Rear gears
Drifting
Joined: Aug 2009
Posts: 1,346
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From: new iberia la
are you trying to decide what gear you want in your car , or just curious? Gear ratio must match the engines power range and weight.. just going higher ratio does not necessarily mean you are faster
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Safety Car
Joined: Jan 2008
Posts: 3,791
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From: Aarhus, Denmark
Just wondering.
Please also note, I'm not racing.
Back in the days, you could order with different gears, in the same car, with the same engine, I know what you mean. But I not racing, on "normal driving", with a bit of street fun :- )
Last edited by c3_dk; Jul 24, 2016 at 10:17 AM.
Race Director
Joined: Jul 2004
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From: Scottsdale Arizona
From what I've seen and read, it isn't particularly linear. The rear end works best depending on what you're planning to use the car for, engine power band and transmission.
Assuming you have a 4 speed, I'm not sure that you'd get to 60 any faster with gears bigger than 3.70. One particularly interesting article that I read (Hot Rod maybe?) had a fairly stout 400 with a 5 speed. His quarter mile times improved steadily as he lowered his rear end ratio to around 2.90.
Assuming you have a 4 speed, I'm not sure that you'd get to 60 any faster with gears bigger than 3.70. One particularly interesting article that I read (Hot Rod maybe?) had a fairly stout 400 with a 5 speed. His quarter mile times improved steadily as he lowered his rear end ratio to around 2.90.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
From what I've seen and read, it isn't particularly linear. The rear end works best depending on what you're planning to use the car for, engine power band and transmission.
Assuming you have a 4 speed, I'm not sure that you'd get to 60 any faster with gears bigger than 3.70. One particularly interesting article that I read (Hot Rod maybe?) had a fairly stout 400 with a 5 speed. His quarter mile times improved steadily as he lowered his rear end ratio to around 2.90.
Assuming you have a 4 speed, I'm not sure that you'd get to 60 any faster with gears bigger than 3.70. One particularly interesting article that I read (Hot Rod maybe?) had a fairly stout 400 with a 5 speed. His quarter mile times improved steadily as he lowered his rear end ratio to around 2.90.
Look at Freiburger when he installed a hellcat engine in his old Charger, he went faster going from down in gear, I think it was from 3.7 to 3.55 (I'm not ure)
Race Director
Joined: Jul 2004
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From: Scottsdale Arizona
Wouldn't surprise me. A hellcat or LS engine is kind of "cheating" since the power band is so big. If you've ever driven a modern LS engined car, I think you could make a very satisfactory strip car with a power glide and 3.70s. Just push the gas pedal and ignore the revving until you cross the finish line.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
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From: Aarhus, Denmark
Wouldn't surprise me. A hellcat or LS engine is kind of "cheating" since the power band is so big. If you've ever driven a modern LS engined car, I think you could make a very satisfactory strip car with a power glide and 3.70s. Just push the gas pedal and ignore the revving until you cross the finish line.
But in general, with a "normal" maybe even stock engine (not race engine), going from 0-60 must be faster if you have a 3.08 and change to 3.55 or 3.70?
Race Director
Joined: Jul 2004
Posts: 12,676
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From: Scottsdale Arizona
I would think so. I'm currently running a very stock crate engine with a 200 4R transmission. I noticed a significant improvement in acceleration by changing from 3.08 to 3.55.
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Thread Starter
Safety Car
Joined: Jan 2008
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From: Aarhus, Denmark
You got "performance" in both ends, the TH2004R has a nice fast 1th gear compared ti TH400
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Safety Car
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From: Aarhus, Denmark
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
0-60 mph is not a very good car test. Shifting a manual takes time. so a high powered motor with a 4.11 might have to shift before reaching 60 mph.
Even 1/8th mile drag racing isn't always a good test. 1/4 mile or even better One mile drag racing is better. You can find online drag racing gear calculators to determine optimal gearing. I owned a 1/4 dragster and it went faster when we changed from 4.30 gearing to 4.88 because of the rpm and tire diameter
Performance car magazines actually list 0-100-0 or 0-150-0 mph. That is real performance!
Even 1/8th mile drag racing isn't always a good test. 1/4 mile or even better One mile drag racing is better. You can find online drag racing gear calculators to determine optimal gearing. I owned a 1/4 dragster and it went faster when we changed from 4.30 gearing to 4.88 because of the rpm and tire diameter
Performance car magazines actually list 0-100-0 or 0-150-0 mph. That is real performance!
