Man-Trans Jeep Transmission Conversion Articles Section 1

Deciding which components to use in the build up of a Jeep can be mind boggling. If your project goes anything like they way mine has then you will probably change your mind a hundred times. In this current incarnation of my project my drive train is cemented and will not change before the Jeep is drive-able. I will be running a Tuned Port Injection 305 Chevy V8 mated to an NV4500 5 speed transmission supplied by ManTrans, LLC out of Florida. To split the power out to the axles I opted to retain the Dana 18 transfercase that was under my 1970 CJ-6 the day I bought it. After really taking a look at the drive train in my CJ when purchased it was pretty obvious that everything was original, nothing had been rebuilt and everything was getting pretty tired. I knew that in order to use my transfercase I would need to rebuild it and if I was going to have it apart I might as well make some improvements. Above you can see the pics of my tranny bolted to my finished Dana 18. Read along while I detail how to get your Dana 18 back into top condition and what upgrades would be a good idea to make.
	When deciding what components I would use I did some research in both the off road magazines and on the Internet trying to get a feel for what products had a good reputation and what parts would fit the final vision I had for my transfercase. To the left you can see my original case on a table with several others I had available for parts. It was a single stick unit with a lot of brackets and oddities bolted/welded to it to assist the factory installed PTO drive in running the large trencher that was originally mounted in the bed of my 6. All of these needed removed but I wondered what I would be able to retain.
Upon inspection the gears were in surprisingly good shape but I wasn't particularly happy with the 2.46 to 1 low range that the factory gears offered. I got in touch with the gentlemen out at Teraflex and they got a set of their Teralow 3.15 to 1 low range gears on the brown truck to me as quick as they could. While they do send out a gasket and seal kit as well as a small parts kit and even an intermediate shaft I turned to Novak Adapters for a full rebuild kit. Not only did this kit come with the bearings which were not featured in the Teralow kit but to me the key was that Novak makes and includes a special intermediate shaft that utilizes rubber O-ring on each end of the intermediate shaft to help keep oil from leaking out of the case on either side. In case you just want the special intermediate shaft you can buy it separately. To round out the project I enlisted the help of Tri-County Gear. They make a killer transfercase girdle that strengthens the case itself. In some extreme cases Dana/Spicer 18 transfercases have been known to actually break in half right at the intermediate shaft. While this is not too common cracking is and either way you will have to replace the housing if it does happen. The step by step process below should help you through some of the tricky parts of a Dana 18 build up.
	1.) To the left you can see what my original transfercase looked like when we started. Years of oil leaks left the case crusted in an oily sludge. I stripped the case down and cleaned everything with a putty knife and a parts washer after which all of the external parts were bead blasted to bring the case right down to bare metal. Because detailed instructions are available to walk anyone through the process of tearing down and rebuilding a transfer case I will just run through the build up and highlight the important parts. Because of this I HIGHLY recommend getting a good manual before your build up. The primary manual I used was the 46-71 Jeep CJ Rebuilder's Manual by Moses Ludel. This book does a good job in covering the step by step process and provides lots of pics. The couple of discrepancies that I found in my later model case from what Moses covered were easily figured out and one or two of the trickier ones are covered in later steps.
	2.) Here you can see all of my parts laid out ready to get started. I removed the factory drum brake and chucked it in the trash as they never work well anyhow and I removed the PTO and traded it for the components to change my singe stick transfercase over to a twin stick model. The biggest reason I did this was because my single stick shifter would have needed modifications to get it to clear the NV4500 and the twin stick does not. This conversion requires all of the items bolted to and including the front output shaft housing so you will need that plus the anti-rattle clips, shifter sticks, shift rails, and cross shaft. Components such as the springs and poppet balls, interlock pills and so on can be from either housing and are inner changeable.
	3.) I started by assembling the front output housing. In this part of the build up you will be installing the front bearing, the 4wd shift rail and fork, the front output shaft and the front output shaft seal. The old seals proved to be very difficult to remove with just a simple screw driver. I would highly recommend visiting a parts store and picking up a cheap seal removal tool. They made a WORLD of difference. Not having one made a 10 minute job turn into a 45 minute job!
