Ford Sierra aficionados and super-geeks on diff ratios

[AshleyO]

I have used a Ford Sierra Sapphire GL 4 door saloon 1,769cc engine
I now need to know the diff ratio
I know the original engine number (engine now in a bin somewhere!)
Anyone got an idea where I would get this from
Many thanks in advance

ASHLEY

[DJ.]

I would think it is a 3.92. It's one of the lower powered engines and a heavy car.

[David T]

There should (could still) be an ali tag on one of the diff rear casing bolts. This has details that can be decoded on the web. As Duncan says, most likely the 3.92 that I and many others have. Do you know which one you would like/need?

[kenjohn]

I sold two Sierra diffs on eBay last year. When I took the rear cover off to check the teeth for wear, the ratio was written on the main gear of both of them.
John

[AshleyO]

There should (could still) be an ali tag on one of the diff rear casing bolts. This has details that can be decoded on the web. As Duncan says, most likely the 3.92 that I and many others have. Do you know which one you would like/need?

THanks for this. There is indeed a tag and I have tried to clean and read it tonight. I've even taken photos and magnified them, trying to make some sense, but they really are faded too much. From web research, it would seem that 3.92 is the fave. I will try this on the speedo calibration and see if its anywhere near the GPS speeds to ensure Mr IVA is happy

[Fury1630]

From web research, it would seem that 3.92 is the fave. I will try this on the speedo calibration and see if its anywhere near the GPS speeds to ensure Mr IVA is happy

You generally get a chance to calibrate the speedo on the day, if you can get to the back of the speedo. I left mine loose in the dash as it was in the "safe zone" the other side of the steering wheel.

[Nash]

My orignial diff came from an '88 Sierra 1.6 Sapphire and was a 3.62 Now this is where it gets interesting the Ford Diffs of tht era are 7" casings but the early ones have 6.5" internals so when I came to put a 3.92 ATB LSD inside it wouldn't fit. Ended up getting a repalcement case. Apparently Road & Race have a lot of these diffs (6.5" int) on the floor at there workshop and can't give them away. All Open diffs.

Hope that helps?

........Neil

[Richard]

http://www.super7thheaven.co.uk/compone ... ferential/

[AshleyO]

so we THINK it is 3.36 but tonight my daughter is going to count 100 turns of the rear wheel whilst I count how many turns of the propshaft that equates to. Then we have the real answer for sure. Nothing better than the hard way!

[Nash]

so we THINK it is 3.36 but tonight my daughter is going to count 100 turns of the rear wheel whilst I count how many turns of the propshaft that equates to. Then we have the real answer for sure. Nothing better than the hard way!

I'd be surprised if its 3.36. Looking forward to the answer now!!