Rockwell 2.5-ton axles
Three of them, all geared 6.72. Lockers in both rear axles.
Dodge Off Road project truck
Three axles. One Cummins. Six 45s.
Our 1998.5 Ram 2500 regular cab: a 24-valve Cummins on three Rockwell 2.5-ton axles with 6.72 gears, full hydro steering, and coilovers with a 4-link at every corner.
- 1998.5 Ram 2500
- 24-valve Cummins
- 3× Rockwell 2.5-ton
- 6.72 gears
- 45″ SX2
01
The truck
It started as a 2nd-gen 1998.5 Dodge Ram 2500 regular cab with the 24-valve Cummins. We put it on three Rockwell 2.5-ton axles and built it to crawl and pull rather than run fast.
Here's how we described the project, in our own words:
“1998.5 Dodge Ram 2500 Cummins 24 valve 6×6 project, using Rockwell 2.5 ton axles, 45″ Super Swamper SX2s on 20″ Hutchinson aluminum double beadlocks, lockers in both rear axles, full hydro steering, coilovers and 4 link on every axle. This truck is currently being built, we will add a custom flatbed and then button up the suspension and steering, and it will be ready to drive. It won't go fast but it will go anywhere, and it can be used to haul our gooseneck trailer if needed. With 6.72 gears it will pull anything.”
- Base1998.5 Dodge Ram 2500
- Cab2nd-gen regular cab, blue[1]
- EngineCummins 24-valve, internally stock, tuned and breathing a lot more air than stock
- DrivetrainStock 47RE automatic transmission
Stock NP241DLD transfer case; the two rear axles are linked by driveshafts through pass-through pinions - BrakesBus-style disc brakes on all 6 hubs
- AxlesThree Rockwell 2.5-ton, 6.72 gears
- Suspension2.5″ remote-reservoir coilovers with 16″ of travel and dual-rate springs; parallel long-arm 4-link on every axle; auxiliary airbags on the two rear axles
- SteeringFull hydro, front steer only
- WheelbaseAbout the same as factory, within an inch or so (front hub center to the midpoint between the rear axles)
- WeightRoughly 11,300 lbs (about 6,200 stock + about 5,100 added)
- StatusOngoing build, worked on in our spare time; not finished yet
02
The build so far
This is an ongoing build that we work on in our spare time, and it isn't finished yet.
Since our early notes, the custom flatbed has gone on: a steel flatbed with a headache rack. The truck is still a work in progress, and the suspension and steering are being buttoned up as we go.
Next on the list: the engine running now is an internally stock 24-valve Cummins with high miles that was ragged on by previous owners. It's tuned and flows a lot more air than stock. Once the rest of the truck is done, we'll install a built 24-valve and do power upgrades.
03
Parts & specs
Ram 6x6 · build data plateVerified rows only
| Item | Spec | Source |
|---|---|---|
| Base truck | 1998.5 Dodge Ram 2500 | Our build notes |
| Cab / body | 2nd-gen regular cab, blue | Our photos |
| Engine | Cummins 24-valve diesel | Our build notes |
| Engine internals | Stock; high miles, and ragged on by previous owners | Our build notes |
| Engine tuning | Tuned; flows a lot more air than stock | Our build notes |
| Axles | Three Rockwell 2.5-ton axles | Our build notes |
| Gearing | 6.72 | Our build notes |
| Transmission | Stock 47RE automatic | Our build notes |
| Transfer case | Stock NP241DLD | Our build notes |
| Third-axle drive | Driveshafts link the two rear axles; the top-loader Rockwells take a driveshaft on both sides of the pinion (pass-through) | Our build notes |
| Lockers | Both rear axles | Our build notes |
| Steering | Full hydraulic (full hydro) | Our build notes |
| Steer axles | Front steer only (no rear steer); turning radius about the same as stock | Our build notes |
| Suspension | Coilovers and a 4-link on every axle | Our build notes |
| Coilovers | 2.5″ remote-reservoir, 16″ of travel, dual-rate springs | Our build notes |
| Links | Parallel 4-link, long arms; 2″ OD × .250″ wall DOM tubing with 1.25″ shank Currie Johnny Joints | Our build notes |
| Auxiliary air | Airbags on the two rear axles | Our build notes |
| Tires | 45″ Super Swamper SX2 | Our build notes |
| Wheels | 20″ Hutchinson aluminum double beadlocks | Our build notes |
| Brakes | Bus-style disc brakes on all 6 hubs (not top-loader pinion brakes) | Our build notes |
| Bed | Custom steel flatbed with a headache rack | Our photos |
| Wheelbase | About the same as factory, within an inch or so, measured from the front hub center to the midpoint between the two rear axles (the turning pivot) | Our build notes |
| Weight | Roughly 11,300 lbs: about 6,200 stock + about 5,100 added (flatbed ~1,500, extra axles ~2,100, extra wheels & tires ~1,500) | Stock 6,174 lbs (2500 reg cab long bed 4x4 Cummins auto): Dodge towing chart, via Diesel Database. Added: our build notes |
Every row above comes from our own build notes or our photos of the truck, except the stock curb weight, which comes from a reprinted Dodge towing chart.
