Transmission Installation

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Transmission Plate

  There are two different types of transmission plates available for four- speed transmissions (one type for the five-speeds). One is a ‘fixed’ plate and the other is ‘adjustable’. I use both types depending upon the particular project.

The plate on the left in this photo is the adjustable type and the chromed plate on the right is the fixed type. If you look closely, you can see that the mounting slots on the chromed plate are about three-eighths of an inch shorter in length so that indicates it was designed to be used on bikes 1965 and up.

You can still adjust the tranny in the fore and aft direction if you’re using a fixed plate by installing the so-called ‘even-pull’ adjusting bracket.

Depending upon the model year, between 1936 and 1984 when Harley made the four-speeds the plates differed slightly in configuration, but the bolt patterns are identical.

In 1965 the factory came out with the cast aluminum primary covers and from that point forward in time the plates had short ‘slots’ to accommodate transmission fore and aft movement since primary chain adjustment was accomplished within the cover and not by physically moving the transmission. The ‘long-slot’ pre 65 plates in my opinion are the best to use.

Transmissions

Harley introduced the four-speed transmission in 1936 along with the new Knucklehead motor. The unit stayed in production through 1984 with minor modifications over the years but there are really only two things a builder has to consider when selecting what tranny to use. The first consideration is whether or not you’re planning to run with a cast aluminum primary and the second is what type of shift mechanism you’re planning to use.

The transmission case itself was altered in 1965 with the addition of ‘ears’ extending fore and aft from the main shaft containing threaded studs that mated to the new cast aluminum inner primary cover. These cases are easy to identify as seen below.

In the above photo also note how long the taper is on the main shaft. We’ll talk about that a little later. If you’re not going to be using the cast covers then you’ll want to use a pre-65 tranny or what most folks call an ‘earless’ housing as shown below.

The difference is readily apparent in the two types of cases when viewed from the sprocket side. The cases without ‘ears’ are intended for bikes running stamped steel primary covers where primary chain tension is accomplished by moving the entire transmission.

The second consideration being the shift mechanism gives the builder three options. The first is what’s called the ‘Jockey’ top, the second is the ‘Ratchet’ top and the third is the ‘rotary’ top, also called a ‘cowpie’ top. The ‘tops’ are actually the ‘lid’ of the transmission case and contain the entire shifting mechanism.

Below is photo taken from the Jockey Journal that shows a Jockey and Ratchet lid side by side.

Note that on the Jockey shift lid, shown on the left, the shifter arm is just a short, stamped link but that the Ratchet top, on the right, consists of a large 4-inch diameter cylindrical ‘drum’ that houses the actual ‘ratchet’ components.

The third lid or top is commonly called the ‘cow-pie’ by bikers, the ‘rotary top’ by the factory. You’ll sometimes here them referred to as ‘washing machine’ or ‘pancake’ tops,

The units were made from 1979 to 86 so they were contemporaneous with the more conventional transmissions.

These are easy to spot but rarely used for chopper projects. I got this snapshot from eBay. These are actually very good transmissions from a mechanical standpoint but just never lent themselves to the ‘chopper image’ sort of thing. There are a few outfits that make Jockey shift handle mechanisms for them but for the most part they are ignored by a large majority of builders.

Shift Patterns

The original Jockey top transmission was designed to be shifted from a hand operated lever mounted high up on the frame that extended through a ‘gated’ bracket on the fuel tank. Linkage ran back to the small lever shown the photos above. The sequence of the shift pattern was 1st all the way forward and then back for neutral, back again for second, and third in progression. You could easily skip a gear if necessary, when downshifting. In technical manuals the shift pattern is said to be 1,N,2,3.

In 1947 the pattern was reversed and first was located closest to the rider and fourth furthest forward.

Hot Rodder’s in the late forties and fifties decided to eliminate the cumbersome shifter set up and made handles bolted directly to the transmission shifter arm and the ‘Jockey’ shift came into being. The name came about due to the similarity of the bike rider reaching down and back to shift much as a horse racing jockey is seen in the same posture with his whip.

The shift handle on a true Jockey top transmission moves in its position as each gear is selected and then stays in that position until you select another gear so you can tell just by glancing down what gear you’re in. The true Jockey top shifter is very fast since all shifts are made just by slapping the shift knob with the palm of your hand once you’re in first.

The Ratchet top jockey shift pattern is exactly like the name implies you ‘ratchet’ through the gears with the handle remaining in the same relative vertical position between shifts. The foot shifting pattern is one down for first and then up in sequence for neutral, second, third and fourth. You can’t skip a gear without doing a ‘double tap’ with the pedal.

It’s cheap and easy to convert a ratchet top transmission to a jockey style but the ratchet shift pattern will still remain.

The jockey shift pattern with a ratchet top is slapping the knob back four clicks to 1st and then having to slap the knob forward for neutral, second, third and fourth.

Baker now makes a top they call the N1 and this shift pattern is well suited for ratchet shifting since neutral is all the way at the end of the pattern and then first, second, third and fourth follow in sequence.

The foot shifted ratchet tops can easily be converted to a Jockey shift operation simply by removing the stock shift arm from the drum dust cover and installing an aftermarket shift handle in its place.

The operation takes about ten minutes at the transmission but then you’ll have to install a clutch pedal and linkage to replace the old hand operated clutch.

A good transmission can easily set you back financially almost as much as a basic ‘starter’ engine. The picture below shows two examples of quality.

The unit on the left is a ‘Baker’ that comes in at a base price of around $3500 and the unit on the right is a generic Brand-X sold at numerous cycle part outlets with prices ranging from $780 to around $1100 as of May of 2020.

Outwardly there is not much difference until you start to look closely. The less expensive unit uses slotted head fasteners. The sprocket does not appear to be heat treated. The kicker arm is just begging to be broken and the finish is raw sand blasted aluminum. The Baker uses stainless socket head fasteners, has a hardened sprocket, a massive kicker (not shown) and the finish is a finely blasted and anodized. Internally there is a cosmic difference between the units and that’s primarily what you pay for.

The entry level tranny, new or used, will usually work just fine behind a mild motor driven by a conservative rider. If the unit is new and you don’t Hot Rod it too much, you’ll probably get a year or two out of it before having any problems. The high-end Baker will take some serious horsepower in front of it and some significant abuse from a rider and keep on working, sometimes for decades before needing any work.

Tranny Installation

Early on we already verified that the transmission plate mounting holes matched the frame mounting points but it’s also a good idea to make sure that the holes in the plate also match the studs on the bottom of the transmission. Most of the time you’ll have no problem here but it’s worth checking. If all is well, go ahead and loosely bolt the plate to the frame.

When dealing with the transmission it’s easier to work from the left side of the frame even though these snapshots are taken on the right.

Grab your tranny and place it into position on the plate being careful not to ding up the threads on the studs in the process, the studs are 3/8-24 (fine) so it’s easy to mash up a few threads.

Fit the nuts to the mounting studs and make sure you can move the tranny back and forth by an inch and a quarter.

When the unit is pushed all the way to the rear you should have at least an inch, preferably a little more, of clear space between the seat post and the edge of the tranny case as seen below.

When you push the tranny forward it should actually contact the post. This frame has had the post dimpled since it’s set up to handle the larger 5-speed cases as well as the old 4-speed so we have no problems here as we can push it up until it just barely contacts the post.

You can barely see it at the top of this photo but the oil tank mounting plate on the seat post will sometimes interfere with installing the tranny once the plate has been bolted into position. If this happens to you all that is needed is to loosely bolt the plate to the tranny and then install both components as a single unit onto the frame mounts.

We'll add more detail to this section as the build progresses.