Swapping a Dana 18 with a D20

In the early eighties my brother swapped a SBC and a Saginaw car 4 speed into his early 60's CJ5. He wants to swap his fiberglass body/engine/tranny onto a '74 chassis I have. For the centered Dana 44 to work he would also need to use the D20 that came with the frame. Back in the 80's he used an Advance Adapters kit to bolt the D18 to the Saginaw. Will the D20 bolt right up? I am assuming we will need to use the D20 bull gear. Are D20 bull gears the same between a T14, T15, T150?

 

It is reaching back a ways, but I think all the AA tailhousings were for a big hole transfercase so it should bolt up. The AA mainshaft will very likely be 6 spline so this may pose a problem as at least the t14 dana 20 used a 10 spline input.

 

T-14 uses a 10 spline output shaft and all the rest uses a 6 spline so it depends on what was installed at the time as both were offered. "most" Saginaw 3 and 4 speed adapter kits had the provision for both large hole and small hole, you just had to use the right bearing adapter/retainer depending on which transfer case you were using. The small hole adapter used the rear T-90 bearing plate and the large hole uses the T-86 rear bearing adapter/retainer. The earlier adapters didn't have this provision. Most likely yours has the provision to use either but you'd have to pull the transfer case to be sure. They are a press fit in and can be a pain to get out but can be removed. Make sure the bearing spacer between the output shaft and output bearing is in place if you need to swap the bearing plate/adapter/retainer or when you tighten down the gear retaining nut it will pull in the center race of the bearing and damage the bearing or lock everything up.
The T-150 transfer case input gear (bull gear) has a seal surface machined in it which is specific to the T-150 but can be used if the transfer case is swapped to another 6 spline output shaft transmission. The 20 and 18 use the same bolt pattern to the transmission so that should be no issue. The 20 is a single stick shifter as well and the twin sticks of the '60's CJ (if equipped) will not work on the 20.

Realize that the the frame and nose of the '74 is roughly around 4" longer than the '71 and older CJ and there are other differences as well, but the conversion can be done.

 

Thanks Nick! The '74 frame has a D20/T-15 and I have several D20/T-150 set-ups. When my brother put his 5 together the Saginaw adapter came out of a '67(I believe) 225 powered CJ5 so it may indeed have replaced a T-86. We realize the frame is longer which is one of the things he wants because of the tightness of the SBC swap. When he put it together he used a late 70's steering column and a manual box out of an intermediate.

 

The first jeep I owned had that swap done but it still ran the Dana 18 t-case. The drive shaft look like it wouldn't work but, I drove it as a daily driver like that for 5 years until it was wrecked in an accident.