Originally the T-18A manual transmission came out of a J-20
Pickup and the T-18A's input shaft ran though a 5 inch adapter before emerging
into the bell housing. This T-18A's new life will be lived out in a CJ-7
which has a shorter wheelbase when compared to the J-20. To properly fit
the transmission into the CJ-7 the 5 inch adapter would need to be removed.
After removing the adapter it becomes necessary reduce the length of the input
shaft. Hicks 4x4 Specialists in California sells a
short shaft kit for the T-18A. Through OK 4 Wheel Drive, who I preferred to deal
with, a kit was ordered from Hicks and OK was able to match the price Hicks gave
me for the kit. Swapping the input shaft require that the transmission be
disassembled so this is a perfect opportunity to rebuild the T-18A to ensure
good reliable service for many years to come. The kit was also ordered
through OK 4Wheel Drive.
The Short Shaft Kit comes with three items. The Shaft, the
shaft housing and a pilot bearing.
The T-18A rebuild kit comes with 2 main bearings, new needle
bearings, new spacers, new snap rings, new synchronizers, new Teflon guides and
new gaskets for all the openings.
Mike from www.JeepFan.com
who has the same transmission and had gone though the same process of rebuilding
his T-18A and swapping the input shaft offered to help with the rebuild.
This was much appreciated since he remembered all the little quarks and issues
he had to deal with as well as avoiding some of the mistakes he encountered
while doing his own.
Input Shaft comparison.
Preparation for the Saturday afternoon job included taking
inventory of the parts we would need, getting tools together and also adding a
sheet of 16 gauge galvanized steel to the top of the work bench. The sheet
metal is a great addition to the work bench.
of the tools we needed to have on hand above and beyond the standard set of
sockets and wrenched were a soft mallet (copper), snap ring expanders, a 1 inch
dowel about 12 inches long, a Haynes manual for the CJ which had a blowup of the
T-18A that proved to be handy, petroleum jelly for the needle bearings, ziplock
bags for marking bolts and parts as it was disassembled, gasket sealer, carb
cleaner, Simple Green Degreaser and a camera. One thing I can say is don't
hesitate to take notes. I know it's great to just dive in and ripe it apart
but remembering how it came apart and what snap ring goes where makes the
job go much easier. Also bag and mark old parts. Doing this
helped keep track of what went where and made it easy to find bolts and parts
when it was time to reassemble. Taking pictures is a good idea
too. Having a digital camera was nice because if needed I could
review an image taken earlier for whatever reason.
|Mike remembered much of the process and was very helpful but if
this job would have been done by myself alone or with someone who has not
rebuild a manual trans before, the notes taking and pictures would have been
very useful. I recommend having a second set of hands. In some
cases such as extracting the upper gear set from the case, having two people
handling this large and heavy gear set was almost a necessity. Also having
a manual to reference and a blow-up image of a T-18 was also very useful for
understanding how it came apart and even more important, how it goes back
together. For your reference the image to the right links to a printable
image contained in a Word document of a T-18 exploded view illustration.
JPG Image only
||1 inch dowel is needed for replacement of the needle
bearings. Pictured on the dowel is the tubular spacer between the 4
sets on needle bearings. On either end is a washer that spaces out
the sets of needle bearings.
|Above is the stock input shaft of the T-18A that
came out of the J-20. This needs replacement because of the removal of the
5" adapter between the T-18A and the Bell housing. Hicks 4x4 provided
a Short Shaft Kit.
We kick off the project by removing the top of the T-18A
exposing all the guts of the beast. Removal of the stick shift is not
necessary. Behind the workbench was a table where we could layout all the
Next we removed the rear shaft bolt and the output gears.
Next we removed the front snap ring and the front bearing using a break tool.
This is one area where two people come in handy. Removing
the gear sets. We removed both at the same time pulling them in opposite
directions while lifting them where they join together. Roller bearings from
between both gear sets dropped all over.
