Question about 1937 McLaughlin-Buick Century

[Pete Phillips]

This '37 McLaughlin-Buick (Canadian-built) Century has been at my shop for about two years now, undergoing its restoration, which is just about done. This week,  I drove it out on the highway for the first time. I"ve driven it on local streets several times, but decided to drive it on the highway to the paint shop about 8 miles down the highway for its final buffing. I was very disappointed to discover that the car won't do much more than 50 miles an hour, unless you want to push it (I'm estimating) over 3500 rpm or so. This thing was screaming for relief by the time I had it up to 45 mph or 50mph in high gear. There is no way this car could have the usual 3.9 Century rear end ratio that one finds in the U.S.-built Buick Centurys of the 1930s. It acts like it has a 4.7 or even numerically higher than that! I felt like I would have the engine bust apart in a million pieces if I forced it to go up to 60 mph. There was an inch or so of accelerator pedal travel left, but I'm just not going to thrash an old engine like that. Suffice it to say, I'm very disappointed in the car and I think the owner will be also. He has never driven it yet.

 

So my question is, does anyone have experience with other McLaughlin-Buick Centurys from the 1930s? Did they not use the 3.9 rear end in Canadian Centurys? In the parts of Canada that I have been to--Ontario and Quebec--the land is quite flat and I find it hard to believe that Canada would need a numerically higher rear end ratio in its Buick Centurys.

Pete Phillips, BCA #7338

[billorn]

Are you sure its spinning that fast? Old cars sound busy. I found that if you push thru that rpm band they usually settle down into a groove a bit. Its prolly ok.

 

I bet it's ok just a little louder than you expected.

[Marty Roth]

Pete,

 

The easiest way to check the ratio, considering the torquetube drive,

is to pull the sparkplugs,

raise one rear wheel,

shift the transmission into 3rd gear, 

mark the lower front pulley or the flywheel,

have someone rotate the rear wheel until it makes a complete rotation - (or two rotations - since the other wheel is on the ground, or rotate both rear wheels at the same time only one rotation)

Count the number of rotations of the pulley/flywheel

 

That should give you the differential ratio

[Buicknutty]

 I have some info on McLaughlin '37s, and it indicates that it should have a 3.9, like my '41 had as stock. Perhaps someone changed it out for a series 40 ratio, which is 4.4?

 Keith

[jvelde]

On my '39 Special I took the differential cover off and could see the markings showing the gear ratio (see photo).   

[1939_Buick]

You could take the cover off and count teeth

Series 40 40/9 teeth ratio 4.444

Series 60 39/10 teeth ratio 3.900

1936 to 1939 had the same ratio(teeth count) but different part numbers

The teeth count changed from 1940

 

jvedle image 3.9 ratio

ring part no. 1303405

pinion part no.1310355

 

 

Edited October 31, 2018 by 1939_Buick (see edit history)

[nzcarnerd]

Shouldn't be hard to rig up a tachometer to it to prove just what revs it is pulling. As has been said these things sound busy compared with a modern car.

 

Agreed with others re how to check the rear end ratio.

[nzcarnerd]

Am I right in saying that the Century and Special rear ends are not interchangeable? I thought I read that here somewhere.

[1939_Buick]

5 minutes ago, nzcarnerd said:

Am I right in saying that the Century and Special rear ends are not interchangeable? I thought I read that here somewhere.

For 1937 and later interchangeable. Must be the same year, up to 1939.  But from 1940 to mid 50's can use the same rear end.  In 1940 Buick finally stopped making changes year to year on rear ends, but not torque tubes (length)

And the series 60 Century have wider brakes

Edited October 31, 2018 by 1939_Buick (see edit history)

[BuickBob49]

For what it is worth I get some gear pitch noise at highway speeds with my 39 Roadmaster--a whine.  My mechanic, who is 80, tells me that this is normal.  We put in an NOS cluster and lightly used 1st-reverse and 2nd gears during a rebuild.  We didn't touch the differential.

[MCHinson]

Pete,

Are you judging the speed with a gps device or the speedometer? If the speedometer, perhaps the speedometer is reading slow. If it has the correct Century differential, it should be happy at 60 to 65 mph. My 1937 Century Model 61 keeps up with traffic without a problem. I have driven it from NC to Indiana while keeping up with traffic on the interstates.