VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Closed Drivetrain vs Open Drivetrain?

I did a lazy search and decided to ask the experts. What is the difference between an open drivetrain and a closed drivetrain?

You mean open vs closed driveshaft/driveline, not drivetrain?

To make it simple, if you can't see the U-joint(s), like on our torque tube setup, it is 'closed'.

If you can see the U-joint(s), it's open.

Google "open vs closed driveline" and you'll see plenty more opinions...

Also with open you can actually see the drive shaft turning.
1955 was the first Chevrolet car to have open.
Chevrolet closed up through 1954, Ford up through 1948, Buick about 1958 and Nash the same.
Much more common in the '20's and early '30's.

As an interesting side note, sprint cars still use a torque tube set up

Thank you gents. It seems that some folks are anxious to go to open drivelines. Does one setup offer an advantage over the other? I could only guess that Chevrolet switched to open drivelines as an improvement.

The torque tube set-up was less flexable aand would transmit more thrust to the chassis. With an open drive shaft the springs absorb some of the thrust. One reason


Chevrolet and Buick stayed away from the old 4 speed Hydramatic as it already could have jerky shifts and with a torque tube was worse. Also the torqe tube made for more unsprung weight + it was just plain old fashioned. and made adding optional overdrive more difficult.
not to mention the vibrations it could transfer into the body.

Fast forward to 1999-2000, Chevy went back to a concealed driveshaft for the Corvette. No big deal considering it was only something like 24" long, maybe less...:)

What do I need to do to enable my 38 Master Deluxe to run highway speeds 65 without modifying engine?
Thank you
Michael

Turn on the ignition switch, push the gas pedal, once started put in first gear and then end up in third. Push gas pedal until you reach 65 mph.

A '38 should be able to sustain 65 mph for extended periods.

I drove my '39 with the 4.22 axle ratio at 65 MPH for years and many interstate miles. In about 2000 we began using the car for 6 Cylinder Tours that were often 500 or miles away so I installed the 3.73 gears I had on the shelf for yesrs. That made 65 to 70 smooth and quiet and gas milsage increase about 2 MPG.
In 1937-1940 the straight axle leaf front spring cars had the 3.73 "economy ratio".
Killed the exceptional hill climbing power a little but made interstate travel a joy.
If your engine is "loose" or had any knocks I would not drive it that fast.

Did you change out stock gears for 3:73 gears? I was told that tranny and reared need to be changed. The closed driveline limits or eliminates any modifications.
Thank you

I had a new ring gear and pinion "in stock"
You can either install a new or good used ring gear and pinion (not a job for a beginner) or find a used torque and rear end housing from a Master (3.73) and switch it with yours. No ring gear set-up required for that cahnge. Also the speedometer gears will need to be changed while the U joint is apart.

That sounds promising. Most of the events I want to attend are 50 plus miles away with 90% being highway. Everyone is racing somewhere in the San Fran Bay Area. I'm trying to slow my pace down a bit.
Thank you for the tech advice.

I found this article installing 3:55 gears in a closed driveline on a chevy truck rear end.

http://www.hotrod.com/how-to/chassi...-of-the-40s-3-55-1-ring-and-pinion-swap/

Can the 3:55 gears be installed in my 38 sedan rear end? Chev of the 40's sells the 3:55 gears and said it can be installed on the 38 with modifications. Any comments on this?

https://www.chevsofthe40s.com/detail/3316/Chevrolet_Ring_And_Pinion_Conversion_3551.html

"With modifications"...to make a long story short, you need to take the driveshaft out, cut it shorter, and do some precision welding.

Can be done, yes, but if you want it done right, you may have to cough up some $$$ any pay a machine shop to do it right....not sure about your area, but in my area, probably will cost me somewhere in the $1500 range to have it done (if I bring the axle & driveshaft into their shop).

You would probably want to install a 235 or 261 at that point.