Project Off Road Buggy Dana 60 Axles - Fun Buggy B-Gun Part 1Posted in Project Vehicles on August 1, 2005
I have wanted to build a rock buggy for years now, but the problem is that I don't know how. I'm fairly good with wrenches, and I'm not bad with a welder, but I've never built a complete buggy from scratch. So it would be pretty dumb of me to tell you how to do it, unless I worked with some of the most experienced folks in the business and showed you what we did. The plan here is simple, build a sicko rig that can be hammered and hammered hard until I learn to drive better, and hopefully cover everything we do so you can copy it. I don't expect to see a hundred clones of my Fun Buggy on the trail next year, but if you can steal a few tricks or ideas here and there, then this whole project will be worthwhile. If you decide you need to have the exact same thing, I'm sure all the shops and suppliers in these articles will gladly build said parts for you. I know this is going to be expensive for most of you, but I also know that many of us like to read about the super-cool gnarly stuff even if we will never do it ourselves. (Why do you think Playboy magazine is so successful?) So here is the compromise, for every part I install I'll try to give a cheaper alternative. I may not use the budget bits in my buggy, but I also don't want you to think that the high-dollar way is the only way to go. I've seen tons of cheap-built wheelers out there, and I believe that 90 percent of what I'll be building can be duplicated with other parts.
This month we will start with the axles. I have laid awake many nights trying to decide what would be best for my buggy. Toyota axles can be built tough, but I want to run at least 37-inch tires and preferably 40s, 42s, 44s, or 47s. Rockwells are cool, but this thing needs to see highway miles and I'm not fond of that axle's weight. The 9-inch axles are pretty tough, but I'm a little concerned about the smaller ring gear. Portals are awesome, the ground clearance can't be beat, and I was really close to having custom 9-inch/Mogs built, but I have also seen them break, and the maintenance parts are not available at your local NAPA. So I returned to Dana 60s. Yes, we've done that before, but 60s are also axles that anyone can get at their local junkyard. However, I decided to build the toughest Dana 60s available. Let me get this out of the way right off, this is not an entry into Cheap Truck Challenge. These parts are some of the best you can assemble into an axle, and other than the brakes and some of the gears and bearings, they are all a step beyond a stock Dana 60, and as such they are not inexpensive. I am having the front built to standard Ford high-pinion widths-69 1/2 inches wheel mount to wheel mount-so you could copy it. My rear axle is a high-pinion rear-steer axle, an axle never available in a production vehicle, but there are other options. My first choice in junkyard rear axles would be a GM 14-bolt, after that a Dana 60 or 70. Folks here at the office have said that I don't need rear steer, but my argument is I also don't "need" to go wheeling, but I want to, and I want rear steer. I've seen it live in a 9,000-pound Avalanche, so I think it will be fine in a buggy that's half that weight. Plus it is fun to play with, and that's the whole point of this rig, having fun.
If you want to see more photos of this buggy buildup and read more about what I'm doing to get it on the trail and road, be sure to follow along on our Web site (www.4wheeloffroad.com), where I will be doing updates. Plus feel free to e-mail me any questions or comments you might have at firstname.lastname@example.org.
1. The Dynatrac Pro Rock 60 housing is often touted for having more ground clearance than a Dana 44 housing, but that's not the reason I chose it. I figured that ground clearance is good, but I can always adjust my line to keep moving up the trail. In fact, I was ready to use a junkyard 60 housing for my front axle when I started looking at the part of the housing where the axletubes are pressed in, and realized just how much thinner they are than the Pro Rock housing. Notice the holes drilled for the plug welds; the stock housing is just 1/4 inch thick where the Pro Rock is just over 1/2 inch. That-and the fact that the Pro Rock was specifically designed with abusive four-wheeling in mind, where the Dana unit was built for moderate four-wheeling (do you think the Dana engineers ever imagined their axle being driven up a rock cliff in Johnson Valley or Moab under a 1-ton truck?)-was enough for me.
2. Dynatrac usually builds all its axles with ball-joint knuckles, and despite abusing the front and rear steering axle in the Ultimate Avalanche as well as driving it for 50,000 miles, I have never had any problem with them. However, this time I decided to go with the older-style kingpin knuckles. The reason was that I wanted these axles to be similar to what the average wheeler could get his hands on. Since I was looking to upgrade from stock, I got four new forged inner Cs and cast knuckles from Dedenbear. They both have had material added over the stock design to strengthen them, and the crew at Dynatrac quickly welded on new pieces of 3 1/8-inch DOM tubing with 1/2-inch wall thickness, 1/8 inch thicker than stock.
3. The tubes are machined so that they have a tight fit when pressed together, and the pinion angle and caster must be known before assembly. In the front I went with 6 degrees up in the pinion angle, and 6 degrees back in caster. This should allow good driveshaft angles without affecting steering return to center at speed. In the rear I went with 0 degree caster with 0 degree pinion angle. Then if the pinion is turned up to point toward the transfer case, it will give the knuckles more positive caster. However, rear-steer caster is less important since it will not be used at high speeds.
