1941 Buick Transmission Differences 248ci vs 320ci

[Grant Z]

Can anyone tell me what are the differences between the two different transmissions used behind the 2 different straight 8 engines (248 & 320) in a 1941 Buick (and perhaps other years)?

 

No doubt the big 320 used a significantly stronger transmission than the 248 engine, but what made it stronger internally? What engineering differences were there and how are these 2 transmissions identified. No doubt they had different cases etc. Did the big 320 use a similar or same transmission as was in the Cadillac?

[Bloo]

The big Buick is is a completely different transmission family. The quickest way to tell is a 5 bolt top on the small transmission and a 6 bolt top on the bigger unit.

 

The famous Cadillac/Lasalle transmission may share some design features with the big Buick, maybe even some internal parts, I'm not sure on that point. The Buick transmissions are both toploaders and the Cadillac/LaSalle is not.

 

This is a Pontiac, but it is the Buick large transmission family. Ignore the tailshaft, because Buick would have a huge torque ball there. Look at the shape of the top cover.

 

 

That top cover still had the same shape back in 38 or so when the shifter was still on top. Internal parts changed over the years too, but the basic shape of the case and the top opening remained the same on the big transmission. Note the top has 6 bolts. Now here is an older one with top shift, another Pontiac, but it is still the Buick large family. Note the tall rather normal looking shift tower.

 

 

Now the small Buick family. This is a 39 Buick small transmission, top view. Note the more oval shaped opening at the top. Those pans look different on different years, some are flatter with stamped cross ribs. Also note 5 bolts holding it on.

 

 

The whole transmission is smaller and so are the parts inside. It is much lighter duty. Back around 38 when the small Buick transmission still had the shifter on top, the top opening was a different shape than the 39 pictured above.

 

This is a top view of a 36 Pontiac with top shift. It is of the small Buick family. Note that the top opening is less oval on this version with a top shifter, and more like the shape of the big Buick opening. The holes marked in red are not bolt holes, so there are still only 5 bolts.

 

 

Here is the same 36 Pontiac transmission in the car. Note the shift tower and how odd looking and short it is. Even with it's black rubber boot on top, it barely sticks through the floor half an inch on most cars. I know of no other transmission that looks like this. If you see this odd short shift tower, you are looking at a transmission of the small Buick family that is old enough to have a top shifter. Still 5 bolts on the top cover.

 

 

Here is a column shift LaSalle. This is laying on it's side, and the bolted cover at the right is the bottom of the transmission.

 

 

And here is what it looked like in 1937 when the shifter was still up on top.

 

 

 

Edited November 1, 2022 by Bloo (see edit history)

[Grant Z]

2 hours ago, Bloo said:

Many thanks for all that information. It is much appreciated.

I will get to see a transmission from a 1941 Roadmaster Convertible Coupe (76C) soon as I'm in the process of purchasing one. The car needs full restoration, and I'm looking forward to the task (I think).

Regards, Grant Zippel

 

[Shootey]

Didn’t the hot Rodders use the La Salle trans for drag racing? Why was it superior?

[Bloo]

It was less prone to breaking under that sort of abuse than most other things that were available at the time.

[Oldtech]

Rule no 1 with Buicks. Almost nothing interchanges between the small and large models. 😁

[1939_Buick]

12 hours ago, Grant Z said:

Can anyone tell me what are the differences between the two different transmissions used behind the 2 different straight 8 engines (248 & 320) in a 1941 Buick (and perhaps other years)?

 

No doubt the big 320 used a significantly stronger transmission than the 248 engine, but what made it stronger internally? What engineering differences were there and how are these 2 transmissions identified. No doubt they had different cases etc. Did the big 320 use a similar or same transmission as was in the Cadillac?

As above 248 vs 320 transmission are 99.99% different.  Top cover 5-6 bolts most obvious difference.

1939 is the first year of column change. 1938 and before floor change.  Different top design - case.

For 1939 and before Buick changed transmission design - part numbers every years / 2 years. Many 1 year only parts. 

1940 and later more commonality.

For a 320ci transmission from 1940 to late 40's, maybe early 50's they are the same or very close. Many part numbers the same.

For a 248ci transmission from 1940 to late 40's, maybe early 50's they are the same or very close. Many part numbers the same.

But no 248 320 interchange.

 

The large 320ci transmissions hard to get to AU as few 1940-1941 series 60-80-90 (320ci) cars sold compared to series 40 (248ci).  And fewer after WW2. Most post WW2 sales seem to be S40 248ci specials.  Until GM started making-selling the Holden brand, when Buick sales stopped.

 

 

 

Edited November 1, 2022 by 1939_Buick (see edit history)

[Grant Z]

14 hours ago, 1939_Buick said:

As above 248 vs 320 transmission are 99.99% different.  Top cover 5-6 bolts most obvious difference.

1939 is the first year of column change. 1938 and before floor change.  Different top design - case.

For 1939 and before Buick changed transmission design - part numbers every years / 2 years. Many 1 year only parts. 

1940 and later more commonality.

For a 320ci transmission from 1940 to late 40's, maybe early 50's they are the same or very close. Many part numbers the same.

For a 248ci transmission from 1940 to late 40's, maybe early 50's they are the same or very close. Many part numbers the same.

But no 248 320 interchange.

 

The large 320ci transmissions hard to get to AU as few 1940-1941 series 60-80-90 (320ci) cars sold compared to series 40 (248ci).  And fewer after WW2. Most post WW2 sales seem to be S40 248ci specials.  Until GM started making-selling the Holden brand, when Buick sales stopped.

 

 

 

Hi mate, many thanks for that information. Most helpful.

