Outer Limits 4x4 Board

Hmmm just swapped my 6:5 tcase which is supposed to be 20% lower than standard in high, with a 1ltr case and it hasnt changed the revs on road at all. Is that right. Do i have to change diff gears if i want to lower the on road revs a bit ?

mrRocky wrote:Hmmm just swapped my 6:5 tcase which is supposed to be 20% lower than standard in high, with a 1ltr case and it hasnt changed the revs on road at all. Is that right. Do i have to change diff gears if i want to lower the on road revs a bit ?

Mate your 6.5 case IS 20% lower in high range. Unfortunately for you, its 20% lower than a 1.3L case. A 1L case is 12% lower than a 1.3L case from factory. So really, with the 6.5 case, you are really only 8% or so lower than a standard 1L case.

thats freaky-weird!

my 5.14 tcase is 18.3% (i think) reduction hi-range and has brought my RPM back very close to stock... maybe check the specs on where you got the 6.5's from - perhaps the low range is lower but the high range isnt as low? (doubt it though).

Why'd you change to the 1L case anyway?

what else did you change at the time?
tyres etc?
and how are you measuring the speed ?

sitting on 85 on the speedo (92 on gps) my tacho reads 3900rpm
before and after i swaped back to the 1ltr case.
Its really annoying, i want to be able to sit on 100 on the speedo doing about 3900rpm not at 85. I will put the 6:5's back in when i want to go crawling or do comps but the at the moment its weekends away that are on the agenda and 85 is a major p.i.t.a.

thats bizarre!!

So you're running 31's, and 1L tcase and doing 3900rpm at 92km/hr? Being a NT - are your diffs 4.11??? diffs would be the only other thing to check.

I think mrRocky's car is a Maruti so 4.1 diffs.

yeah i have 4.1 diffs coming out my ears. If i drop to 3.9's will that make a noticeable difference.

that'd do it... Nicbeer runs 1L tcase and 4.11 diffs and 31s on his - maybe he can chime in with RPMs at speeds? (or you could PM him)

4.1 diffs 1ltr transfer 31" tyres on mine in 5th gear is 100 @ 3500
in 4 gear 100 is 4000 on the GPS

maybe i have a earlier 5 spd if i sit on 100 on the speedo engines reving at about 4300 rpm, stupid mutant car.
wheres gwagonsteve with all the answers when you need him

used to run the 1ltr case til i took it out to rebuild a while ago....

running 3.9s and std 1.3 transfer and 31s equals about 4k at 100 from memory

hey mr rocky, did you go from a 12% (1lt) case to a 20% case expecting it to lower the revs what gearbox are you using? my numbers say at 100ks with 31s, 4.1diffs, .864 5th and 1.58 maruti tranfer you should be revving at 3761 rpm. if you go to a 3.7, it will drop it to 3394rpm. but these numbers are well down on what you say you are getting.
when i did the 1.6 and 5speed in to my maruti it was still screaming in pain at 100. changed to 3.7 and made it a lot more comforable ( no tacho, just going buy noise). this has been on stock tyres for 18 months and has been ok. i trialed some 265/70/15 on it last week and i think the gearing in high range is perfect. by the calculator its at 3554 rpm at 100.
hope some of this helps

mrRocky wrote:yeah i have 4.1 diffs coming out my ears. If i drop to 3.9's will that make a noticeable difference.

4.1/3.9 = 1.05.

so this would change your revs by 5% so instead of 85km at 3900 your would do 89km/h. so sweet fark all.

sierra gearing is a PIA.

some one metioned 0.864 5th gear as well. didnt most 5 speeds come out with an approx 0.78 - 0.79 5th gear?

ok, i went from a 1ltr 4 spd with 4.1 diffs and 6:5 tcase, to a 1.6 baleno with mystery 5spd and now back to the 1ltr case to try and lower the revs which with an extra gear and a 1ltr case i thought it would make a bigger differance.
just got an 89 hardtop so i might swap the diffs over, will they be 3.7 or 3.9 in the hardtop.

wait for it

89 should be early wt, so 3.7.
going from 4.1 to 3.7 is what your after. should drop your revs by about 400rpm.
ps. is there any chance your 31 measure about 28?

mr green wrote:ps. is there any chance your 31 measure about 28?

thats a good point

hmm there 31" maxxis buckshots with about 45% tread so i think its more like 30's.