1920s differentials

[Tonz]

I am amazed by the inner workings of a diff. And I admire the brilliant minds that designed them.

I have two photos here, one is of my 26 Chrysler diff, the other is of a late model LandCruiser. They look very similar.

It seems that after nearly 100 years modern automotive engineers are still happy with old technology.

This would go for things like Bendix starter motors and beaded rim tyres. Even driving controls steering wheel, foot clutch/throttle, gear stick. My 26 Chrysler is basically the same to operate as a modern manual tranny car.

Here's to our clever forefathers 👍

[hook]

9 hours ago, Tonz said:

I am amazed by the inner workings of a diff. And I admire the brilliant minds that designed them.

I have two photos here, one is of my 26 Chrysler diff, the other is of a late model LandCruiser. They look very similar.

It seems that after nearly 100 years modern automotive engineers are still happy with old technology.

This would go for things like Bendix starter motors and beaded rim tyres. Even driving controls steering wheel, foot clutch/throttle, gear stick. My 26 Chrysler is basically the same to operate as a modern manual tranny car.

Here's to our clever forefathers 👍

Yes, sometimes it's hard to improve a design that works and functions for the need. I was very surprised when I visited the Auburn, Cord, Duesenberg museum and saw the constant velocity joint for the front wheel drive Cord was the same ball and knuckle design used today. With todays cars, all the mechanicals are similar to yesterdays cars. It's all the electronics and neat little extras like self parking, backup cameras, vibrating seats, and automatic nose wipers, etc., etc., that's going to do-in restorers of the future.   

[Str8-8-Dave]

Ahhh- but there is a huge difference.  Look at the picture of the Chrysler differential and note how the pinion gear housing is centered over the ring gear.  Then compare it to placement of the Land Cruiser differential and note how the pinion gear housing is offset low on the ring gear.  In the old days the body of the car was mounted with floorboards above the frame and driveshaft.  Later bodies began to drop over the frame and a tunnel appeared in the floor pan sheet metal to package the driveshaft.  To minimize the tunnel height the differential was redesigned to lower the driveshaft line and minimize tunnel height.  That was a paradigm shift in third member gear design, manufacturing and lubrication requirements. 

 

In the early days of differentials (like 1900-1920) the pinion housing was centered and ring and pinion gears were straight tooth bevel gears and they were noisy.  Gear sets for these early axles could be made with pretty simple tooling.   Mineral oil, common at that time, provided adequate lubrication.

 

To get rid of the noise they improved the gear sets in the centered pinion differential to spiral bevel which required serpentine teeth made on much more advanced tooling.  The spiral bevel gearsets like the ones in the subject Chrysler differential were much quieter due to their much longer tooth engagement and they were still happy with mineral oil.  

 

When the pinion gear housing was offset, like the Land Cruiser differential, the gear design requirement moved to hypoid gear design which is quiet and favorably packaged but requires special tooling and these gearsets require hypoid oil to keep the gears happy.  

 

 

Edited January 19, 2022 by Str8-8-Dave
Correct car title- Land Rover=>Land Cruiser (see edit history)

[Bloo]

@Str8-8-Dave, you are spot on but I think maybe you made a typo, Land Rover for Land Cruiser (Toyota). That appears to be a Toyota diff in the second pic.

 

I only point this out because Land Rover really did use old fashioned spiral bevel gears (no offset) well into the 2000s. They were to my knowledge the only company to do so. Spiral Bevel designs were abandoned in the US before WWII, and as far as I know, abandoned in the UK by the 1950s with one glaring exception: Land Rover.

[Str8-8-Dave]

13 hours ago, Bloo said:

Land Rover for Land Cruiser

You are correct Bloo- Not the UK diff- the Japanese diff...

 

Hell- I'm getting so old by the time I get half done writing I can't remember what I was talking about... 

 

Dave

[NewOldWood]

The other advantage to a hypoid gear is added strength, the farther you offset the pinion the stronger it gets. This is where the 9 inch Ford gets it's strength. The down side is an increase in internal friction, a reduction in efficiency, which was the downfall of the 9" and why they quit making it.

[Carroll_1]

I've got the differential out of my 1918 REO touring car, and I'm amazed at the adjustability in it's design. The pinion gear is adjustable fore and aft, and the carrier assembly is adjustable side to side, all with fine pitch threads. The pinion adjustment and bearing preload is adjusted with a castle nut and lock pin, while the carrier location and bearing preload is help by locking clamps.  Seems like a pretty innovative design for the early 1900's.  I suppose, though, it has pros and cons. Pro: it's completely adjustable. Con: It's completely adjustable.