[607CHA]

sbbunno wrote:

607CHA wrote:

I was thinking of running 6.5's with 30's and 3.7 diff gears. Would this be close to 31's with 3.9's? And I don't wanna spend the money for 5.14's when atm 6.5's are only $475 on lowrange.

that ends tomorrow i think, though i thnik i agree.
how would i know what gearing my diffs are

Damn I wanted to get some soon but not that soon

[Built4thrashing]

The 6.5:1 gears only adjust highrange by 20%. And im guessing your tyres are pretty close to that much bigger.

My sierra had 3.9 diffs, and 6.5 gears and ran 31 xtremes. it wasnt over reving at 100kmh

[matfan]

I'm running 4.9's, stock wt diffs and 30' m/t's and it's pretty much spot on for me. The 187% low range reduction with the 6.5's is a little too low in my opinion unless you only ever use low to crawl. I haven't personally ever felt like my low wasn't low enough. I've seen enough blokes with crazy reduction starting their climbs in 2nd or 3rd gear to know that lower isn't always better.
Again, just my 2 cents.

[shep]

fucken hell there is some bullshit spread around about 6.5 gearsets.

try a gearing calculator, 6.5s with wt diffs and 31s is stock revs at 100kph ie 3600rpm.

changing transfer case gears will not change the speedo reading only different tyres
or different diff gears will change the speedo.

ya dont have to just use 1st gear in low range as there are 4 other gears in the box.

i reckon 6.5s and 31s are a perfect combination and i have had
1.3 sj 50 on 32s with 6.5s
1.3 sj 50 on 31s with 6.5s
1.6sj50 on 31s with 6.5s
1.3 sj51 on 31s with 6.5s
1.3 sj51 on 33s with 6.5s.
on all those combination's i have driven everything from rocks, mud,
touring, towing trailers and using as a daily driver, never have i thought
that the 6.5s were not the best option.

with the 6.5s my sierra has 10 very usable forward gears and it must suck
trying to wheel something without such a broad spread of gears.

[jonno_racing]

6.5s ftmfw every time.

[sbbunno]

sounds like everyones keen on the 6.5s. now i gotta wait for pay day again

[appsie]

another vote.have ran 6.5s with 31s and stock 3.7 diffs for over 3 years now both with a 1.3 carb and then later a 1.6 efi

the carb engine wouldnt of had a hope in hell without the gearing
the 1.6 sits on 3650ish at 100 off the gps.gets driven most at my place as a daily,play toy,occasional bigger trip and camp and has done a few larger highway trips.
i like slow rock crawling style 4bn and off camber gullys etc so there is no other option for me

[SierraDan]

appsie wrote:

i like slow rock crawling style 4bn and off camber gullys etc so there is no other option for me

x2 i couldnt settle for anything else for my terrain.

[alien]

mines all WT gearing except 5.14 tcase gears and 31x10.5 tyres... 100km/hr is 3400, 110km/hr is around 3600... IMO its spot on, but i've also got a 1.6EFI engine.

if you do the maths 5.14 is better suited to bringing a 31" tyre back to stock RPMs - however a 6.5 would help counter the added wind and rolling resistance (which a 1.6L engine also does).

[troopy]

I run 31's and a carby vit motor with the 6.5s in my small zook and while they are very slow you also have another 4 gears to chosse from in low range if you feel you need more speed.

if you would like to find out for yourself what the 6.5 gears are like you can drop round and take mine for a drive

[sbbunno]

cheers for the help fellas.

troopy i may take you up on that, just not for a little while as im flat out at work. the 5.14 seemed like a good option but are bit pricey compared to the rest, im thinking 6.5's are the go any ways.

[masterA]

I was definatelly keen on the 4.9 or 5.14 but reading the above it seems that everyone is happy with the 6.5s and they're cheaper which is a bonus

Does anyone run the 6.5s on 30" tyres...what are the revs at 100km/h?

[TryHard]

30S and 6.5s run fine cant remember what it revs at dont think its much dif from 31s maby few hundred RPM lower 3800 or something

[Moph]

^ wrong way round ... 30's would be higher revs for same road speed compared to 31's, due to less distance travelled per wheel revolution. Depending on actual tyre rolling diameter (which varies from tyre to tyre) you'd be looking at about 3800rpm at 100kph, 4150rpm at 110kph.

[Munster]

Munster wrote:

I have been running 6.5 with 3.7 diffs and 32" tires for about 2 years now, mainly as a daily driver as well as bush beast. Very happy with them.

4000 rpm gives me 114 kph according to the GPS and my speedo which has been calibrated.

[skyman]

Sheps is right you have to look at the gear calcs. too may people assume that if a 4:1 s=is low, a 5:xx lower, then 6:5s' gotta be mad baby crawling slow in high gear. That is Not always so. The low range redux is much much greater than the high range reduction with a 6:5 case. So while your 4by low is low, that doesn;t necessarily ean high range is going to be craw slow too.

I like to run a 4:1, or a 5:xx case and fine tune with diff gears to spread the load between the diffs and the case...But, that is more expensive, you have to install two more diffs, and I think we have more diff ratios common (read cheaply) available here.


He is also right that the diffs gars and tires change your speedo, a geared case will not.

One thing to note. if you run big tires with only a case, make sure you beef up your arms and mounts. That is a lot of reduction in one spot, it makes the case want to do barrel rolls in it's mounts.

