By Christian Sturtz, [email protected]
Photos by Christian Sturtz
The undisputed best transfer case ever put in a Jeep is the Dana 300. It’s gear-driven, strong, compact, and easily adapted to most applications. It does have a few shortcomings- they are noisier and harder to work on than newer aluminum chain-driven transfer cases. A common complaint on the Dana 300 swapped into late model vehicles is it has a narrow offset, meaning the distance from the centerline of input to the center of front output is less than many of the other transfer cases. Remember, the Dana 300 was designed for smaller vehicles with mainly standard transmissions. So, when swapping into something with a late-model automatic, you might have some clearance issues. Sometimes, even behind the GM turbo 350, it is necessary to clear the transmission oil pan.
The Dana 300 also only came factory-configured with a passenger-side front output. I really wanted to run a Dana 300 in the Swap site to Competition rig build, but the front output is on the wrong side for my axle. So, I decided to do a flip kit on it and throw in a few upgrades that are sure to make this thing hold up in competition. (Figure 1) Behemoth Drivetrain sourced me with their 300 flip kit, twin-stick shifters, longer input gear, master overhaul kit by USA Standard Gear, and billet front output cover. Behemoth Drivetrain also offers several other Dana 300 and NP205 parts, as well as, full replacement billet cases that allow driver or passenger side front outputs. Behemoth does Strongbox under drives and full builds in-house. They always have something new in the works, so check out their website. https://behemothdrivetrain.com/
For the additional performance upgrade, I turned to a long-time Jeep and off-road drivetrain source, JB Conversions. John, the owner, is a great wealth of knowledge and “has been there, done that,” he also has no problem telling you if something will work or not. JB Conversions is a small company that sells and produces top-notch products with excellent fit and finish. JB Conversions sourced me with a 4-to-1 gear kit and front/rear heavy-duty 32 spline outputs. I also needed to install a clocking ring on the transfer case to fine-tune its positioning; I left this up to Advance Adapters. The 300 that I had to build was a survivor! I swear this thing had never been touched, or had the oil changed. The fumes and grease started to fly as soon as I touched it. This thing was gross! So I dug in and removed the front and rear yolks, speedo drive, and oil pan. I then unbolted the retainer and used a brass punch to knock the idler shaft out. With the shaft removed, the idler gear and thrust washer can be taken out of the case. There are needle bearings inside the idler gear that may fall out, be careful. (Figure 2)
Onto the shift forks and rails, I removed both Allen set screws then the 4×4 sensor switch and the detent covers. This process is quite in-depth; thankfully, JB Conversion has detailed instructions on this process on their website. My shifter rods were sort of a pain- I normally start with the one connected to the small shifter fork, but it was frozen in there. This forced me to remove the other rod first. With both shifter rails removed, the shifter forks were then lifted out. The Allen screws were removed from the front bearing retainer, and the front retainer and input were removed and disassembled. A press is the easiest way to push these pieces apart. Often, there is a shim under the input bearing; this may need to be reused on a new input gear. (Figure 3)
A 2-jaw puller can be used to pull the rear output housing off. I have never had luck doing it this way, because a puller will often crack the housing. *Tip: I normally slip the slider off, set the case facedown on the bench where the front input goes, put the pinion nut and washer back on, and tap the shaft out of the housing. There are shims under the rear outer bearing; don’t lose them if reusing the rear output. The front output housing was then unbolted and removed. To remove the front side output bearing, grab the gear with a 2-jaw puller to pull the gear and bearing off. The front output plate was then removed. Make sure to keep the shims; they may need to be reused if you are not replacing this plate. (Figure 4)
To get the shafts out of the case, you have to use a press. The gears on the front output sit pretty flat, and if positioned correctly, the shaft will press right out. The gear on the rear shaft must be supported. The case will side-load the gear and break it or chip the teeth. The rear shaft has a thrust washer between the bearing and gear; if reusing the rear output, this will need to be kept. The bare case was degreased, wire brushed, and painted. The case had to be notched for JB Conversions 4-to-1 kit. I didn’t notch it enough the first time. It would have been perfect if I had gone to the outside of my line and done smaller radiuses in the corners. The rest of the transfer case parts were also cleaned up. If you do this complete job, you won’t use most of the original parts, but it’s easier to work with everything when it’s clean. (Figure 5)
