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Change Of Gearing


need4speed
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When fitting 35" tyres it obviously raises the gearing a lot.

I know the simplest way to lower the gearing to suit would be via the transferbox, but in my case my tbox has just been totally rebuilt and i dont fancy messing about with it again for a long time (fingers crossed).

The only unknown on my Defender are the diffs. All i know about them are that they are TD5 vintage. I havent had them apart, so with this in mind would i be better changing the cw&p ratio to suit 35" tyres while im in there? And if so, what would be the best ratio to go for?

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TD5 90s are standard LONG NOSE 24 spline diffs FRONT AND REAR

Choices are wide :

3.50 ratio, with a tooth count of 28/8

4.12 ratio, with a tooth count of 33/8

4.37 ratio, with a tooth count of 35/8

4.75 ratio, with a tooth count of 38/8

Less teeth = stronger !...I have a 3.50 in the workshop at the mo for a rebuild ....HUGE gearset, will shove a pic up laters !

Late TD5s - ie post the horrible Salisbury unit - TD5 110s 130s etc are Short Nose P38 type diffs

For these there is only 4.1s : http://www.ashcroft-transmissions.co.uk/ring-pinions/4-10-r-p-for-the-p38-type-diff.html

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TD5 90s are standard LONG NOSE 24 spline diffs FRONT AND REAR

Choices are wide :

3.50 ratio, with a tooth count of 28/8[/size]

4.12 ratio, with a tooth count of 33/8[/size]

4.37 ratio, with a tooth count of 35/8[/size]

4.75 ratio, with a tooth count of 38/8[/size]

Less teeth = stronger !...I have a 3.50 in the workshop at the mo for a rebuild ....HUGE gearset, will shove a pic up laters ![/size]

Late TD5s - ie post the horrible Salisbury unit - TD5 110s 130s etc are Short Nose P38 type diffs

For these there is only 4.1s : http://www.ashcroft-transmissions.co.uk/ring-pinions/4-10-r-p-for-the-p38-type-diff.html

As sig its a 110 i have ;)

I will try to find the serial number on axle to see if i can id it. Unless someone could post a pic of the 2 possible different types so i could maybe id it by having a quick look?

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Ok. If im reading things right, my choices are limited here.

Ive had a looksee under the 110 and its definately not a salisbury rear as there is no pressed steel plate on the rear.

As Nige says, if its not a salisbury then its the P38 type i have. Now this raises more questions than answers..

1. Am i right in thinking that all i can do is go 4.10 on the rear and 4.12 on the front?

2. Wont the difference between the 2 (slightly) different ratios kill something very quickly?

3. For 35" tyres wont the 4.10 still be too high?

4. Will it just be better for me to junk the P38 axle and look for a salisbury so i can go 4.75 front & rear?

5. Any other options ive maybe not thought of?

Sorry for all the questions... :(

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I can help but not till next week as at mums funeral tomm... :(

But reckon next week will need something to take my mind off things

But

No don't go fitting a Salisbury ffs

Ratio difference to minimal to worry....that's about 5 psi difference on pressure as an equivalent

Go 4.2 and if not right change tbox gears

Be in touch

Nige

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I can help but not till next week as at mums funeral tomm... :(

But reckon next week will need something to take my mind off things

But

No don't go fitting a Salisbury ffs

Ratio difference to minimal to worry....that's about 5 psi difference on pressure as an equivalent

Go 4.2 and if not right change tbox gears

Be in touch

Nige

Sorry to hear about your mum Nige. You have my condolences.

There is absolutely no rush. Like you need to be reminded of that on my build right ;) Seriously though im just getting my info together as i dont even have the big wheels/tyres yet. Who does 4.2 cw&p?

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