Gearbox Gear Ratios ... ?

[skydso]

Hi all,

I know this question has been asked before but the search option doesn't seem to be working properly, and I think that 4 hours solid on the pc here and quite a few mugs of tea are enough to make me stop searching and just ask!

Anyone knows the gear ratio of the first gear on a 1991 Surf 3.0l V6 auto tranny? I just want to find out what gear ratio I'm running in low so I decide which size of tires to use for optimum all round driving. I have two sets of wheels: a set of 15"x31" which seems a bit too high for the gearing I have in the diffs, being most probably 4.11 since it's still stock, but then I have another set 16"x(what seems to be)120 which I had bought without checking the size and was told they were 750's (29") but they're actually 2" bigger in diameter... making them 33"?

Thanks

Dave

[fourwd1]

Why do you need the 1st gear ratio to figure the best tire size?
It's the diff gearing that's important.
And what tranny do you have, and what's diff gear ratio?

The tranny model and axle codes are on the VIN plate on the drivers doorjamb.

[skydso]

I'd like to end up with a 55:1 ratio in low, and I can only do it by changing the low gear on the transfer case because I do not want to compromise the standard gear driving ability.

I have an auto box but no idea about the model and if not mistaken I have 4.11 diffs. WIll check to make sure though.

[fourwd1]

Jun 25, 2008 8:59:17 GMT -5 skydso said:

I'd like to end up with a 55:1 ratio in low, and I can only do it by changing the low gear on the transfer case .

You can't do that to the transfer case mated to the auto tranny.
Only to the gear driven t-case that came behind the 4 cyl manual trannies.

Right now your crawl ratio is around 42:1 (3.9*2.6*4.1)

[skydso]

Why not? Is it coz I won't find it commercially available or is it just coz it's impossible period?
Coz if it's just a question of fabrication, I have access to a good machine shop where I can get it done.

[fourwd1]

1 - the auto and t-case are integral and 2 - it's chain drive not gear.

[skydso]

Oh, ok ...

Guess I'll have to lower the diffs only then! I'll go with 4.88 I think!

Thanks fourwd1

[fourwd1]

If you had a manual tranny it would be different, there are options there.

[rockcrawlintoy]

Jun 26, 2008 8:32:33 GMT -5 fourwd1 said:

If you had a manual tranny it would be different, there are options there.

or u can get the inchworm adapter that allows you to put dual cases behind it or just one gear driven case

www.inchwormgear.com/store/product_info.php?cPath=21&products_id=86

[skydso]

WAAAHEEEYYY!

NOW YOU'RE TALKING!