Outer Limits 4x4 Board

Can everyone (or at least as many as possible) help me with this.

I have the 5.12 vitara gears, but am not sure what tyres and transfer gears I am going to run as yet.

I do want to be able to use the vehicle off-road, but I don't want to be reving the crap out of the engine on a trip.

Can I get some info from people that have different gearing to std post what revs they are doing at 100km/h (real speed) and what diff/transfer gearing and tyre size they are running at those revs.

Any help or tips would be greatly appreciated.

I`m running 33`s , 4.16 rock crawler gears , and 5.12 diffs.

If my speedo is on 100km/h in 5th gear the motor is revving at 3900rpm.
But my actual speed is about 95km/h.

I had a chart which shows you all the different gearing combinations for a zuk. Also shows you crawl ratio and rpm at 100km/h (5th gear) for each gearing combo.

I`ll try to find it

31's, 6.1, 3.7's

100km/h = 3900rpm

26" + Rockhoppper 3 + std w/t diff gears

100kph = 4100rpm

If you want the exact same revs for your engine per road speed - you will need to increase your tyre size by the same percentage that you have increased your diff ratios.

i.e. you have increased your diff ratio from 3.7 to 5.125, so you can say that you have increased it by (5.12 / 3.7 = 1.384) 38.4%...

So, all you need to do is multiply your stock tyre size (26") by 138.4% to get the exact tyre size you need to run to get the same engine revs per road speed...

26 x 1.384 = 35.97.

Notes: This formula does not take into account other issues like wind resistance that will become more of an issue now that you are going to have a much taller car. Nor does it consider how hard the fitment of a 35" tyre will be on a sierra. Another thing to note is that it is working on the theory of a measured tyre (not one that says 35" on its sidewall), so this formula will only be true if you actually measure the new tyre with a tape measure.

However, please also realise that the sierra could use alot more gearing from its stock form to behave nicely on and off road for both daily driving and heavy crawling duties... For example, with the gearing that i am running (cappaccino gear box, series 3 rockhopper and 5.12 diff gears), i should be running a 38.52" tyre (if i wanted to have stock revs at road speed)... but I am only running a 34" tyre and find that the extra revs that it allows the engine to hold at speed works out pretty well...

Hope that helps.

Cheers.
Greg

I haven't got a tacho in mine but I can tell you that my gearing is 7% lower than stock 1 ltre gearing. I now run 6.1 transfer, 4.55 diffs, and 33's.

was running 2.1 TF, 4.11 diffs, with 215's.

31x10.5s
Petroworks 4.89:1 reduction T Case 1.66:1 in high
5.43:1 ring and pinions
ORR of 97:1
100 KPH (true) = 4850Rpm.
LM

Luigi Malone wrote:5.43:1 ring and pinions

Luigi, what / where have you gotten these fellows from?

greg wrote:

Luigi Malone wrote:5.43:1 ring and pinions

Luigi, what / where have you gotten these fellows from?

Back about 93 or 94 I bit the bullet and ordered them from Calmini.
Bling bling for sure as I couldn't install them and had to pay the man.
But I wanted so I gotted. There wasn't anything else available.
LM

Can someone with a stock widetrack please tell me what revs they are running at either 100kms?

Thanks

just over 3500 I think, it feels high, with 28 inches on I run at just over 3000 rpm if I sit on 90 which is really a hundred. I like it better with this I dont feel as if the engine is working as much

I sit at around 3500 at 100ks on 29 inch tyres standard running gear.

Sorry I must have been on drugs last night its actually 3100 @ 100ks.

I bought a sierra with a blown motor and have only just just taken it for a spin with the new 1.6 carb vit motor. Running std tires and rims I was doing 4500rpm to sit on 100k/hr . Anyone know what cause such a difference from std. I thought it could be diff ratios but didn't think they would make so much difference ??

Your ideas would be very appreciated.
Jason

SLOWLJ wrote:Anyone know what cause such a difference from std. I thought it could be diff ratios but didn't think they would make so much difference ??

Are you in fifth?

The motor used to sit ahead of a 1:1 ratio T case. Now it sit's ahead of a 1.416:1 Tcase. Also some wheelbarrow wheels. Fit some 31's at least, and don't rev the snot out of the 1.6.
If you like rev's, fit a swift Gti, then go out on the highway and make all those big bullies in turboed diesels pay.
LM.

Luigi Malone wrote:The motor used to sit ahead of a 1:1 ratio T case. Now it sit's ahead of a 1.416:1 Tcase. Also some wheelbarrow wheels. Fit some 31's at least, and don't rev the snot out of the 1.6.
If you like rev's, fit a swift Gti, then go out on the highway and make all those big bullies in turboed diesels pay.
LM.

I'm not so sure that this answers the question luigi.

The motor replaced another motor that was already there (as i understand it)... So the question is - why is the vitara motor revving harder than a stock sierra motor setup would be reving.

The answer is - it shouldn't be reving harder at all.

Therefore, there are a few possible issues:

1. You're gearing is very low (x-fer case, 4th or 5th gear)

2. You're tyres are too small or diff ratios are too low and you are getting your speedo reading from a GPS.

Well - at least that's what i understood from the question...

Yeah it was in 5th. I couldn't believe it I will be fitting 31" goodyear MTR's but I will also be fitting a calmini T-case gearing (5.14) so this might make it rev to much for highway use.

SLOWLJ wrote:Yeah it was in 5th. I couldn't believe it I will be fitting 31" goodyear MTR's but I will also be fitting a calmini T-case gearing (5.14) so this might make it rev to much for highway use.

Is it in an LJ or a Sierra? What year is the running gear in the sierra?

Does it already have a rockhopper (1 or 3) in it?

Update now with the 6.1 transfer and 31' simex I do 3600 @ 100'ks

xtreem wrote:Update now with the 6.1 transfer and 31' simex I do 3600 @ 100'ks

That's not too bad. I might have to hurry up and fit some bigger tyres to mine, cause the combination of 6:1's and 235's produces a very slow zook on the road!

greg wrote:
Is it in an LJ or a Sierra? What year is the running gear in the sierra?

Does it already have a rockhopper (1 or 3) in it?

It is a 90 model sierra with Std running gear (as far as I'm aware, std wt diffs, unsure of the centres)

I'm thinking it must have some kind of reduction in the T-case, but I don't know for sure. I won't be able to test it for a coulpe of days because it's at the muffler shop and then getting a new windscreen put in

If it has T- case gearing it will hardly move when in 4low, correct?

It's certainly sounding more and more as though it must have a reduction x-fer case in it already (bonus )...

If your revs are acurate, and the other folks data is acurate too - then i would suggest that you are around 20 - 25% slower than normal - this would suggest a 6:1 x-fer case (rockhopper 3) - which is 22% lower in high range.

hehe well I hope so anyhow It's probably just something giving me a bad reading but who knows
I couldn't even think straight with the extractors finishing below the passenger seat

I will find out when I pick it up next week.