I started reassembly by putting the front input together. I checked the clearance underneath the snap ring, and it should be 0.0000-0.0015,” if it has more clearance than that, it needs to be shimmed. My original shim gave me 0, the seal was installed, it was pressed together, and snap rings were installed. The rear output was then pre-assembled, pre-load was shimmed, and then it was taken back apart (I like around 0 end play). The rear output was put into the case along with the large gear and directional thrust washer. The shaft was supported, and the bearing was tapped on. Then, the speedo gear was installed. I applied a layer of silicone sealant to the mating surfaces, installed shims, bearing, and seal retainer along with the yolk, and tightened everything up. The slider was installed, front input mating surfaces were coated with sealant, and input was bolted in. *Tip: I install sealant to any bolts that are threaded into transfer cases; even though some of the holes are blind, it won’t hurt anything, and it acts like a light threadlock. (Figure 6)
For the front output, the race and seal are pressed into the Behemoth front-bearing retainer. Behemoth makes these in two different designs: one for the standard spline and one for the 32 spline. They include seals for the 1310-1330 yolks and the 1350+ series. The front output was then assembled, and the bearing was pressed on. The front output also uses a directional thrust washer; it goes on right before the bearing. The assembled front output shaft was installed into the Behemoth housing, the yolk was slid on, and the nut was tightened. The Behemoth housing was then slid into the case, the slider and large gear were slid on, and the housing was tightened. I cut the cage off one of the old bearings and used the inner race to tap on the rear front output bearing. The Behemoth billet output cover is pretty slick. You have to use the spacer in combination with shims to reach a spec pre-load of 0.002-0.005” of endplay. I like it closer to 0. (Figure 7)
The last step with the gears is the idler gear and idler shaft. I always check the hardness of the new shaft by trying to cut where the retainer tang is with a hack saw. Cut’s real easy? Junk it! Doesn’t hardly cut? It has good heat treating, keep it. Luckily, the USA Standard uses a good shaft. In the picture, the shaft on the top is an example of a competitor’s new shaft that is soft. The bearings and spacers are stacked and placed inside the idler gear. I used sockets as a dummy shaft and transmission grease to hold the bearings in place while the shaft was installed. The new thrust washers were stuck to the inside of the transfer case with transmission grease. Make sure the thrust washers’ tangs are in the pocket of the case. Next, the idler gear was slid into the case carefully not to knock a thrust washer down. The idler shaft was slid in, and the sockets slid out. *Tip: I always clean the bore and smear a little sealant on the inside of the case, where the pin goes, also on the o-ring side. I have had 300s leak oil around the shaft. (Figure 8)
All that was left was a few small finish-up things and then the Behemoth flip shifter cover. I put the speedo drive back in, installed ¾” brass freeze plugs in the shifter shaft tube locations, and put a pipe thread plug in the JB Conversions’ rear output housing. Then, I coated the gasket with some copper spray, lined up the shifter cover, and bolted it down. The Behemoth’s cable shifter mount allows cables to come in the front or back, whatever works best for your application.
The Advance Adapter’s clocking ring bolts directly to the face of the transfer case. This will allow me to index the transfer case to the desired angle. I just started the studs; they will need to be adjusted during the install. I am very happy with the outcome of this transfer case. Behemoth Drivetrain, JB Conversions, and Advance Adapters all make top-shelf parts with impeccable fit and finish. This thing is sure to slow me down before I start flip’n out. (Figure 9)
Parts Used:
Behemouth Drivetrain
Dana 300 Twin Stick Flip Kit, 32 Spline
Billet Aluminum Cable Shifter Twin Stick
Twin Cable Mounting Bracket
Billet Front Output Cover
23 Spline Long Input Shaft
Bearing Kit
JB Conversions
4 to 1 Kit: 2307
Front 32 Spline Output Upgrade: 15-1103
Rear 32 Spline Output Upgrade: 2308
Advance Adapters
Dana 300 Clocking Ring: 50-8603
Sources:
Behemoth Drivetrain
609 Salt River Rd.
Leitchfield, KY 42754
855.928.1984
JB Conversions
337.625.2379
Advance Adapters
4320 Aerotech Center Way
Paso Robles, CA 93446
1-800-350-2223
