1950 cruising rpm

[Robberbach]

Has anyone ever used a tach to see what rpm there car is running at down the road? I have a 1950 Special, manual, that sounds like it needs to be shifted again at 55 mph. Just wondering if anyone ever checked the rpm at cruising speed.

[60FlatTop]

When you get used to model cars with overdrive, sometimes 2 OD's on a 6 speed, you are going to to get that feeling. When I drive my '64 riviera 425 its the best, 1:1. OD is around .8:1.

A lot of times when I get within a mile of town I drop my model stuff out of OD and into Drive. Feels good.

I would guess 55 MPH is between 2000 and 2500 RPM on the '50 Buick. My '05 Silverado does that around 1700 at 70 MPH.

Bernie

[Guest kaycee]

My old '50 Super came from California when I got it many years ago. It was a 3 speed with a Dynaflow rear axle which had a higher ratio rear end. I'd shift into 2nd when passing on the highway and out of 2nd at up to 85 mph, with a top end of over 110. ' Wish I still owned it. It was a great looking 2dr. htp, and a very good road car.

kaycee

[Joseph P. Indusi]

I do not know your wheel size or your differential ratio but let's assume a tire size of 7:60X15 and rear end ratio of 4.1 to 1.

Under these assumptions your engine will be running about 2800 RPM at 55 MPH. Some Buicks of this vintage came with 4.45 to 1 ratios and they would be running 3000 RPM engine speed at 55 MPH.

I had a 3.4 to 1 ratio differential installled in my 1948 Special because I too felt it needed another gear at about 45-50 MPH. It came woith a 4.45 to 1 rear.

Joe

[Guest kaycee]

My '50 super had a 3.6 Dynaflow rear end versus the 3.90 that came originally with 3 speed stick shifts and yes the engine was 'winding', but these were standard ratios on the 1950 from what I've seen. It made it an excellent highway car at high speeds and did'nt seem to sacrifice at lower speeds.

kaycee

[Robberbach]

I do not know your wheel size or your differential ratio but let's assume a tire size of 7:60X15 and rear end ratio of 4.1 to 1.

Under these assumptions your engine will be running about 2800 RPM at 55 MPH. Some Buicks of this vintage came with 4.45 to 1 ratios and they would be running 3000 RPM engine speed at 55 MPH.

I had a 3.4 to 1 ratio differential installled in my 1948 Special because I too felt it needed another gear at about 45-50 MPH. It came woith a 4.45 to 1 rear.

Joe

Yea, I found a rpm calculator, and these are the correct values. Thank you. It just seems like it is really winding and running a lot of rpms at 55 mph. I generally don't drive it anywhere that the speed limit is over 55 mph.

Happy motoring.