Diff Ratio

[Guest paul thompson]

Hi Guys,

Can any one with a haynes manual to hand tell me what diff ratio a 2.0l GLSi Sierra from 1987 had as a diff ratio. I am trying to calculate how close the Capri dash I have is to the sierra speedo. I calculate based on 3.09 Capri diff ratio and 185/70 13 tyres that at 3,000 rpm (not engin but gear box ouput shaft) the Cpri would be travelling at 107 Kph in top gear. All I need to do is calculate the same for my 195/50 15 tyres and what ever the diff ratio is to see if it's the same. i.e. if the diff ratio is 3.14 at 3,000 RPM I will be travelling at 103 Kph. but the speedo will be showing 107 Kph so I'm OK.

Any one help as I won't see my Haynes until Friday.

Paul

[Guest paul thompson]

Well I managed to get hold of a haynes manual and guess what? They don't tell you any of the ratios are, for the transmission or the diff. Anyone got an owners manual by any chance or got access to this info by any other source? If I need to get the speedo done, I have time to do it now before I get too far or to switch back to Sierra dash for SVA until such time as I have it doctored.

Help!!!

[Guest DaveB]

HI Paul

 

PM me the full model number and VIN number and I should be able to look it up for you.

 

Cheers

 

Dave

[Guest DaveB]

Hi Paul

 

 

The Sierra was fitted with a 3.62 : 1 as original and the Capri would have had a 3.44 : 1 fitted.

 

HTH

 

Cheers

 

Dave

[Guest paul thompson]

Thanks Dave,

According to my calcs then the capri with it's 185/70 13 tyres and 3,000 box o/p revs would be travelling at 96 Kph. The Sierra with it's 195/50 15 tyres at 3,000 box o/p revs would be travelling at 90 Kph. Therfore if the speedo from the capri was accurate in the first place it would be showing 96 but I would be travelling at 90. Sounds like within tolerance for me, close enough, in goes the capri das unmodified, Hurah!!!

 

Paul

[Guest DaveB]

No Probs Paul glad to be of help.

 

Dave B

[Peter Bell]

Paul, the injection 2l Sierras (manual gbox) had a 3.92 diff so you may be a bit further out than you think I am afraid .

Peter.

[Longboarder]

If you still have the donor plate Simon Bateman posted the info that a 3.92 diff is identified by a D in the axle section as below.

 

Nigel