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Author: Subject: changing sierra diff ratio
smart51

posted on 26/9/07 at 02:08 PM Reply With Quote
changing sierra diff ratio

Given these Sierra diff ratios:

44 : 14 = 3.14
44 : 13 = 3.38
47 : 13 = 3.62
47 : 12 = 3.92

could you just swap the crown wheel to convert a 3.62 to a 3.38? If money were no object, could you have a 40 tooth crown wheel made and convert it to a 3.08 or does it not work like that?

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Fatgadget

posted on 26/9/07 at 02:22 PM Reply With Quote
Ummm I think if it was doable somebody would have done it already!
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02GF74

posted on 26/9/07 at 02:28 PM Reply With Quote
well i am no gear expect but I would expect that the crown wheel has to match the pinion.

if you are adding or removing teeth from the crown wheel and it is the same diameter, then the teeth will become larger or smaller - the teeth on the pinion would need to change in the same way to mesh properly - the teeth are curved bevells (is that the right name?) I would have thought.

Or if the teeth on crown wheel are the same size, the diameter of the crown wheel has to increase or decrease as you add or remove teeth. Now in this case you would need to move position of the pinion, and the bit I am not sure of, is the angle of the pinion teeth need to change again to mesh correctly. You may be lucky that the angle won't change so much when you have a large number of teeth but I would expect it to not work well - there are enough horror stories about correct backlash with Land Rover diffs and those use matching crown wheel/pinion to suggest it won't work and/or last long.

[Edited on 26/9/07 by 02GF74]


VVVVVV mr bearing kit has sumarise all that ^^^ far better.

[Edited on 26/9/07 by 02GF74]

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smart51

posted on 26/9/07 at 02:32 PM Reply With Quote
I was thinking that maybe there is a range of sizes that will work and as they have 13 tooth pinions in the 3.38 and 3.62, they may be the same. There is a bit of slack in the sierra diff after all.
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BearingKits

posted on 26/9/07 at 02:35 PM Reply With Quote
Each set of gears is made as a matched pair.

If you look on the edge of most crownwheels you will see a number written with an engraving tool. The number will also appear on the pinion either on the flat surface where the teeth end or between the two pinion bearings.

Normally Ford gears have 3 digits like 121 for example.

Mixing pairs of the same gears is not advisable.

You cannot mix different gears as they will not mesh.

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blakep82

posted on 26/9/07 at 02:36 PM Reply With Quote
were all sierra the same ratio? atlas axles are easy enough to get new ratios for. kits are always crown wheel and pinion. so yeah, a new pinion gear would be needed





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stevec

posted on 26/9/07 at 03:15 PM Reply With Quote
quote:
Originally posted by BearingKits
Each set of gears is made as a matched pair.

If you look on the edge of most crownwheels you will see a number written with an engraving tool. The number will also appear on the pinion either on the flat surface where the teeth end or between the two pinion bearings.

Normally Ford gears have 3 digits like 121 for example.

Mixing pairs of the same gears is not advisable.

You cannot mix different gears as they will not mesh.



What he said.
Steve.

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mcerd1

posted on 26/9/07 at 03:55 PM Reply With Quote
quote:
Originally posted by smart51
If money were no object, could you have a 40 tooth crown wheel made...


if money really were no object you could get a new pinion made too

there are already 4.1 and 4.44 kits out there for sierra 7" diffs

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BearingKits

posted on 26/9/07 at 05:46 PM Reply With Quote
3.14 are also available

quite expensive tho' at around £540+vat

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Simon

posted on 26/9/07 at 07:01 PM Reply With Quote
Much as I hate to have to ask, but does anyone know a good engineering company in the far east where we can all get 3.14 f/drive sets made for about 70 quid.

ATB

Simon






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ReMan

posted on 26/9/07 at 09:08 PM Reply With Quote
If money were no object, you definatly would'nt be using a Sierra diff at all
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bj928

posted on 26/9/07 at 09:26 PM Reply With Quote
quote:
Originally posted by ReMan
If money were no object, you definatly would'nt be using a Sierra diff at all


i'm not using a sierra diff, i'm using a mustang 8.8 with a nice 2.73 gear, if your running a 7.5 sierra diff, you may be able to get a few extra ratios from america.

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James

posted on 27/9/07 at 01:31 AM Reply With Quote
Thought this was Locostbuilders???

What's wrong with using a couple of discs of metal and an angle grinder????







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