[Treemonkey]

Hey all
Wondering why would be the best reduction gears for 94 Sierra running 30 inch tyres? Keeping in mind this is also my daily driver? Will it fix my speedi also
Any advice is appreciated
Thanks
Matt

[SierraDan]

with 3.7 diff ratios. I'd suggest 4.9 reduction gears. It would bring the gearing back to a better spot for nicer driving and give good offroad control wthot being too low.

But no, it won't fix your speedo reading.

[BlueSuzy]

1L transfer

Or

4.9's in your case

Won't fix your speedo. Only diff gears or speedo adapt/box will do this

[Treemonkey]

I should of mentioned im looking at transfer case reduction gears?

[Treemonkey]

Also the calmini 4.16:1 says recommended for 30inch tyres? So all the reduction gears will do is make it easier for my clutch gearbox and engine?

[SierraDan]

Yep. It will make driving much better and clutch changes less frequent.

[masterA]

SierraDan wrote:

with 3.7 diff ratios. I'd suggest 4.9 reduction gears. It would bring the gearing back to a better spot for nicer driving and give good offroad control wthot being too low.

But no, it won't fix your speedo reading.

x2

Got 4.9s in my sierra on 30s and it's a perfect combo for a daily driver

[Treemonkey]

Who sells the 4.9 ratio?

[tanshi]

www.lowrangeoffroad.com

[SeanusMaximus]

Trail Gear are very good for reduction gears. I ordered 6.5s for my zook on 31"s. Delivered within 10 days and include everything you need. For half the price of here in Australia.

[abclarke]

SeanusMaximus wrote:

Trail Gear are very good for reduction gears. I ordered 6.5s for my zook on 31"s. Delivered within 10 days and include everything you need. For half the price of here in Australia.

You dont find the reduction to be too much?

[SeanusMaximus]

It's a little more than i'd like but would be perfect with 32"s. Low range makes it worth it though. Third gear in low is like first in low before the change. I'm running at 4000 rpm at 110 kph, allowing for the error in the speedo, in fifth as a guide to the change.

[SierraDan]

Depends on what you drive though.

Third gear is like the old 1st!? SHould be lower than that!!

[BlueSuzy]

If you only want 30's. Don't get 6.5's.

Depending on brands depend on the real size of the tyre.

[SierraDan]

BlueSuzy wrote:

If you only want 30's. Don't get 6.5's.

Depending on brands depend on the real size of the tyre.

I reckon they're too low even for 31's..

Yeah, brand new Bighorn 35's measure 33.5". My Hankook 31's measure 30.9". Nankang 33's were the same height next to each other as my 31's.

[skyman]

Yeah, 6:%'s are a tad low for 30-31" tires.

Take a look at the charts, there is more to the gearing than you would think. One would assume that a 6.4:1 gearset would be considerably lower than the 4.9:1 in high range.

The fact is that the differece between the 4.9:1 case and 6.4:1 case in high range is only 1%
The huge difference is in the low range, where the 6.4 case is 66% lower than the 4.1, and 181% lower than stock.



That's why some people love the 6.4 case (especially those with a tired worn engine), With a 17% reduction in high range, they get their power back on road, and off road the crawl a tractor.

Myself, I like having all the torque and power I need to idle up or down and obstacle. However, there comes a point when too much gearing becomes not only too slow to useful, but adds so much torque you start breaking transfer mounts, and axles.

IMHO
For the low range and off road just about any aftermarket gearset will do, shit they start at 85% reduction -- should be plenty fore a for a 30 - 31" tire. They will all give you enough power to wheel.

Some will give you Über torque and a first gear you can get out and walk beside, while others will give you more wheel speed when in low range.(better for mud)

If you drive your rig on road, and are sticking to a 30-31" tire, look at the HIGH range reduction, and pick the case that will put your hi-way cruise RPM in the sweet spot for torque and economy.

On a side note; say you pick a 4.1 case and it is not quite enough gear, you can always add a set of NT or Vit diffs, to fine tune your ratio and get the RPM's where you need them. On the other hand if you gear your t-case too low there are no options for fixing that, except for swapping it out for a high geared case.

I hope that helps, and did not add to the confusion.

[abclarke]

All good points skyman! Gave me a little more to think about when trying to decide between an already torn decision haha...

Prick...

[skyman]

Ah... ya' welcome mate, anytime aye?

[skyman]

Here is my experience what I found when gearing. I had a hot 1.3 (H/C pistons etc), 33 inch BFG M/T's, and a 4:1 case to start.

Off road I had plenty of power and did not need to slip the clutch(even with 33's) It was not super slow in low range, but I did have plenty of torque and power to wheel with.

On road: In town the 4:1 case and 33's worked well. It was Zippy, accelerated quick, and the economy was good everywhere.

On the freeway at cruise, the RPM's were just a little too low for the 1.3 to be happy(ok it sucked). I found I was either revving to 4700Rpm in 4th gear, or lugging out in 5th at 3000Rpm or under, and losing speed. Running with no weight or on the flat it did ok and could hold speed, but was definitely nothing to write home about.