[Red89]

Based on the videos you have posted in the past sbbunno 6.5's would suit the terrain and your style of driving very well offroad.

[MrRocky]

my w/t running 4.1 diffs with 6:5's and 31"s reved at 4100rpm at 96km/phr
and was gay onroad but sensational offroad, even on the beach.

[31zook]

4.16 tc, 4.8diff, and 36.5s..... Going to get 6.5s so I can crawl like a mad dog!

[sbbunno]

Red89 wrote:

Based on the videos you have posted in the past sbbunno 6.5's would suit the terrain and your style of driving very well offroad.

. Good to know that people follow my bids haha, yea I love the idea of crawling off road it was inroad the concerns, though now I'm loving the idea altogether

[masterA]

skyman wrote:

Sheps is right you have to look at the gear calcs. too may people assume that if a 4:1 s=is low, a 5:xx lower, then 6:5s' gotta be mad baby crawling slow in high gear. That is Not always so. The low range redux is much much greater than the high range reduction with a 6:5 case. So while your 4by low is low, that doesn;t necessarily ean high range is going to be craw slow too.

I like to run a 4:1, or a 5:xx case and fine tune with diff gears to spread the load between the diffs and the case...But, that is more expensive, you have to install two more diffs, and I think we have more diff ratios common (read cheaply) available here.

He is also right that the diffs gars and tires change your speedo, a geared case will not.

One thing to note. if you run big tires with only a case, make sure you beef up your arms and mounts. That is a lot of reduction in one spot, it makes the case want to do barrel rolls in it's mounts.

Reading the above and from what you and shep have said...if for example you're running 30" Bighorns and did the 6.5 transfer...the only way to get the revs down would be to put 3.7 diff gears in?!
Or would a different combination of diff gears/transfer case gears be a better option to get the revs down/back to stock?

[Gwagensteve]

It surprises me how much people struggle with this.

ALL transfer case gears except 4.1's offer between 16 and 20% reduction in high range.

30" tyres are about 15% over stock. 31's are about 19% over stock.

Road gearing will be quite acceptable regardless of which combination of 30's/31's and gears you use.

Worst case either way will be revving about 180rpm faster or slower than stock at 100km/h.

In any case it's pretty much possible to choose the gears that will put cruise revs exactly back to standard for a given tyre diameter in this range.

The bigger issue is are 6.5's too slow for 30" tyres in low range? Maybe. If you have lockers and like technical driving they will be fine. If you regularly run sand or have open diffs you're going to struggle with the reduction of 6.5s. 31's are a bit better though.

It requires a big change in driving style to work with the reduction of 6.5's. I see lots of people put them in and still attack everything in 1st low like they did before their gears. You need think a bit more laterally with revs and gear selection - I'm often in 3rd or 4th low, and regularly launch in 3rd low to clean the tyres and get some wheelspeed.

Steve.

[sbbunno]

Gwagensteve wrote:

It surprises me how much people struggle with this.

ALL transfer case gears except 4.1's offer between 16 and 20% reduction in high range.

30" tyres are about 15% over stock. 31's are about 19% over stock.

Road gearing will be quite acceptable regardless of which combination of 30's/31's and gears you use.

Worst case either way will be revving about 180rpm faster or slower than stock at 100km/h.

In any case it's pretty much possible to choose the gears that will put cruise revs exactly back to standard for a given tyre diameter in this range.

The bigger issue is are 6.5's too slow for 30" tyres in low range? Maybe. If you have lockers and like technical driving they will be fine. If you regularly run sand or have open diffs you're going to struggle with the reduction of 6.5s. 31's are a bit better though.

It requires a big change in driving style to work with the reduction of 6.5's. I see lots of people put them in and still attack everything in 1st low like they did before their gears. You need think a bit more laterally with revs and gear selection - I'm often in 3rd or 4th low, and regularly launch in 3rd low to clean the tyres and get some wheelspeed.

Steve.

The only way to learn is to ask the question. currently i drive a 100 on little more than 1100 revs which i liked hence the origional question.

[Gwagensteve]

I understand sbbunno - I wasn't directing my comments towards you, only the way this thread has been answered.

I understand the combinations fairly well and have my own gearing calculator for working it all out, but most of the responses in this thread confused me.

It's not hard - X gears are Y% reduction in high range.... tyres are Y% bigger than stock= stock gearing on the highway.


Steve.

[JrZook]

Q: What is the max speed you guys are getting out of your 6.5's/tire combos in lowrange?

[Gwagensteve]

About 25km/h.

34" swampers, 6.4 transfer (TT) and 5.12 diffs.

I don't use 5th low - There's no point spinning the gearbox, jackshaft and 1/2 the transfer at the equivalent of 130km/h of road speed for the sake of it IMHO

Steve.

[3cyl]

With 6.5 transfer in mine low 4th is near enough the same as high 1st. My 1st is 3.835.

[Gwagensteve]

And that's pretty much the same for me.

Steve.

[masterA]

Gwagensteve wrote:

It surprises me how much people struggle with this.

Thats why we have people like you to enlighten us

Thanks for the info....and on that note i'll be spending $25 extra for the 4.9's

[Teracis]

I still use 5th low and I have 6.5's. Like Gwagensteve says though, It's not for going fast, I only use it to keep the revs down if I'm on a longer flat stretch, keeping the revs at say 2500 or so, as mentioned if you go to hectic with it it's like highway driving for your drivetrain.