Thread: Diff gearing change

Do a search for a gearing calculator and you'll find all sorts of helpful things. However, unless you've got enormous tyres then 4.7 will be too low. You don't hear of many people doing that. Also, it's a weaker gear because there are that many more teeth. It sounds like 4.1 is more popular.

Anyway, find a gearing calculator and have fun seeing what revs and kmh you'd be doing with what gears and tyres.

From what I understand I'd be better putting in a defender LT230 for a lower high gear set. But what about low range?

If I could get 4.11 internal to match my splines (which are???) then that would be a better combo for road?

I had a S3 Lightweight with a V8 that had RR diff centers but I understand that certain RR to S3 is OK but not the other way around because of spline and halfshaft length.

It's all quite confusing.

this calculator is perfection ->
Ashcroft Transmissions - Ratio Calculator

Originally Posted by manic

this calculator is perfection ->
Ashcroft Transmissions - Ratio Calculator

That's very good - thanks for that.

Cheers - Gav

Your side gears should be 10-spline, just like a Series. But instead of swapping diffs, you can just change the C&P.

You can change the high range gears in the transfer, but low stays the same. Ashcrofts sell gear sets for when people have changed tyre size, among other reasons. You just put the numbers into their gearing calculator to work out what would suit you the best.

That's a great tool with the preloaded ratios.

With the 265/75R16's I'm running and with 4.7 diff ratios it's giving 2790rpm at 100kph.

With 33's that I plan it's down to 2690rpm at 100kph.

I don't think either are unreasonable. It would make it a fair bit nippier around town and I usually cruise at 90kph to allow the defenders to keep up .

The weakness of the 4.7's is a worry though, I guess they wouldn't be up to the V8 power. But then I'm not a lead foot anyway.

i've got a tdi D90 with r380 44A, 1.22 transfer and 3.54 diffs, 33 inch tires and it struggles a bit to get going.. the ashcroft calc would suggest a one up to 3.75 diffs would sweeten it up nicely.

So if you are on 3.54 going up to 4.7's that would make a huge change! If your RRC is not to badly geared as it is then I think 4.7 certainly take you too far the other way. Not had a V8 but 2790rpm at 100kph in 5th on a TDI would make it hell on the highway.