Drive Train Gearing Bible

[McSumWay]

Just a quick note on these Prado fronts. The crown wheel is exactly the same size as the rear at 8".

The only difference between the two is a slightly different pinion.

Oh and of course they run in the reverse direction.

These are being installed as we speak and I will have results after the Newvember trip.

Warren

[Hilux Max]

Just came across an awesome gearing selection versus tyre diamter chart for toyotas which will help many people that choose to change diff gears....

http://www.4wheelparts.com/aux_incl/gear_ratio.html

click on the chart to enlarge.

[Antz]

Just saw this Prado diff on ebay. The ratio is correct but is the 90 series Prado compatible? Those in QLD may be interested.

http://cgi.ebay.com.au/Used-Front-Diff- ... 25581ffc75

[rodw]

Just saw this Prado diff on ebay. The ratio is correct but is the 90 series Prado compatible? Those in QLD may be interested.

http://cgi.ebay.com.au/Used-Front-Diff- ... 25581ffc75

No good mate. It has to be Prado 120, I'll try and get some pics of the set I have organised as soon as got my hands on them.

[Antz]

OK, not looking for myself. Just thought it may help someone else. If you fit the 120 series Prado to the front of an SR, would that give you full time 4WD? Just trying to get my head around all this.

[McSumWay]

No mate the fulltime comes from the transfer case at the rear of the gearbox

[rodw]

OK, not looking for myself. Just thought it may help someone else. If you fit the 120 series Prado to the front of an SR, would that give you full time 4WD? Just trying to get my head around all this.

The Prado front will have the actuator for the ADD on the axle tube, but I think it would be quite a drama to fit it up, So I will just be swappng over the centre.

The Hilux is a Part time 4WD so you select it with the t/case lever when you want it. Full time 4WD is more the domain of softroaders....

[rodw]

Just an update on this diff upgrade after checking part numbers between the Hilux and the Prado and this picture shows the incompatile parts.



Basically the diff centre is the only bit that is interchangable. Apparently, even the bearings and seals have different part numbers so I will probably replace them while I am at it so I know it is all good to go.

[Lancair]

So, in my case I have a diesel manual, running 32', so I need the 3.9 diff gears to get back to close to original gearing, as McSumway has done.

My options to get the gears are, (as I can work out) buy them new from toyota at considerable expense or somehow find a current model prado at a wreckers and get those gears. (I recently tried to find some parts for a 06 model mazda 6 from wreckers and had no joy at all)

I think it would be easier to find a 120 prado and get the 4.1 gears, then Id be slightly high on revs ?

Whats cost effective is the real answer I guess.

[rodw]

Lancair, You are on the money. I have just added another post about what to look for when buying a Diff from the wrecker so you can identify the front diff when it is out of the vehicle.

This article has a table of all the RPMS I calculated out for different ratios.

http://www.vehiclemods.net.au/toyota-hilux-150vigo.html

I calculated that you car was doing 2581 RPM at 100 km/hr on stock 29" rubber. You are now running at 2,339 rpm at 100 k's

Actually, I think I misled you in my PM.The 4.1's are also the best option for you as you will then be doing 2573 RPM at 100 km/hr which is only 8 rpm away from stock gearing.

It will be interesting to hear from McSumWay his reasons for selecting the 3.909's but they are still a pretty good match.

[Hilux Max]

Rod,

I beleive McSumway chose 3.9's because he has a manual which comes out with 3.5:1 diff ratio, so 3.9's would be ideal on his 32's....

[rodw]

Rod,

I beleive McSumway chose 3.9's because he has a manual which comes out with 3.5:1 diff ratio, so 3.9's would be ideal on his 32's....

Max, that is what I thought his reasoning was. I forgot to paste in the link above but I have edited my last post to include it.

The table on the VMN web site shows that the 4.1's are -8 RPM from stock and the 3.9's are -128 rpm away from stock at 100 km/hr for the Manual with the 3.5 factory gearing done. They are still a pretty good match.

The spreadsheet I created the table from seems to be at work, so I can't check it for errors over the weekend, but I think all the maths was correct. Send me a copy if I emailed it to you.

I think the format I have presented the data in the VMN table is a lot easier to understand but it is very hard to display on the NewHilux forum.

[rodw]

Hmm, I see where McSumway made his decision. Based on my first posting in this bible. I wonder if I got it wrong somewhere?

[McSumWay]

Rod I had already chosen them long before the table. I used simple maths (for a very simple man).

My 32" tyres were roughly 10% larger then the 29" stds so I reckoned that 3.5 + 10% was 3.85 so 3.9 was the go.

I have modded this to return my gearing to stock not for rock crawling as I plan on quite a few outback trips with this version of the Hilux.

[rodw]

Rod I had already chosen them long before the table. I used simple maths (for a very simple man).

My 32" tyres were roughly 10% larger then the 29" stds so I reckoned that 3.5 + 10% was 3.85 so 3.9 was the go.

I have modded this to return my gearing to stock not for rock crawling as I plan on quite a few outback trips with this version of the Hilux.

Yeh, that makes sense mate, sometimes simple is best. I think my table must be wrong on my web site but the 3.9 in the first post above must be right.

How did you do the regearing. Did you buy second hand diffs or just the ring gear?

[McSumWay]

New truck so I bought new CW&P from Toyota - that and with a good friend in parts I was able to score a good deal - about the same as buying used.

The benefits are very clear cut with the manual. I can feel the takeoff is better. I suppose the auto might mask the problems of gearing a little.

[rodw]

New truck so I bought new CW&P from Toyota - that and with a good friend in parts I was able to score a good deal - about the same as buying used.

The benefits are very clear cut with the manual. I can feel the takeoff is better. I suppose the auto might mask the problems of gearing a little.

You may be right, but I think it might show in the auto fuel consumption. Based on my fuel logs and looking at the fuel increase as tyre size goes up, if I can gain back some it might save up to 600 litres a year (at 20,000 km per annum). The next tank full will be interesting.

I will say the difference was noticeable the moment I drove out of Ryano's driveway with spinning wheels screeching!

I was also keen to revert back to stock gearing as I do as most of my miles are city and highway driving not rock crawling.

[McSumWay]

Unfortunately I couldn't compare fuel figures as mine went in before i'd finished its first tank of fuel.

However it is getting better figure than the old truck.

[Lancair]

Rod, Im not sure your table on VMN site is correct. It shows no change in RPM with manual diesel betwen stock and 3.7gears ? ? The table linked in the post by mmaaxx, http://www.4wheelparts.com/aux_incl/gear_ratio.html I thnk is correct. Therefore the 3.9 gears are the closest match.

So I need to find 3.9 CW and P gears from a current prado for the rear and a complete front diff assembly with 3.9 gears, or 3.9 gears and buy an ARB air locker for a Prado front. Is that correct ?

Andrew

[McSumWay]

Thats the one Lancair.