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Question for drag racers

nutfinnnutfinn Member Posts: 12,808 ✭✭✭
edited September 2018 in General Discussion
So, with 3.15 gears, 12.86. I know there are lots of variables, but how much do you think I could shave off with 3.55 gears?

41218036964_246c606a1b_h.jpg

Comments

  • Don McManusDon McManus Member Posts: 23,695 ✭✭✭✭
    edited November -1
    As you state, there are too many variables.

    If you have the torque to handle the 3.15 ratio, you may not save a whole lot overall, though you will be a faster start with the 3.55s.

    How many gears in your transmission?

    What gear are you in at the end of the run?

    What RPM are you running at the end of the run?

    I would guess that a 3.55 ratio will require you to shift at least one additional time. Does the added torque at the line give you enough of a boost to justify an extra shift?
    Freedom and a submissive populace cannot co-exist.

    Brad Steele
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    It's a six speed automatic, I am on on 3rd gear when I cross, no idea on the rmps, but it is likely about to change in the 4th (sounds like it) [:I]
  • Don McManusDon McManus Member Posts: 23,695 ✭✭✭✭
    edited November -1
    quote:Originally posted by nutfinn
    It's a six speed automatic, I am on on 3rd gear when I cross, no idea on the rmps, but it is likely about to change in the 4th (sounds like it) [:I]


    I can't guess how much time you would save, but with an automatic finishing in 3rd gear, I would think you would shave a noticeable amount off your overall time.

    If everything it tuned and time correctly, you can theoretically put 12% more torque to the rear tires throughout the run. While you won't see a 12% reduction in your time, it may be possible to see something approaching 10%, which would put you around 11.5 - 11.6.
    Freedom and a submissive populace cannot co-exist.

    Brad Steele
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    Thank you Sir [:)] I was hoping something like this.
  • GrasshopperGrasshopper Member Posts: 17,042 ✭✭✭✭
    edited November -1
    If you are only in 3rd then you can do much better. Lot's of power wanting to be let loose. I used to know the formula ect. but that's been a long while.
    I had a big block with 4:11 gears in a 4 speed manual and it went across at 6000 rpm so your six speed auto and motor would need something to the right of that. ?
  • grumpygygrumpygy Member Posts: 48,464 ✭✭✭
    edited November -1
    Think now you will start running into traction Problem's.
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by grumpygy
    Think now you will start running into traction Problem's.


    I am hoping I won't

    43631730692_2c365fbf8a_h.jpg
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    Next question [:)]

    - would you go with a used (33k miles) entire rear end, like this delivered to my house for $950? Just planning on using the differential. Selling or keeping the rest for spares??

    44527312802_f10aa3107d_o.jpg

    - or with this one, for about the same price?

    42767232380_9c5344d713_b.jpg
  • TRAP55TRAP55 Member Posts: 8,292 ✭✭✭
    edited November -1
    Get the Ford unit, there isn't any "unknowns" there. I assume that it's new or re-manufactured? Either way, break it in, and fluid change before you hammer it on the track.
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by TRAP55
    Get the Ford unit, there isn't any "unknowns" there. I assume that it's new or re-manufactured? Either way, break it in, and fluid change before you hammer it on the track.
    It is brand new
  • perry shooterperry shooter Member Posts: 17,105 ✭✭✭
    edited November -1
    YOU WILL DO MUCH BETTER YOUR 6 SPEED WITH A HIGHER NUMBER REAR SOMETHING LIKE A 411 THE BEST WOULD BE ALMOST RED LINE IN rpm IN FIFTH GEAR FOR DRAG RACING BUT GAS MILEAGE WILL SUFFER ON THE STREET T
  • TRAP55TRAP55 Member Posts: 8,292 ✭✭✭
    edited November -1
    Ford will probably have break in instructions with it. The first fluid change is important, and it needs to be drained, as in rear cover off to do it right. It needs to be cleaned out after the break in, and install a magnetic drain plug while you're at it. Don't let some lube place suction it out and refill.
    Is that automatic 6th gear an overdrive?
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    I just ordered the differential, I will let you know how it does. Also ordered the friction modifier 4 OZ that they recommended.
  • TRAP55TRAP55 Member Posts: 8,292 ✭✭✭
    edited November -1
    quote:Originally posted by perry shooter
    YOU WILL DO MUCH BETTER YOUR 6 SPEED WITH A HIGHER NUMBER REAR SOMETHING LIKE A 411 THE BEST WOULD BE ALMOST RED LINE IN rpm IN FIFTH GEAR FOR DRAG RACING BUT GAS MILEAGE WILL SUFFER ON THE STREET T

