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New diff ratio needed for a 1928 chrysler


statusman2010
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Not sure what model you have, but, for comparison, I have 1928 model 65 owners manual. See Below. With these axle ratios, cruising speed would probably be between 30 and 35 MPH. In 1928 there were probably not many roads you could travel greater than 35 MPH for any extended time. Drive the car as designed.

IMG_20210622_0001.jpg

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Some have been successful in installing an overdrive in-between the gear box and diff giving them the benefit they were looking for.

" I’ve used the original 3 speed box and fitted the overdrive just behind it. Pete that has helped me with my engine and the rest of the car has done this on a few of his dodge’s and it adds about 10 mph to the top speed"

This has been done to a few Chrysler's as well

 

Overdrive.jpeg

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The question should be.......what is a safe and sustainiable driving speed for the car. The cost and effort to get it to lets say 45 mph and be comfortable? You can't make a ocean liner out of a row boat. I have driven the big 1928 Chryslers and they seem fine as is.........not sure on your series car. It may be time to rethink the car BEFORE you do anything else.

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I find it hard believe a 1928 Chrysler anything   is so limited to 30 MPH from the factory.

Even a Model T in only fair condition can grunt along at 35 pretty well and one in fine stock mechanical shape on good wheels can clip along closer to 40 ..some in to the high 40s if the engine balance and trans are trued up.

 

 

.

 

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That car should go 40-45 MPH pretty well. If you're driving it by sound, it may seem a little busy but you're not hurting it. With today's quiet, insulated, overdrive cars, it feels strange to zip along at 2800-3200 RPM and it can seem like you're really working the engine too hard. You're not, it just sounds that way. It's possible that you have something amiss with the engine that makes it sound sickly, something like noisy valves that need adjusting, but whatever the gear ratio in your Chrysler, it should be able to cruise at 40 MPH without doing any damage as long as the engine is healthy.

 

My 1929 Cadillac was pretty comfortable at about 48 MPH and it had 4.75 gears. Yes, it sounded busy, but there was no harm done and I drove it that way for years without issues.

 

Push past 30 MPH and I bet you'll hear the engine get into a better groove and feel more comfortable.

Edited by Matt Harwood (see edit history)
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several  rear diff ratios used by Dodge in 1928.

51-9,  51-10, 49-9, 41-8, 51-12

 

What is model of your car?

What is ratio in your car?

 

There are others that can work, but you must know number of splines on axle shaft to side gears.

 

 

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9 minutes ago, Larry Schramm said:

If you tend to "over drive" the car faster than it's "sweet spot", you will tend to break things.  Just my experience and a lot of others.

 

In addition to Larry's very appropriate comment, above,

remember the capacity of your car's braking system.

Comfortably holding higher speeds with less engine revs/noise is one thing,

but being able to safely stop is even more critical.

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Just now, Marty Roth said:

 

 

In addition to Larry's very appropriate comment, above,

remember the capacity of your car's braking system.

Comfortably holding higher speeds with less engine revs/noise is one thing,

but being able to safely stop is even more critical.

 

Forgot the brakes.  Everything that I have has wooden wheels and rear brakes only.  To me that is just a given on brakes.

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On 6/23/2021 at 8:54 AM, Hans1 said:

several  rear diff ratios used by Dodge in 1928.

51-9,  51-10, 49-9, 41-8, 51-12

 

What is model of your car?

What is ratio in your car?

 

There are others that can work, but you must know number of splines on axle shaft to side gears.

 

 

My 29 DB 3/4 truck has a ratio noted as 51-1 and I feel most comfortable at the 35-40 range. I can even start driving in 2nd gear with no lug down on engine.

These trucks were designed to move good and not for quick trips.

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My 1928 Chrysler had four wheel contracting hydraulic brakes. The engine pilled me as fast as I wanted to go with the original gearing. Try making a few panic stops while the shoes and drums are wet before making the car go faster. Zeke 

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On 6/22/2021 at 7:25 PM, statusman2010 said:

Diff ratio ???   My 1928 Chrysler is maybe a 30 MPH vehicle. What do other vintage car guys do to get them to manage 5PH or almost highway speed??

Irrespective of your diff ratio, your car should be able to achieve better than 30mph. My first thought is that something is wrong with the engine.

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Just asked my dad who had a 1929 Chrysler daily driver when he was young and he says 40mph is your cruising speed and at 50mph things will go bang:) If your 1928 only does 30mph, then you have some other issue to resolve.

 

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3 hours ago, Borough Essex said:

Just asked my dad who had a 1929 Chrysler daily driver when he was young and he says 40mph is your cruising speed and at 50mph things will go bang:) If your 1928 only does 30mph, then you have some other issue to resolve.

 

I am not sure what 28 Chrysler we are taking about, but, if it is a model 52 it had a 4 cylinder engine with 38 HP. The smallest 29 Chrysler was a 6 cylinder had 65 HP. Hardly a comparison.

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I can cruise at 30 - 35 comfortably in my '31 Imperial  eight.

At 45 things get real busy, and the fan noise takes over.

My brakes have new linings and cylinders, but it takes looking well ahead to motor safely.

 

Mike in Colorado

P_20181122_110337 (1).jpg

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I have a 1929 Chrylser model 65 and have the same problem. By ear I feel 30-32mph is the good for the car and the engine. Originally it has 4 differential ratios, mine is the shortest (44-9)unfortunatelly. Factory made 44-9 46-10 43-10 and a 43-11.The longest is 16% longer but I could not find yet. 1st gear is very short, you can start with 2nd if the car is not full with people.

 In winter I think I made a longer version, or build in a Volvo overdrive not sure which is better.

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Yeah it would really help to know which 1928 model the OP is talking about. That said my 29 model 65 sedan(lowest ratio) seems happy at 45-50 mph and a friend just up the road from me has one that he has had on the road for the last 40+ years and he cruises everywhere and has never had any major engine issues. As far as stopping goes I find my one stops really well but then again I’m use to driving cars with rear wheel brakes. 
Overdrive vs taller diff ratio probably depends on how keen you are on originality and what sort of driving you are doing. If you are mainly driving on the flats with no major hills etc the taller diff ratio would probably be fine but if you are up and down hills a lot a separate overdrive box is great as you can split gears as well effectively giving you a six speed. I’m not sure of the ratio of the Volvo box but you also need to mindful not to go too tall as the motor will run out of legs. Personally on my Chrysler 65 I don’t see any need for a higher diff ( too many hills here) and no real need for an overdrive as at 50mph I’m happy. 

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22 hours ago, aron_budapest said:

Could you measure your rpm at 50mph? What is the "red line" for this 6cyl engine? And one more, how is your mpg?Mine is about 12mpg at steady 35mph.

Yeah not sure of my rpm at 50mph or what the redline is. My fuel consumption is around the 18-20mpg but I’m very lucky to be running a rebuilt Stromberg U2 that I picked up at a swap meet for 50AUD.

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