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Drive Train Gearing Bible

PostPosted: Wed, 06 May 2009 7:04 +0000
by rodw
Here is the New Hilux Bible for the Drive train.

Many thanks to Max for digging up all of this technical info, we have collated all of the information we can about the Hilux drive train.

First let's look at the gearing specs from the brochure
Hilux Drive Train Specs
Diesel
Code: Select all
Gear          1         2         3         4         5       Rev    Diff     T/case
                        
Manual    4.313     2.330     1.436     1.000     0.838     4.220    3.583     2.556
Auto      2.804     1.531     1.000     0.071     -----     2.393    3.727     2.556


Petrol

Code: Select all
Gear          1         2         3         4         5       Rev    Diff     T/case
                        
Manual    3.830     2.062     1.436     1.000     0.838     4.220    3.583     2.556
Auto      3.520     2.042     1.400     1.000     0.716     3.224    3.583     2.556


The standard tyre sizes on the Hilux vary about 0.2" between the SR and the SR5 but for all intents and purposes, let's call them 29 inches in diameter. As you are aware increasing tyre sizes affects gearing and because the Hilux has a 1:1 straight through configuration in the transfer case, this cannot be changed so let's look at the the theoretical Diff ratio required so that the drive chain is returned the stock specification. This varies based on the stock diff ratios from the table above.
Diesel Auto (3.727:1 Diff)
Code: Select all
Tyre    Percent  Required   
Size     Stock      Diff
(in)    Size      ratio
*****   *******    ********
29      100.00%    3.73
30      103.45%    3.86
31      106.90%    3.99
32      110.34%    4.12
33      113.79%    4.24
33.5    115.52%    4.31
34      117.24%    4.37
35      120.69%    4.50

Petrol Auto, Petrol Manual, Diesel Manual (3.583:1 Diff)

Code: Select all
Tyre    Percent  Required   
Size    Stock    Diff
(in)   Size    ratio
*****   *******    ********
29      100.00%    3.58
30      103.45%    3.71
31      106.90%    3.83
32      110.34%    3.95
33      113.79%    4.08
33.5    115.52%    4.14
34      117.24%    4.20
35      120.69%    4.32


Now the reason we are quoting a 33.5" size is that this is what you get from the 255/85 R16 that Just Fishin has fitted and is probably the best tyre size when going larger tyres as it fits in the guard nicely with the right offset.

So to return to stock gearing, what can be done to the Diffs? Max has kindly sourced this info which I have collated:
Rear Differential
Code: Select all
Ratio   Teeth   Vendor   Part#        Notes
*****   *****   ******   *****        *****
3.583   43:12   Toyota   4120109010   Fits standard Hilux Carrier
3.727   41:11   Toyota   4120109350   Fits standard Hilux Carrier
3.909   43:11   Toyota   4120180177   Fits standard Hilux Carrier
4.100   41:10   Toyota   4120180724   Fits standard Hilux Carrier (updated part # 26/9/13)
4.556   41:9    Toyota   4120180182   Fits standard Hilux Carrier


Front Differential
Code: Select all
Ratio   Teeth   Vendor   Part#        Notes
*****   *****   ******   *****        *****
3.583   43:12   Toyota   4120179095   Fits standard Hilux Carrier
3.727   41:11   Toyota   4120180194   Fits standard Hilux Carrier
3.909   43:11   Toyota   4120180195   Requires Prado Carrier
4.100   41:10   Toyota   4120810196   Requires Prado Carrier
4.556   41:9    Toyota   4120180198   Requires Prado Carrier
4.556   41.9    JD's     T8S-456RT-NG Thick Cut, fits standard Hilux Carrier
4.88    ?       JD's     T8S-488R-NG  Standard Cut, Requires Prado Carrier


Where JD's is listed as the vendor, this refers to Just Differentials in the US See http://www.justdifferentials.com

A Note on Diff Carriers

A lot of these diffs are sourced from the Toyota Prado and they have a different diff Carrier for the front diff. So if you go to a ratio lower than 3.727:1 (ie. The number is bigger than this), you will have to purchase new a front diff carriers.

Whats a Diff Carrier?
Bull wrote:Sometimes called the diff centre. It's the thing that the crown wheel bolts to and the other gears sit inside of. When you choose a full strength traction aid like the ARB Air Locker or a Detroit locker, you replace the factory carrier. If you choose the factory style plate type LSD or a "budget" auto locker you keep the factory carrier.


This is a list of the Prado Diff Carriers available from Toyota:

Prado Diff Carriers
Code: Select all
Carrier              Part#       List* 
*******              **********  ****
Front    (09/02 on)  4131135090  $360
Front    (08/04 on)  4131135100  $360

*as at 05/2009


You can avoid this additional expense by installing an ARB front locker at the time you regear and you have saved $360 odd to put towards the front locker.

Just Differentials in the US (see http://www.justdifferentials.com) list some thick cut gear sets that fit into the Hilux standard Diff carrier and would be useful if you already have a Hilux Locker in the front you want to retain

How to Use This Data

well it is pretty simple really. If you want to restore stock gearing to your truck, you check out the tyre size you want to fit and look at the theoretical diff ratio required to restore stock gearing.

Then you select the closest available gear set from those listed and either scour the wreckers to find the parts or buy the parts from Toyota or JD's and quote the part numbers provided. Note that Max has received a quote from Just Differentials at the time of writing and their parts are quite expensive, so by the time you land a set over here, it might be just as cheap to buy the carrier from Toyota unless you already have a Hilux locker which you wish to retain.