So I figured if I geared the rig so that the engine was in it's power band in 5th gear at cruise, the low range would work itself out(ending up )lower than it was already). Doing the calcs, I found that if I added 4:30 diffs to my 4:1 case it would raise my RPMs in 5th to about 3700 at 60Mph (or about 95Kph at 3700 Rpm). So I bought a set of 4:30 gears for my diffs.

The gearing worked out perfect, and I couldn't be happier with it. I can cruise at 90k all day long, up down hills etc. I can also put my foot in it to pass slow traffic when I am in the mood. Off road gearing is lower than it was, and good all around for rocks and trails, and mud.

So what I am saying to gear your rig so the engine is somewhere in it's power band when you are at cruise speed in 5th gear. For me and the 1.3 a good RPM was 3500-3800Rpm in 5th at 95kph/60Mph. With the least amount of reduction Lowrange offers coming in at 85% in low range, you should have no problem off road with any t-case you buy. It's making sure that you get enough reduction in the top end, without over doing it that's the trick.

BTW...
Make sure that you measure the actual true tire height you are goign to run, or the calcs and your RPM will be way off (that would suck).


These are the calcs I used. After you get the ratio for the transfer gears figured out, pop it into the second link I left for a more accurate read.

T-cases are a big buy, so I had a hard time picking gears myself. Definitely something you want to get right the first go round. Hope that helps a ya a bit .


http://www.lepayne.com/gears.html


http://www.grimmjeeper.com/gears.html

[jono165]

Another option is the calmini 5.14 gears. They are a little more expensive but its not worth cheaping our on something if it will be annoying every time you drive the car. These give an 18.3% high range reduction and a 127% low range reduction. As an example a bfg Km2 is stated to be 29.8" on their data sheet. A set of 5.14 gears would give you about 3500rpm at 100km/h. If you do decide to go 31's down the track 18.3% may still be enough in high range reduction.

Skyman has a good point work out where you want it to rev at cruising speed and the rest should sort itself out. I am about to go through the same with my Sierra. The lepayne calculator above is a very handy tool.

[wolf_rt]

I recently got the 5.14 gears and put them in my bog stack suzi.
the low range reduction is spot on imo... low 1st for crawling only, low 2nd gives some speed for carrying momentum over obstacles, and low 3rd for wheel speed in bog holes ect.
I also didn't find myself needing to change into high range when on the tracks.
On the road (on 215/75's) it was far better to drive around town than stock, with heaps more apparent power. On the highway the revs were a little high at 3700 at 100kph in 5th, but not over the top.

I have now fitted 30's, and while the on road gearing is better than stock (215's stock gears) taking off in 1st needs a few revs and a slip of the clutch again... Highway driving is spot on at 3400rpm in 5th.

if i went 31's or 32's i would consider getting 3.9 or 4.1 diffs to bring the high range gearing back to where it is now.

the extra 2% highrange reduction of 6.5's would be hard to pick in my opinion
i went for the 5.14's for the low range ratios, as i felt the 6.5's would be TOO low, i am happy with my choice, and happy to have spent the extra $130.

[abclarke]

Yeah playing with that gear reduction calculator tells you alot!

If im planning to stick with 31s i think id be quite happy to go with either 4.9s or the 5.14s...

Decisions decisions

[skyman]

One of the company's either trail tough, or Calmini sells a set of 5:xx gears that are made in Japan, and really high quality. They are a good pick, and a very quiet set.

Here local we have a guy that wheels with us that does our diffs, and gears. That was all he was recommending for a very long time, and they worked out well.

I would call trail Tough and ask about the Japanese set of 5:xx gears (check they may be a slightly different ratio). If you can get the Japanese set and the gearing suits you, they are very very well worth it. Seriously nothing is better than a nice quiet transfer case when you are doing any time on the freeway.

[want33s]

Mr Sky,
I don't know about the calamari stuff but ALL the Trail Creeper by Trail Gear sets are made in japan.
As are all the TG toyota gearsets.
I'm sure Rockhoppers are made out of recycled pushbikes in some 3rd world country.

[skyman]

ahh Ok Thanks Jas, I had no idea they were mostly all Japanese made..For some reason I thought the majority were made in China, except for stock and the 5:xx'ers

I know the 5:xx had a good reputation for being quiet and strong when we were all gearing our cases here local, but..... a lot has changed in the U.S Sierra parts market in the last few years. I am hoping/assuming they are the same sets that were sold 2 years ago.

[wolf_rt]

I got the calmini 5.14's and they are fairly noisy... even shimmed it properly...

[SierraDan]

wolf_rt wrote:

I got the calmini 5.14's and they are fairly noisy... even shimmed it properly...

Yeah they have a decent whine to them.

[skyman]

Must be the Trail Tough gears then, I will see if I can get a hold of him in the next few days and ask him what brand they were that he installed so many of. I have one of those cases here, and he runs them in his, they have been a good gearset with no breakages for us.

[want33s]

I like the whine Reminds me a bit of my 351C with Gilmer belt drive.

[SierraDan]

Mine sounds like a supercharger