Changed gears - 4.56's 33's MTZ's 6spd JK Hunty

[Hunty]

I have a 2007 JK - it came with factory 3.21's & I run 33' MTZ's - it could barely pull the skin of a rice pudding LoL

on Factory 3.21's @110kph I was doing 1800ish on the Tacho
after regearing to 4.56's the tacho now reads 2850 @ 110kph!

2nd gear now on 4.56's is approx the same rpm as 1st was on 3.21's

slip it into 4low and 4.56's give 1st a real rock crawler feel.

I also got rid of the rear exhaust muffler and fitted a straight through pipe / hotdog - Jeep sounds great now and I think I picked up a little more down low HP.
fuel economy has suffered a little - was around 12-14L/100 now I get 14-16L/100

I totally recommend changing to 4.56's
the jeep has gone from sluggish to Yee Haa
I tow large trailers regularly and am very happy to be able to drive with a heavy trailer attached from Sydney to New Castle and not have to drop below 5th

cheers Hunty - ps this photo post dates the lake lyel run in which I ....... mud hole LoL
http://i685.photobucket.com/albums/vv217/ashunty/My%20Awesome%20Kids/MotoJeep.jpg

[SteveC]

What was involved in changing the gears - Id be interested to read this Hunty

[Jaffas]

To change gears, you are essentially pulling the crown and pinion geasr out of the diffs, putting new ones in and putting the diffs back together. usually a job best left for the real mechanics out there... you don't want to get the preload wrong on your bearings and seize a diff up!

I went to 4.56 years ago when I built my truck and it really is a good thing to do for 33's and 35's. stock ratios are designed for stock tyre diameters! big ratio's for big tyres!

my philosophy is that you decide what tyres you want to run, then build the drive line to suit, then build the suspension to suit, and the last thing you do is put the big tyres on. that was the car will handle them and be strong enough..

Enjoy it.

[casey]

hunty: did you re-calibrate your computer for the new gear ratios so the tacho/speedo/esp work correctly?

[Hunty]

Hi Casey
I own a PROCAL - its a programmer i bought in the USA at a jeep fair for $50 it allows some simple reprogramming - you can re calibrate by different methods
1. Speedo
2. Tyre size
3 Gear ratio's
4. Headlights on auto whilst driving
5. Engine idle rpm - useful when crawling to just bump up the idle 500rpms or so and winching to save your battery
6. how many blinks the blinkers do when you just flick them momentarily
7. Clear engine codes, and even has a feature to help align the vehicle perfectly for optimal ESP performance. tells you when the steering wheel and ESP are aligned - trust me you want this perfect all the time or you will get false activations/corrections from the ESP (stupid yellow light that flashes around tight or fast right hand corners and puts on the brakes)

I totally recommend them - after i first got it, i fitted 35's - reprog'd the speedo and discovered that it also reprogrammed the ESP to suit the larger tyres COOL HUH i then changed down to 33's (to get engineered) used it again - it was awesome and finally i used it to change gear ratios.

On its first connection to your vehicle it reads your vehicles computer serial number and locks it in memory - never connect it to anyone else's Jeep or it will become useless to you (its programmed to only ever work on 1 vehicle and to punish you for trying to use it on a mates it is programmed to shi@ itself - LoL
Cheers Hunty