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#1 |
Junior Member
Join Date: Dec 2017
Posts: 53
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Liked 4 Times in 4 Posts
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I originally intended for my truck to run Super Street (hence the name), but I'm still gunshy on boost and fueling. Right now it runs 12.0's (7.70's) in fair weather with a 4" pulley which is a good spot for that index class.
With a 3.70 pulley it runs 11.60's (7.40's) and I plan on getting a 3.55 pulley as well - that will be my fastest pulley as a 3.40 will spin the impeller past the rating. I want to be able to run 7.0 index as well. The truck has a full float Ford 9" so gear changes are easy. But I don't know what gear ratio I want to go to. Right now I'm running 4.10 with DOT 3354R's (28"/88"). I already have a set of FSS 3060R (30"/93") slicks. The taller tire will help combat spinning off the transbrake while making up for the short gear at the other end. Right now I'm slipping 15% at the 1/8 and 5% at the 1/4. In February I went 7.41 and this weekend I went 7.49, both on the 3.70 pulley. So weather doesn't seem to affect it much with the EFI. Based on my math, 5.13's would compliment the taller tire if the slip stays at 5%, but 4.71's if it stays at 15%. How do converters typically react after a gear change? In my mind, as long as the driveshaft RPM and power output are the same, then engine RPM should be the same, regardless of track length. But does reality follow this or another direction? Guidance is appreciated. For the table, the left stack is driveshaft RPM and the right stack is engine RPM. I used the truth numbers from the logger for 4.10/3354R and extrapolated the rest of the data. Last edited by DailyDriverSst; 08-30-2023 at 02:40 AM. |
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#2 |
Senior Member
Join Date: Apr 2020
Location: Phila, PA
Posts: 658
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Liked 584 Times in 315 Posts
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I have always run a manual trans.
Based on one person I know. Making only a change to a lower gear ratio reduced his convertor slippage. Stan |
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#3 |
VIP Member
Join Date: Jan 2003
Location: Allentown,PA
Posts: 2,443
Likes: 805
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Making a change from a 4.29 rear gear to a 4.56 gear reduced slip on my converter from 12% down to 5 1/2% . of course the converter flash stall dropped about 300 rpm .
overall trap rpm increased 200 rpm and MPH increased by 2 MPH.
__________________
Tom Goldman 1500 SG , 1506 STK |
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#4 |
VIP Member
Join Date: Dec 2001
Location: phoenix
Posts: 1,451
Likes: 57
Liked 691 Times in 274 Posts
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My bracket car had 4.30 gears and went to 4.88 converter is 500 tighter on leave and 10% slip at 1/8 mile. Down from 13% car runs 6.50 in 1/8
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#5 | ||
Junior Member
Join Date: Dec 2017
Posts: 53
Likes: 0
Liked 4 Times in 4 Posts
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Thank you for the feedback. |
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