6th gear, MPH and rear end ratio determination?

[Detlef]

I just bought a Viper and think I have some gears other than the stock 3.07 ones. It feels snappier than my previous stock Viper and the freeway RPM in 6th gear are higher. Running in 6th gear, a rough estimate by looking at the gauges is:
<ul type="square">
[*]1500 RPM for 60MPH
[*]1750 RPM for 70MPH
[*]2000 RPM for 80MPH
[/list]

Is there a formula that allows me to convert transmission gear and MPH into a rear end gear ratio or do I have to take the differential cover off?

 

[Travis]

Easy...just jack up the rear of the car,place the tranny in 4th gear and count how many turns of the drive shaft it takes to make the tires rotate once(IE roughly a little more then 3 turns would indicate you have the 3.07s). My guess is that you have the 3.55's.

 

[AviP]

I think 2000rpm and 80mph is stock.

 

[Dave Dugal]

I've got the stock rear end and I'm turning 1600 RPM at 80 MPH. 2000 RPM is ~20% higher, so I'd guess you've got a rear end that's ~20% higher (numerically) than stock, or about 3.55:1.

 

[FE 065]

1.25 x 1600 = 2000. It's 25% higher.


Using a tire diameter of 25.5", at 2000 rpm a 3.73 is at 81.4mph, and a 3.55 is at 85.5mph.

 

[Marv S]

With stock size tires (gen one or gen 2):
you've got 3.73 gears with those numbers.

2000 rpm in 6th:

stock 3.07 = 98 mph call it an even 100mph

. 3.55 = 85 mph

. 3.73 = 81 mph

I just bought a Viper and think I have some gears other than the stock 3.07 ones. It feels snappier than my previous stock Viper and the freeway RPM in 6th gear are higher. Running in 6th gear, a rough estimate by looking at the gauges is:
<ul type="square">
[*]1500 RPM for 60MPH
[*]1750 RPM for 70MPH
[*]2000 RPM for 80MPH
[/list]

Is there a formula that allows me to convert transmission gear and MPH into a rear end gear ratio or do I have to take the differential cover off?

 

[joe117]

I'd say you have a 3.73

 

[Detlef]

Thanks, that sounds about right and it sure makes a huge positive difference for street driving.