[BRENT in 10-uh-C]

Originally Posted by Ruth

But if you really want to run 4.33 gears, I say go for it. Just be aware your engine will be screaming at 35-40 mph in high. Not much fun in a "speedster".

I sure don't know about that. I have ran several 4.33 gears in my speedsters with plenty of success. In hill climbing, I can start in 2nd gear and shift to high which is faster than shifting from 1st to 2nd. I raced my speedsters on dirt with 4.33 gears running at WOT on ½-mile dirt tracks without an engine issue. I guess it is all in what you like with a speedster, but 4.33 gears were fun for me. My son is restoring the old 'Crash' Brown Model-A sprint car, and we will be putting a 4.33 in that too.

Originally Posted by Ak Sourdough

Brent, I don't know anything about the manufacturing process used in the Model A assembly plant. However, you are right in your first post that the gear tooth shape could not be the same for different ratios even though the tooth count for the pinion is the same.

My experience is entirely with the more modern hypoid gears not the early spiral bevel gears used in the Model A. They are always sold and installed as sets because they are lapped together in final manufacturing steps. That according to a movie shown in automotive trade school in the early 70's about rear axle manufacturing and assembly.

Yes, I agree with the hypoids sets being lapped however nothing that I have ever found in researching this has ever given any proof that Ford lapped them during Model-A production. I would expect this would have been an expense he was unwilling to include, and I am certain this is the major contributor to why 600wt. lube was used in the transmission & rear ends. With the higher viscosity, they would not have needed to have a lapped tooth to still be quiet.

Originally Posted by john charlton

Just wondered if someone has put together a 3.78 rear end out of "orphan" parts and did it work OK ???.

Yes John, I have on a couple of different occasions. In one instance, my father drove a '29 Phaeton to the MARC Nationals in Jacksonville, FL. En route, the pinion bearings came apart and killed the R&P gears. We sourced used parts from several vendors in the swap meet and the mis-matched gears were assembled. That assembly was as quiet as a mouse. Another time was on the Great Race when a team from Iowa broke a tooth on a drive gear. Parts came from everywhere that night from local hobbyists and we assembled it and it did well. With the proper weight lube, and the backlash correctly set, you should not experience any issue unless one of the gears is severely worn.