Outer Limits 4x4 Board

i am just about to get a rockhopper

an i want somthin lower then 4.16
so i think my only other option is a 6.1
as i dont want to buy from America

so has anyone on here used a 6.1 with 31's?
what would the rpm's be on 90km?

Thanks
Tim

Tim
I've got the series 3 rockhopper and 33's,but i was also running 5.12:1 diff ratios so mine was flat out at 90.
I would'nt think a series 3 would affect you that much with 31's on the highway.It will naturally increase the RPM, but if your worried about it being to high go for a series 2 rockhopper which is not as low.
Do you do alot of road driving with it?

Jamie

redzook wrote:i am just about to get a rockhopper

an i want somthin lower then 4.16
so i think my only other option is a 6.1
as i dont want to buy from America

so has anyone on here used a 6.1 with 31's?
what would the rpm's be on 90km?

Thanks
Tim

Hey Redzook,

Assuming that you can do 90kms in 5th now (i.e. you will still be in 5th once you put the hopper 3 in), you can perform this simple equation to work out what your RPMs will be with the 6.1...

First up, we know the the 6:1 is 22% lower in high range right? so that make it 78% of the current gearing.

So,

(Current RPMs / 78% of gearing) x 100% of gearing = new RPMs...

for example:

If you were currently doing 4000RPMs to be doing 90kms

(4000 / 78 ) x 100 = 5128 RPMs.

simple.

Notes:
1. That obviously is a rough guide and no doubt other factors will affect it a little bit too - but that does give you an idea.
2. Remember that your low range will be heavily affected by the 6:1... I cant do more than 30kms in low range 5th gear now.

Cheers,
Greg

I have a series 3 with a toyota gearbox and 4.1 diff gears on 34" Swampers (6.1 x 3.54 x 4.1 = 88.5) and on road doing 100km/h I am doing about 3000 rpm. As greg said offroad the drop in gearing is phenomenal. With the 31s it would be lower again making for some awesome wheeling, although tyre speed if needed could be a problem

Fourwheelin wrote:but if your worried about it being to high go for a series 2 rockhopper which is not as low.


Jamie

who sells a series 2?
i thought we only had series 1 an series 3

thanks Tim

Sorry tim i meant to put series 1,slight typo on my behalf.

Regards Jamie.

Redzook,If your car has standard diffs 3.90 and i think s3 is 1.78 -1
fifth 0.790-1 so 90ks = 3343 rpm. 110ks = 4086rpm
overall crawl = 85.41-1
at a slow walking pace 2mph your engine will be at 1,851 rpm.
Possible varaitions are : you may have 3.70 diffs your tyres are probly 29.5.
Larry.

thanks for that info dozoor :wink: