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  1. #1
    Lurker
    Join Date
    Sep 2016
    Location
    victoria
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    6

    2.8L diff/tyres/RPM's/power

    Hi everyone.

    Just a thought, thinking of 5th and 6th gear ratios in my 2.8L auto prado. They seem so tall that the 6th rarely gets used (or hunts constantly between 5th/6th). I've looked at some diff/drive calculations and considered the following:

    4.11 gears Nitro front/rear
    4.56 gears Nitro front/rear

    I currently run the normal sized 265/65/17 (KO2s), and currently pull ~1650RPM at 100kpm in 6th (GPS, 105kph speedo). Im considering upgrading to 32inch (close to it, 265/70/17 (31.6")). With that setup the calculations are
    3.909 - Current ratio @ 1650 100kph (30.6")
    4.11 - Nearly 1700RPM for the same speed. (31.6")
    4.56 - Just over 1850RPM for the same speed. (31.6")

    I am thinking of the 4.56 as the slightly higher revs might fix some sluggishness issues, and allow it to hold 6th easier on the highway without dropping to 5th (2500+RPM) all the time. The kits are around $1350USD which is front and rear. I am wondering if I have failed to consider anything here? In the near future, and before doing the ratio I will prob install Steinbauer, and was thinking of doing a rear E-locker at the same time. If anyone has done anything similar please let me know the info, I've searched without success.

    Thank you,

  2. #2
    Senior Member
    Join Date
    Oct 2016
    Location
    Melbourne
    Posts
    282
    Hi,

    I don't have any Experiance with this upgrade but have the exact same opinion as you, car is now setup for off-road work, but have held off on tyres until I embark on a more serious trip, also have held off due to the 6th gear issue. I think low range is also not low enough in factory trim so this will only worsen with larger tyres
    looking at your figures the 4.56s look good what will the Rpms be at 110 ? If there under 2000 that all seems fairly good

    Please keep me posted with how you go and who you get to do the work as we are both in vic

  3. #3
    Member azzss's Avatar
    Join Date
    Dec 2011
    Location
    Bushfield Vic
    Posts
    224
    Im interested in this as well, they are way way to tall geared! anything around the 1800-2k rpm at 100 should be the norm in a 4 cyl diesel 4WD.
    2016 1GD GXL 6 speed auto, ARB colour coded summit bar, LED driving lights, duel batteries, BF Goodrich tyres, window tint.

  4. #4
    Why not go a bit faster and raise the rpm then? speed limit is 110km/h 115 before getting booked surely?

  5. #5
    Lurker
    Join Date
    Sep 2016
    Location
    victoria
    Posts
    6
    I guess it's only 110kph in some areas, otherwise it's 80-100 and stuck behind someone wanting to do 5 under. So it's be handy having the car geared 4 the speeds it most often does, rather than 115-120kph.

  6. #6
    Senior Member
    Join Date
    Oct 2016
    Location
    Melbourne
    Posts
    282
    I put a set of 265/65r18s ( 31.6 ) on yesterday and at 100km/h it sits in 5th at 2000rpm and does not want to select 6th unless it is on idle. So your basically running a 5spd box. It's not very often we see 110km around here

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