Regear or up boost question

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Jul 16, 2014 | 07:51 PM

Shownomercy

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Regear or up boost question

In the land of theory here, so bear with me.

Car is mechanically limited via gearing and cam to roughly 143mph. 6400 shift, 3.73s, and 28s. pt76gts turbo, 10-12psi area

Question arises on whats easier; add boost in quicker and try to ET quicker, or re-gear for a better ET?

Again in theory, a shallower gear set, 3.54 area should build boost much faster. But, if I do toss 3.54s in, and the turbo runs out of steam, its all for nothing and I waste a lot of money.

Thoughts?

Jul 17, 2014 | 02:39 AM

Busa_rob

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Pull some gear out of it. Turbos need to be able to lean on somthin. With my experience in turbo hayabusas the less the gear the better. I've never had to say it needs more gear.

Jul 17, 2014 | 05:54 AM

yenkomike

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From: oxford mi

this is true I changed from a 3.42 to a 4.00 gear in my buick when I went to a 9" axle and the car slowed down half a second. I had a 3.00 gear so I put it in for street driving and it felt so good I ran it at the track and it was .3 faster than my best with a 3.42. never changed it. the strange thing is the 3.00 gear was the fastest 60' as well.

Jul 17, 2014 | 07:57 AM

RonSSNova

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I was just looking at logs from my track runs.
I'm 3.73 gears and a 30" tire TH400.

I don't get full boost in low gear. But I do in 3rd. About 2 psi difference.

I ran 143 mph at 6800. Converter slip.

I'd like to go to a 3.31 gear.

Ron

Jul 17, 2014 | 08:28 AM

Ryans99ls1

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From: OH & MI

what size motor? itd have to be pretty big for that thing to run out of steam at such low boost. I actually have 76GTS-H and i know its got more than the 16psi ive had it up to on my 346

at the very least put 3.50s in

Jul 17, 2014 | 12:33 PM

Shownomercy

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383ci, and can only go to 3.54s (S60)

Jul 17, 2014 | 02:09 PM

Old Geezer

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run the math

Quote:

Originally Posted by Shownomercy

383ci, and can only go to 3.54s (S60)

and see how much help you'll get w/ the 3.54 and say a 29 or 30" tire.

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Jul 17, 2014 | 04:04 PM

stevieturbo

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From: Norn Iron

I doubt there would be any downsides to using the taller gear even if you may still not hit 150.

Jul 17, 2014 | 04:18 PM

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toytech93

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From: wilson,nc

3.73 TO 3.54, is it really worth the cost of changing ?

just doesn't seem cost effective. just my .02

Jul 17, 2014 | 05:34 PM

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Shownomercy

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So even if I don't utilize the gearing to get max speed, they won't hurt the current power level's ability to ET?

Jul 18, 2014 | 12:40 AM

#12

Busa_rob

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Quote:

Originally Posted by yenkomike

Yep. And it's funny cuz you tell a nitrous or blower guy that your gonna put that tall of a gear in and they look at you like your retarded. But it works so damn well. And hell when you got a th400 like me you gotta love being able to do 70 on the highway and not revving the **** out of it.

Jul 18, 2014 | 02:53 PM

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Shownomercy

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So, is it worth selling the S60 rear to fund a ford 9 with say 3.08/3.23s or should 3.54s work sufficiently?

Jul 19, 2014 | 07:56 AM

#14

Old Geezer

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Is this a converter car? If so, what kind of slip are you seeing? [I see no mention of it, is why I ask.]

Jul 19, 2014 | 08:15 AM

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F110Mech

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Quote:

Originally Posted by Old Geezer

Is this a converter car? If so, what kind of slip are you seeing? [I see no mention of it, is why I ask.]

pretty sure that he has a 4L80e

Jul 19, 2014 | 10:08 AM

#16

Shownomercy

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80e, triple disk converter, and its locked.

Jul 21, 2014 | 11:24 PM

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coolmanvette75

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Matt if you wanna keep the S60 throw the 3.54s in it. I can only see it going faster. I don't think the gear swap alone will hurt the efficiency of the turbo more than it already is. If you wanna go through the trouble of pulling that rear back out and selling it, get a 9in with 3.23s

Jul 22, 2014 | 01:35 AM

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dezlfrek

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From: sonoma ca

I have a little 302cid 4.8 and 3.25 gears in my 9" going 142mph in the 1/4 on low 14psi boost.. and it cruises down the highway at 2800 going 76 mph with 28" tires..
people have always told me you can never have to much gear just not enough power to pull it..

Jul 22, 2014 | 07:47 AM

#19

Ryans99ls1

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FWIW I had 3.25s in my 6 speed car last year, which most consider way too low. Car had absolutely no issues getting through the power band and my butt dyno tells me its faster because . The only issue was that 6th gear was useless untill about 90mph haha.

I put 3.50s back in this year but i threw on 28" tires so its still the same final drive as having 3.25s, i love it.

Last edited by Ryans99ls1; Jul 22, 2014 at 08:03 AM.