Tech Tip #41: SAE Bell Housings Made Easy!

Helpful table for SAE bell housings

For those of you purchasing a new or replacement WPT Power®, NACD®, Rockford™ or Twin Disc® Power Takeoff or simply installing a new transmission on a Perkins® marine engine, identifying the SAE Number of your bell housing is the first step.

First things first. A group of smart people got together years ago formed a group called the Society of Automotive Engineers. This group, now simply called “SAE”, came up with a system to categorized bell housings into standardized sizes. The higher the number the smaller the bell housing. I know this sounds counterintuitive, apparently engineers don’t always see things the way we do.  Today, all engine manufacturers including Deutz®, Ford® Industrial, and Perkins use SAE standard bell housings.

How To Determine The SAE Number? Take a look at the chart below. Stand facing the bell housing of your PTO or the flywheel housing of your engine (to line up properly both will have be the same SAE size).  Now, simply from the center of one of the mounting bolt holes across the housing to the center of farthest bolt hole on the opposite side.   Take your measurement to the chart below and you will find your housing SAE size.  Of course, as confirmation you can also count the number of bolt holes, bolt diameter, and bolt size. Generally speaking, most small engines like a Perkins 4.108 are SAE 5, engines from 60 to 80 HP like a Continental F163 or Perkins 4236 are usually SAE 4 or 3, and engines above 150 HP, such as a Perkins 6.354 or Perkins 1006T series, are usually SAE 2 or larger. That said, the housing size is typically a determination made between the engine manufacturer and the equipment manufacturer in order to match the engine with the machine doing the work.  While you may not see the SAE 1/2 that often, they are out there, so we have added it to the list just in case.

SAE BELL HOUSING SIZES MADE EASY