Le Mans Master
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From: Lebanon Township New Jersey
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
0-60 mph is not a very good car test. Shifting a manual takes time. so a high powered motor with a 4.11 might have to shift before reaching 60 mph.
Even 1/8th mile drag racing isn't always a good test. 1/4 mile or even better One mile drag racing is better. You can find online drag racing gear calculators to determine optimal gearing. I owned a 1/4 dragster and it went faster when we changed from 4.30 gearing to 4.88 because of the rpm and tire diameter
Performance car magazines actually list 0-100-0 or 0-150-0 mph. That is real performance!
Even 1/8th mile drag racing isn't always a good test. 1/4 mile or even better One mile drag racing is better. You can find online drag racing gear calculators to determine optimal gearing. I owned a 1/4 dragster and it went faster when we changed from 4.30 gearing to 4.88 because of the rpm and tire diameter
Performance car magazines actually list 0-100-0 or 0-150-0 mph. That is real performance!
My 69 project car, has a SBC Dart 427 EFI, TH2004R and I have a 3.70 in stock (car has 3.08 today), 255/60 rear wheels, but I was thinking about 4.11 instead.
What do you think??
It will be a street car, NOT drag race.
Thread Starter
Safety Car
Joined: Jan 2008
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From: Aarhus, Denmark
I trying to tell them that a 3.70 or more and a TH2004R (or TH700) will give a "kick" compared to what they have today.
And if they start with "only" 3.70, then is it is cheap and fast fix. (but RMP will go up a bit)
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
You need to go to an online rpm, tire diameter, and rear end ratio site and figure out your cruising down the freeway speed
Thread Starter
Safety Car
Joined: Jan 2008
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From: Aarhus, Denmark
I had 4.11 for 20 years and 700R4. I had it setup for no 4th gear kick down. So it would not attempt to down shift if I used WOT. It just increased speed at a rapid rate. I thought that 3.90 might have been better to just drop a few rpm when I went to a 427 sbc
You need to go to an online rpm, tire diameter, and rear end ratio site and figure out your cruising down the freeway speed
You need to go to an online rpm, tire diameter, and rear end ratio site and figure out your cruising down the freeway speed
With this car (69 Coupe, sbc 427 car), I'm not so concerned about RPM (in generally I'm not)
I do have the TH2004R to bring RPM down, so my question is more, will I benefint going from 3.70 to 4.11?
Will a sbc 427 like a 4.11 more then 3.70?
Stall is 2300-2400
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
This is how I looked at it. I had a 427 that really came on strong at 3500+ rpm clear to 7000+ rpm.
our OD was similar .67 for a 200R4 with a 27 inch tall tire and 4.11 you are only doing 3427 rpm at 100 mph in OD. So then I could just WOT my Vette and go. At 150 mph you are only doing 5100 rpm and with my cam I was not even at max HP yet. Now I have a 5 speed and .64 OD
http://www.csgnetwork.com/multirpmcalc.html
our OD was similar .67 for a 200R4 with a 27 inch tall tire and 4.11 you are only doing 3427 rpm at 100 mph in OD. So then I could just WOT my Vette and go. At 150 mph you are only doing 5100 rpm and with my cam I was not even at max HP yet. Now I have a 5 speed and .64 OD
http://www.csgnetwork.com/multirpmcalc.html
Last edited by gkull; Jul 26, 2016 at 03:10 PM.
Thread Starter
Safety Car
Joined: Jan 2008
Posts: 3,791
Likes: 428
From: Aarhus, Denmark
This is how I looked at it. I had a 427 that really came on strong at 3500+ rpm clear to 7000+ rpm.
our OD was similar .67 for a 200R4 with a 27 inch tall tire and 4.11 you are only doing 3427 rpm at 100 mph in OD. So then I could just WOT my Vette and go. At 150 mph you are only doing 5100 rpm and with my cam I was not even at max HP yet. Now I have a 5 speed and .64 OD
http://www.csgnetwork.com/multirpmcalc.html
our OD was similar .67 for a 200R4 with a 27 inch tall tire and 4.11 you are only doing 3427 rpm at 100 mph in OD. So then I could just WOT my Vette and go. At 150 mph you are only doing 5100 rpm and with my cam I was not even at max HP yet. Now I have a 5 speed and .64 OD
http://www.csgnetwork.com/multirpmcalc.html
I use this
3427 rpm is no problem. But will I fell the extra "power" going from 3.70 to 4.11?
Is it worth it? (going from 3.70 to 4.11)