Dave Patten wrote:I missed the telltale sign of an OD dogleg gearbox.
Look at the initial picture Okayfine posted. Just forward of the transmission mount is a large flanged nut that points at the ground when the transmission is installed. This is part of the shift linkage and holds a bell crank that reverses the direction the 4-5 shift rod travels. If you have never taken apart a dogleg gearbox, this part is a PITA to align and engage when installing the tailshaft housing.
There is a selector arm that swings side to side within the tailshaft housing as you move the shifter right and left thru the neutral area. This selector arm engages in a slot in the end of the shift rods and as you pull the shift lever fore and aft it engages the gears in that part of the "H" pattern by pushing/pulling on that particular shift rod. You pul the shift lever back and the engaged shift rod moves forward because of the shift lever fulcrum action.
The dogleg OD gearbox uses this bell crank linkage to change the direction the 4-5 shift rod moves. In 4th gear the transmission runs straight thru the input shaft to the mainshaft for the 1:1 ratio. This means the 4-5 shift rod needs to move forward to engage this coupling ring. The fulcrum of the shift lever pulls the selector arm rearward not forward. This is why 4-5 uses a bell crank between the selector arm and the shift rod , so it will reverse the shifter action to the 4-5 shift rod.
The flanged nut is the telltale that the 4-5 shift linkage includeds a bellcrank.
Most interesting info. Always wondered about the shift action and that bolt.
Dave Patten wrote:datzenmike,
I would assume the OD comp boxes were the same shift pattern as the DD comp boxes. I have owned all 4 ratios of direct drive comp boxes and they were all dogleg patterns. It is sweet for racing, no ugly 4-5 shift. Very few times would you ever use 1st on the track so the complex dogleg 2-1 down shift is avoided. Makes it a simple 2-5 "H" pattern.
Duly noted, DD competition boxes are dogleg pattern.
Here is a 71B and a dogleg and you can see by eye that the 71B has larger bearings and gears because if the large 71mm spacing.