    Came back to edit and saw Perry Shooter beat me to it. If 6th is OD, and it's street driven, 3.70's might be your best happy medium.
  • Old-ColtsOld-Colts Member Posts: 22,697 ✭✭✭
    edited November -1
    quote:Originally posted by TRAP55
    quote:Originally posted by perry shooter
    YOU WILL DO MUCH BETTER YOUR 6 SPEED WITH A HIGHER NUMBER REAR SOMETHING LIKE A 411 THE BEST WOULD BE ALMOST RED LINE IN rpm IN FIFTH GEAR FOR DRAG RACING BUT GAS MILEAGE WILL SUFFER ON THE STREET TCame back to edit and saw Perry Shooter beat me to it. If 6th is OD, and it's street driven, 3.70's might be your best happy medium.I agree with the 3.7X gearing! I ordered my 1970 Z/28 Camaro with 3.73 gears and that was one of the best all around rear-ends for the street and strip that I ever owned!

    If you can't feel the music; it's only pink noise!

  • CbtEngr01CbtEngr01 Member Posts: 4,340
    edited November -1
    Maybe you can find something here. This is a good site.


    http://wallaceracing.com/Calculators.htm
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by CbtEngr01
    Maybe you can find something here. This is a good site.


    http://wallaceracing.com/Calculators.htm
    Thank you
  • Jim RauJim Rau Member Posts: 3,550
    edited November -1
    The ideal is to be topped out IN YOUR HIGHEST GEAR when you hit the traps. If you are still in 3rd you have along way to go to get the right gears. That said you must be able to get the power to the pavement. I ran 5.34 and 5.67 gears in my Boss 302 to hit the traps at 8K in high gear to do that.[8D]
  • Jim RauJim Rau Member Posts: 3,550
    edited November -1
    quote:Originally posted by nutfinn
    So, with 3.15 gears, 12.86. I know there are lots of variables, but how much do you think I could shave off with 3.55 gears?

    41218036964_246c606a1b_h.jpg
    I see you are a neighbor of mine!!![:)]
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by Jim Rau
    The ideal is to be topped out IN YOUR HIGHEST GEAR when you hit the traps. If you are still in 3rd you have along way to go to get the right gears. That said you must be able to get the power to the pavement. I ran 5.34 and 5.67 gears in my Boss 302 to hit the traps at 8K in high gear to do that.[8D]
    Actually I was in 4th gear, not 3rd. I had couple of beers in me while I watched the video [8)]
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by Jim Rau
    quote:Originally posted by nutfinn
    So, with 3.15 gears, 12.86. I know there are lots of variables, but how much do you think I could shave off with 3.55 gears?

    41218036964_246c606a1b_h.jpg
    I see you are a neighbor of mine!!![:)]
    Where you be?
  • Mr. PerfectMr. Perfect Member, Moderator Posts: 66,437 ******
    edited November -1
    You'd be well served to go with a high stall torque converter as well.
    Some will die in hot pursuit
    And fiery auto crashes
    Some will die in hot pursuit
    While sifting through my ashes
    Some will fall in love with life
    And drink it from a fountain
    That is pouring like an avalanche
    Coming down the mountain
  • remingtonoaksremingtonoaks Member Posts: 26,245 ✭✭✭
    edited November -1
    If you're only in 4th gear by the time you finish, you're not getting enough traction to the pavement...

    Were as hi 12s are respectable, I think your car with its gear ratio can do better evident by the fact that you haven't even got out of 4th gear. Have you thought about stickier/wider tires to get more traction?
  • TrinityScrimshawTrinityScrimshaw Member Posts: 9,350 ✭✭✭
    edited November -1
    Nutfinn, What are you running this time in?

    That is the same best time my 70 Cougar Eliminator ran back in 1976.

    I had an internally stock SCJ 428 with headers, and a Mallory dual point. Sure wish I still had that car.

    Trinity +++
  • nutfinnnutfinn Member Posts: 12,808 ✭✭✭
    edited November -1
    quote:Originally posted by TrinityScrimshaw
    Nutfinn, What are you running this time in?

    That is the same best time my 70 Cougar Eliminator ran back in 1976.

    I had an internally stock SCJ 428 with headers, and a Mallory dual point. Sure wish I still had that car.

    Trinity +++
    2015 Mustang GT
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