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HIZNHRZ · 09-29-2007

I'm going to go with the 4.10 gears. I got as much information as I felt I could and when it came down to decision time, Marc provided his usual timely logic. He never said that 3.90's or any other alternative was not the way to go, what he shared with me is why recommends the 4.10s for a car with a stock bottom end...

Here's what I think I learned:
- Marc does not have a source for a high quality Dana gear set in the 3.90 ratio. Other manufacturers make a 3.90 ratio but he has not been able to make them run silently.
- Marc would happily install 3.90s if a slight turbo like noise was acceptable to me.
- Marc does not use the Viper gear, he uses the Dana gear which is from a truck application.

I looked at the transmission gearing and RPM and MPH with difference rear gears and difference shift points. With this information I had additional questions from Marc. The following is what I understood to be his response:

- My math was correct. With the 4.10 and 3.90 ratios the gear ratio drop of the transmission's 6th gear causes the engine speed to drop below the peak power band. Thus the car is RPM limited to top speed in 5th.
- Marc recommends the 4.10 ratio because my engine speed will be at about peak power (about 6200 rpm at about 118 mph) as the 1/4 mile is completed.
- We agreed that this is an ideal gearing strategy for a rookie drag racer.
- the 4.10 ratio calculates to an ~.3 improvement in the quarter. The net improvement, however, will be about .2 second faster because of the loss to due load and shifting.
- Fuel economy will drop from about 27 to 24 MPG in 6th gear at 70 MPH.

I understand that hope is not a good strategy. I hope I made the right choice. I did my homework and I feel like I'm going with a proven and solid approach. Half the fun, however, is learning from experiences; even the expensive ones that might not work out as planned. Just being able to consult with someone like Marc already has been a worthwhile experience. If I don't like the 4.10s, I'll change them. Good luck on your decision.

09-29-2007	#13
HIZNHRZ Join Date: Apr 2004 Location: Germantown, MD Posts: 732	Re: Rear Gears I'm going to go with the 4.10 gears. I got as much information as I felt I could and when it came down to decision time, Marc provided his usual timely logic. He never said that 3.90's or any other alternative was not the way to go, what he shared with me is why recommends the 4.10s for a car with a stock bottom end... Here's what I think I learned: - Marc does not have a source for a high quality Dana gear set in the 3.90 ratio. Other manufacturers make a 3.90 ratio but he has not been able to make them run silently. - Marc would happily install 3.90s if a slight turbo like noise was acceptable to me. - Marc does not use the Viper gear, he uses the Dana gear which is from a truck application. I looked at the transmission gearing and RPM and MPH with difference rear gears and difference shift points. With this information I had additional questions from Marc. The following is what I understood to be his response: - My math was correct. With the 4.10 and 3.90 ratios the gear ratio drop of the transmission's 6th gear causes the engine speed to drop below the peak power band. Thus the car is RPM limited to top speed in 5th. - Marc recommends the 4.10 ratio because my engine speed will be at about peak power (about 6200 rpm at about 118 mph) as the 1/4 mile is completed. - We agreed that this is an ideal gearing strategy for a rookie drag racer. - the 4.10 ratio calculates to an ~.3 improvement in the quarter. The net improvement, however, will be about .2 second faster because of the loss to due load and shifting. - Fuel economy will drop from about 27 to 24 MPG in 6th gear at 70 MPH. I understand that hope is not a good strategy. I hope I made the right choice. I did my homework and I feel like I'm going with a proven and solid approach. Half the fun, however, is learning from experiences; even the expensive ones that might not work out as planned. Just being able to consult with someone like Marc already has been a worthwhile experience. If I don't like the 4.10s, I'll change them. Good luck on your decision. Last edited by HIZNHRZ; 09-29-2007 at 11:34 AM.