Buick Rear Axle Ratios through the Years

[B Jake Moran]

I was thinking the other day about axle ratios and how they have changed over the years.  What year is your Buick and what is the axle ratio?  

 

This started because of a conversation I was having regarding the post war horsepower and accessories "wars" that developed most of our modern technologies we take for granted now. 

 

I don't remember all of my ratios because I have owned 260 vehicles but -

 

1964 Buick Electra posi traction 3.08

1971 Riviera 2.73

1985 LeSabre 2.56 (I think) 

1968 Riviera 3.08 

[EmTee]

1938 Century, 3.9:1

1967 Riviera, 3.08:1

[JohnD1956]

56 Super: 3.36

69 GS 400 ( automatic) 2.97

72 Electra 2.73

Not sure of the other two but I did have a 95 Riviera (Supercharged) with a 2.97 and a 93 Regal with a 3.06 ( I think).

 

Had to edit mine. The '56 is a 3.36, not a 3.56. 

Had to edit mine a 2nd time. The Electra is a 2.73 not a 2.97

 

[Ben Bruce aka First Born]

1950  Special

  4.10    changed to 

   3.36

 

  Ben

[B Jake Moran]

13 hours ago, Ben Bruce aka First Born said:

1950  Special

  4.10    changed to 

   3.36

 

  Ben

Interesting Ben.  This is one of the reasons I asked.  Was to get a perspective of why at a certain time.  

 

1950 Specials had what?  the 248 still?   Developed 125 hp or so.  All Buicks in 1950 were considered premium GM products, you still got an 8 cylinder and OHV operation with a Buick.  Pontiac had smaller bodies and either a flathead 6 or 8.  

 

But in 1950, the horsepower and technology race was on.  Roads were improving, you could go faster.  4.10 seems about right to get the old girl up to speed especially with a Dynaflow. 

[Ben Bruce aka First Born]

Dynaflow came with a 3.9 with3.6 optional in the Spcial.   Synchromesh was 4.1 with 3,9 optional.

 

 My car could handle faster [ lower numbers ] at hwy speed,  but about as fast as practical at dead stop take off. 

 

  Ben

[NTX5467]

Other than the typical roads for the time the particular cars were built, there was also the issue of "shiftless driving with a manual transmission".  Where you started in "low" and got into "high gear", and then drove around town in "high gear" at various speeds.  Only downshifting to go around slow corners or stopping, etc.  For which the 4.10s and such worked pretty well.  Saved on clutches, too.

 

As engine sizes and horsepower increased in the post-1957 era, then rear axle ratios of down to 2.69 became available (not on Buicks, though) to allow for "relaxed cruising" on the new/soon-to-be Interstate Highway System.  When coupled with the then-new 3-speed automatics (not on Buicks, at that time).  Kind of like the later 3-speed w/OD automatics of the 1980s, in effect.  Lower low gear (2.45 or so) and 2.69 rear axle gave at least as good of acceleration as a 2-speed automatic with a 3.25 axle ratio.  In that time frame, many Buicks were still in the 3.64 or so range, with DynaFlows, but got down to the 2.71-2.93 range with the 1965 SP THM400s in 1965, as I recall.

 

On a few side notes -- It was not until I was sharing a shop with my machine shop operative in the 1980s that I realized that most, if not all, of the really "hot" drag racer 1957 Chevies usually had 4.56 gears in them.  Which let the 283s scream and perform to the max. // I had always noticed that the 1961 Chevy Impala always came with a 3.36 rear axle ratio, but similar BelAir and Biscayne models had 3.08s (with the same engine, usually a 283).  I asked my machine shop operative about that.  He smiled and noted the Impalas were a bit heavier (better seat foam, sound deadening, and more options), so they got a notch lower rear axle ratio to ensure that "the best Chevy" did not get beat (at the red light) by a lesser-than-best Chevy.  Considering the various marketing things at play back then, it made sense.

 

Back in the 1980s, as many GM divisions were looking at OHC and such, Buick was firmly "cam in block, OHV" in nature.  When a magazine operative asked about upcoming Buick OHC V-8s and such, the Buick engineer allegedly replied "For our customers, acceleration stops at the other side of the intersection".  Which meant off-idle response was "king", rather than 6000rpm power.  Which also gets back to the smaller carburetors Buick tended to use for 2bbls, back then and into the earlier 1970s.  Great off-idle response and good fuel economy.  Larger cars/engines got 4bbls.  Holley now has Sniper EFI for the small and large pattern Rochester 2bbls!

 

Sorry if I got a bit off-topic,

NTX5467

[Marty Roth]

Trying to recall the differential ratio for my 1937 80C Roadmaster Phaeton (convertible sedan)?

 

Classiccardatabase claims 4.22:1

http://classiccardatabase.com/specs.php?series=323&year=1937&model=2524

Is this correct?

Differential Ratio

4.22 to 1

Edited December 18, 2021 by Marty Roth (see edit history)

[MrEarl]

I have a '54 Roadmaster (72R) with a 3.9, standard is 3.6. This is the same Roadmaster with the 322 with adjustable rockers, so go figure.

