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1941 Buick Limited Limousine


Matt Harwood

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On 10/18/2023 at 3:39 PM, Fox H. said:

I must admit, I was very excited when I saw the notification that this thread was getting some attention! Definitely one of my favourite cars on this forum and makes me want to buy a 320 ci '41 Buick sometime soon.
 

Can't wait to see what all you'll be doing to it. I'll be following with poorly veiled enthusiasm. 

  As the owner of a '41 Roadmaster which I restored to be a nice driver, with higher speed rear gears from a 50's Buick I cannot recommend them enough. As long as the car is properly sorted out they are great drivers!

Keith

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2 hours ago, Buicknutty said:

  As the owner of a '41 Roadmaster which I restored to be a nice driver, with higher speed rear gears from a 50's Buick I cannot recommend them enough. As long as the car is properly sorted out they are great drivers!

Keith

Hi Keith, what ratio were in your Roadmaster, and what ratio have you moved to (and from which year)?

 

Here in Australia, we have many open spaces and I do long miles occasionally (our nearest interstate capital is 500 miles), so I'm very interested in having better mileage in my 41 Roadmaster (under full restoration now).

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21 hours ago, Grant Z said:

Hi Keith, what ratio were in your Roadmaster, and what ratio have you moved to (and from which year)?

 

Here in Australia, we have many open spaces and I do long miles occasionally (our nearest interstate capital is 500 miles), so I'm very interested in having better mileage in my 41 Roadmaster (under full restoration now).

 Grant, mine had the 3.9's, which were the stock ones, and here most had this ratio, though 3.6's were optional. I got a set of 3.4's out of a '55 Century plus I have a recalibrated speedo so I know what speeds I'm going. I did drive it for a while with the 3.9's in it after I got it on the road and it wasn't horrible, but the 3.4's are better. Less engine noise too. It seems to be comfortable driving in the 65-70 MPH range for long distances as I've done that in it. Metric, that's 110 or a bit over.

 My self imposed speed limit is 75 MPH, or about 120 KPH, it's got lots more but I figure that is plenty fast enough.

 I also run wide white radials, Diamondbacks, and they help with the driving experience.

 

 I hope this helps.

Keith

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3 hours ago, Buicknutty said:

 Grant, mine had the 3.9's, which were the stock ones, and here most had this ratio, though 3.6's were optional. I got a set of 3.4's out of a '55 Century plus I have a recalibrated speedo so I know what speeds I'm going. I did drive it for a while with the 3.9's in it after I got it on the road and it wasn't horrible, but the 3.4's are better. Less engine noise too. It seems to be comfortable driving in the 65-70 MPH range for long distances as I've done that in it. Metric, that's 110 or a bit over.

 My self imposed speed limit is 75 MPH, or about 120 KPH, it's got lots more but I figure that is plenty fast enough.

 I also run wide white radials, Diamondbacks, and they help with the driving experience.

 

 I hope this helps.

Keith

Hi Keith, many thanks for your prompt response. I'm not sure what ratio my car has yet but probably 3.9's. I'm getting closer to restoring the torque-tube & differential (plus the engine & trans) so will know soon. 3.4's sound excellent.

 

I can convert miles to kilometers no problem as have grown up with both. I would also like to use the Diamondback radials. I use Firestone non-radials on my model 44 which is fine but think the Diamondbacks would be a great choice as I've heard they are fabulous.

 

Thanks again Keith.

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9 hours ago, Grant Z said:

Hi Keith, many thanks for your prompt response. I'm not sure what ratio my car has yet but probably 3.9's. I'm getting closer to restoring the torque-tube & differential (plus the engine & trans) so will know soon. 3.4's sound excellent.

 

I can convert miles to kilometers no problem as have grown up with both. I would also like to use the Diamondback radials. I use Firestone non-radials on my model 44 which is fine but think the Diamondbacks would be a great choice as I've heard they are fabulous.

 

Thanks again Keith.

I seem to remember the Series 40's and Series 50's have a ratio 4.10 or higher (4.56?) due to the smaller engine. Maybe someone else can confirm this.

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21 minutes ago, Fox H. said:

I seem to remember the Series 40's and Series 50's have a ratio 4.10 or higher (4.56?) due to the smaller engine. Maybe someone else can confirm this.

 

Small series cars have either 3.90 (very rare), 4.10, or 4.44 gears.

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20 hours ago, neil morse said:

Based on the red paint mark and the way it behaves on the road, I believe my '41 Super has the optional 3.9 rear end.  However, I have not confirmed this by looking inside.

Neil, i don’t know if you’ve ever opened your diff cover but the ratio is clearly stamped on the end of the pinion gear. Mine is the 4.1 in my 1941 special wagon. it doesn’t say 4.1 but rather the number of teeth on each of the ring and the pinion. 

 

thom

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I think my last post oversimplified things. I think to view the end of the pinion one needs to remove the spacer, the shaft and the four small gears. And maybe even slide the axles out a bit. Even then, you need to get up close, wipe the grease off and have a bright light. Attached is a photo of a pinion. It is a 4.4 ratio for a 1941. I thought of using it on my car if the current pinion was bad. It turns out the current pinion was fine. I also learned that the 4.4 requires a  differential case different from the case for the 3.9 and 4.1. 

EE27AB01-2D0F-4ACE-8A24-9D424C1C736F.jpeg

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1 hour ago, Shootey said:

Neil, i don’t know if you’ve ever opened your diff cover but the ratio is clearly stamped on the end of the pinion gear. Mine is the 4.1 in my 1941 special wagon. it doesn’t say 4.1 but rather the number of teeth on each of the ring and the pinion. 

 

thom

As I said, I haven't looked inside.  And based on your description of what's involved, I'm not about to try!  Maybe once you get your car on the road, we can take some comparison drives to see how my car compares with yours and see if we can detect a difference.

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On 10/26/2023 at 1:02 PM, drhach said:

Does this mean 4.0 ratio?

Diff.jpg

No.  See Shooteys response above and the photo below of a ring gear from my parts car showing the gear teath count confirming the 3.6 rear end:

 

IMG_6169.JPG.cafe7a51d5ff14bea6da6efb5d9d98ef.JPG

 

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On 10/26/2023 at 12:51 PM, Shootey said:

I also learned that the 4.4 requires a  differential case different from the case for the 3.9 and 4.1. 

I didn't know that but I am not surprised. It is true of most rearend designs that when the ratio changes enough, the case has to change. The case in a differential is the spinning part the ring gear mounts to. The taller the gears get, the bigger the pinion gets. At some point the ring gear would be too thin if manufactured to fit, and so a case with the ring gear flange further away from the pinion is needed.

 

On 10/26/2023 at 1:05 PM, neil morse said:

As I said, I haven't looked inside.  And based on your description of what's involved, I'm not about to try!  Maybe once you get your car on the road, we can take some comparison drives to see how my car compares with yours and see if we can detect a difference.

If you want to know and you don't want to take it apart there is a way. The torque tube complicates things but it is not impossible. You need two people some tape, and maybe a small mirror Take all the spark plugs out and jack up one (only one) rear wheel. Put the transmission in high gear. The first guy rotates the tire slightly to take all the slop out of the gearing. I usually do this in the direction the wheel would be turning to drive forward. With the slack out of the gearing, the first guy puts a tape mark at the top of the tire. With the first guy still holding tire with the mark straight up, the second guy puts a tape mark on top of the harmonic balancer or front pulley.

 

The first guy, with the slack still taken up, slowly turns the tire two full turns while the second guy watches the balancer and counts turns. The number of full turns of the balancer plus the clock position of the mark on the balancer tell the story.

 

3 turns and stopped at about 7 or 8 o clock? 3.6-1. 3 turns and stopped somewhere around 10 or 11 o clock? 3.9-1. 4 turns and stopped at one or two o clock? 4.11-1. 4 turns and stopped at about 4 or 5 o clock? 4.44-1.

 

It's kind of a pain but I'd rather do it than take a rearend apart. In some cases you might need a mirror to see the stopping point. Of course you need to know what the possibilities are for the gear ratio, and we do in this case. It would still give you a pretty close guess even if you didn't know that.

 

Edited by Bloo (see edit history)
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You can also remove the distributor cap and watch as the position of the rotor changes.  Since the distributor turns at half the crankshaft speed, the rotor position essentially provides a vernier scale to provide a finer resolution readout of crankshaft position.

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