Off Roading Forums banner
1 - 7 of 7 Posts
G

·
Discussion Starter · #1 ·
Hello, I am new to the board. I receintly rebuilt a '42 GPW from the frame up. I installed a 225 V6, SM420, Dana 18 T/C, and 427's in a 44 rear/ 30 front axles. I also added Sagnaw power steering. I am curious about the warn/saturn overdrive that mates to the Dana 18. Someone has one in a local classified and I am planning on checking it out. Does anyone have experience in this unit? What should I look for and what is a resonable price?

 
G

·
Discussion Starter · #2 ·
I had one in my old 70 CJ5 with 225 V6, SM420, and 4.88:1 gears. There are a couple of different versions of the Dana18 transfer case.
There is a small hole and a big hloe version. I believe they also had different spline counts on the shafts. You have to match the overdrive
to the version of Dana18 you have. I had no problems with mine and it sure made the Jeep much more liveable on the highway. If you can
get one it's a great addition to your Jeep.

Gary

Gary
 
G

·
Discussion Starter · #3 ·
There are three models of Warn/Saturn overdrive:

1. There is the version for the early 26-tooth Model 18 transfer cases. These were used in early post WWII jeeps, were all small hole
cases and had either 3/4" or 1 1/8" intermediate shafts.

2. There is the version for the later 29-tooth Model 18 transfer case when connected to a T-90, T-86 or T-98 transmission with a 6-spline output
output shaft. This could have been a big-hole or a small hole transfer case dependent upon which transmission was bolted up. They
all had 1 1/4" intermediate shafts.

3. There is the version for the later 29-tooth Model 18 transfer case when connected to a T-14 transmission with a 10-spline output shaft.
These were all big-hole cases with 1 1/4" intermediate shafts.

If you used the original Model 18 transfer case from the GPW in your buildup, it has a 27-tooth input gear and there is no overdrive
available for it. It also has a 3/4" intermediate shaft. I suspect your SM-420 has a 6-spline output shaft.

Reasonable price varies by location and condition, $400-$600 seems pretty typical. (they're ~$1200 new)

Jim Kyser
[email protected]
1946 Willys CJ-2A

Jim Kyser
[email protected]
1946 Willys CJ-2A
 
G

·
Discussion Starter · #4 ·
There are three models of Warn/Saturn overdrive:

1. There is the version for the early 26-tooth Model 18 transfer cases. These were used in early post WWII jeeps, were all small hole
cases and had either 3/4" or 1 1/8" intermediate shafts.

2. There is the version for the later 29-tooth Model 18 transfer case when connected to a T-90, T-86 or T-98 transmission with a 6-spline output
output shaft. This could have been a big-hole or a small hole transfer case dependent upon which transmission was bolted up. They
all had 1 1/4" intermediate shafts.

3. There is the version for the later 29-tooth Model 18 transfer case when connected to a T-14 transmission with a 10-spline output shaft.
These were all big-hole cases with 1 1/4" intermediate shafts.

If you used the original Model 18 transfer case from the GPW in your buildup, it has a 27-tooth input gear and there is no overdrive
available for it. It also has a 3/4" intermediate shaft. I suspect your SM-420 has a 6-spline output shaft.

Reasonable price varies by location and condition, $400-$600 seems pretty typical. (they're ~$1200 new)

Jim Kyser
[email protected]
1946 Willys CJ-2A
 
G

·
Discussion Starter · #5 ·
Jim, thanks for the info, the T/C is out of a '53 jeep and originally mated to a T90. I have an Advanced Adapter to the SM420 but could not remember the tooth or spline count, I guess I should pull the PTO cover to be sure.

 
G

·
Discussion Starter · #6 ·
Yeah, pulling the PTO cover and counting the teeth on the input gear is the easiest way to be sure. You can also confirm the
spline count on the SM-420 at the same time. That way you'll get the part you want and not be looking for someone to swap
with because you got the wrong one.

Jim Kyser
[email protected]
1946 Willys CJ-2A
 
G

·
Discussion Starter · #7 ·
Be sure to check the condition of the planet set in the overdrive also,they burn up easily if the t-case was run with low oil levels. The parts are available from Advanced Adapters but they can be expensive. They also have a very good booklet on these units that I recommend you read before you buy one. there is only one way these units come apart but the booklet explains it well. I ran one in my '61 CJ-5 with a 283 and a T-98 with 4.27 gears and 31-10.50 tires, it really made a difference in highway rpm and it allowed gear splitting off-road. There is nothing like 16 forward speeds, 4 reverse speeds, and 3 neutrals! Good luck.

 
1 - 7 of 7 Posts
Top