Diff Ratio Calcualtor????

[RKZ234]

Does anyone out there know of a site or program which you enter known data like, engine RPM, top gear ratio and tyre rim combo, so that it will tell you what diff ratio your car has.

A mate has an 3spd Auto VL Berlina V8. All appears factory except that it has had a shorter diff centre put in it by the previous owner.

The car does about 2850 RPM at 110 km/h on the Fwy, which is just nuts and is also why he only drives it at upto 80km/h or gets a lift!!!

We already know;
3rd gear is 1:1
Engine rpm is approx 2850 at 110 km/h
Tyre combo is 225 x 50 R16

By my rough mental calculations, I'm guessing it has a 3.45 centre.

The objective is to get as close as possible to 2000 RPM at 110km/h, as the car will be doing lots of Hwy k's once it is sorted out.

Any advice on the ratio fitted and/or directions to a website to do the calcualtions as well as the correct ratio to fit will be greatly appreciated.

[AirStrike]

From memory the V8's were all factory fitted with the 3.08 ratio but it might have been changed for a I6 or T6 ratio (3.45)
AirStrike

[vlv8vic]

yup mines 3.08. sits on about 2700 (i think) at 100k's. Same 3 speed trimatic. drinks the juice for that reason.

[Stewart1000]

it would be 1.08 for sure

[vkberlina]

these might help
http://members.westnet.com.au/scottl...gearratios.htm

cheers
Scott

[burnz]

Does anyone out there know of a site or program which you enter known data like, engine RPM, top gear ratio and tyre rim combo, so that it will tell you what diff ratio your car has.

A mate has an 3spd Auto VL Berlina V8. All appears factory except that it has had a shorter diff centre put in it by the previous owner.

The car does about 2850 RPM at 110 km/h on the Fwy, which is just nuts and is also why he only drives it at upto 80km/h or gets a lift!!!

We already know;
3rd gear is 1:1
Engine rpm is approx 2850 at 110 km/h
Tyre combo is 225 x 50 R16

By my rough mental calculations, I'm guessing it has a 3.45 centre.

The objective is to get as close as possible to 2000 RPM at 110km/h, as the car will be doing lots of Hwy k's once it is sorted out.

Any advice on the ratio fitted and/or directions to a website to do the calcualtions as well as the correct ratio to fit will be greatly appreciated.

a moroso power speed calculator is 10/15 dollars from any reputable speed shop it will calc power speed ratio tire et rpm mph weight shifted

[RKZ234]

Thanks for the replies people. He's decided to keep the 3 spd auto and go for a 2.6 diff, which aparrently will delver about 2100rpm at 100 km/h.

The cost of fitting a VS 4spd and tailshaft was just just too much for the boy.