Rear end ratios
06-23-2022, 04:11 PM
#22
Team Owner
Back in the 1960s I had 3 different cars all with my favorite rear end ratio. 3.91 They were all Mopars. Those rears back then were all removable center sections, easy to change. Pull the pumpkin, clean things up and work right on a bench to change ratios. We switched out two 3.23s and a 3.55. Course working at my buddies speed shop garage made the costs easy to handle.
I was very heavily into street racing back then.
My cars were considered fast street cars and with those 3.91s and a good set of slicks did well at the drag strip also. With Mopars and many available pumpkins I tried all gear from 3.23 to 4.88 and as this is a street car (my only vechicle in upper NY state) settled on 3.91!
I was very heavily into street racing back then.My cars were considered fast street cars and with those 3.91s and a good set of slicks did well at the drag strip also. With Mopars and many available pumpkins I tried all gear from 3.23 to 4.88 and as this is a street car (my only vechicle in upper NY state) settled on 3.91!
06-23-2022, 05:26 PM
#24
Team Owner
more carburetor thinking, some cars don't need a tune if it counts axle revolutions.
06-23-2022, 05:41 PM
#25
Melting Slicks
One thing you will notice quite quickly.
Your rear tires will wear out much faster than the front tires.
I'm not entirely sure what the exact reason for this is, but it's been the case in all of the muscle cars that I've ever owned.
Changing the rear gears numerically higher, say 3.54:1 to 4:11:1 will cause the rear tires to just melt off of the wheels.
It's a mystery.
Crabs
Your rear tires will wear out much faster than the front tires.
I'm not entirely sure what the exact reason for this is, but it's been the case in all of the muscle cars that I've ever owned.
Changing the rear gears numerically higher, say 3.54:1 to 4:11:1 will cause the rear tires to just melt off of the wheels.
It's a mystery.
Crabs
06-23-2022, 05:47 PM
#26
Melting Slicks
Increasing gear ratio is for helping slow cars
You should be lowering the numerical ratio and adding power not increasing the number to make up for lack of power
The faster the car the lower the number in the differential gear, the higher the top speed of each gear
You should be lowering the numerical ratio and adding power not increasing the number to make up for lack of power
The faster the car the lower the number in the differential gear, the higher the top speed of each gear
06-23-2022, 06:12 PM
#28
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The Cam happy spot is also big difference in the two cars.
I wouldn't touch the gear in the Caddy, I would change, down Pipe, pulley, intake, tune
06-23-2022, 08:20 PM
#29
Safety Car
The difference is very noticeable. According to GM, the lower axle ratio shaves 1/2-second off the 0-60 time and 1/2-second off the 1/4-mile time.
Even my Corvette mechanic noticed the car was more peppy than other auto C5 Vettes. He was puzzled as to why this was since he knows my car is 100% stock. Once I told him about the rear axle ratio, he understood why.
WRT to reduced top speed, I'd imagine that your CTS V is aero-limited, like the Corvette. So, your top speed won't change, but your mileage will go down slightly.
On a recent cross-country trip, I averaged 26 MPG instead of the 29 MPG others report getting in their Vettes.
06-23-2022, 08:35 PM
#30
Banned Scam/Spammer
Actually, maybe not. I swapped the gear in a 1990 Mustang 5.0 from 2-something to 4:10's and it had the exact opposite effect. With the tall gear once the tires broke loose it would boil the hides...4:10 gear took the spin out of it and it just hooked and went.
06-23-2022, 08:43 PM
#31
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Performance, acceleration, street racing, etc.? Going back more than 50 years, it only matters out of the hole, assuming you can hook up.
It will definitely FEEL MUCH FASTER (but really isn't) but once out of low gear it won't really make any difference at all. All else being equal, the better driver wins.
Flame away, kiddos.
06-23-2022, 09:08 PM
#32
Banned Scam/Spammer
There you go kiddo...
06-23-2022, 09:10 PM
#33
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06-23-2022, 11:22 PM
#35
Le Mans Master
Had the 3.91 in my 1LE Camaro. Swapped one into my non-1LE as well. Eaton TruTrac
06-23-2022, 11:57 PM
#37
Drifting
Get a gear calculator and you can see the difference on a graph with shift points and engine RPM, and experiment with other combinations.
I'd say the 3.73 will accelerate quicker and make the car feel a little lighter.
I'd say the 3.73 will accelerate quicker and make the car feel a little lighter.
06-24-2022, 03:58 PM
#38
Team Owner
I'll agree with this. My 1980 T/A had 3:73's when I bought it. I just changed from the TH400 to a T56 and 3:42's. It will also have a pretty health 402 LS stroker so I wanted the extra gearing and better fuel economy.