VP V8 IRS Diff Ratio....

[broderikb]

Hey all, the speedo in my senator always displays the wrong speed. When it says Im doing 80 im actualy doing 60 & when it says im doing 120 Im doing 100 ect ect.

It also goes through the gears very quick(4spd auto with stg2 shift kit) & runs along at 2000rpm at 80kmh in 4th.

I am unsure if it has the standard diff center, but would a taller diff ration be the reason for the speedo being out & doing 2000rpm at 80kmh?

[NOGEN 3]

Sounds like you had a ratio change b4 you bought it? Lift the rear end and mark the talshaft and the tyre spin the tail shaft once and get a rough ratio.Obviously, 3.08, roughly 3 tyre revolutions, 3.46 roughly 3 1/2, 3.73's, 3 3/4's?...

[1991_Vn2nV]

With the speedo off by that much it sounds like 3.91's...

How many rpm are you sitting on in overdrive at 100km/h?

[broderikb]

about 2,200-2,300rpm.

[greenfoam]

Sounds like it has at least 3.45s in it

[1991_Vn2nV]

I would say 3.45 or 3.73... My 3.9's rev much higher at 100... But definitely sounds like a diff gear change.

[NOGEN 3]

Just check it your self. You'll work it out...

[statomatic]

yep thats 3.91 mine is the same

[broderikb]

I would say 3.45 or 3.73... My 3.9's rev much higher at 100... But definitely sounds like a diff gear change.

Is yours a V6 or V8.

yep thats 3.91 mine is the same

Cool, but damn at the same time. I am about to go for a 600km drive.

[vq~gangsta]

Hey all, the speedo in my senator always displays the wrong speed. When it says Im doing 80 im actualy doing 60 & when it says im doing 120 Im doing 100 ect ect.

It also goes through the gears very quick(4spd auto with stg2 shift kit) & runs along at 2000rpm at 80kmh in 4th.

I am unsure if it has the standard diff center, but would a taller diff ration be the reason for the speedo being out & doing 2000rpm at 80kmh?

That sounds identical to my car. My car has a 3.45 ratio in it from a VL turbo.

[1991_Vn2nV]

Is yours a V6 or V8.

V6, but the revs wont be that different. 3.91 in my car gives me about 2450rpm at 100km/h instead of the stock 1900rpm or whatever it is.

[TVR-190]

hey m8 can i tune my car, than later get a diff change and dont tune it again

please dont bump old threads for a model of car different to yours mmk.

answer: yes, u will need speedo recalibrated though