T18 transmission rebuild with short shaft kit, Project CJ-7

T-18A Rebuild and Short Shaft Kit
An article provided from www.offroaders.com - part of Project CJ-7

Dcp_1558.jpg (18424 bytes) 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.

shafted.jpg (9365 bytes)

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.

Dcp_1571.jpg (10272 bytes) Some 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.

PDF

broom-stick.jpg (7439 bytes)

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.

Dcp_1545.jpg (10694 bytes)

Dcp_1544.jpg (19939 bytes)

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.

Dcp_1546.jpg (12577 bytes)

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 pieces.

Dcp_1547.jpg (9769 bytes)

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.

Dcp_1551.jpg (9818 bytes)

Dcp_1552.jpg (10822 bytes)

Lower 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 shifting.

Everything was then cleaned using a combination of carburetor cleaner and Simple Green in a basin of hot water.

Dcp_1555.jpg (14621 bytes)

Dcp_1561.jpg (9899 bytes)


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.

Next 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 Dcp_1564.jpg (12646 bytes) 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.

Dcp_1574.jpg (10721 bytes)

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.

Dcp_1568.jpg (14093 bytes)

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.

Dcp_1577.jpg (11667 bytes)

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.

PTO plate was remove later, cleaned painted and attached with new gasket.
Clean top half, remove old Teflon guides and replace with new from kit.

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.