This exposed the lower gears.
gears were removed by sliding the rectangular plate up out of the slots in the
shafts and then driving the shafts out using a 1 inch dowel rod or a brass
drift. The larger Countershaft is driven forward. The small
reverse idler shaft shaft will clear internal parts when driven inward however
it is possible that the small shaft is tapered on some models at the rear of
the transmission and should be driven out (rearward) from the inside. We
drove it inward towards the front without any issues but to be safe, you
should drive it rearward.
|Note: The T98 and the T90 are similar in design to the T18 but they
have a tapered reverse idler shaft and must be drive out from the
inside or you'll damage the case.
Rear set of gears were disassembled to get to
synchronizers. Don't forget how it came apart. Also be aware of
some spring loaded bearings that lock the gear set in place during
Everything was then cleaned using a combination of carburetor cleaner and Simple
Green in a basin of hot water.
Cleaning and inspecting the parts. Everything looked
pretty good. Gears were in good shape with very few chips in the
leading edge of the 1st gear.
we packed needle bearings into lower shaft. Used petroleum jelly to hold it all
together. The petroleum jelly will disintegrate once exposed to the gear
oil. This is where the one inch dowel rod comes into play. Each bearings
set gets 22 bearings. The bearings go in in specific order with the tub in the
center of it all. Moving outward from the tub each side (front/rear) gets a
ring, 22 bearings, a rings, 22 bearings and a final ring.
This is the tricky part. We then lowered the gears
into case while holding shims and washers at each end. Refer to your
manual for which shims and washers go where. I used a short piece of the 1
inch dowel to help hold the washers in place while lowering the gear
set. It took a few trys but we got it lined up right. Next we tapped
the lower shaft into place pushing dowel rod out while keeping pressure on dowel
to prevent it from bouncing out to fast.
Next we packed the input shaft with needle bearings using petroleum jelly again
to hold them in place. No dowel with this set of bearings. Then we
lowered both of the upper gear sets into case with the front and rear going
though the case openings and gently lowering the center putting them
together. Remember those needle bearings will move easily so be careful.
Once together we put new main bearings in the front and rear of the case. Take note
of width of bearings. Larger width in rear, narrow in front. I had been
informed that some people were getting the two main bearing and they were the
same size when there should have been different sizes for front and rear.
Those people had to re-order a bearing or reuse the old one that wasn't
included. I had the right sizes. Gentle tap bearings onto shafts.
Use a pipe or gentle tap on inner part of bearing with a wooden block and a
hammer. Alternate sides if using a block.
The Front bearing needs to be in right place (close to the snap
ring on the shaft) or shaft cover will bind the bearing. I discovered this
when I went to bolt on the shaft cover for a test fit. I had to tap
shaft in using a piece of aluminum sheet metal to cover the end of the shaft and
hit it with a hammer. I then greased the seal that's part of the shaft cover,
applied gasket sealer, gasket, more gasket sealer and put shaft cover on with
port side down. Not too much sealer around port as not to clog the port but
enough to seal it.
The top half was then cleaned and the casket and gasket sealer
was removed using a wire wheel on a drill to brush off the silicone sealant.
T-18A to Dana 20 Adapter
I had to get a new rear seal.
I removed the seal with WD-40 can and cleaned the adapter. I couldn't find a
gasket that is to go between the T-18A and the adapter so I made a gasket.
|I then put the new seal in using the old bearing from teh T-18A
which fit perfectly over the seal. The main thing is to push on outer rim of
seal only as not to damage the seal. I then cleaned the adapter again, applied
gasket sealer, the gasket, more sealer and bolted it on. Cleaning the bolts too
helps to seal it better.
Before filling with gear oil and sealing it up I did a test fit
of the top for proper alignment of gears. I put a few bolts in to test run
gears. Everything worked well and I removed the top without moving the gear
position. It was then filled with an 80W 90 GL-5 gear oil to to fill bolt
(maybe a little more). The seal area was cleaned again and on went the sealer,
gasket, sealer and the top. A final run though the gears again before a torque
down of all the bolts.
Test fit of the cleaned and
painted V8 bell housing.