04
The T-Rex trucks that came first
Dodge built a 6x6 Ram of its own once. The T-Rex was a factory concept truck, shown at the SEMA Show in Las Vegas in November 1996 and never put into production. In our view it was decades ahead of its time: built with what was available back then, and it worked really well. It inspired this build and plenty of others.
- DebutSEMA Show, Las Vegas, November 1996Chicago Tribune, Nov 17, 1996; Motor1, “Ram T-Rex concept”
- EngineModified 8.0L Magnum V10 (gasoline), 497 hpFour Wheeler first drive, July 1997 (MotorTrend); dodgeram.org T-Rex page (Wayback Machine)
- AxlesThree Dana 60sFour Wheeler first drive, July 1997 (MotorTrend)
- SuspensionComputer-controlled air suspensionFour Wheeler first drive, July 1997 (MotorTrend); dodgeram.org T-Rex page (Wayback Machine)
- ProductionNever producedFour Wheeler first drive, July 1997 (MotorTrend); Motor1, “Ram T-Rex concept”
| Side by side | Dodge T-Rex conceptFactory concept, SEMA 1996 | Our Ram 6x6Dodge Off Road project truck |
|---|---|---|
| Axles | Three Dana 60s | Three Rockwell 2.5-ton axles |
| Suspension | Computer-controlled air suspension | 2.5″ remote-reservoir coilovers with 16″ of travel and a parallel long-arm 4-link on every axle, plus airbags on the two rear axles |
| Engine | Modified 8.0L V10 gas, 497 hp | Cummins 24-valve diesel |
| Who built it | Chrysler / Dodge, as a factory concept | The Dodge Off Road crew |
We think our build has the edge, especially in the suspension, and that's mostly thanks to how far suspension technology has come since 1996.Our own view, not a measured comparison.
That's not a knock on the T-Rex. Its builders worked with the parts and technology of the mid-1990s, and long-travel remote-reservoir coilovers and long-arm 4-links have come a long way since. Our truck benefits from those decades of progress.
Two different T-Rex trucks
The bright green 6x6 Ram that often shows up in T-Rex searches is a separate truck from the Dodge concept above: a homemade T-Rex built by Stan Prueitt of Los Alamos, New Mexico, on a 1995 Ram 2500, which Four Wheeler featured in December 2002.[6] Building a 6x6 Ram in your own garage takes real ambition, and we tip our hats to it as well.
To keep them straight: the 1996 T-Rex is Dodge's factory concept, the green truck is Stan Prueitt's homemade build, and neither one is our truck. Both were ahead of their time, and both inspired us.
05
Why 6x6, and why built this way
“It won't go fast but it will go anywhere.”
The Dodge Off Road crew
Our stated goals are simple: go anywhere, haul our gooseneck trailer if needed, and, with 6.72 gears, “pull anything.”
We wanted one truck that could do it all. It articulates like a rock crawler, but it can still carry several tons on the flatbed and tow whatever we need it to. It does everything well except go fast.
It isn't a highway truck. It can be driven on the highway when it needs to be, but it's really meant for off-road use.
Coilovers + 4-link, every axle
Each of the three axles gets 2.5″ remote-reservoir coilovers with 16″ of travel and dual-rate springs, located by a parallel long-arm 4-link. The arms are 2″ OD × .250″ wall DOM tubing with 1.25″ shank Currie Johnny Joints, and the two rear axles also get auxiliary airbags.
Full hydro, front steer only
Steering done by hydraulics, with no mechanical drag link from a steering box to the axle. Only the front axle steers. We did rear steer on our V10 build and kept this one simple, and it turns about as tight as it did as a stock regular cab long bed.
Pass-through rear drive
The transfer case is the stock NP241DLD. Out back, driveshafts connect the two rear axles. Rockwells are top-loaders, so the pinion can take a driveshaft on both sides and pass power through to the third axle. It's very simple, and probably the easiest part of the whole thing.
Built to work, not to race
It flexes like a rock crawler, but it can still carry several tons on the flatbed and tow whatever we hook to it. Highway-capable when it has to be, but built for off-road.
Disc brakes on all 6 hubs
Another interesting thing: instead of top-loader pinion brakes, we run disc brakes similar to those used on a bus, on all six hubs.
06
Gallery
