Tech Tip #233: Common Questions about Flywheels, Ring Gears, and Power Takeoffs

Dr. Diesel
Written by Dr. Diesel


Dr. Diesel™ is on the phone all day long helping people with parts for Deutz and Perkins industrial engines, Rockford power takeoff clutches, and industrial flywheels. He never gets bored. However, after a while, he sees a pattern showing up.  He asked us to put his thoughts in a Tech Tip so that he could share the common questions with you. Hopefully, they will be helpful to you.

  • Flywheel or ring gear?


Many people call us looking for a flywheel when all they really need is a ring gear. A ring gear is a removable item that is installed on the flywheel and engages with the starter drive. Most have part numbers on them. All have critical dimensions. We at one time did so many ring gear installations that we had a dedicated custom ring gear oven. To install a ring gear, just use a torch and light that sucker up to install it.


If you need to replace a ring gear, we do need numbers and dimensions from the old ring gear.  Because we stock every Deutz ring gear offered, if you can’t give us the model and serial number, we can work with your OD, ID, and a tooth count from the old ring gear. We stock a huge variety of Perkins and Deutz ring gears and should be able to same-day ship one to you.


If you don’t need a ring gear, but do need a flywheel, we stock new clutch-type flywheels for the Cummins B Series, John Deere Series 300, and other industrial engines.


If you are running a John Deere, examine your flywheel carefully. The circle of bolt holes around the pilot bearing is too close to the pilot bearing hole and often the John Deere flywheel is damaged. Not to worry, we stock this clutch-type flywheel and can ship you one with your WPT, Twin Disc, or Rockford clutch order.

  • The SAE rules


Or why you can’t always use a Deutz engine for a home-made Zamboni. We get at least 4 calls a day from people who have big dreams about building a power unit in their back yard. Some even have plans to use an engine from a school bus that has been parked during Covid. Sorry guys, but if you have plans to mount a Rockford or WPT power takeoff clutch to the back of a school bus engine, you first need to locate an SAE bellhousing.  See Tech Tip #114 for our SAE Bell Housing chart.

  • Flat-faced vs. step-type flywheels


Dr. Diesel™ to the rescue. So, you have an engine all lined up and ready to be transplanted into your project’s chassis. But the flywheel on the engine is a “flat-faced flywheel” and won’t accept a Rockford style clutch. Dr. Diesel™ can usually hook you up with a suitable flywheel for under $1000. But keep in mind that you have to have the correct SAE bellhousing.

  • Variable vs. Fixed speeds


OK, you’ve done your homework and read this far. But before you pull the trigger on your little project and rip a Perkins engine from a low hour ONAN generator set, you need to understand, almost all generators run at a fixed 1800 RPM. That may be too slow for the V8 snow blower project you have cooked up.


Dr. Diesel
Written by Dr. Diesel
Knowledge is power. Power to build ties to engine users. To build a relationship with our customers, we share with you our 105 years of knowledge in many ways. We have this special section called “Ask Dr. Diesel™” where you can pose questions about engines, transmissions, industrial hand clutches, exhaust scrubbers, etc.

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