Shot peening the best post production way to strengthen metal and when it comes to transmission gears you can not get the increases in strength and durability that shot peening brings from any other process period. The most demanding applications, where failure is not an option, use shot peening to increase the service life of the component. Be it aircraft landing gear, the compressor & turbine blades in a jet engine or the connecting rods that are inside your racy engine, they are all shot peened. The reason is because if you need to make it stronger, but can’t make the part larger or make a material change to the part, then shot peening is the best solution.
Shot peening is a cold metal working post process which is done to the gears to make them tougher and last longer. The gears are stacked onto a mandrel and loaded into our shot peening machine that uses 45 HP worth of compressed air to hurl the highest quality of specially conditioned cut-wire steel shot available at the gear. As the shot strikes the gear it peens the surface, leaving very small indentations or dimples. These overlapping dimples develop an even layer of metal in residual compressive stress. This compressive stress is a good thing for it is well known fact that cracks will not initiate or propagate in a compressively stressed zone, such as the root radius of the gear teeth, where nearly all gear teeth failures start. Rule of thumb: shot peened gears generally will exhibit strength of a gear that is 25% larger in cross section. Try to get that kind of improvement in strength without changing the material of the gear and is the reason why a car that makes over 725 ft-lbs of torque has been able to use our transmission 4 years without failure or gear replacement.
In 2004 I quietly started sending parts out to get shot peened to see how the gears held up against non-shot peened gears. The results were amazing, with the shot peened gears tooth breakage issues seemed to vanish while at the same time the surface finish of the gear teeth were looking like new even after a season of hard use. Realizing the benefits from shot peening and how much I was spending to get it done elsewhere, I had to get one of these machines. After looking for nearly a year one showed up at an auction that was specially built for a college university and that’s what TRE is using to shot peen. Recently I decided to not only shot peen the parts that we use inside our transmissions but to start shot peening all the highly stressed gears that we sell. The reason for this is because most people are wanting to build a stronger transmission but haven’t heard of shot peening or they don’t realize just how good of a service shot peening really is in the first place. If you’re looking to rebuild your transmission you should buy your parts from us because they now come shot peened and will prevent your transmission from giving up the ghost before you’ve had a chance to completely kick its ass.
Not to be confused with an ordinary shot blaster that closely resembles a lawn fertilizer spreader, the type you commonly find at an engine shop, the machine that TRE uses is a specialized piece of equipment that was designed and built for the purpose of shot peening gears. This machine allows for calibration to provide the correct level of intensity, shot pattern and coverage of the work piece. We do a 2 stage process and use premium quality specially-conditioned & sorted cut-wire steel shot. This is ideal for shot peening gears because of it’s uniform size & roundness and proper hardness. The shot peening machine is semi-automatic allowing precise control over all parameters for perfectly shot peened gears every time.
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There are many parts to the drive train that can be strengthened from shot peening:
- shift rail ends
- input shafts
- intermediate shafts
- center differential housings
- spider gearsets
- cross shafts
- output shafts
- differential housings
- transmission housings
- transfer case pinion shafts
- ring & pinion gears
- axles & axles cups
- hub & sleeves
- shift forks
Shot peening speaks for itself and I have personally experienced impressive results. Many manufacturers of high-end transmissions also shot peen their gears to improve strength to maximize the strength of their gearing for high torque applications.