What are you looking for with a visual inspection?
Mostly cracks which could lead to broken gear teeth, but also signs of excessive heat, chips, and wear patterns. The lower quality gears are going to have machining marks in them right out of the box. And with those lower-quality gears you will see stress cracks show up almost immediately because the machining marks left behind create areas for the stress cracks to originate.
Make sure to look for quick-change...
Make sure to look for quick-change gears made from high-grade 9310 steel. The higher quality steel also makes aggressive lightening programs possible.
With higher-quality gears, you have steps taken during the manufacturing process to prevent the stress cracks from showing up. For example, we offer an extremely high-end quick-change gear. The majority of your gears are hobbed to create the gear teeth, and that's all that done. (Ed. note: Hobbing is a machining process which uses special type of milling machine that progressively slices into the piece being milled in a series of cuts. Compared to other gear forming processes it is relatively inexpensive.) But our gears are stone ground as an additional process, and that smoothes out the surface of the gear teeth. The process creates a perfect tooth mesh overlay for very efficient, trouble-free operation. You would think that the very high-end gears like this would be exclusively for the big money touring teams, but a lot of my crate guys are using them because they exhibit less friction and that, in turn, also heats the oil less. The result is these gears transfer more horsepower to the rear tires and you also get an improved gear lifespan.
Speaking of, if you aren't tearing up gears with abuse or a wreck on the racetrack, what is the useful lifespan of a set of quick-change gears?
Even if you're buying a quality set of gears—and especially if you're racing the same track weekly so you have the same set of gears in the rearend all the time—I would definitely recommend cycling them out at the end of the season. I understand that everybody is working under a budget and you hate spending money that you don't have to, but if you want to eliminate the chances of a catastrophic failure you need to cycle those gears out before they have a chance to fail on you. After all, the cost of a new set of gears is a lot less than the cost of making repairs to your rearend if hang onto a set of gears too long and they go out during a race. That may sound a bit extravagant, but even a set of high-quality gears is less than the cost of a right rear tire.
One of Bulldog’s super lightweight...
One of Bulldog’s super lightweight live axle quick-changes for Sprint Car racing.
I'm mainly speaking about the racers running 410 Sprint Cars or Unlimited Late Models where they are pushing 600 horsepower or more. If you are running crates, you can probably get by with changing out your quick-change gears less often. You can always give us a call with your specific setup and track and we'll try to give you a safe estimation of how long you can go before needing to cycle out your gears.
Is there a gear oil that works best?
We have an oil made specifically for our equipment, which is a 70-90 weight fully synthetic gear oil that we developed specifically to our requirements. We spent two years field testing it in what we consider the most severe conditions in the country—which is 410 Sprint racing in Central Pennsylvania—and came up with a formula that we feel is superior to the rest. We worked with an oil manufacturer to help us develop the product and they did a lot of dyno testing independent of our own tests that backed up our findings.
A quick-change uses a jackshaft...
A quick-change uses a jackshaft that runs through the bottom of the bell to spin the quick-change gears in the back of the rearend.
When it comes to what's most important for a racing gear oil, the answer is “everything.” It has to provide excellent lubrication, it has to have a wide heat range, and it has to resist breaking down. If it can't do everything well, it isn't going to be able to do the job on the racetrack. That's why we went to the trouble to develop our own gear oil specifically for our quick-change rearends.
How often should the gear oil be changed?
After break-in you should fully change the oil. With the high-horsepower stuff like the 410 Sprint Cars or Super Late Models, they are fully broken in after one race. Obviously, after break-in we recommend a complete dump and flush. After that, we usually recommend replacing your gear oil at 150- to 200-lap intervals. And that averages about every four races.