[shep]

What are peoples thoughts on optimum gearing for a auto Sierra? I have bits in the shed to make it 2920 rpm@100kph or 3854rpm@100kph but would've nothing inbetween. Also the higher revs are Toyota diffs and I would prefer to avoid them for now. Just remembered I do have a few sets of vit 5.12 diff gears but they would make it rev way to much.

What sort of revs should I aim for keeping in mind that it is a auto and I am building it to be a off road tourer an it will be on the heavy side.

[shep]

That is with 33s. If I go back to 31s it is 3111 rpm@100kph

[christover1]

Although you don't have any,
I'd consider 4;6 Vitara diff gears.
More common and cheaper, because they haven't been scrounged by a billion Sierra owners.
And I believe they are a lot tougher, but I'm no engineer.

[Gwagensteve]

Really Chris? I'd like to find your source of plentiful 4.6's. Only carby auto vitaras had them and two carby autos have to get wrecked for one sierra.

Shep- I reckon both options are crook. I reckon you need to be 3300-3600 rpm

2900 is too low for the weight and profile of your car. 4k is too high.

[jdk81]

I'm watching intently for experienced input, as I am looking at this situation too.

g16b max torque is 4000 rpm
stock vit is 3000 rpm at 100km/h

aw4 is
1st 2.826
2nd 1.493
3rd 1.000
4th 0.730
5th N.A.
Rev 2.703
High range 1:1, low 1.816:1
Diff 5.12

I was sort of looking at (sierra 6.4 gears, and aw4, 33 tyres)

3900 rpm with 5.12 diffs
3500 rpm with 4.6 diffs (can buy these from LROR too).
3300 rpm with 4.3 diffs
3000 rpm with 3.9 diffs
2900 rpm with 3.7 diffs

I'm probably going the 4.6 diff gears, as 4.3 would be too hard to find.
But id love experienced input, especially about heat generated at cruising if it doesnt lock out etc

[atari4x4]

Gwagensteve wrote:

Really Chris? I'd like to find your source of plentiful 4.6's. Only carby auto vitaras had them and two carby autos have to get wrecked for one sierra.

Manual SV420's have 4.6's

[christover1]

atari4x4 wrote:

Gwagensteve wrote:

Really Chris? I'd like to find your source of plentiful 4.6's. Only carby auto vitaras had them and two carby autos have to get wrecked for one sierra.

Manual SV420's have 4.6's

Thats a relief, couldn't remember where else they hide.

Also 4.3's out of the GV steel diffs we Vitara drivers steel, may be useful?

[shep]

So if I go g16, 4 speed auto, 6.5 transfer gear and 4.3 diffs for 3396rpm & 100kph I should be about right.

What are my chances of finding a pair of 4.3 r&p to fit Sierra diffs? 4.3 is easy to find for my Toyota diffs but I would rather stay suzuki.

[atari4x4]

every manual V6 GV front from memory... 98-06ish

[303zuke]

jdk81 wrote:

3500 rpm with 4.6 diffs (can buy these from LROR too).

Just be aware that Vit, or genuine Suzuki 4.6 diffs are 4.625, while the LROR (or US aftermarket) are 4.556. Close enough to roughly call both 4.6, but different enough to cause problems if you mix and match. You must run 2x 4.625 diffs, OR 2x 4.556 diffs or risk transfer case wind-up which can shear the engagement dogs on the front output gear.