4. With the housing pressed together and welded, it was finally time to install the guts. One thing I decided to do is upgrade to 40-spline axleshafts. Most Dana 60 steering axles come with 1.5-inch 35-spline inner axles and 1.28-inch 30-spline outer stub axles. My 40-spline shafts measure 1.71 inches in diameter and are made by Superior Axle and Gear from 4340 chromoly. In matching material, stepping from 35-spline (top) to 40-spline (bottom) is equal to nearly a 50 percent increase in torsional strength, and going to chromoly increases that even further. Superior makes these shafts here in the United States and sells them exclusively through Dynatrac. Dynatrac is working on an upgrade kit to make any kingpin or 35-spline Dana 60 accept 40 splines.
5. In the Pro Rock housings I decided on 5.38 gears, which is plenty low for big tires. I began to worry that the stock 27-spline pinion would be the weak link with the 40-spline axles. Of course, it is upstream of the torque multiplication, but I knew my transfer case was going to have 32-spline outputs, so why go back down to 27-spline? I had initially gotten some Spicer gears from Drivetrain Direct (left), and then I found that Yukon gear offered even bigger 35-spline pinion Dana 60 gears, but only for high pinion, and only in 5.38s. So I decided to do a test. I'll put the Spicers in the front, and I ordered the Yukons from Randy's Ring and Pinion and will run them in the rear. When a high-pinion axle is run in the back of a vehicle, it is turning on the coast side of the gear, and as such is weaker and more prone to break, but the bigger pinion shaft and stiffer Pro Rock housing should help keep the gears flush. In order to run the 35-spline pinion, I also need to run a special yoke that is only available for a 1350-series U-joint, where in the front I will run a Spicer 1410 yoke that I got from High Angle Driveline. The larger 1410 will give me more angle of movement over the 1350, but the rear driveline will most likely have High Angle's 1350 CV at the transfer case and not need as much angle at the pinion. In addition, the 35-spline Yukon gears (which are made in the U.S.) need special bearings and the shims are installed in a special billet shim case due to the larger diameter, but the pinion seal is the same as stock.
6. In order to keep all four of my tires turning, I decided to go with Detroit Lockers in both axles. They are the only company I found that offers off-the-shelf lockers for 40-spline axles, unless I was to go with a spool. Plus I have been running them in my Chevy Army truck, Ultimate Avalanche, and Tacoma for a few years now and really like the always-ready-to-wheel mode. Minor issues with Detroits include difficulty turning in some applications, which I shouldn't have since I'll be running both front and rear steer; locker breakage should an axle or joint fail, which is less likely with both the Dana 60 locker and the 40-spline shafts; and noise from on-the-street unloading, which is something I've never been bothered by.
7. When running kingpin-style axles, you need to sometimes rebuild the kingpins and bearing. The kingpin rebuild kits are still available and I got mine from Drivetrain Direct, but the lower kingpin that bolts to the bottom of the knuckle is getting harder and harder to track down. I found that Parts Mike is a great source for standard Dana 60 parts as well as Dana 44s and other drivetrain components.
8. When ordering my Superior Chromoly shafts, they asked what U-joints I was going to run, and I answered "CTMs." Again I've been running these billet 300M joints in the Avalanche and the forged version in the Tacoma with no problems. The Avalanche has even had them in the rear steering axle where they get tons of abuse both on the trail and on the street towing. In fact, I have gone through four different ring-and-pinions in the rear of the Avalanche but never have I changed the U-joints. I'm not gonna lie, I have seen them break in competition rigs, but that was under severe abuse and before a recent redesign. There are other U-joints on the market, but until the CTMs let me down, I'll be running them in my trail rig.
9. Part of the reason I chose the Dedenbear knuckles (here with black paint over their normal orange powdercoat) is because of the five-bolt mounting system for high-steer arms. As I've said before, I'm not the best driver, and I've been known to kill a few tie rods, so using these billet high-steer arms from OTT Industries will get the tie rod up high out of harm's way, and the five-bolt mounting system helps in locking the arms in place. I will get the arms drilled for the tie rod once I know exactly where the hole should be.
10. Another issue with the big 40-spline shafts is the need for a larger spindle to clear the bigger shaft. This requires the use of a larger-than-stock outer hub bearing, but the standard inner hub bearing is retained. When building a five- or six-lug axle, Dynatrac actually uses a shorter-than-standard spindle and stub shaft. But since most folks running eight-lug axles could be putting them under a heavy vehicle, Dynatrac kept the standard spread and used the 12-inch stub shaft. I decided on eight-lug since if I ever tow this buggy, I'm sure my tow rig will have eight-lug tires and wheels and that keeps spare tires and wheels universal in my garage. By going to the Chevy kingpin knuckle, we also had to track the somewhat rare Chevy brake caliper stands. We found some new old stock units at Boyce Equipment, but along with the lower kingpins we think someone should consider remaking these units.
11. Another issue is brakes, hubs, and drive flanges. Dynatrac is having custom hubs made to clear the larger spindle bearings, and I chose to run stock 12 7/8-inch rotors and single-piston calipers since these will most likely be parts I need to replace some day, and I can find them at most any auto parts store. Plus, they should offer plenty of stoppage for a medium-weight buggy. Running drive flanges in the front will require perfect driveshaft angles to reduce vibrations while at highway speeds (yes it will be on the highway, but that step is for a future article). If by chance I do have vibration, I could always pull the slugs and just let the hubs spin while on the road, at least until someone comes out with the 40-spline selectable hubs that are in the works.
12. So there you go, a set of axles that should take the abuse and be strong enough that the weak link will hopefully be gravity. Next month we'll move upstream and discuss the rest of the drivetrain, and after that we'll start building the chassis.