Garage76 Diesel Performance and AutomotiveGarage76 Diesel Performance and AutomotiveGarage76 Diesel Performance and Automotive

Ram 1500 DS GVM Upgrade 4200 Kg


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GVM Upgrade Specifications   The JMACX GVM kit not only strengthens the diff but also the rear wheel hubs and bearings are upgraded to suit the increase in load carry capacity.... Read more


GVM Upgrade Specifications


The JMACX GVM kit not only strengthens the diff but also the rear wheel hubs and bearings are upgraded to suit the increase in load carry capacity. The rear wheel bearing area and wheel bearing itself is the major issue. Extra engineering for SSM (Second Stage Manufacture) is included in the GVM upgrade. The premium suspension solution includes JMACX’s signature Alpha Shocks, high quality coils and high pressure in coil airbags providing 2 inches in the rear and levelling in the front.

Under testing the factory braking system was found inadequate for a GVM upgrade as it failed the braking test due to excessive heat which caused component failure. So this GVM upgrade includes JMACX Ram 1500DS brake upgrade as standard, with larger slotted rotors, 6 pot callipers, and high performance brake pads to reduce glazing and brake fade via heat dissipation, allowing the vehicle to carry more load safely.


Frequently Asked Questions


“Can I just apply the QLD 10% GVM upgrade by re-rating my axle?”

No, you cannot exceed the manufacturer’s axle load rating under the QLD 10%.  You can increase your GVM in QLD by approximately 7% based on factory axle load ratings.

“Can I just add bracing to the factory diff?”

Bracing still leaves the diff with an inherent weakness as it stops at the backing plate and is well before the compromised bearing. Bracing the factory diff does not resolve the point of failure, but can increase the impact on the loading point of the bearing due to stiffening of that rear housing.  See below for failure example.

  Failure for RAM 1500 wheel bearing area

“Can I get a GCM upgrade on my RAM 1500DS?”

JMACX will not provide a GCM increase in addition to your GVM increase on the RAM 1500DS due to excessive loading on the chassis.  There is plenty of evidence demonstrating this failure in the current market.





The engineers at JMACX have developed a procedure of modifying the end of the tube, welding on a thicker tube axle and a full float bearing hub assembly. This allows for larger wheel bearings to cope with the additional axle load. Internally, the diff is strengthened by a full inner tube. Full floating bearings offer greater handling of larger loads. The JMACX diff upgrade increases the axle capacity to 2500kg.


In addition to the modified diff housing as above in option 1, with new fitted upgraded diff bearings, and new air locker.  ***Air locker availability TBC***


The JMACX 9” diff option with air locker is the ultimate choice, as the strongest diff available. With bigger gear sets, upgraded parts and with the longest warranty. With a factory replacement diff close to $24,000, the 9” JMACX diff represents quality and value.

***Note: All RAM DS diff upgrades are on an undamaged core exchange basis where your factory diff is exchanged for a modified or new replacement differential.***


Canberra, Sydney & NSW

Diesel Performance & Tuning

Based in Canberra, Garage76 are your complete 4WD and Diesel Performance Tuners. From basic upgrades, to complete pre-registration vehicle builds, we have the knowledge and products to build, maintain & repair your ultimate diesel 4wd.



From a safe and reliable tune of your OEM ECU through to wild diesel performance upgrades, we've got 20+ years of diesel tuning under our belts and can tailor a package to suit your performance or touring needs.

(10-30% INCREASE*)

Our Stage One kits (vehicle depending) will always include an ECU remap and a tune on our in-house dyno. 
No two vehicles are the same and every diesel performance package we book spends time on our dyno.
  • G76 Custom ECU Remap

(30-50% INCREASE*)

Once you are looking to go beyond the performance of our basic Stage 1 Package, you will reach the limitations of your factory turbocharger. At this point a turbocharger upgrade will be required, along with appropriate upgrades to the exhaust, air intake system and intercooler. With these upgraded items we are able to squeeze more performance than a stock setup will ever provide.
  • G76 Custom ECU Remap

  • Upgraded Exhaust

  • Upgraded Snorkel & Airbox

  • Upgraded Turbocharger

  • Intercooler Upgrades Or Intercooler Fans

(50+% INCREASE*)

Looking for maximum GRUNT without compromising factory reliability? Our Stage Three Package is for you! This package will give you the ultimate in diesel performance, with massive gains available in power and torque. 
The main difference between our Stage Two and our Stage Three Package is the addition of high flow fuel injectors. In a diesel engine, more fuel = more power, provided you have the air to burn it! We also only have a small window of crankshaft rotation available to inject the fuel. High flow injectors allow us to increase the amount of fuel delivered to the engine during this window, resulting in huge gains in power and torque.
  • G76 Custom ECU Remap

  • Upgraded Exhaust

  • Upgraded Snorkel & Airbox

  • Upgraded Turbocharger

  • Intercooler Upgrades Or Intercooler Fans

  • High Flow Injectors

  • Upgraded Fuel Pumps

*power and torque numbers will differ between vehicle models and final diesel performance packages and tunes. Our increase numbers should be used as a guide only. Different vehicle makes will have variations in the packages we offer, not all packages come with intake cleans.
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Ram 1500 DS GVM Upgrade 4200 Kg