Best rear axle ratio?
 

Guys a buddy of mine has a newly purchased 36 coupe. It’s running a warm 24 stud flatty, he hasn’t driven it enough yet to know how much power the motor has. Anyway he needs to purchase a new crown wheel and pinion. He has bought 750-16 tyres. Standard 39 transmission. He lives in the country so wants a high ratio, just doesn’t know whether to go with 3.54 or 3.2. With his 750 tyres what recommendation ratio should he aim for? Not sure if he has a 9” or 10” clutch.
Thanks in advance Dan.

Re: Best rear axle ratio?
 

dan with those tires 4.11 would be the go

Re: Best rear axle ratio?
 

If your choice is 3.54 or 3.2, go with 3.54 as the larger than stock tire size reduces the ratio below 3.54 and 3.2 with 600 x 16 tires is not great in hilly conditions.

Re: Best rear axle ratio?
 

im running 354s on 600/16s and cant complain about the speed but can be difficult on hill starts as tends to get minor clutch shudder

Re: Best rear axle ratio?
 

We are running a 3:54 in our 32 with the stock 18" rims and tires, on flat land its wonderful, hills...not too bad, mountain's have to be climbed in first gear!!! OH, and "stock" 32 Flathead with stock 32 transmission.

Re: Best rear axle ratio?
 

With the 7.50s I'd go with the 3.54s. It might help if the trans has the 15/29 gearset. I have that combo in my 41 pu with 6.50s and it's fine. I also have 3.54s in my roadster with 7.50s but that is a lighter car. That has the 16:28 gearset.

Mart.

Re: Best rear axle ratio?
 

Last summer I rebuilt the banjo rear in my '35 fordor sedan, and installed a 3.54:1, six spline pinion gear set. I also rebuilt the original #48-7006 transmission case using the later style '46-'48 side shift trans gear set with 29 tooth cluster and 15 tooth input gear. This transmission & rear gear combination using 6:00 x 16 tires works perfectly when starting off in 1st gear, on flat, or hilly ground, and climbs hills and mountain roads well in 3rd gear. The engine is a '35 babbitted main bearing, 21 stud, 221 cu in, 85 hp, bored 0.030" over, plus both the deck and heads have been milled for higher compression. This little engine runs amazingly well.

Re: Best rear axle ratio?
 

Thanks John. My buddy has already decided on a 3.54 ratio based on the above comments. Thanks to all who responded.

Re: Best rear axle ratio?
 

Interesting. I sourced an original 3.54 R& P and may switch over from 3.78’s for a winter project.

Re: Best rear axle ratio?
 

I actually have a beautiful original 3.54 in my roadster but that’s being removed to fit a Columbia axle.