Well, this may not be a scientific response but I have been driving a 2008 JKU since new and have gone through some various stages of suspension and vehicle mods which has increased the weight to where I am at now. Currently I have a Gobi Rack, Front and Or-Fab bumpers / tire carrier with winch and jerry cans, hi lift jack, dual battery, on board air, a few extra skid plates and rock rails along with 35" Goodyear Wranglers. This along with my recovery gear and other essentials in the jeep would lead me to believe that I am close to or exceed the stock ratings.
The reason I post is that I noticed with the stock suspension, when I carried a heavy load or even just had four passengers and my dogs on board that the vehicle handled poorly. So I started looking at how to improve this:
Stage 1: I added 2 1/2" spring spacers and wheel spacers which improved the ride dramatically. Handling was much better than stock. The ride still suffered with a full payload though. And of course I wanted a winch and a front bumper that could handle it. So...
Stage 2: Added the front bumper/winch and the the front end took a dive and handling / braking was poor. So I added a 3" Teraflex Suspension, adj. track bar, with springs and shocks. Also added the 35" tires, rear bumper, and rock rails, etc increasing the vehicle weight quite a bit but the ride went back to normal and the handling was better than stock with no payload problems! This lead me to believe that the stock springs are a big part of the problem with the weight capacity of the vehicle. Also had little impact on the mileage -went from 17 to 16mpg. Leading to :
Stage 3: I added a Gobi Rack, dual battery system, and probably several more things I am missing. This cost me mileage - went to about 13mpg. I swapped out the gears to 5.13, added heavy front control arms and added axle gussets to the front axle. Even loaded down with extra camping items on the roof, travelling offroad, and a full payload of passengers and dogs, the Jeep handles much better than stock. Mileage went back up to about 14.5mpg with the gearing. Towed a 900# off road trailer with RTT for a few thousand miles which dropped me to about 13mpg.
Stage 4: Never thought there would be a stage 4, but I recently had some vibration in the front end and traced it to a bad drag link. I added the AEV hi steer kit and the AEV geometry correction brackets to the front. The combination of the two made the Jeep handle better than I would have imagined it could. Very little steering lean and braking is better than ever. I highly recommend both to everyone that has a JK, it truly made it much more fun to drive.
I have 66,000+ miles on my rig over a lot of various terrain with a lot of weight on this heavy vehicle and towing my RTT trailer and have had no problems. I would say that replacing the factory springs was the biggest contributor to the improvement in payload capacity but I share the story of my vehicle stages to show that every modification that you make certainly impacts the vehicle and needs to be accounted for. I believe that the frame and axles are excellent and have not seen or heard of problems with the factory D44 rear or non Rubi - D30 front axles as mentioned previously. If you want to increase payload I would look to the factory coils and shocks first. I have heard of overheating of the Tranny in my vintage of JK but havent had that problem myself - I would add a tranny cooler if that became a problem.
The reason I post is that I noticed with the stock suspension, when I carried a heavy load or even just had four passengers and my dogs on board that the vehicle handled poorly. So I started looking at how to improve this:
Stage 1: I added 2 1/2" spring spacers and wheel spacers which improved the ride dramatically. Handling was much better than stock. The ride still suffered with a full payload though. And of course I wanted a winch and a front bumper that could handle it. So...
Stage 2: Added the front bumper/winch and the the front end took a dive and handling / braking was poor. So I added a 3" Teraflex Suspension, adj. track bar, with springs and shocks. Also added the 35" tires, rear bumper, and rock rails, etc increasing the vehicle weight quite a bit but the ride went back to normal and the handling was better than stock with no payload problems! This lead me to believe that the stock springs are a big part of the problem with the weight capacity of the vehicle. Also had little impact on the mileage -went from 17 to 16mpg. Leading to :
Stage 3: I added a Gobi Rack, dual battery system, and probably several more things I am missing. This cost me mileage - went to about 13mpg. I swapped out the gears to 5.13, added heavy front control arms and added axle gussets to the front axle. Even loaded down with extra camping items on the roof, travelling offroad, and a full payload of passengers and dogs, the Jeep handles much better than stock. Mileage went back up to about 14.5mpg with the gearing. Towed a 900# off road trailer with RTT for a few thousand miles which dropped me to about 13mpg.
Stage 4: Never thought there would be a stage 4, but I recently had some vibration in the front end and traced it to a bad drag link. I added the AEV hi steer kit and the AEV geometry correction brackets to the front. The combination of the two made the Jeep handle better than I would have imagined it could. Very little steering lean and braking is better than ever. I highly recommend both to everyone that has a JK, it truly made it much more fun to drive.
I have 66,000+ miles on my rig over a lot of various terrain with a lot of weight on this heavy vehicle and towing my RTT trailer and have had no problems. I would say that replacing the factory springs was the biggest contributor to the improvement in payload capacity but I share the story of my vehicle stages to show that every modification that you make certainly impacts the vehicle and needs to be accounted for. I believe that the frame and axles are excellent and have not seen or heard of problems with the factory D44 rear or non Rubi - D30 front axles as mentioned previously. If you want to increase payload I would look to the factory coils and shocks first. I have heard of overheating of the Tranny in my vintage of JK but havent had that problem myself - I would add a tranny cooler if that became a problem.
