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.
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Gearing And Engine Revs on a Sierra
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
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
--------ZUKZILLA--------
"chicks dig body damage"
"chicks dig body damage"
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.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
DMA Founding Member #1 - Now Retired
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
It's better to have LIVED for a day than to have EXISTED for a hundred years.
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
I thought it could be diff ratios but didn't think they would make so much difference ??
Your ideas would be very appreciated.
Jason
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.
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.
It's better to have LIVED for a day than to have EXISTED for a hundred years.
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...
DMA Founding Member #1 - Now Retired
SLOWLJ wrote:Yeah it was in 5th. I couldn't believe itI 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?
DMA Founding Member #1 - Now Retired
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.
)...
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.
DMA Founding Member #1 - Now Retired
It's probably just something giving me a bad reading but who knows Who is online
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