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Discussion Starter #1
I'm just curious to what rear end ratio's other Hot Rodder's are using with a Tremec 6 speed. Matched with a BBC red- lining at 5500 rpm's.


Wanting to know where your Top end speed is with which rear end ratio.


I have a 300 rear end and I will probably be changing to something more for the street than the highway. But still wanting to cruise the turnpikes.


Any input from other owners would be appreciated. Thanks in advance.
 

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RedLine Stage 4 ZL1 650rwhp
1971 BB Chevelle
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547 Posts
I was running a ZZ572 in my 67 El Camino SS; 12 Bolt 3.73 / Tremec TKO 5. I could cruise 80 mph all day long at like 3200 RPM, I had a 5th Gear Final Ratio of .82

Your Rear Tire Height and Final Ratio will tell you all you need to know using a Calculator like this


My ZL1 has a Tremec TR6060 with a 6th Gear Final Ratio of .63
9.9" Rear w 3.73 Posi and 28 x12 Rear Tires. At 100 MPH in 6th I'm under 3,000 RPM

To be honest I never ever use 6th and barely use 5th, even on the parkways which I drive often. I've been 130 MPH in 4th and 80MPH in 5th is under 3,000 RPM. My Motor likes RPM so 6th is pretty useless to me unless I'm well into the triple digit MPH
 

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If I were doing this, I'd probably use a rear gear somewhere between 3.90 and 4.10.

1st gear 2.66 with a 4.00 rear gear (10.64 final drive) and 28" tire will go 43 MPH @5500
2nd gear 1.78 with a 4.00 rear gear (7.12 final drive) and 28" tire will go 64 MPH @5500
3rd gear 1.30 with a 4.00 rear gear (5.20 final drive) and 28" tire will go 88 MPH @5500
4th gear 1.00 with a 4.00 rear gear (4.00 final drive) and 28" tire will go 114 MPH @5500
5th gear 0.80 with a 4.00 rear gear (3.20 final drive) and 28" tire will go 143 MPH @5500
6th gear 0.64 with a 4.00 rear gear (2.56 final drive) and 28" tire will go 178 MPH @5500

6th gear 0.64 with a 4.00 rear gear (2.56 final drive) and 28" tire will go 65 MPH @2000, 81 @2500.

I'm choosing this rear gear and tire because first gear works real good with a ratio between 9.00 and 11.00 when you have a real close second gear ratio like the 1.78 in this gearbox. 1st gear will get you across the intersection quickly.

Use this calculator to find other speeds.....
RPM/MPH From Gear Ratio Calculator by Wallace Racing
 

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Discussion Starter #4
Thanks for the input and the calculator. Exactly what I was looking for. I have .63 6 gear also.


I need to put more miles on the motor, its still breaking in. The 502 barely fit into 34 Ford Body with AC & PS, the motor hums , but the radiator size is limited. Under the midrange it will run around 180, when I start running over 3000 the temp will climb , but stays reasonable and cools back down. So I am putting 5 & 6 to use, keeps the motor cool. Cant use 6 on the street though at 45mph barely over 1000rpm.


The 300 gear is overkill so I will be looking to bring it up. the 15 gallon gas tank is also a factor if I start doing road trips! Right now I'm around 10mpg if I don't play around. The 3.73 gear you have has good numbers with the Tremec.


Thanks again.




I was running a ZZ572 in my 67 El Camino SS; 12 Bolt 3.73 / Tremec TKO 5. I could cruise 80 mph all day long at like 3200 RPM, I had a 5th Gear Final Ratio of .82

Your Rear Tire Height and Final Ratio will tell you all you need to know using a Calculator like this
http://www.csgnetwork.com/multirpmcalc.htmlhttp://www.csgnetwork.com/multirpmcalc.html

My ZL1 has a Tremec TR6060 with a 6th Gear Final Ratio of .63
9.9" Rear w 3.73 Posi and 28 x12 Rear Tires. At 100 MPH in 6th I'm under 3,000 RPM

To be honest I never ever use 6th and barely use 5th, even on the parkways which I drive often. I've been 130 MPH in 4th and 80MPH in 5th is under 3,000 RPM. My Motor likes RPM so 6th is pretty useless to me unless I'm well into the triple digit MPH
 

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Discussion Starter #5
Thanks for all the info and that's a great calculator! It takes the guess work out of what I want to do.


I also ran some of my current speeds per gear with rpm and its right on the money.


I'm not sure what I am going to do yet, the 3.00 gear is overkill, I need to put more miles on the car, its a new build, I want to break it in and see how I'm going to use it the most. Originally I planned on doing road trips with it, but not sure I will be going that route. Thanks for your help!




If I were doing this, I'd probably use a rear gear somewhere between 3.90 and 4.10.

1st gear 2.66 with a 4.00 rear gear (10.64 final drive) and 28" tire will go 43 MPH @5500
2nd gear 1.78 with a 4.00 rear gear (7.12 final drive) and 28" tire will go 64 MPH @5500
3rd gear 1.30 with a 4.00 rear gear (5.20 final drive) and 28" tire will go 88 MPH @5500
4th gear 1.00 with a 4.00 rear gear (4.00 final drive) and 28" tire will go 114 MPH @5500
5th gear 0.80 with a 4.00 rear gear (3.20 final drive) and 28" tire will go 143 MPH @5500
6th gear 0.64 with a 4.00 rear gear (2.56 final drive) and 28" tire will go 178 MPH @5500

6th gear 0.64 with a 4.00 rear gear (2.56 final drive) and 28" tire will go 65 MPH @2000, 81 @2500.

I'm choosing this rear gear and tire because first gear works real good with a ratio between 9.00 and 11.00 when you have a real close second gear ratio like the 1.78 in this gearbox. 1st gear will get you across the intersection quickly.

Use this calculator to find other speeds.....
RPM/MPH From Gear Ratio Calculator by Wallace Racing
 
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