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Ford Banjo Rear End Open Drive Conversion

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In this tech article I will be showing the process of installing an open drive conversion on an old Ford Banjo rear end. This particular rear end is being installed in my ’29 highboy roadster. The car I am building aims at being a traditional style car like they would have built the ‘50s. I really look forward to having a quick change someday, but until I find an old vintage “Culver City” Halibrand, I am going to settle for a stock banjo over a modern 9” or 12" bolt Chevy.

This particular rear end was removed from a ’41 Ford sedan by a good friend of mine in Indiana. His car was destined to become a Street Rod. Yeah, it is the kind of car that is now painted in monochrome, sports a 9”, and Lexus seats. Not a bad car, I like those types of hot rods too, but my roadster is a different build. I love traditionally built hot rods, so anytime a friend wants to part with original Henry Ford parts I am happy to help them out!

Speedway Motors offers a wonderful kit to utilize an original banjo rear end and convert it to an open drive. This does away with the original torque tube and driveline allowing you to use a more modern style drive shaft.

If you are purchasing an open drive conversion there are two options for you depending upon what spline your differential is. You can purchase either a 6 spline, 10 spline, or Model A kit.

My 41 Ford is a 6 spline and I only found this out after taking care of step #1, removing the original torque tube.

Once I had the kit in hand I admired the nicely machined parts. I decided to give them a quick coat of paint.

After painting the parts I gathered up some tools and other materials that I needed to do the job.

  • Shop towels
  • Silicone gasket sealer or gasket maker
  • Some good cleaner for the mating surfaces (I used lacquer thinner)
  • A hammer and drift punch
  • Thread locker
  • Open ended wrenches
  • Drill
  • ¼ NPT tap

Once I had the torque tube removed the next step was to clean up the mating surfaces for the gasket to properly seal. If you have an old Ford rear end, chances are it will be oily. I used some patience, some towels, and lacquer thinner to work really well during this stage!

Next, I put a very light bead of silicone around the bearing retainer where the gasket installs. I went around each of the mounting holes, which is probably overkill, but am glad to report my rear end hasn’t leaked yet so it might be a good idea! I love Permatex brand silicones because it is what I have always used, but any good gasket sealer should work.

Make sure to align the oil slot in the housing flange with the oil drain hole in the differential housing.

Working in a cross pattern, install the pinion housing on the differential using six 3/8-24 x 1” bolts and lock washers that are supplied in the kit. Leave the bolts loose at first to allow the yoke to alight the pinion seal.

I installed the pinion seal after mounting the housing flange to the differential. It wasn’t a hard task, but if you want to make your life easier, install the seal first!

Be sure to lubricate the pinion seal with some light oil.

Next slide the yoke onto the pinion shaft. Be sure to align the coupler pin hole in the pinion shaft with the holes in the yoke.

Drive the ¼” pin into the couple hole. I had to use a drift punch for this operation. I installed the bottom set screw so it was flush with the surface and then drove the pin against it before installing the second and final set screw. This ensured the pin was centered.

I applied thread locker to both of the 5/16-18 set screws just to make sure they didn’t go anywhere.

To complete the installation of the actual open drive portion of the kit you simply need to tighten the six housing flange bolts.

The final assembly step is to install the required vent. It is important to vent the rear because by converting it to an open drive you are sealing up the original vent, which allowed hot gasses and excess oil out into the torque tube.

This vent needs to be installed on the top, between the differential bearings and the axle flange.

Guessing my rear end is in good enough shape to run without a rebuild I did not want to tear it apart to complete this process. I had anxiety about drilling a hole in a rear end, worried that I would introduce damaging metal filings into the axle tube, so I proceeded with caution.

You need to drill and tap a 1/8 NPT hole for the fitting. I did not have a magnetic drill bit, which works very well for this operation, so I improvised. I happened to have some mysteriously strong magnets from another application that I hooked to the standard drill bit I was using.

It did a great job of grabbing all of the debris from the drilling process! I also drilled the axle hosing upside down so gravity would be working to my advantage making it harder for anything to fall into the rear end.

Of course I did the exact same thing when it came to tapping the threads. The magnets grabbed all of the particles that I didn’t want falling inside the housing.

When finished the hole was clean and ready, and the fitting installed without issue.

With this done, my banjo is ready to go back in the car! With a little luck it will get me down the road long enough to save up money for my quick change center section!

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