Q At the parts store, they call my truck “Frankentruck” since it is built up of parts from many trucks. The short list is as follows: ’50 1-ton Chevy cab and frame, ’04 Dodge dualie bed (narrowed), ’65 Chevy 292 engine, ’94 GMC five-speed transmission and transfer case, ’79 Ford F-250 front axle, ’73 Chevy dualie rear axle, 35-inch tires. The truck drives extremely well, and 65 mph is smooth and easy.
My problem is that the front axle has a 4.10 gear ratio while the back has a 3.73 (I don’t have the front driveline installed yet). I was hoping that the truck would drive well with the 3.73:1 ratio for better fuel economy. I would then change the front axle to 3.73 and be done. Granted, the truck is not exactly aerodynamic. The engine is small, and the 35-inch tires don’t help, but I don’t even get the fuel economy that I expected, let alone good fuel economy! I wonder if I would be better off switching to the 4.10 ratio. I have to wonder if I would see significant gains in economy by switching to the lower gears.
A Going to a lower gear ratio can help fuel economy in certain situations. If you do a lot of stop-and-go driving, or if you do a lot of driving in the hills or mountains, then you want to give your engine all the leverage needed to get you moving. The “taller” highway gears of 3.73 may be maxing out the 292 with the 35-inch tires. You are also hauling some very heavy axles and large tires, and doing it with an old engine designed for much less, so I wouldn’t hold my breath for any major fuel economy improvements. I think going to a 4.10 is your best bet.
New to Tow
Q I just bought a slightly used Chevy 2500 diesel truck. It is my first diesel, and I am excited to have a vehicle capable of towing a large camper trailer with my Jeep inside. I am new to towing, as I have always driven my Jeep to the trail. I’m interested in what upgrades I could or should do to my Chevy to make it a safe towing machine for me and my family.
Little Rock, AR
A Having a tow rig gives you the security to really hammer on your Jeep while four-wheeling and still get home. I’m not sure what year Chevy you bought, but I can give you a few towing upgrades to set your truck straight.
First get a quality trailer brake setup. I have used a Prodigy by Tekonsha (www.tekonsha.com) with great results in the past.
Next I might consider a set of rear airbag helper springs. I have these on my tow rig and have found they help stabilize the truck when pulling big loads or on windy days.
I would also consider an auxiliary transmission cooler if you notice trans temps rising when towing, but I’ll assume you have the Allison trans, which is renowned for strength.
I wouldn’t have a problem recommending an aluminum differential cover either such as those made by Mag-Hytech (www.mag -hytec.com). These covers dissipate heat, have a magnetic drain plug to catch debris, and are designed for added capacity for even more cooling of the axles gears when towing. The company also offers transmission pans for various automatics.
Other than that, I’d double-check all the hardware on your trailer hitch and your trailer bearings and tires, as they seem to be the biggest detriment to towing.
Nuts, I’m Confused
Front 14 or 60?
Q I am planning on building a crazy rock buggy similar to what the guys in the southeast are building. I’m confused about what front axle to build. I have been looking for a high-pinion Dana 60, but I am also wondering about a front 14-bolt. Which is stronger?
A I discussed this question with Randy Lyman, head of Randy’s Ring & Pinion (www.ringpinion.com), and he had some very positive things to say about the 14-bolt:
“To start off, the 14T [he refers to the 14-bolt as a 14T—FW] diff is my absolute favorite differential design for many reasons.
• It has an overhung pinion with a total of three bearings for excellent pinion gear support.
• Late-models use very large pinion bearings.
• The ring gear is set far to the right side of housings so the left carrier bearing is not overloaded by reducing the combination of axial loading from gear tooth separation and radial load due to rotational torque resistance when the gear tooth load is moved closer to the left side bearing. This means the carrier bearings last a lot longer than a Dana 60 and provide much better ring gear support.
• It uses huge ring gear bolts.
• It has a very sturdy carrier case for excellent ring gear support.
• It is easy to install a Grizzly Locker into standard carrier case.
• It has a beefy crush sleeve that virtually never loses tension and lends to easy pinion preload adjustment if the support is set upside down in a bearing press to crush the sleeve 90 percent of the way.
• A solid spacer is also available from Yukon to replace the crush sleeve if so desired. This makes yoke changes easy without having to install a new crush sleeve and also allows the pinion nut to be tightened to a higher torque. It also keeps the pinion bearing preload consistent in case the yoke is bashed hard on a rock.
• It has a removable pinion support, which (noted once again) in addition to making setting the pinion bearing preload easy, also allows for fast and easy pinion depth shim changes without having to disassemble the pinion bearings.
• It has a very strong housing.
• It has pinion yokes available in both 1350 and 1410.
• Lots of ratios are available.
• It holds a lot of fluid.
• It has a larger hypoid offset, which helps gear strength but hurts ground clearance, especially when compared to a reverse-rotation D60.
• Backlash and carrier bearing preload is easy to adjust due to screw-type side adjusters, which also hold up very well under heavy loading.”
So a front 14-bolt may seem like the perfect axle, but the high-pinion Dana 60 is quite strong and it runs on the proper side of the gear teeth when used as a front axle. Plus there are easy-to-find, off-the-shelf axleshafts and complete used axles, which means Dana 60s are cheaper. The fact that it is a high-pinion is an even better bonus since it keeps the front driveshaft up out of danger’s way.
There never has been a factory 14-bolt front axle, so it would need to be built from scratch. (However, in my research on the AAM axle in this and last month’s issue I did learn that there had been a few prototype AAM 101⁄2-inch front axles that never made it to production under military Dodge trucks.) To build a custom front you will need a 14-bolt housing and all the steering knuckles, inner Cs, spindles, hubs, brakes, axle seals, and axleshafts. It will be expensive. Since 14-bolts run a special 30-spline axleshaft you will need custom axleshafts made. The majority of front axle parts will be based off of a Dana 60 1480 steering joint. But you could find or have parts made to run large CV joints, such as from RCV (www.rcvperformance.com) or 1550 Joints in one-off shafts built by a shop like CTM Racing Products (ctmracing.com). Getting enough axletube for a long side needed on a front axle may also require retubing the housing, thus adding even more cost.
In the end, the front 14-bolt will give you strength over the high-pinion Dana 60 front axle, but this is based on a factory used Dana 60, not necessarily an aftermarket version like a Dynatrac Pro-Rock or Currie Rock Jock 60. Also, the front 14-bolt will cost more to build than a rehashed junkyard 60, will require custom parts (which can be a problem if you break something like an axleshaft), and will result in a lower front pinion and less ground clearance.
I have heard a lot of grumbling about 14-bolt front axles and think your question deserves to be the Nuts, I’m Confused letter of the month. I’ll be sending you a copy of the Ultimate Adventure DVD from last year so you have something to watch if you’re not in the shop working on your rock bouncer.
Confused? Email your questions about trucks, 4x4s, and off-roading tech using “Nuts, I’m confused” as the subject and include a picture (if it’s applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I’ll be checking the forums on our website (www.4wheeloffroad.com), and if I see a question that I think more of you might want to have answered, I’ll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245 fax to: 310.531.9368 Email to: email@example.com