many of the parts are interchangeable and it is possible to put T90 guts in a T84 case.

Maybe you should look for a T14? It has a 3.10 first but I know there were two different input shaft lengths so I’m not sure how easy this swap truly would be. (Bellhousing issues too? Not sure) At any rate is seems to me that if you need a big hole 18, you need transmission that originally came with one or vice versa.

Not sure how much all this really helps….

 

[Ggg]

The large bore Spicer 18 was made from 1966-1971, only found behind the V6 with either T86, or T14 trans. IIRC it never came from the factory behind the 134 engine. The T90 was factory mated to spicer 18 cases but only the small bore versions.
The large bore T18 is the same case as the Spicer 20 and all internal parts are interchangeable. The shifter linkage is different from the small bore 18 and large bore 18.
The trans mount bolt pattern of all Jeep Spicer 18's is the same from the Bantam, MA, MB, Pygmy, GPW,CJ, to the FC and trucks. The T90 can be adapter to the Spicer 20 case with an adapter/output bearing retainer.

 

[tow_hook]

It is unclear if the large hole 18 was ever used with the 134 I4/T90 combo and is generally believed not. After CJ3B SN 54-12506 the intermediate shaft was changed to an 1-1/4” with a 26 tooth input gear. The big hole 18 was used with the Dauntless V6. The big hole 18 case and the 20 case are the same case and I do not remember ever seeing a T90/D20 combo as the Dauntless V6 typically came with a T84 or T14. However many of the parts are interchangeable and it is possible to put T90 guts in a T84 case.

Maybe you should look for a T14? It has a 3.10 first but I know there were two different input shaft lengths so I’m not sure how easy this swap truly would be. (Bellhousing issues too? Not sure) At any rate is seems to me that if you need a big hole 18, you need transmission that originally came with one or vice versa.

Not sure how much all this really helps….

i've come across the same info, as far as shaft lenght and what models the small bore came with... not sure if a t-14 would bolt up... novak only offers a a np435 trans swap to the f head... it's a little larger then what i was hopping for

 

[tow_hook]

The large bore Spicer 18 was made from 1966-1971, only found behind the V6 with either T86, or T14 trans. IIRC it never came from the factory behind the 134 engine. The T90 was factory mated to spicer 18 cases but only the small bore versions.
The large bore T18 is the same case as the Spicer 20 and all internal parts are interchangeable. The shifter linkage is different from the small bore 18 and large bore 18.
The trans mount bolt pattern of all Jeep Spicer 18's is the same from the Bantam, MA, MB, Pygmy, GPW,CJ, to the FC and trucks. The T90 can be adapter to the Spicer 20 case with an adapter/output bearing retainer.

yep i've learned most of what ya have there but... The T90 can be adapted to the Spicer 20 case with an adapter/output bearing retainer. do know who sells this.. i've been looking around for one... thanks !!!!

 

[jps4jeep]

Why not install a T18 transmission.

Also, you could add a range box infront of the Tcase that offers an additional 2.72 reduction. it will be similar to a warn overdrive unit, but it contains reduction gears. Advanced adapters makes it.

 

[tow_hook]

Why not install a T18 transmission.

Also, you could add a range box infront of the Tcase that offers an additional 2.72 reduction. it will be similar to a warn overdrive unit, but it contains reduction gears. Advanced adapters makes it.

thanks... i'm keeping the orginal f-head..i was looking a swaping in a t-98, ( 6.40 first gear )it bolts up the the orginal bell housing, but like the t-18 ( 6.32 first) i still need a large hole dana 18 or 20 to bolt to the back . and both trans. are 4" longer so the old shafts would have to be worked, or replaced... i did look at the range boxes a advanced adpater but didn't see any like the marlin crawler boxes...... i did see the saturn over drive boxes....

i was trying to spend around a 1,000 $ on the regear. i can find a used dana 20 for about 100-200$ plus the 3.15 gear set 700$ and a t-case rebuild kit 185$ puts me up around 1100-1200$ with shipping/ tax/ etc.

i just found that novak makes a t-90 to dana 20 reatainer adapter bearing and snap ring assb. prt# 90-20 no $$ price.. listed WHHHoohhhoooo

i'm willing to check out different ideas, but trying to keep it that 1200$ buget. so far i saw that novak makes a f-head to a np435 bell housing plate for 569$ and another 516$ to put the dana 18 back on! and advanced adapters makes notta for a f-head...


so in the end i guess i stumbled on to my own answer..... thanks for input and ideas..

 

[Ggg]

Novak adapter #90-20 should be the output bearing retainer you need. Oops I just read you found it.

 

[tow_hook]

yep... i'm still gonna look to see if some makes a adapter for t-18 to a f-head... i found some one who has one pretty cheap... and if priced right could work..

thanks for the ideas and help...

 

[tow_hook]

wow no suport for those f-heads... still looking but other then that np 435 notta..