Suspension Mod

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So, one of the things with the Promaster chassis is that it’s setup for hauling big weight. Now that’s all great if you’re a stone mason who’s hauling a flat of stone to your next project… but if you are building a light weight camper you are left with a nose low tail high stance, that jolts over each bump in the road. The mod that has become popular is to remove the secondary leaf spring. Once you have the spring off the remaining spring is much more compliant. In the process it lowers the rear of the van by 3 inches as well. Now it sits much more level and has a softer ride. At the same time I added some Sumo Springs which are a urethane bumper to replace the factory bump stops. The difference is they are a softer material and provide variable resistance as they take up the load. So they actually are setup to touch the spring in the lightly loaded condition. This provides protection as you load the vehicle and stops some of the body roll as well. I think this will be a great combination for the weight that I will be hauling with this van.

Tools I used

  • 7/8″ deep socket
  • 9/16″ socket
  • 3/8″ air impact driver
  • 24″ breaker bar
  • Hammer
  • Cold chisel

First up are some before pictures. You can see the 2 springs and the orange factory bump stops. You remove both U-Bolts to release the springs.

Here you can see how much distance there is before the factory stop comes into play.

Here you can see the secondary spring that’s on the bottom of the primary. This is the one we will be removing.

Once you remove the u-bolts there is a cover that comes off. Under this cover there is a nut that needs to be removed. This is the bolt that holds the springs together and indexes the springs to the rear axle with a little hole for the head of the bolt. It’s best to spray some liquid wrench on this nut and then leave a little pre-load to keep the head from spinning. I hit it with an air impact wrench and it came right off.

Here you can see the rear shock mount that also needs to be loosened and removed. Once that bolt is out the axle drops free of the springs and you can remove the bolt and secondary spring. re-installing that shock bolt is made much easier if you have a secondary jack under the axle. This way you can very slowly raise the axle in place until the shock bolt just slips back in place and you can tighten everything up.

Just looking at the other side, this will come next.

Here is the Sumo Spring which replaced the factory orange bump stop. You can already see how much longer it is. You just hand tighten it with some loctight on the threads.

Here you can see the new shorter bolt secured in place. This is a shorter grade 8 bolt that’s just there to secure the head into that little depression on the top of the axle to keep it in place once things are tightened back down. The bolt I was using was just a touch too long to fit under the cover plate, so I drilled out the hole in the center that’s already there to enlarge it to allow the end of the bolt to fit in the hole. It comes up to just flush with the top of the plate.

The u-bolts go back in to secure the spring in place. Just one spring now so the bolts are quite a bit longer than needed, but it all works fine. I took the u-bolts off and cleaned them up with a drill mounted wire brush to remove all the undercoating so the nuts would spin on further as needed. I’ll re-coat the undercoating once it’s all done.

Once the second side was done you can see how the Sumo Spring contacts the spring seat just enough. It’s not very tight in the lightly loaded condition.

The job is made much easier if you have a secondary floor jack to raise and lower the axle while the van body is secured with the factory jack on the body mount.

Another picture of the Sumo Spring.

And here’s the final view of the van with the rear now lower. Much more normal looking. I think this will be a great setup.

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