After several trail runs with my 78 CJ-5 equipped with a T-150 3
speed trans it became obvious that a gear change was essential. My CJ has 3.54 rears, a
Dana 20 transfer case (2:1 low range), and low a gear in the T-150 that is only
2.99:1. This equates to approximately 21:1, this is rather pathetic, I found I spent
a lot of time having to slow down to prevent running into the Jeep in front of me and
having to do the old bump-bounce-stop over rocks. Not exactly rock crawling if you
ask me.
After some extensive research I decided on a T-18A swap. The
T-18A was a factory option in the late 70's CJs and is equipped with a 6.32:1 low gear.
This combo will make the CJ's crawl ratio about 48:1, more than twice what I had.
The most appealing things about this swap is that it is essentially a bolt-in
operation. The big problem with this swap is finding a trans to use. Amazingly
a friend of mine knew of one sitting in the back of a Jeep pickup at a local junk yard.
The T-18A also was a factory option in Jeep pickups. These transmissions
require some modification to fit a CJ. First I must say that this trans is massive,
next to my T-150 it is 3.75" longer and about 3" taller. It will be
necessary to alter the drive shafts due to the increase in length. I am probably
going to use a CV style rear drive shaft since it will only be about 14" long.
Also my dual exhaust system may have to go but I will worry about that when everything is
in.
The Jeep truck models use a different input shaft which is about
15" long. The bell housing is deeper and it also uses a 5" spacer between
the trans and bell. I learned that the input shafts are interchangeable and better
yet I found a place Hick's 4X4 in California that
sells a kit to do this. The kit came with a new input shaft, pilot bushing, and a
new bearing retainer. I also ordered a rebuild kit which came with gaskets,
bearings, synchronizers, and seals.
I completely disassembled the trans (not a job for the mechanically
challenged) and cleaned it up. I found a couple of strange pieces in the bottom
which turned out to be pieces from the shifter fork rods, at first I got worried but
luckily there was no damaged components. I then reassembled the trans with the new
and old parts. After a new paint job it was ready to go in.
I gave a quick call to Mike at
OK
4wd looking for a new clutch, we decided on a Centerforce clutch and disc. The
T-18A uses the same bell housing and clutch configuration as the T-150 so everything fit
perfectly. I also sent my flywheel out to be resurfaced (this is essential for a
clutch to properly break-in.
This transmission probably weighs 100 pounds, my dad and I wrestled
it under the Jeep and managed to get it bolted to the bell housing with the help of a
floor jack. A few times I almost pictured this anchor called a transmission coming
crashing down on us. The skid plate on the Jeep needed to be moved back but there is
existing holes in the frame and the plate bolts-in. I had to make some minor
modifications to the trans mount since this trans came out of a Jeep pickup.
After the trans was all bolted in I attached the transfer case,
next I had to extend the rods attaching the 4WD selector to the transfer case. This
was due to the fact the trans is 3.75in longer.
I did a little measuring and the sent off my old
drive shafts to be
redone to facilitate the length change of the new trans. I had the front
lengthened and the rear shortened. I also had a CV style joint installed on the rear
drive shaft to reduce vibration.
As soon as I picked up my new
drive shafts they were installed and
the project was nearly finished. Just an adjustment of the clutch and also a set of
4 degree shims in the rear axle.
I fired up the Jeep and out the door I went. High range
driving using the 2-3-4 gears is all but identical to the old 3 speed. But slip it
into 1st (or Low) and you creep along. Even in high range. Low range is really
cool, Lo gear is incredibly low. I would say I can do 5mph at 3500 rpm, I found I
can just let the Jeep idle and I can crawl up on most anything. Reverse is even
lower which makes it even easier to backup on the trail.
My first off road trip with my new trans was the most fun I'd had.
I now could let the Jeep idle and creep over anything in my path. It is a
rare occasion that I had to use the clutch or the Jeep stalled. It took me a while
to get used to which gear I should be using, sometimes I was going to fast in 2nd and
sometimes too slow in 1st. One draw back with this trans is that 1st gear is not
synchronized and if I am in 2nd I have to stop to go into 1st.
In summary this was the most dramatic and worth while change I have
done to this Jeep yet.
New Information - After
two years of driving with the T-18 I am still pleased, one problem I have had is
a clutch binding issue. I determined that the problem was in the bell
housing and would not be easy to fix due to the transmission being extremely
heavy and cumbersome to remove. I have been living with the problem for
about a year and after the last off-road trip I had enough. Apart the Jeep
came.
After removing the all the
stuff I discovered that the nose cone (a & b) of the transmission was worn
very badly from the throw-out bearing. Something came to at this point, I
remembered reading an article on a similar T-18 swap where the original T-150
fork needed to be ground for clearance of the driver side stud transmission
mount.
I could see the wear on the
head of the stud from the fork binding against it. What was happening is
the fork would hit the stud (c) causing the fork to twist. In turn the
throw-out bearing was binding and wearing away the transmission's nose
cone. Obviously the cone needed to be replaced, and after a call to OK
one was on the way along with a new throw-out bearing.
I also needed to grind the
fork (d), this took almost no time and was easily accomplished with a
die-grinder. I wish I would have remembered that article in the
beginning. The Jeep is now back together and my clutch and I are happy.
The article I found this info on was on the www.off-road.com
website. Click here
for the article
