Re: New trans is in order.
[Re: Greenwood]
#2826226
09/28/20 07:37 PM
09/28/20 07:37 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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It will make the 1-2 shift worse (higher RPM loss), but I would guess the converter would take care of that?
Boffin Emeritus
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Re: New trans is in order.
[Re: Greenwood]
#2834877
10/20/20 07:47 AM
10/20/20 07:47 AM
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Joined: Jan 2003
Posts: 11,705 Portage,michigan
B3422W5
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 11,705
Portage,michigan
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So, last weekend of the year, and my 904 gave up the ghost coming out of the burnout box on Saturday morning. It appears that the sprag called it a day, but we won't know until it gets yanked. At least that gives me a reason to up the ante on the converter. I'll step up to one that can flash to over 5000. The current unit will hit 4700 on the t-brake, but only flashes to 4000 when I footbrake it, and the t-brake is worth a tenth in the 60' right now. What are people's thoughts on the value of a 2.74 low gear behind a 360 that makes modest amounts of torque in a 3000 lb car? I am running a 5.13 gear already, so I would think that adding 12% more gear along with another 1000 rpm of converter should really make this thing leave. Something way wrong elsewhere if there is a tenth difference between the foot and the brake. I have never seen any difference to speak of either way, same 60 foot either way if convertor is correct for the build. Regards flash, the convertor flashes only one way/ amount . Drive at 10 Mph in the pits in high gear and whap the throttle. Watch the tach, where the needle jumps to is the flash. You might be talking about the rpm you can hold the car with at the starting line before it moves foot braking.. That will definitely be less than the flash. Its supposed to be. Its a combination of how good your brakes are, front tire size, how loose the convertor is, etc. Lots of factors. Some/ many cars actually work better launching off the foot at a lower rpm( like 1500 or 2000) because the suspension is more “ relaxed” or you get a better run at the convertor. Trying different launch rpm can be used to dial in reaction time too. Light 3000 pound car i wouldn't bother with a low gear. Get the convertor right, it will 60 fine. It spreads out 1 st and second gear to much for my liking
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight 418 BPE factory replacement headed stroker, 565 lift solid cam Best so far, 10.40 @127 1/4 1.41 best 60 foot 6.60 at 103.90 1/8
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Re: New trans is in order.
[Re: B3422W5]
#2835024
10/20/20 12:59 PM
10/20/20 12:59 PM
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Joined: Jan 2003
Posts: 16,923 NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,923
NC
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Light 3000 pound car i wouldn't bother with a low gear. Get the convertor right, it will 60 fine. That is my feeling as well. A 5.13 rear gear and tires around 30" or less tall is plenty of starting line ratio. Converter.
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Re: New trans is in order.
[Re: B3422W5]
#2835164
10/20/20 05:07 PM
10/20/20 05:07 PM
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Joined: Oct 2007
Posts: 4,205 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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I agree, the converter is key. Also: if you change both you can't compare them as to effect. Leaving the stock 1st gear means you don't need to adjust your shift point.
Boffin Emeritus
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Re: New trans is in order.
[Re: polyspheric]
#2835402
10/21/20 01:24 AM
10/21/20 01:24 AM
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Joined: Sep 2017
Posts: 339 Red Deer, Alberta
Greenwood
OP
enthusiast
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OP
enthusiast
Joined: Sep 2017
Posts: 339
Red Deer, Alberta
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Hey, thanks all for the input. I see where going to the 2.74 gear may not be the most bang for the buck. Now, as for converter flash, when I footbrake the car, I have found the best overall launch to be about 1200 rpm of pre-load. More rpm against the brake makes the car react quicker, but the 60 ft falls off, as does the ET. The converter stalls to 4500-4700 rpm on the brake. However, my in-car videos show a 4000 rpm "flash" when I launch off the footbrake. The tach only hits 4k on the hit, and that's all. I suspect that's why the 60 ft improved dramatically going off the t-brake. That leads me to think a lot more converter is in order.
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