Overdrive Transmission - Input Shaft

We headed over to Icon Engineering, where proprietor Mike Schultz showed us the basics of what it takes to cram the Passon goodies into an existing A833 Chrysler four-speed. If you've never rebuilt a manual transmission, you might want to get some help from somebody who has. It can be a little tricky for the uninitiated, and a large hydraulic press is needed. In our situation, the Passon components cost $2,339.50, $1,695.00 of which paid for the basic OD Hemi conversion kit, and the rest of which paid for service parts and the modified shift handle. Icon Engineering charges about $700.00 for labor to convert a transmission (not including removal or installation in the car) for a total cost of just over three grand. That's very competitive with the other Mopar overdrive solutions on the market, but again, this is the only one that hides in plain sight and requires absolutely no vehicle modifications. Scope it out.

CRUISING RPM
FOURTH GEAR	TIRE SIZE	REAREND RATIO	RPM	SPEED
1.00:1	28 inches	4.10:1	3,248	65 mph
80:1	28 inches	4.10:1	2,580	65 mph

A833 GEAR RATIOS
	STOCK	OVERDRIVE	STOCK REAR RATIO 1:1 FOURTH	ADJUSTED REAR RATIO WITH OVERDRIVE
First	2.65:1	2.66:1	3.23:1	2.58:1
Second	1.93:1	1.59:1	3.54:1	2.83:1
Third	1.39:1	1.00:1	3.55:1	2.84:1
Fourth	1.00:1	0.80:1	3.91:1	3.13:1
			4.10:1	3.28:1
			4.56:1	3.65:1

Schultz suggests replacing wear items in the transmission as a matter of preventive maintenance. Here, a new rear main-shaft bearing is pressed on.
Schultz suggests replacing wear items in the transmission as a matter of preventive mainte
Likewise, a fresh input-shaft bearing is pressed into position.
Schultz poses with the boxes of Passon Performance overdrive conversion goodies. The surgery takes about one full day, and everything Passon supplies is brand-new; nothing is remanufactured.
Schultz poses with the boxes of Passon Performance overdrive conversion goodies. The surg

The pen points to the key wear areas on the shift forks. The light marks shown here are acceptable for reuse, but Passon sells brand-new replacements if yours are shot. If you see iron forks in your transmission, they're factory original. Bronze forks are a typical replacement part and offer greater lubricity for extended service life.
The pen points to the key wear areas on the shift forks. The light marks shown here are ac
The custom shifter (left) is a $289.00 Passon option that accepts a stock, Inland-style, reverse-lockout shift handle. This tranny is going into a sleeper-themed '66 Dart, and the customer wants stock appearances inside and out. The pen points to the stock Hurst bolt-on shift-handle configuration; notice the difference.
The custom shifter (left) is a $289.00 Passon option that accepts a stock, Inland-style, r
Here's a look at an original, aluminum-case Chrysler OD four-speed. Note that the bolt-on shift arm for the 3-4 shift rod points down (pen) versus the upward orientation of the two other shift arms. Chrysler's original overdrive tactic employed this inverted shift arm, a redesigned 3-4 shift rod, and a new 0.76 Third gearset (from 1.39) to trick the transmission into OD status. The original Fourth gear remained at 1:1 but now was positioned in the shift quadrant where Third gear would normally be. Unfortunately, Chrysler's budget strategy included an undercut main shaft to suit the new Third gearset that limits reliability to the 300hp level. Passon's custom gearsets retain fullsize main-shaft diameters and sidestep this issue.
Here's a look at an original, aluminum-case Chrysler OD four-speed. Note that the bolt-on