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View Full Version : Do I need to switch rear gears now? 6 speed question



bowtieguys
02-19-2006, 11:47 AM
Hello, I have a Richmond 6 speed behind a 600+ hp 468ci BBC. Everything is new and I have never driven it yet. My concern is that I have 3.27/2.13/1.57/1.23/1.00/0.76 Gear ratios in the transmission along with a new 3:73 posi rear(I was planning on using a 4 speed), I am running a 235/45/ZR18 up front, and a 255/35/ZR20 out back. What will this combo yield RPM wise? Will first gear be useless? Will this work for a street car? What ratios would someone recommend? Thanks for the help in advance.

dhardison
02-19-2006, 12:21 PM
Rich, With a 3.27 1st and a 3.73 rear your final 1st gear ratio will be 12.2:1 (3.27*3.73) which is pretty darn steep (good thing). With my Tremec 5-spd my 1st gear final is 11.25:1 and 1st gear is pretty quick to red-line.

For your 6th gear rpm, it all depends on what you can live with on the road. Given your current 3.73 here are the rpms you'll experience at differing mphs.

The following numbers were based on a 27" tall tire (255/35), 3.73 rear gear and 0.76 6th gear ratio.

55mph = 1900rpm
60mph = 2100rpm
65mph = 2300rpm
70mph = 2500rpm
75mph = 2650rpm
80mph = 2800rpm

This will help - http://www.richmondgear.com/101032.html

Dan

bowtieguys
02-19-2006, 05:14 PM
Rich, With a 3.27 1st and a 3.73 rear your final 1st gear ratio will be 12.2:1 (3.27*3.73) which is pretty darn steep (good thing). With my Tremec 5-spd my 1st gear final is 11.25:1 and 1st gear is pretty quick to red-line.

For your 6th gear rpm, it all depends on what you can live with on the road. Given your current 3.73 here are the rpms you'll experience at differing mphs.

The following numbers were based on a 27" tall tire (255/35), 3.73 rear gear and 0.76 6th gear ratio.

55mph = 1900rpm
60mph = 2100rpm
65mph = 2300rpm
70mph = 2500rpm
75mph = 2650rpm
80mph = 2800rpm

This will help - http://www.richmondgear.com/101032.html

Dan

Thanks for you help. I really appreciate it. Do you think I should go ahead and try to run it as is first?

dhardison
02-19-2006, 05:45 PM
Rich, I would run it as isand see how you like it. I think you'll be pleased, especially on the open highway. I have a 3.42 rear gear and with my TKO-500, I pulled down an average of 15.5mpg on last year's Power Tour. As a matter of fact I now wish I had gone with 3.73s as well.

Dan

bowtieguys
02-19-2006, 08:44 PM
Rich, I would run it as isand see how you like it. I think you'll be pleased, especially on the open highway. I have a 3.42 rear gear and with my TKO-500, I pulled down an average of 15.5mpg on last year's Power Tour. As a matter of fact I now wish I had gone with 3.73s as well.

Dan
Dan, thanks for all of your help. I'll keep it as is, and let you know soon. I appreciate your time:cheers: