'37 Special diff gears upgrade

[Guest McLaughlin-Buick]

Greetings to all. This is my first post as I have just joined the forum recently. I am looking for some advice on upgrading the rear end ratio on my '37 McLaughlin-Buick Special. I'm sure many have asked this question before, but I couldn't fine the posts for it. I have owned this car since 1997 and been driving it since 2000. It is mechanically original (refurbished) and very reliable. We even drove it from our home here near Ottawa Ontario to St. John's Newfoundland and back in 2001, a distance of about 4200 miles with no issues.

With the existing ratio of 4.4 to 1, I have always thought the engine seems to turn faster than I feel comfortable with at highway speeds, 55 to 60 mph (especially on a 75 year old engine), so I usually keep it 50 or less. This creates a problem with holding up traffic and engine temp tends to go high on sustained over 50 speeds, normal temps at 50 or less (I know there may be a coolant circulation problem but that's for another post). We live in a rural area and to go anywhere we must take the highway, most all 2 lane. The goal is to lower engine RPM for more comfortable and quieter cruising.

I know 3.9 to 1 Century gears from '36 to '38 would be the best way to go, if you can find them and very pricey if found anywhere. Overdrive add on would be sweet, but too costly for me as well (I am retired). Does anyone have info or has heard if gears or complete rear axles from any post-war model Buick would fit with or without some modifications?

[jscheib]

There was an attempt to build new gears for a better ratio for late '20s, early '30s Buicks and cruising, but there were not enough interested to do this at a reasonable cost, so the project was discontinued. For late '30s, there may be some later rear ends that could be adapted, but others may be able to advise you on that.

John

[jeff]

The '37 / '38 Buick publication is available on-line, and it has a number of technical articles on fitting later model (post war) rear axels to your '37. Too me, the modifications look pretty significant, others may disagree. I decided to stick with the back roads of Ohio.

Jeff

[1939_Buick]

www.1937and1938Buicks.com is web site reference above. There are several articles on this modification over the years. Can be downloaded

The common method

(a) buy an early to mid 1950's differential housing with higher gears

( machine 0.25" from the 1950's casing so 37 axle shafts align within the 37 housing

© modify (cut & weld) the drive shaft, as the number of splines are different 1937 to post war

Edited February 7, 2013 by 1939_buick (see edit history)

[Guest McLaughlin-Buick]

Thanks for the responses. Years ago I used to belong to the 1937 and 1938 Buick club before it folded. They were a wealth of information for those year cars. I didn't know that the past issues were archived and available for viewing. I will check it out. Thanks for the direction.

Greg

[Joseph P. Indusi]

I seem to remember an article in The Torque Tube some years ago that described a change of the pumpkin on a pre-1940 car to a later and taller ratio pumpkin from a post 1940 car. I seem to remeber that it required cutting the drive shaft and welding on an end from the later car.

Another option might be to obtain the entire rear end assembly from a 1950's Dynaflow Buick and mount it into the earlier chassis. There still might be a problem with the splines at the rear of the transmisssion matching the later driveshaft as well as the length not being correct.

For later cars, the 1940-1955 pumpkins will all bolt up into the rear end housings from these years. Only thing I am not sure on is if this is true for Series 90 cars.

Joe, BCA 33493

[Guest JR9162]

51-52 Special rear axle, and use 54-55 Century gears in it. They're available in 3.36, 3.41, and 3.56 (3.60) ratios. You'll need to clean the 51-52 mounts off the axle housing and adapt the 37 Special bits to it. Driveshaft mods will be required. If you want bigger brakes mount 55 Roadmaster units on all four corners. You'll need everything from backing plates outward. All this info can be found in various issues of the Torque Tube pdf files. Suggest you go to a dual reservoir MC as well. Scarebird makes brackets front and rear to convert 50-52 Buicks to disc brakes on all four corners if that's your preference. Haven't looked at dimensions on the 37 Special front steering knuckles/spindles, but I have ascertained 51-52 Special units will fit on a 38 Special. John

[1939_Buick]

A typical sketch. One of the methods

From 1937-38 club torgue tube Vol XIV Issue 2 Nov - Dec 1995. Also has text instructions

Edited January 24, 2020 by 1939_Buick (see edit history)

[Guest McLaughlin-Buick]

Hi Guys.

I found and accessed the 37-38 Buick club tech tips web site and found all the answers I was looking for pertaining to the rear end swap. What a great archive of information! Several people have done the 50's pumpkin to the 37 housing swap and have described the procedure very well. It looks pretty straight forward and quite doable. Today I located a '53 Super in an old wrecking yard 2 hours away from me that may hold the rear end I need. The old V8 and Dynaflow trans have long been removed, but the complete rear end still resides in it. According to the specs the tech tips provided it should have the 3.6 to 1 ratio which may be just right. It is buried in snow now, but when spring comes in a couple of months I will be checking it out.

Thanks again for everyone's help.

Greg

MBCC 1614

[1939_Buick]

Glad we helped. I have done a study of these methods and trying to extend to 1939

1937-38 owner's have several methods using the 1937 housing/axles or the later housing/axles (as post 7)

Please come back in (your) spring to tell us how it all went (and we like photos)

____________________

From www.1937and1938Buicks.com have noticed the following are missing

Volume VIII Issue 1 (October 1989)

Volume VIII Issue 2 (November 1989)

Volume XI Issue 8 (June 1993) was it issued ?

Volume XI Issue 9 (July 1993) was it issued ?

If anyone has a hard or soft copies would appreciate a copy or pdf

Have no idea who maintains / pays for the site: does a good service

Edited February 9, 2013 by 1939_buick (see edit history)