Regarding getting a 320ci transmission here, I don't need to worry about that as it's not for my current car (1941 Special Coupe Model 44). I'm actually in the process of purchasing a 1941 Roadmaster Model 76C Convertible Coupe which requires a full restoration (but is very complete and heaps of NOS parts & chrome/die-cast done already). I will post on the forum when it arrives (from Perth) and the work begins.

I simply wish to get my head around the transmission differences purely out of interest and to understand the car I'm buying and it's differences mechanically to what I currently own.

Thanks again, Grant

 

 

[Shootey]

A Buick owner who often posts here mentioned to me by phone that he adapted his 1941 Super to accept a big series transmission. He said it was much stronger which I’m sure it was. 

[DonMicheletti]

Why do you want to go to the larger transmission? I have never heard of anyone breaking one of the smaller transmissions.

I have both a Special and Rodmaster ('38's) and have rebuilt both  while restoring the cars..

As mentioned, the two are entirely different. The gears in the larger trans are significantly wider than in the smaller trans - as expected. The larger trans is much heavier and longer too.

Unless the engine is highly modified, I'd see no reason to go to the expense and work to change over.

Additionally, parts for the smaller trans should be cheaper (?) and more available.

 

I remember when having a Roadmaster floor box behind a hopped up flathear FORD V 8 was a big deal.

[Grant Z]

9 hours ago, Shootey said:

A Buick owner who often posts here mentioned to me by phone that he adapted his 1941 Super to accept a big series transmission. He said it was much stronger which I’m sure it was. 

I’m not wishing to put a ‘big’ trans behind my 248. I’m just interested in knowing the differences as I’m in the process of purchasing a Roadmaster which of course has one. Thanks anyway. 
Cheers Grant

[Grant Z]

8 hours ago, DonMicheletti said:

Why do you want to go to the larger transmission? I have never heard of anyone breaking one of the smaller transmissions.

I have both a Special and Rodmaster ('38's) and have rebuilt both  while restoring the cars..

As mentioned, the two are entirely different. The gears in the larger trans are significantly wider than in the smaller trans - as expected. The larger trans is much heavier and longer too.

Unless the engine is highly modified, I'd see no reason to go to the expense and work to change over.

Additionally, parts for the smaller trans should be cheaper (?) and more available.

 

I remember when having a Roadmaster floor box behind a hopped up flathear FORD V 8 was a big deal.

I’m not wishing to put a ‘big’ trans behind my 248. I’m just interested in knowing the differences as I’m in the process of purchasing a Roadmaster which of course has one. Thanks anyway. 
Cheers Grant

[2carb40]

On 11/7/2022 at 10:23 AM, DonMicheletti said:

Why do you want to go to the larger transmission? I have never heard of anyone breaking one of the smaller transmissions.

I have both a Special and Rodmaster ('38's) and have rebuilt both  while restoring the cars..

As mentioned, the two are entirely different. The gears in the larger trans are significantly wider than in the smaller trans - as expected. The larger trans is much heavier and longer too.

Unless the engine is highly modified, I'd see no reason to go to the expense and work to change over.

Additionally, parts for the smaller trans should be cheaper (?) and more available.

 

I remember when having a Roadmaster floor box behind a hopped up flathear FORD V 8 was a big deal.

I have a 1940 Super with factory 4.40/1 rear ratio and 5 bolt top cover trans. It will get a better highway ratio, but RE trans differences, the 6bolt has a slightly different 1st gear  ratio. I thought of swapping that in, but I acquired a 3.40/1 from a 55 Century. 4.40 gears allow you to fight for second gear by the time your in the middle of an intersection! Design in 1940 was accomadating a national average speed of approx 45mph, much different conditions from current. Just a few thoughts.

[Joseph P. Indusi]

I realize that the 248 engines were certainly not as powerful as other car engines were but they were not terribly underpowered.   However, Buicks in the 1940's, even into the early 50's used ratios such as 4.40 and 4.45 in many Specials and Supers.  I always have thought they did this because they did not have an automatic until 1948 so with these ratios once you were on the move the engines had enough torque so you did not need to shift frequently.   Just my thought because I have no way to know what Buick engineers were thinking then.

Joe, BCA 33493 

[Ben Bruce aka First Born]

On 11/8/2022 at 6:34 PM, 2carb40 said:

I have a 1940 Super with factory 4.40/1 rear ratio and 5 bolt top cover trans. It will get a better highway ratio, but RE trans differences, the 6bolt has a slightly different 1st gear  ratio. I thought of swapping that in, but I acquired a 3.40/1 from a 55 Century. 4.40 gears allow you to fight for second gear by the time your in the middle of an intersection! Design in 1940 was accomadating a national average speed of approx 45mph, much different conditions from current. Just a few thoughts.

 

 I installed those same gears in my 1950.  MUCH better hwy gears.  I do shift to 2nd more in town.

 

  Ben

[Grant Z]

9 hours ago, Joseph P. Indusi said:

I realize that the 248 engines were certainly not as powerful as other car engines were but they were not terribly underpowered.   However, Buicks in the 1940's, even into the early 50's used ratios such as 4.40 and 4.45 in many Specials and Supers.  I always have thought they did this because they did not have an automatic until 1948 so with these ratios once you were on the move the engines had enough torque so you did not need to shift frequently.   Just my thought because I have no way to know what Buick engineers were thinking then.

Joe, BCA 33493 

Hi Joseph, yes I agree with you when you say that the 248 engine is not under-powered. I'm very happy with mine after having driven a '48 Chevy with a 216 Stovebolt. I cannot imagine what I'm in for when I get my Roadmaster and finish restoring it. No wonder they call the Roadmaster Convertible "the Banker's Hot Rod".