In an earlier article I outlined the payload differences between the Chevy Silverado 2500 and 3500 HD, the primary differences being the leaf springs, tires, and rims. As needs change—like when choosing a larger, heavier camper—payload management becomes more important.
Having already employed airbags, sway bars, and 1,300-pound leaf springs, Truck Camper Adventure’s review on Cooper Discoverer AT3 tires was timely in that I needed new shoes and the 4,060-pound, 129/126 S-load rating was another plus keeping the my Arctic Fox 811 truck camper under control. This was the single most significant upgrade and after 60,000 miles the Coopers performed so well, they were replaced with a second set.
Seeking solutions to overload conditions, we explore after market solutions by combining rims, tires, airbags, SumoSprings, Timbrens, Stableloads, leaf springs, and 19.5-inch wheels. Anything to bring sway or squat under control, because the number one job when driving a truck camper is maintaining control of your vehicle no matter the configuration or driving conditions. The key is looking at specifications, doing the math and deciding if you’re going to improve performance or struggle with an overload condition.
Recently, while traveling through eastern New Mexico, I came upon construction traffic, lifted the gas pedal and heard a low rumble. Thinking it was brake shoes finally wearing out after 300,000 miles, I pulled into a rest stop, removed the tire, and to my surprise saw 1/4-inch remaining on the pad indicator.
Working back to the differential, I moved the drive shaft at the pinion gear 1/8-inch in all directions. In the never-let-a-maintenance-repair-go-without-improving-performance mind set, this was an opportunity to take an often overlooked payload component and return the original performance of hill climbing and towing of the 4:10 differential.
When we make changes to manage payload, it affects the overall camper and truck combination. Recall I changed from 17-inch steel rims to OEM 3500 HD 18-inch alloy rims. This increased the tire size from 245 to 285 and changed the differential ratio from 4:10 to 3:72, a 9 percent difference. A benefit doing this was getting one additional mpg, however, the truck suffered in both hill climbing, and more important, changes in the transmission shift point because rpm was lower at a given speed. While climbing California’s moderately high (4,060 feet) Tehachapi Pass one day, I had to keep the motor “on the boil” turning well into mid 5,000 rpms. The solution was replacing the 4:10 ring and pinion set with a 4:56. This would restore original 4:10 performance.
Having a plan to replace the ring and pinion is quite different than getting it done. Business is good and I opted to have West Coast Differential do the work only to be informed the soonest available date was 45 days. Required to be in Oklahoma in 10, I gave them the pinion to preload and installed the ring gear onto the differential, then headed to Harbor Freight securing the tools I needed to do the repair myself.
I never replaced a differential, so I looked for a YouTube video showing how it’s done. I managed to replace the unit and while that far into it, went full Monty rebuilding the entire axle assembly. Word to the wise…that snap ring holding the inner wheel bearings is a bear and requires a special tool. Also replace your axle oil seals at 100,000 to 150,000 miles. The rubber cracks and if they leak, parking brake shoes get coated in gear oil. But that wasn’t all. Recalling Mello Mike’s article on destroyed rims, I noted two alloy spokes cracked completely through. Think about that…3500 HD alloys rated at 4,000 pounds with undeclared engineered over percentage, cracked under the payload of the Arctic Fox 811 and tongue weight of 20-foot equipment trailer. Needless to say, I removed the alloys and switched to 18-inch STEEL rims.
So what’s the verdict? Was switching ring and pinion worth it? After 4,000 miles and without reservation—yes. Transmission shift points are back to normal and climbing hills puts the pull at 2.250 to 4,600 rpms. A recent westbound trip got 10 mpg traveling at 60 mph showing 1,850 rpms with just a little tail wind. On-ramp transitions are less dramatic and no longer had to keep track of the 9 percent difference in odometer reading verses GPS mileage.
It falls on us to configure our mounts safely while traversing our travels. The changes I made, along with driving at a lower than posted speed limit, allows me to claim this is the best truck configuration to safely manage my payload puzzle in all conditions, while traveling roads across the country.
Keep in mind most trucks with 300,000 miles often perform light duty and never have make major repairs. My truck has been at payload or towing 10,000 pounds or both for 99 percent of its life and required a rebuilt top end transmission and now rear axle. With the exorbitant price of new trucks, my “old” Chevy will soldier-on doing the work asked of it.
To learn more about your truck’s payload rating and how to effectively manage it, check out our popular article How to Raise Your Truck’s Payload.
Getting your truck weighed is a vital tool to effectively manage payload.
Michael,
Nice piece. You show yet another pathway to haul heavier payloads without being on the very edge.
I’m assuming you have some version of a GM V-8 gas engine that will turn 5500 rpm.
Of all the gear ratios I’ve had in jeeps and trucks over the years, I’m still liking the 4.10’s.
Why? It has the beefiest RG&P without being low numerically geared like a 3.55 or 3.31.
I bought the new Ford 7.3L V-8 gasser, 10 speed auto, with the factory 4.30’s gears.
Conveniently, replacing the stock Goodyear Kevlar AT 32’s (on 18 inch rims) with the 35 inch Cooper AT3’s with the 4060 pound rating drops the apparent ratio to the magical place i like for trucks that haul down to 4.10.
I”ve used a couple sets of Coops on our Dodge RAM CTD 6 speed manual (with 410.’s) and agree that they are one of the best “fixes” for controlling heavy loads.
I am surprised you thought your brakes wore out when you heard the noise, I check mine at every oil change along with the wheels, tires, driveshaft/ u-joints and more. When I went to the 18” on my truck I also changed the ratio in both of course since I have 4wd. I did the change in the computer for the correct speed. I had 3.73 and went 4:10. But my turned up Cummins pulls most any hill at 1750.
I did my first differential rebuild in 1966 though. You probably did it right by doing it yourself and if there is a problem you don’t have to travel back to the shop that did it.