GM Medium Duty door hinge
problems and corrections
 
   
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Beginning in 1988 GM revised the door hinge system on their medium duty and full sized pickup trucks. The biggest change was the elimination of traditional 'bolted on' hinges and the introduction of welded hinges. The hinges were no longer attached to the door or body with bolts, but were now robotically MIG welded to the door and body from the back side of the hinge. The doors were then attached to the body using a replaceable pin and bushing design. This same system was first used on 1982 S-10 series trucks. The primary purpose of these changes was to simplify production of these vehicles, and improve serviceability of the hinge pin and bushings.

This hinge system worked very well while these vehicles were relatively new, but with the passage of time some significant problems began to appear.

  • The flange of the top bushing in the upper door hinge would wear away and allow the bushing to fall out of the hinge.

  • The hinge pin could then begin to wear away at the bushing bore in the hinge. Or the pin would wear completely through the bushing wall, and then against the hinge itself.

  • The replacement of the worn out bushings and pins was often made more difficult because the new bushings would not stay firmly fixed in the hinge because the bushing bore in the hinge had become worn oversized.

  • The locations where the hinge pin 'anchors' in the hinges would also become worn to the point where they were unserviceable and would no longer firmly hold the pin in position.

These problems eventually lead to a condition where the doors will not close properly even with new hinge pins and bushings installed. This problem is further aggravated when the vehicle is used in a commercial application. One of our customers has a fleet of beverage delivery trucks that experience in excess of 150 open/close door cycles per day. To keep some of these vehicles in operation the hinges themselves must be replaced. A ghastly and very time consuming process even for the experienced professional or fleet garage technician, the old welded hinges must be cut from the body and door, and then the new hinges bolted in place. This also involves readjusting the door position within the cab door opening. Another problem with retrofittingreplacement hinges, which are attached with bolts is the inability to match the structural integrity of the original welded hinges. If the worn out hinges are not replaced, they will eventually cause cracking of the door and in some cases, the cab itself. We have witnessed several situations where the entire cab was replaced on a municipal vehicle due to cracking and wear of the cab at the hinge and striker area. On this particular vehicle the sagging door had actually worn a hole in the cab.

The heart of this problem is the lack of being able to properly lubricate the hinges. Aerosol lubricants are commonly used to lubricate these hinges, but only lubricate the exterior of the hinge joint.

Our repair system includes a provision for pressure lubrication to ensure the hinges will last the life time of the vehicle. To accomplish this we have designed an advanced hinge repair system, utilizing the latest aerospace and machining technology. The system design has bushings made from a long wear life material and pins made from aerospace grade steel which is heat treated and plated to exacting specifications. Our pressure lubricated design is currently Patent Pending and unique in its application. The complete repair process is very straight forward and requires no specialist training or expertise. The step by step photo instructions on this CD illustrate the straight forward process and allow the mechanic to understand the complete process before undertaking the task. It is also a useful reference whilst the repair is underway.

We have a custom made step drill to drill the hinges precisely to accept our bushing for a perfect press fit with a custom made mechanical press to do so. We even make a special Anchor Repair (AR) bushing to replace the area of the hinge where the hinge pins are fixed into the hinge.

The entire system is designed to be installed using readily available hand tools; angle drill, hammer, punch, ½" wrenches, small grease gun with nozzle adapter. We also have available a specially designed door holding fixture to hold the door securely and safely during the repair procedure.

 

GM Replacement Hinges

In early 2000 GM replacement hinges began to incorporate a stamped sheet metal bushing which utilized Teflon® lining inside the bushings. The lining works very well when the bushing is new, but the sheer weight of the door acting on the hinge will quickly extrude the lining materiel from the bushings. The new style bushings cannot be replaced with the old style bushings, therefore the new style can only be replaced with new style. Beginning with the 2003 model all GM medium duty trucks use the new style bushings. The new style bushing simply cannot match the structural integrity of the old style bushings. Even though they have a Teflon type lining they have a much smaller surface area. They are manufactured using the die stamp method on sheet metel. This creates a non precision part, made very cheaply. The poor service life reflects the cheap and basic manufacture of the door hinge parts.

We have developed a special bushing to be used in place of this new style bushing. Our bushing incorporates a provision for pressure lubrication and has enhanced structural integrity. Installation of our bushing requires drilling the original bushing location slightly oversize to accept our bushing which is then a press fit.

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©Andy L. Sherrer 2006