Drivetrain Advice Needed

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Fortunateson

Well-known member
I have a '32 5W which will be running a 276ci engine and a '40 rearend with 3.78 gears. I have three possible transmission gear setups... a 16:28, a 15:29, and a 18:26. LZ (although I think I'll be replacing the input shaft and second gear on that one due to wear).

So which combo would be best for a little snap off the line and possibly driving highways around 65? To get to 65 would I need the 3.54 rear gears?
 
With your light 32 and the 276 engine with 3.78 gears you should easily have a little snap off the line. If you changed to 3.54 gears and used the 15:29 gear set you would get the same snap off the line in 1st or 2nd (the trans is 10% lower in those gears) and get your cruise where you want it.

The LZ gears are for drag racing (not just a little snap) being close ratio and usually used with a 4.11 rear end. Of course LZs had an overdrive for cruising.
 
The 3.78 gears will provide your highway speed regardless of the transmission gearing, as 3rd gear is 1/1 ratio anyway. LZ gears are not well suited for a light coupe for street use, 1st gear being almost useless unless all you want is to own stock in Firestone.
 
I agree with Juergen's advice. You didn't tell us what size rear tire you plan to use, but the 3.54 axle will be better for the 65 mph cruising. A 3.78 axle with a 28 inch diameter tire calculates out to 66 mph @ 3,000 rpm. With the 3.54 axle, the same 66 mph can be achieved at a little over 2,800 rpm.
 
I currently have my '35 fordor sedan set up with 3.54:1 rear gears, 29/15 ('46-'48) transmission gears, a basically stock '35, 21 stud engine that's bored 0.030" over, with a slight increase in compression by milling the heads, and 600x16 tires. I absolutely love the performance this combination gives me.

PS....I like this gear combination to the point I'll be doing this same conversation in my '35 coupes and tudor sedan....if I'm lucky enough to live that long :)
These cars are drivers... on back roads as well as Interstate highways. I'm well beyond the age of street racing, drag racing, and the desire to break any land speed records at Bonneville. To me, Lincoln gears are for those who like bragging rights.
 
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First off, for what it is worth, zephyr gears are stronger than other stock gears. The 25 tooth being the strongest. It is not the steel, it is the laws of physics.
Next, you won't notice any difference in rear end ratio with that engine driving around on the street. You may get a half mile per gallon better mileage on the highway with the 3.78's.
You can plug all kinds of numbers into formulas and get all kinds of different answers but until you have ACTUALLY TRIED the various combinations IN PERSON, you are wasting your time. One thing for sure is, 4.11 and zephyr gears for a street modified flathead is better than 3.78. If need be you can still go 120 at Bonneville with it. Been there, done it all.
 
Fortunateson said:
Interesting comment regarding th physics. I'd like to read your explanation...
Click to expand...

By "physics", it's the difference in "torque multiplication" created with different gear ratios that affects the overall strength of a transmission case and the gear set itself which is CONTAINED by the case. When two gears mesh and torque is applied, the gear pair with the highest numerical ratio (greater torque multiplication) will impart the greatest forces upon each other, as well as on the transmission case itself which is charged with containing the gear set. When any two gears apply torque against each other while in mesh, those two gears attempt to push away from each other in opposite directions. For instance, a 15/29 input gear/cluster gear combination will apply more force upon the front of the case, (attempting to drive the cluster downward, and the input gear upward) than a 16/28 input gear/cluster gear combination.....given an equal amount of torque input. It's the amount of torque MULTIPLICATION created that constitutes the "physics" aspect.

A transmission's torque limit is usually based on the FIRST GEAR multiplication ratio. A good example for a realistic comparison is the T5 transmission. An "S-10" T5 with a 4.03 1st gear has a much lower torque rating than a V8 Camaro T5 with a 2.95 1st gear. You should also remember that in 1st gear, the rear end of the cluster gear is also meshing with the 1st gear slider riding on the main shaft above it. Those two gears are also physically ATTEMPTING to push themselves apart from each other, with only the main case keeping them in mesh. Both gear sets share the same aluminum main case!
DD
 
Personally with 3.78s I'd go with the 16/28 gearset.
The 15/29s can be dismissed as a heavy car/commercial application.
Can't comment on the Lincolns, never any first hand experience on those.
For what it's worth in my roadster I have 16:28s and have run it with 4.11s, 3.78s and 3.54s all with 7.50:16s and it goes well with all of them, it is very light though.
In my 41 pickup I have 3.54s and as it's a commercial and may carry a load I used a 15/29 gearset to offset the tall diff.
In my currently under construction 32 sedan I have 3.78s and a 16:28 gearset.
Mart.
 
For Interstate cruising I put 3.25 rear end gears in my '41 coupe, a heavier car than your '32. I have the 16/28 transmission and was prepared to change to 15/29 to get a low enough low gear for slow speed maneuvering and starting on hills. With the great torque of my 284 inch engine, I have decided that the lower gear is not necessary. Cruises 65 mph at about 2500 rpm; good mileage and relatively quiet.
 
V8COOPMAN,
That's for the phsysics lesson. Make sure total sense. Now, when will the quiz be? LOL
 
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Well I think I've been convince to forget about the LZ set. The 15:29 is the best set in terms of condition though. I live in an area with a number of hills but th ehigway of course is very flat for the most part so I'm still not 100% decided between the 15:29 vs the 16:28.

Hanks for all the replies guys, I really appreciate it!
 
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Fortunateson said:
V8COOPMAN,
That's for the phsysics lesson. Make sure total sense. Now, when will th Equis be? LOL
Click to expand...

If you'll type "Equis" into your browser, you'll find that quite a few DIFFERENT topics come under that nomenclature. Give me a clue as to which type of "Equis" you're referring to, so that I can maybe give it a shot. DD
 
15/29 and a 3.54 are the clear winner for me, and if you have enough hp, then 15/29 with a 3.25. I live in the hills and you wouldn’t catch me dead with LZ gears in one of my cars. They are great for racing but I HATE them fir street use.
 
Fortunateson, highways are normally run in top gear, so in that situation the gearset is irrelevant. If you will need to start on hills then the 15/29, as stated would suit well.
 
Contrary opinion here on the LZ gears.

In my 32 roadster, 268CI, dual 97's and .400 Offenhauser heads; I have the Lincoln Zepher 14-25 clusters with 29 tooth main and 3.78 to 1 rear end.

I love the ratios and definitely would not want a lower 1st gear in the transmission, 4.11s would be good but not necessary at all. It is hilly where I live. I also have a Columbia two speed rear :-)

I did some cut and paste of information on Vanpelt's site http://www.vanpeltsales.com/FH_web/flathead_trans-gearratios.htm
for comparison purposes.

Glenn


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Here's a Columbia chart that lists different transmission ratios/rpm
Worried about going 65--?? The 39 with the 60hp , 4:44 rear had no trouble cruising at 65-70 on the level ground, when it dropped to 40 on the hills it went to second gear to keep the fuel mileage up
 

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I have to believe that adding a Columbia to the equation takes this discussion to an entirely different level.
 
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