Transmission case swap

[Headofpan]

Hi everyone,

My panhead is running with a revtech 4 speed transmission that has had the rear ear for the support bracket crudely cut off.

This was done before my ownership.

I believe that this may be a shovelhead transmission fitted with a shorter main shaft (hence the bracket being cut off) but I am definitely not an expert on transmissions so if anyone could shed any light on what I have that would be great!

My real question is:

Are the internals on 4 speed transmissions (repro and OEM) interchangeable. Can I swap the internals from this case into a repro panhead transmission case? Is this feasible? Im not looking to create a show bike but the cut off bracket does look unpleasing.



My other option is to dress the area where the old bracket was to tidy it up. My only concern is there being enough "meat" on the case as to not create a hole in the side of the case.

Appreciate your thoughts!

Cheers,

Tom

[Mongrel505558]

Not knowing about the aftermarket transmission I can only assume, but I don't think Rev Tech or anyone else would deviate much from the four speed design. The internals between a pan 4-speed and a shovel 4-speed are interchangeable to a large extent, but there are still a few curveballs depending on the year of the shovel transmission. Obviously the mainshaft: There were three different lengths, not counting ones for belt final drive. The pre-65 kickstart only was the shortest. Some length was added for the 65-69 electric start models, and more length was added for the alternator '70 and up. The pre-'65 cases didn't have the "ears" to attach to the aluminum inner primary chain case and can only be used with the tin primary or open belt (which can be made to work with anything). Be aware that the countershaft changed in early 1977 from a loose roller design to two needle bearings similar to the inner cam bearing. The diameter of this countershaft is slightly different and different case bushings are used to support it. Don't know what's in the aftermarket box. Third gear design changed some time in the late fifties from a bronze bushed gear to a plain steel gear. The shifter fork shaft changed slightly during the shovelhead years. You can mix and match parts as long as you are consistent with things like mating gear tooth counts.

[RUBONE]

There are no internal differences between a Panhead case and a Shovelhead case up until '77. All the internals will interchange , just don't randomly mix parts if you aren't aware of things such as different ratio gear sets, etc. Switch ALL the bits, not select items. And there is no advantage to switching cases, especially running a belt as the shovel case may make alignment easier. You can grind the rest of that ear off and it will look just like a
panhead case.

[RooDog]

If I were gonna grind the rest of the two mounting ears off, I would also lose that Revtech logo too....
And you will need some way to adjust the tranny once installed on the bike....
....RooDog....

[Andygears]

I would empty the trans case and grind off the ears and logo. Then, bead blast the case or polish it for a uniform appearance. Couple external differences to note: the early case has a cast in lug on the bottom to help alignment, and as RooDog noted will need an aftermarket alignment/tensioning setup underneath. Also the front two holes for the later inner primary go thru into the oil and need to be sealed with set screws or bolts. And the countershaft also changed in ‘64/‘65 to an O-ring on the shaft instead of the 4 screw cap on earlier models.

Andygears

[RooDog]

This handy little air driven device, the Crud Thug, with its stainless steel wire wheel is great for reconditioning worked aluminum, polished, ground, machined, back to an almost undetectable sand cast textured finish. Not exactly a perfect match to "as cast", but close enough to not be obvious and catch one's eye. It's better than sand blasting to camouflage repair work, or fabricated pieces. A restorer's delight.
Originally designed to remove auto body seam sealer and undercoating materials, and metal conditioner prior to welding, I found it great for the tasks mentioned.
....RooDog....

Crud Thug.jpg (41.07 KiB) Viewed 127 times

[RooDog]

Tranny adjuster....

DSC01697.JPG (144.09 KiB) Viewed 127 times