[SuziBlu]

I am either hopeless at searches, or it has never come up. Can someone help please.

What are the gearbox ratios and also the transfer ratios in a 1990 sierra.

I want to do some calculations on using 5.12 diff rations and speed/engine revs with different tyre sizes.

I was going o go 33s, but thinking 35s may be open for me.

[tanshi]

gear box is
1st 3.652
2nd 1.947
3rd 1.423
4th 1.000
5th 0.864
Rev 3.466

transfer is
High 1.409
Low 2.268

[SuziBlu]

Cool, thanks very much.

[S13RR4]

there is a awesome excel calculation thing in the downloads section, I think DMAC submitted it, its got all the ratios you need and does the calculations for you.


but I cant find the downloads section now that everything has changed a little.

[SuziBlu]

Sadly since I did an upgrade on my microsoft office, its stuffed, need to get my computer to a doctor to fix up bill gates shit.

Cannot use excell.

[tanshi]

i think that excel doc might be the one highwaystar made up, i have it on my work PC for when i wanna have a play with gearing

[shep]

i think 5th gear is different between sj50 and sj70

[want33s]

WT 5th gear is a fly shit taller (more overdriven) than NT but hardly worth worrying about.

This calculator has everything you need...

http://www.rocky-road.com/calculator.html

[tanshi]

yeah the NT is slightly different, however he said 90 model so i didnt bother with it

[tanshi]

the one i have has calculator for duals, and all the ratios for all the zuks already in it so i dont need to remember

[SuziBlu]

Ok, so Im up against a wall.

engine revs/gearbox ratio/transfer-box ratio/diff ratio x tyre diameter gives speed, yes, no.

[tanshi]

with standard gear box and transfer and 5.1 diffs on 33s you will be doing around 3900 revs at 100ks in fifth

on 35s you will be doing 3700 at 100

[SuziBlu]

So 53s are very do-able with 5.12s and a 1.6ltr.

Cool.

[tanshi]

the only issue you will have is that low range with be complete crap.

total reduction in first low is only 42:1 on 35s that will be really really high

[want33s]

Dave you might want to look into adding some 4.1 or 4.9 transfer gears as well.
4.1 gears will lower your High range by 12%.. low by 84%
4.9 gears will lower your high range by 16%.. low by 115%


The 4.1 gears will up revs to just over 4000 at 100km/h but will give a better than standard low range.
Obviously the 4.9 gears will increase revs by a bit more.

[tanshi]

i will have 35 or 36s on my LJ project, 1.6 efi, 5.1 diffs,
but i will be having 7.4:1 lowrange 106 crawl ratio. 40 odd will be really hard to drive.