[neil morse]

'41 Super (248 ci.) with optional 3.9 rear end.  (4.41 was standard.)  I'm happy my car is equipped the 3.9 as it makes freeway driving very comfortable -- 60-65 mph not a problem.

[Bloo]

On 12/18/2021 at 2:11 PM, Marty Roth said:

Trying to recall the differential ratio for my 1937 80C Roadmaster Phaeton (convertible sedan)?

 

Classiccardatabase claims 4.22:1

http://classiccardatabase.com/specs.php?series=323&year=1937&model=2524

Is this correct?

Differential Ratio

4.22 to 1

 

I believe so. If not, it is very close to that according to the shop manual which I don't have easy access to at the moment. 37 Roadmasters had lower gears than the Century's 3.90 , and higher than the Special's 4.44 . Interestingly, the 37 Roadmaster axle is a different design and the gears do not interchange with the other two models mentioned.

 

 

[Ted "Wildcat65" Nagel]

64 LeSabre Wagon-3.08

65 Wildcats - 3.08 with automatics; 3.42 with  a 4-speed

67 Wildcat - was an open 3.08, now 3.42 

69 and 70 Stage 1 - 3.64

65 Special Wagon- came with 3.23, my favorite.

65 GS - 3.31

65 Riv 3.23

65 Electra - was 3.08 - now 3.23 posi

 

I may be a wee obsessed with them.

I've got 3.91 gears for a special occasion.

[KAD36]

55 Super: 3.40.  
 

Just a little taller than the 3.36 in 56, probably because the 56 transmission had an extra stator for more torque so could get away with a slightly lower gear - or was there a different reason?

Edited January 15, 2022 by KAD36 (see edit history)

[Bloo]

Didn't the axle design change that year? GM history has several instances where the axle design changed and a close but not exact ratio was used in the new design. 3.36 to 3.40 is about a 1% change.

[NTX5467]

As the mid-1960s came upon us with an increasing number of Interstate or Interstate-like highways and toll roads, plus the 70mph national speed limit on most of them, that meant that engine cruise rpms would also increase.  For example, a 3.23 gear with an 8.45x15 tire would result in about 25mph/1000 rpm, which would make 75mph be 3000 rpms.  With the larger engines, that was kind of a waste, to me.  Yet with a 2.73 gear and 8.55x14 (no type) tire size, that meant about a 28.6 mph/1000 rpm cruise, which lowered the cruise rpm a bit and used the more lower-rpm torque of the larger engine to good advantage.  Plus a fuel economy increase, too!  By this time, too, the vast majority of automatic transmissions were THREE-speed automatics, with a deeper "low gear" than the prior 2-speed automatics (generally 2.4 vs 1.7), a progression which continued into the 1980s 4-speed OD automatics with 3.07 (THM700) and .7 OD ratios.

 

In some cases, it seemed to me that Buick was bound to make smaller engines (300 V-8s) work in their cars as other brands aimed more toward 350 CID size engines.  With the smaller engines having a 2-speed DynaFlow behind them, which needed the deeper rear axle gears to work decently well around town, I suspect.   Which meant that it was not until the 300 grew to 340+ that Buick really was competitive in this area.

 

The observed "saving grace" with the later 2-speed automatics was that they consumed fewer horsepower in doing what they did.  By comparison, the Chevy PowerGlide consumed a good bit less power than the later and stronger THM350s, and especially the THM400s.  No doubt, the Buick ST300s were similar?  Which made the base Buick LeSabre 350s with the ST300 (switch-pitch and fixed-stator verions) a decent choice between cost/performance in places (like TX) with large expanses of Interstate highways to travel on for hours at a time, with the later "lower cruising rpm" rear axle ratios.  Remembering, too, that Buick V-8s usually had better lower-rpm torque characteristics than other V-8s of similar sizes did (regardless of what a dyno-curve of power output might state).  Responsive low-rpm torque, although a bit less in number, can make a car more fun to drive with minimal driver throttle input, from my experiences.  No need to "coax it out", for example.  Then tailor the torque converter and rear axle ratio to compliment it for a better combination!  Which is why a Buick 350 V-8 runs nicer than a similar Chevy 350 V-8, from my experiences, in normal driving.

 

By observation, the progression into larger engines, 3-speed automatics, lower-number rear axle ratios, and the promise of long-distance travel on the then-new Interstate Highway System was showcased in the "1959 Ford Buyer's Guide" booklet.  In Ford's case, showcasing their new 352 V-8, Dual-Range Cruise-O-Matic 3-speed automatic transmission (really a Borg-Warner automatic), and the related 2.69 rear axle ratio.  Yet if more power was needed (as in pickup trucks), 3.00, 3.25, 3.50, and 3.89 rear axle ratios were available, too, but each of which would diminish the long-range cruise capabilities a bit.  "Trade-offs" in particular areas of the nation and customer demographics?  

 

By observation, 2bbl engines usually got the more economical rear axle ratios as the 4bbl "HP" engines would get the lower rear axle ratios.  At a time when the normal OEM 4bbl was only about 450-500cfm in size.

 

Just some thoughts and observations,

NTX5467

[michael.stumpf]

I have the following number on my buick rear end

GM

1168995   3

203

What do they mean?

I've been told it is a 3.7:1 final drive but how do I check?

Ta

Mick