	4.) The bearing is a light press in fit. You can simply tap it into place using a brass drift like I did. Once it is installed you should fit the snap ring down into the front housing. The easiest way to do this is to get one end started and try to work it in to the housing by sliding it in a circle. Once it is half way or so installed you can use a screw drive to compress it and get it down into the grove the rest of the way.
	5.) Next I installed the seal. Most people will not have access to a seal installation tool and you can use a large socket like I did or a piece of pipe or large washer. The seal was easy enough to install. One important tip that I found on the Internet was to wait to install the shift rail seals until after the rails are installed. The first time around I installed them before I installed the shift rails. One seal came away unscathed the other one was ruined with the shift rail caught the spring and tore the rubber. I used a piece of pipe to install the shift rail seal that was ruined and I would recommend you wait to install yours.
	6.) Here you can see the front out put shaft seated in the front bearing with the snap ring that was installed in step 4. The shaft that sticks out from the back of the front out put shaft rides in a bushing inside of the main shaft. It should be a very snug fit but still easily turn. I found that my bushing was too worn to be reused so I replaced it. Steps 7a and 7b cover this replacement.
	7a.) Every rebuild manual I looked at told you to check the tolerances on the bushing that you see inside of the main shaft here. This is the brass bushing that part of the front output shaft spins inside of while the Jeep is in 2wd. My bushing was worn to an unacceptable level. All of the manuals recommend that you take this shaft and the brass bushing which is included in all small parts kits to a machine shop to have the old one removed and the new one installed.
	7b.) Instead I used a pilot bushing removal tool PN:120 for a 41-86 CJ from 4wd Hardware. This fit perfectly and easily pulled the bushing out. Once it is out the replacement can be tapped in. There is a lip that will stop it from being tapped any further once it is fully seated. All of the manuals said that there was a good chance that this bushing would need reamed out once installed but I found that in my case the input shaft had a perfect amount of clearance with no reaming.
	8.) Now it is time to install the 4wd shift rod and fork. Take note of the safety wire and bolt that hold the fork to the rod. This is present because I am using the rod and fork from the twin stick front housing and they are from an older case. Although it is not mentioned in the rebuild manual I used late model Dana 18s have a simple set screw to retain the fork. You can see the clutch coupler needs to be inserted onto the fork before installation. Be sure to check that the fork is not severely worn and that it does not have a sloppy fit on the clutch coupler. I ended up using different forks for both shift rods in my case.
	9.) After installing the high/low range shift rod into the main case I put a couple of drops of blue Loc-Tite on the set screw and tightened it down onto the shift rod to keep the shift fork from sliding around. As mentioned above I scavenged a less worn shift fork from a parts case to use in my rebuild.
	10.) Here the low range sliding gear is installed onto the shift fork. This gear pictured is the one from my Teralow gear set.
	11.) Once the sliding gear is installed the front out put shaft gear is seated into the teeth in the inside diameter of the sliding gear.

12.) The next step is to install the Timken roller bearing from the Novak rebuild kit on the rear output portion of the mainshaft. The easiest way to do this is to take the center race out of the original bearings. Above you can see the center of the original ball bearing to the left and the center of a Timken bearing to the right. These worked very well to ensure that the bearing seated properly with out being damaged. Here you can see the bearing being tapped into place with the aid of the inner race, a vice and a rawhide hammer.
	13.) Now the main shaft is inserted into the case through both gears.
	14.) The next step is to install the snap ring onto the main shaft. This was pretty tough to do but straight forward.
	15.) Once the main shaft was installed the intermediate shaft was the next step. The roller bearings are loose and are not in cages and there are washers to go in between each row of rollers. You can use some sort of bearing grease to hold the rollers in place.
	16.) In this picture you can see the rollers and the first two washers in place. I am just getting ready to put the last washer in place. This should be what your bearings look like.
	17.) This was probably the hardest part of the build up. Here you can see the new intermediate shaft from Novak. At the end you can see the groove for the rubber O-ring that goes on that end. What makes this tricky is you have to get the brass thrust washers to stick in place on the side of the case, then slide the intermediate gear down into the case and then put the intermediate shaft through the intermediate gear with out knocking one of the thrust washers out or messing up the bearings. I found the easiest way was to get the intermediate shaft started so that it would keep the thrust washer on that side from sliding down and that way one hand could deal with the other thrust washer while my other hand put the intermediate gear in.
