Sport Truck readers may recognize our Reverse Sleeper project (Feb. '05), where we enhanced off-road prowess and visual appeal to an otherwise mundane '00 GMC Sierra pickup. Now, it's nearly six months down the road and we have been driving the Nittos off the truck, including a few off-road excursions. Nothing outrageous and no big-air jumps or anything, but through it all, a bunch of miles were logged. From all this use and abuse, we acquired a very unwanted accessory-spring wrapup.
Leaf spring wrapup is a terrible thump of a feeling that occurs commonly during stop-'n'-go operation. Pull up to a stop sign with the brakes applied and as you let off the brake, it slaps your truck with an ungodly surge, which is not very good for ride quality-to say nothing of what it is doing to mechanical parts, such as shocks, U-joints, and leaf springs. This simply had to go, but how?
We contacted our friends at Hellwig Suspension Accessories to get some answers to our dilemma. We found our diagnosis was correct and the culprit was the leaf springs. The primary function of a truck's leaf spring is to carry the vehicle's weight and to locate the axle under the vehicle's frame. Spring wrapup will occur under hard acceleration or when torque is applied to the axle through the driveshaft and pinion gear. This rotation of the axle position causes a leaf spring to flex or wrap up from its normal configuration. Leaf springs by their own design will want to unwrap from the unnatural shape they have been forced into by the axle torque. This unwrapping of the spring causes wheelhop. When wheelhop occurs, traction is reduced and wear is increased on the suspension components.
With that knowledge, we now know what our problem is. The big question is how to get rid of wrapup without increasing the stiffness of the springs and shocks, which would reduce suspension travel and ride comfort. The cure was found in Hellwig's Helper Springs. A helper spring is a spring that works with an existing spring to give it more support. These units are easily installed with standard handtools. This configuration reduces the undesirable effects of wheelhop by efficiently transferring engine torque to the ground.
We contacted J.C. Whitney to order a set of these helper springs. In a matter of days, our box arrived and we were out to the garage for some wrench time. Hellwig's Helper Springs are extremely easy to install. Each helper spring attaches to the existing spring pack by means of a U-bolt and crossbar. The kit came complete with all the necessary hardware and well-detailed instructions.
If you have about 20 minutes, including a trip to the fridge, you can fix leaf spring wrapup on your truck. It can be a big problem that has a simple solution.
 1.Miles and abuse have taken...  1.Miles and abuse have taken their toll on our leaf springs, along with the lifting blocks that aggravate the situation. This weakening is the culprit that allows spring wrapup to occur. |  2.This drawing provided by...  2.This drawing provided by Hellwig Suspension Accessories shows the unwanted travel that the leaf spring is going through, causing the wrapup. If you think it looks bad, the feel in the truck is unbearable. |  3.This is the Hellwig Helper...  3.This is the Hellwig Helper Spring kit as it arrived from J.C. Whitney. The kit comes complete with everything needed, including very detailed instructions. |
 4.As shown in the drawing,...  4.As shown in the drawing, the helper spring attaches to the top of the original leaf spring. The bends in the helper spring are for a reason and provide added strength without drastically effecting ride quality. |  5.The installation was simple,...  5.The installation was simple, and within 20 minutes, we were road-testing for results. Problem solved, and there was not even a hint of spring wrapup after the installation. | |