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 Post subject: gear change?
 Post Posted: Wed Oct 27, 2010 5:00 am 
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With some help from Chuck I was able to download the log from Sunday and looks like I was out of it 6.43 seconds into the run and was at 7500 rpm already so I was thinking of a different gear. I would like it at 7500 at the finish line...
I have the 4.57 gear in there now and have a set of 4.30 gears that can go right in and was wondering how much that will kill the rpm..

So that 1000 ft et 6.914 is not true on the gas.. :-k

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 Post subject: Re: gear change?
 Post Posted: Wed Oct 27, 2010 7:59 am 
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Beretta wrote:
With some help from Chuck I was able to download the log from Sunday and looks like I was out of it 6.43 seconds into the run and was at 7500 rpm already so I was thinking of a different gear. I would like it at 7500 at the finish line...
I have the 4.57 gear in there now and have a set of 4.30 gears that can go right in and was wondering how much that will kill the rpm..

So that 1000 ft et 6.914 is not true on the gas.. :-k


Any gear ratio change will change the RPM inversely proportional.
newrpm = oldrpm x (newgear/oldgear)

7106 = 7500 x (4.33/4.57)
So at the same speed that you lifted your rpm would be 7106rpm.

Doing a quick calc shows with 4.33 gear, 105" rollout (added a little for growth) and 4% converter slip I get 165mph @ 7500rpm.

Rick


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 Post subject: Re: gear change?
 Post Posted: Wed Oct 27, 2010 8:01 am 
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Thanks Rick!!!

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 Post subject: Re: gear change?
 Post Posted: Wed Oct 27, 2010 8:06 am 
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he is pretty close just depends on how thew converter likes it. With 4.30's and 105 roll out I hit 165 @ 7600 rpm


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 Post subject: Re: gear change?
 Post Posted: Wed Oct 27, 2010 7:36 pm 
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rick360 wrote:
Beretta wrote:
With some help from Chuck I was able to download the log from Sunday and looks like I was out of it 6.43 seconds into the run and was at 7500 rpm already so I was thinking of a different gear. I would like it at 7500 at the finish line...
I have the 4.57 gear in there now and have a set of 4.30 gears that can go right in and was wondering how much that will kill the rpm..

So that 1000 ft et 6.914 is not true on the gas.. :-k


Any gear ratio change will change the RPM inversely proportional.
newrpm = oldrpm x (newgear/oldgear)

7106 = 7500 x (4.33/4.57)
So at the same speed that you lifted your rpm would be 7106rpm.

Doing a quick calc shows with 4.33 gear, 105" rollout (added a little for growth) and 4% converter slip I get 165mph @ 7500rpm.

Rick


Excuse me but I think that he's going to a 30761 MT tire next spring, which is a 32x16x15s tire so the 105 number will likely be less than that. Next time I have mine off I'll measure them at race air pressure.

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 Post subject: Re: gear change?
 Post Posted: Wed Oct 27, 2010 7:53 pm 
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Ken the Hoosiers that I have now are 104 but when I measured them with 7psi in them there 104 1/2....Hope the Mickeys are more...

But thinking more about the 3084s tire as it's just as wide as the Hoosiers but alot more $$$$ :- ..But if I could get close to two hundred run I will be real happy ;-)

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 Post subject: Re: gear change?
 Post Posted: Fri Oct 29, 2010 5:40 pm 
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Just do short burnouts Barry, these M/T's don't need a lot of heat and rotate them regularly. Good luck this weekend, and you know, you could always short shift and keep the rpm's down a bit too :-k
I hope you can get a 8.40-8.30 et. \:D/

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