Diff ratio change

[Whitey1 Advanced Member Find all posts View Profile Close Whitey1]

Hi guys,
I have been thinking about lowering the gearing(or should that be raising the ratios?) on my 120 series man(6 speed) as I reckon its just geared too tall all round. Especially since picking up a camper trailer the other week. And with the bigger tyres it has made it worse. I was thinking of changing the diff ratios(and while I'm there a diff lock). Has anyone been down this path?

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: Diff ratio change

b4 changing ya diff ratios, dont know anyone who has done it, have you considered a performance chip and changing you exhaust, in the long run it will give a little more power and torque which will make towing easier, IMO changing diff ratios will make it go better no question but you will knock your fuel economy around, just a thought. cheers samo

[Whitey1 Advanced Member Find all posts View Profile Close Whitey1]

Re: Diff ratio change

Its not more power that I'm after, She'll pull the camper fine, its more control that I want. I reckon low range is just not low enough. Also when I'm reversing the trailer I have to put it in low range otherwise I have to ride the clutch way too much to go slow enough. IMO the 120 is geared for an auto box and prob is fine for that, but needs different gearing for the manual box. I mean its got 6 gears for F*** sake, surely they could have made the lower ones lower?

[Mark Smith Junior Member Find all posts View Profile Close Mark Smith]

Re: Diff ratio change

Whitey, duck over to the 90 series drivetrain forum, I posted some info there for ya :wink:

Cheers

Mark

[mcsumway Junior Member Find all posts View Profile Close mcsumway]

Re: Diff ratio change

Whitey

I believe the 90 series and 120 series have different front diffs.

I have done this mod on my Hilux (same front diff as 120 series) and used the 3.9 that you have std.

What size tyre are you running?

I went from 29" std to 32" and this upgrade returned the gearing to factory specs.

You can get 4.1 locally or heaps of different ones from the us - search for ratios for FJ Cruisers.

try these

http://www.justdifferentials.com/ind...Path=22_37_484

[o0X0o Junior Member Find all posts View Profile Close o0X0o]

Re: Diff ratio change

I put 265/70/R17's Maxxis Bighorns on my V6 120, and while there's still plenty of power, the speedo's out, the fuel economy has gone to hell, and the cruise control has become incredibly agressive at highway speeds (usually kicking down 2 gears).

This is to be expected, but I would like to improve the situation without speending thousands on LPG and speedo recalibration (and I'd still have crappy cruise control).

I was thinking that changing the diff ratio's would be the best option, but searches I've done seem to relate to the 90 series, or parts in the US (as per link above). I've been able to do this with other vehicles in the past because (for example) the diesel model had different ratio's, or there were plenty of aftermarket alternatives (just google for cruiser or patrol and see what I mean).

Is there no compatible domestic version (such as from another model) that I can use to rectify/improve the final drive ratio?

[mudboy Senior Member Find all posts View Profile Close mudboy]

Diff ratio change

I have had a quick look into this if your car is an auto u can use the ratios from a manual one

The whole process is not cheep it could cost between 2,500 to 3000 to have done as they are expensive to buy even second hand

[double_d69 Member Find all posts View Profile Close double_d69]

Re: Diff ratio change

I'm having my ratio's changed next week. I currently have the standard 3.73 ratio's with ARB lockers and I run 32" tyres, soon to be 33". I ordered the following from the states (justdifferentials.com); 4.56 ratio Nitro Ring and Pinion T8S-456RT-NG, TV6-456-NG + YOKT60030 (rear pinion flange), and solid preload spacers for the front and rear. The whole lot came to about $830US delivered.

[double_d69 Member Find all posts View Profile Close double_d69]

Re: Diff ratio change

New gears have been in for 2 weeks now. What a difference to drive! Very zippy around town and cruise control holds the gears when going up hills. On the weekend I drove from the gold coast to the sunny coast and I noticed with cruise control on it only dropped 1 gear going up hills, where as it used to drop 2 gears all the time.

The installation had a few hiccups. The front gears went in no probs, but the rear wouldn't line up (pinion) as it was a little too big. Had to grind 60 thou off the end so it wouldn't foul the locker. I called JT in USA and this is what they recommended.

Fuel economy has improved out of sight - My average on the scan gauge was 9ltrs per 100km on the Hwy, and I've been getting 11 around town. The confirmation of these figures will come when I go through the whole fuel tank. Revs has increased about 500rpm doing 110.

This is definately one of the best mods I've done. Highly recommended!!

[photoprado Avid PP Poster! Find all posts View Profile Close photoprado]

Re: Diff ratio change

Fuel economy has improved out of sight - My average on the scan gauge was 9ltrs per 100km on the Hwy, and I've been getting 11 around town. The confirmation of these figures will come when I go through the whole fuel tank. Revs has increased about 500rpm doing 110.

Congratulations on the swap. You can't complain about the price either!

You sure about these fuel numbers and Did you adjust the odometer for the ratio change? Most V6's seem to be well over 10L - Fuelly doesn't have one under 13L/10km average!

Those numbers are about what you might get out of a standard D4D, so there might be a queue of people wanting diff swaps soon

[double_d69 Member Find all posts View Profile Close double_d69]

Re: Diff ratio change

Fuel economy has improved out of sight - My average on the scan gauge was 9ltrs per 100km on the Hwy, and I've been getting 11 around town. The confirmation of these figures will come when I go through the whole fuel tank. Revs has increased about 500rpm doing 110.

Congratulations on the swap. You can't complain about the price either!

You sure about these fuel numbers and Did you adjust the odometer for the ratio change? Most V6's seem to be well over 10L - Fuelly doesn't have one under 13L/10km average!

Those numbers are about what you might get out of a standard D4D, so there might be a queue of people wanting diff swaps soon

Cheers, yeah the installation was $1100, so all up under 2k which is good. My odometer is out by 3% because I run 32" tyres, the change in gearing doesn't effect the speedo/odometer. Once I get through this tank of fuel ill be able to confirm what my scangauge is telling me.

[photoprado Avid PP Poster! Find all posts View Profile Close photoprado]

Re: Diff ratio change

My odometer is out by 3% because I run 32" tyres, the change in gearing doesn't effect the speedo/odometer.

Oh, Ok. So you are saying that there is no change to the speed or odometer? Where is the speed sensor, I thought it was on the gearbox?

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Re: Diff ratio change

double_d69,
Mate, no wonder the ratio change has provided you with a lot more power - there's a huge difference between 3.73 and 4.56 !!

but...

.... the change in gearing doesn't effect the speedo/odometer. Once I get through this tank of fuel ill be able to confirm what my scangauge is telling me.

Ummm.. Changing diff ratios will definitely change the speedo reading. I suspect you'll get quite a surprise on the your next fuel stops...

[double_d69 Member Find all posts View Profile Close double_d69]

Re: Diff ratio change

The speedo/abs sensors are on each wheel, hence why I didn't think the ratios would effect the speedo. I will confirm today with my GPS

[double_d69 Member Find all posts View Profile Close double_d69]

Re: Diff ratio change

GPS confirmed my speedo hasn't changed, still out the 3% from the larger rubber but thats it