|
11-06-2017, 08:53 AM | #1 |
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 |
11-06-2017, 07:35 PM | #2 | |
Senior Member
Join Date: Aug 2006
Location: Pukwana SD
Posts: 858
Likes: 555
Liked 97 Times in 47 Posts
|
Re: ET Differences Between Varying Powerglide Low Gear Ratio
Quote:
|
|
11-06-2017, 07:44 PM | #3 | |
Junior Member
Join Date: Mar 2012
Posts: 54
Likes: 0
Liked 0 Times in 0 Posts
|
Re: ET Differences Between Varying Powerglide Low Gear Ratio
Quote:
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. |
|
11-07-2017, 09:17 AM | #4 |
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 |
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 |
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 |
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 |
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.
|
|
|