	18.) Once the gear is in place the the thrust washers are where they are supposed to be AND you are sure that the roller bearings didn't fall out of place you will drive the intermediate shaft into the case. This was a tight fit and took quite a bit of effort.
I eventually had to use a large brass drift with a larger ball peen hammer. Once it is seated install the retaining clip and bolt. Note the rubber O-ring visible here. This is what makes the Novak shaft worth the money. No matter what route you decide to go with I must urge to be sure that you do not use one of the cheaper intermediate shafts that are supplied with most rebuild kits. The one from Teraflex should hold up and the Novak one is probably the best choice because it will be durable plus have the O-rings but the cheaper ones have been known to wear out after a VERY short amount of use.
	19.) Once the intermediate shaft was installed the front roller bearing was the next step. Note that I used the inner race from the old Timken bearing combined with a socket to tap the new bearing into place.
	20.) After the bearing is seated you will install the outer race for the front and rear roller bearings. You will not need to press these down flush with the case. There are provisions on both the front and rear output housings to press these in the rest of the way. You will want to get them seated so that there is not a lot of play in the main shaft though so that you can complete the rebuild.
	21.) Now it is time to install the front output housing. I used a silicone based gasket maker to dress the paper gasket.
	22.) You will then line up the shift rods and front output shaft and slide it down onto the case. Then you will bolt the front housing down with 5 bolts and torque them to 40 ft lbs of torque. At this point you can install the shift rail seals with out worrying about messing them up!
	23.) At this point your case should look something like this.
	24.) This is another very tricky part of the rebuild and very tedious. There are shims that go between the rear output housing and the main case. These shims control the end play on the rear yoke. The end play should be between .004 and .008 of an inch. With new bearings and all if it is a thousandth or two under that is fine.
The real pain is that to be sure that the end play is right you have to torque the rear out put housing down each time you change the shims and check end play. They get torqued to 40 ft lbs. My original shims were .060 of an inch and I had to add .025 to it before I got proper end play again. I actually needed .030 but I decided to take .005 out so that when I put a skim of silicone between each shim to guard against oil leaks the over all stack wouldn't be too thick.
	25.) You can now install the rear output seal.
	26.) At this point both yokes are installed. Be sure to put the original washer on before torquing each nut down to 220 ft lbs of torque. You can see here that I used a home built tool to hold the yoke. A good pipe wrench might also work but it is pretty tough to get the yokes torqued down.
	27.) In this pic you can see I have already painted the case using a gray color. I chose gray because I figured it would help show any oil leaks down the road. In the repair manual I was using Moses Ludel recommends using an engine enamel. I decided to try it out. The paint seemed to be very durable so far, I got mine at Napa and used New Ford Gray. Here I have installed my first set of gaskets and skimmed both sides with gray RTV Silicone.
	28.) After the first set of gaskets went on I installed my transfer case girdle from Tri County Gear. I did have to slot one of holes for the bottom cover and clearance the holes for the rear cover some. I am unsure if this was because I didn't just use silicone or maybe it was a combo of the paint and the silicone and the paper gaskets or something to that effect. I got all of the holes to line up when I tired to dry fit the girdle. These kinds of hang ups are very common during a Jeep build up. Even with these small inconveniences I was very happy with the quality of the girdle and it is an inexpensive way to add a lot of strength to your case.
	29.) Once you get everything lined up you can then install the bottom and rear cover plates and torque down the bolts. I found that these could not be torqued down as much as the others or the gaskets would split. I used lock washers and tried to make sure that I tightened them down evenly in a criss cross pattern.
	30.) This is the finished product. Here you can see that I have attached the shift levers and cross shaft just to get a test fit and be sure that they cleared the NV4500. Once the drive train is in the Jeep and I have mounted the tub and cut the hole for the shifters I will reinstall them. I also plan in the future to install a rear yoke mounted disc brake to be used as a parking brake as a replacement for the OEM style drum brake. I hope you enjoyed my build up. Below you will find links to both the manufacturers and to some of the parts I used for the build up. Thanks for reading!
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