ET Differences Between Varying Powerglide Low Gear Ratios?

JP Schuster · 11-06-2017, 08:53 AM

I was curious to know how much ET could be gained/lost by changing the low gear ratio of a Powerglide? I know the ratios typically range from 1.76-2.18, but is there a sweet spot for how much harder the car leaves vs. subsequently how long the car is in high gear? Or do the 60' gains outweigh the longer amount of time in high gear?

Background: I currently have a 1.94 low gear PG and I am looking to speed up my 60's. Would a 2.08 / 2.18 low gear be worth the investment?

Thanks,

JP

Jim Hanig · 11-06-2017, 07:35 PM

Quote:

Originally Posted by JP Schuster

I was curious to know how much ET could be gained/lost by changing the low gear ratio of a Powerglide? I know the ratios typically range from 1.76-2.18, but is there a sweet spot for how much harder the car leaves vs. subsequently how long the car is in high gear? Or do the 60' gains outweigh the longer amount of time in high gear?

Background: I currently have a 1.94 low gear PG and I am looking to speed up my 60's. Would a 2.08 / 2.18 low gear be worth the investment?

Thanks,

JP

How much power are you making,and tq. The 2.18 is a pretty weak gear set. I ran a 2.18 in my ss 327 it was about 4 hun in the. 60 ft fasted than the 1.96 I broke it last year but i did run for about 5 years. Lot of thing factor in , weight gear tire etc etc/

JP Schuster · 11-06-2017, 07:44 PM

Quote:

Originally Posted by Jim Hanig

How much power are you making,and tq. The 2.18 is a pretty weak gear set. I ran a 2.18 in my ss 327 it was about 4 hun in the. 60 ft fasted than the 1.96 I broke it last year but i did run for about 5 years. Lot of thing factor in , weight gear tire etc etc/

Thanks Jim,

I have a 3230 lb car with 775 hp and 500 ft lbs of torque. I have also seen that the higher ratio low gears tend to have an HP disclaimer on them.

Jeff Jewell · 11-07-2017, 09:17 AM

A bunch of years back when I was messing with our A/SA '67 Corvette, I had a glide with a 1.98 low. 1.94 - 1.98 always seemed to be the sweet spot. I broke the planetary at a division race and the only spare I had handy was a 1.82 geared bracket glide. Car left like a turd and lost .04 in 60', but only slowed .02 in ET. Most if not all of the .02 was the bracket trans didn't have the lightweight parts and all the other tricks. While all that gear helps the leave, doesn't really make much of a difference in overall ET.

Your mileage may vary...

Crew Chief · 11-07-2017, 09:46 AM

Using a gear ratio - RPM - MPH calculator you can figure out what RPM the engine drops to when the transmission shifts to high gear. If the RPM is below the stall of the convertor, there will be slippage until the RPM reaches the stall speed. Plug in different 1st gear ratios to figure it out.

http://www.wallaceracing.com/gear-speed.php

Angelo DiTocco · 11-08-2017, 09:05 AM

I agree with Jeff especially with the HP you're making. A 1.82 should be more than enough.

2021STK · 11-08-2017, 11:43 AM

Looks to me in that calculator the trans and rear gear data inputs are reversed. Should be: tire diameter, rear gear, trans 1st, trans 2nd, trans 3rd

jimmyparker · 11-08-2017, 08:42 PM

If the same converter is used in low gear comparisons the results may be slightly off. A 1.76 low gear will work the converter harder leaving than a 2.18, the 2.18 will work the converter a lot harder on the high gear shift. At one time I bracket raced an A/SA some, when on slick tracks I would leave in 2nd gear and always saw more quite a bit more flash.

11-06-2017, 08:53 AM	#1
JP Schuster Junior Member Join Date: Mar 2012 Posts: 54 Likes: 0 Liked 0 Times in 0 Posts	ET Differences Between Varying Powerglide Low Gear Ratios? I was curious to know how much ET could be gained/lost by changing the low gear ratio of a Powerglide? I know the ratios typically range from 1.76-2.18, but is there a sweet spot for how much harder the car leaves vs. subsequently how long the car is in high gear? Or do the 60' gains outweigh the longer amount of time in high gear? Background: I currently have a 1.94 low gear PG and I am looking to speed up my 60's. Would a 2.08 / 2.18 low gear be worth the investment? Thanks, JP

11-07-2017, 09:17 AM	#4
Jeff Jewell Member Join Date: Jun 2002 Location: Bangor, PA Posts: 182 Likes: 41 Liked 172 Times in 36 Posts	Re: ET Differences Between Varying Powerglide Low Gear Ratio A bunch of years back when I was messing with our A/SA '67 Corvette, I had a glide with a 1.98 low. 1.94 - 1.98 always seemed to be the sweet spot. I broke the planetary at a division race and the only spare I had handy was a 1.82 geared bracket glide. Car left like a turd and lost .04 in 60', but only slowed .02 in ET. Most if not all of the .02 was the bracket trans didn't have the lightweight parts and all the other tricks. While all that gear helps the leave, doesn't really make much of a difference in overall ET. Your mileage may vary...

11-07-2017, 09:46 AM	#5
Crew Chief Member Join Date: Jun 2003 Posts: 184 Likes: 0 Liked 11 Times in 6 Posts	Re: ET Differences Between Varying Powerglide Low Gear Ratio Using a gear ratio - RPM - MPH calculator you can figure out what RPM the engine drops to when the transmission shifts to high gear. If the RPM is below the stall of the convertor, there will be slippage until the RPM reaches the stall speed. Plug in different 1st gear ratios to figure it out. http://www.wallaceracing.com/gear-speed.php

11-08-2017, 09:05 AM	#6
Angelo DiTocco Senior Member Join Date: Dec 2001 Location: NY, NY Posts: 735 Likes: 155 Liked 172 Times in 38 Posts	Re: ET Differences Between Varying Powerglide Low Gear Ratio I agree with Jeff especially with the HP you're making. A 1.82 should be more than enough. __________________ Angelo DiTocco '98 Firebird SS/HA '98 Firebird B/SA

11-08-2017, 11:43 AM	#7
2021STK Member Join Date: Jun 2007 Posts: 281 Likes: 273 Liked 17 Times in 14 Posts	Re: ET Differences Between Varying Powerglide Low Gear Ratio Looks to me in that calculator the trans and rear gear data inputs are reversed. Should be: tire diameter, rear gear, trans 1st, trans 2nd, trans 3rd __________________ Dave Outten 2222 S/SS/SST/SG/HR 2021 S 1968 SS 1969 SR 1966 1990 Bracket

11-08-2017, 08:42 PM	#8
jimmyparker Member Join Date: Oct 2009 Location: columbus, georgia Posts: 360 Likes: 41 Liked 225 Times in 71 Posts	Re: ET Differences Between Varying Powerglide Low Gear Ratio If the same converter is used in low gear comparisons the results may be slightly off. A 1.76 low gear will work the converter harder leaving than a 2.18, the 2.18 will work the converter a lot harder on the high gear shift. At one time I bracket raced an A/SA some, when on slick tracks I would leave in 2nd gear and always saw more quite a bit more flash.