So let's say you have a Diesel Auto truck and want to run a 33 inch tyre. from the table, you can see this requires a 4.24:1 diff to be exactly the same as stock gearing. The closest sizes are either 4.1:1 or 4:556 so you have a decision to make which way you go. remember that JD's thick cut gear that fits the only comes in the 4.556 so in some instances your decision may be amde for you (eg if you already have a front locker installed). You got to decide which is the best way for your intended use.

Here is what Max had to say to me about this choice for his Auto Diesel with a front locker already installed:

Mmaaxx wrote:and yes for the Auto Diesel, it is either 4.1 or 4.5 that we should be aiming for...... I'll be fitting Just Diffs 4.5 when I'm ready......

you'll get a better low range on 33's than stock hilux does, and around town it'll shift into higher gears a tad earlier and still not rev out too much on the freeway.


This is about 7% over the original factory setup. This difference is pretty much exactly what it would be like driving on 31's with the stock diff and dropping back to the stock 29" rubber. You probably would not notice the difference. I think Max is pretty close to the mark here.

If you have a manual transmission, a 4.1:1 Diff is a perfect match for 33.5" tyres

ARB Air Lockers
Here are the ARB Air Locker Part Numbers see http://www.arb.com.au/media/products/ai ... _chart.pdf

Code: Select all
Rear
*****
Adjuster Nut Models, 50 or 53mm bearing ID (Australia)              RD132
Dana Spicer Shim Adjusted Models (South Africa and South America)   RD133
Front
******
3.91:1 and up                                                       RD111
3.73:1 and down                                                     RD121


Front v's rear Locker?
See this sticky thread: viewtopic.php?f=12&t=2911

Which Rear Locker - Detroit or ARB?
See this sticky thread: viewtopic.php?f=12&t=3986

The next part of the drive chain equation, is crawler gears and dual transfer case setups and maybe even gearbox substitutions.

Crawler Gears and Dual Transfer Cases (Added 7/08/09)

There is no point rehashing this topic here as it has been very well covered in two other threads. However, briefly, the problem with regearing our transfer case is that Toyota has used a planetary gear set, which is very strong but does not lend itself to being regeared in the way a conventional cogged transfer case can be. Furthermore, the front drive shaft exits on the left side of the transfer case and the earlier Hilux's had a "Right Hand Drop" transfer case where the ouptut shaft is on the right hand side. Becasue of this, we can't simply resort to using an older transfer case.

Inchworm Gear in the US have devised a solution for this called the Lefty which converts the old right hand drop box to a left hand drop and it is more or less a drop in replacement for our trucks. Once you have a Lefty, you can add a set of Crawler gears made for the old model Hilux.

So here is the good oil I posted in this thread:

viewtopic.php?f=12&t=3548

rodw wrote:Guys, I finally got my head around the gears etc I talked about on previous threads. If you have not seen it, I collated all of the drive line tech stuff here but keep it clean of posts for now.
viewtopic.php?f=12&t=3554
Still just clarifying some details

Anyway, back to crawlers.
There are two suppliers of Toyota Specific gear:
Marlin Crawlers http://www.marlincrawler.com/
and Inchworm Gear http://www.inchwormgear.com/store/

Of these two suppliers, Inchworm has the superior product from all reports.

The other ones of note are:
Klune http://www.klunev.com/ who make a crawl box
and Atlas which are distributed by Marks Adapters http://www.marks4wd.com/products/advanc ... r_case.htm

These two products are sometiems combined together: http://www.high-impact.net/transmission ... 0Combo.htm

But anyway, Ignore the Atlas and Klune stuff for now and lets go back to Inchworm (becasuse I read enough bad reports about Marlin not to bother with them in any way, shape or form.

Inchworm have developed the Lefty which is a conversion of the old t/case which can accept crawler gears adapted to have an output shaft location to suit our truck. It should fit without any major modification of cross members etc. See
http://www.inchwormgear.com/store/produ ... cts_id=985
They also have a set of of crawler gears fitted to the Lefty so that would change the tcase low range gearing from our stock 2.556:1 to 4.17.

So what if you don't want to go down that low? Why not? Well you might live out west where there are no mountains to rock crawl over and want a higher low gear for mud etc.

Well you can fit another crawl box to the drive line in front of your transfer case. This is essentially the gearing section of the Lefty (or the older Hilux Box) See http://www.inchwormgear.com/store/produ ... ucts_id=71
This comes with 2.28 gears as standard but can be fitted with the 4.17 crawler gears. You could put this in front of your stock transfer case but you would need drive shaft and mounting mods to make it all work.

Now this is where I got confused. At the bottom of this page is the link to the thread which I incorrectly previously referred to the shootout.
http://www.pirate4x4.com/forum/showthread.php?t=592937
I was wrong on this. Inchworm were not bagging Marlin but simply quoting some maths and explaining why a lot of Tacomas blew output shafts when crawl boxes with lower ratios were fitted in front of the stock transfer case (which is the same as the Hilux)

Here is the diagram Jim from Inchworm put up.
Image
Now you got to do the maths with me. Take 100 foot pounds of torque at the front, multiply it by the gear ratios and you get the numbers on the top line. What he is demonstrating is that the right place to put your crawler gears is in the transfer case itself, not in the crawl box in front of the t/case. By putting reduction gears at the front, the torque is multiplied enough to shear the output shaft of the stock Tacoma Gearbox regardless of whether you use his crawl box or the inferior Marlin one.

So the idea of putting a crawlbox like the Inchworm one or the Klune underdrive, will probably result in a busted tcase output shaft. So no, I won't be fitting a Klune in front of my stock t/case. So what are the options? You got to do the maths for your truck based on the drive line ratios I have published in the new bible thread I refer to right at the top of this looong post. Interesting with the Auto Diesel, the torque ratings are lower becasue of the different first gear ratio. I think the options become:

1. An Atlas Tcase with 3.8:1 gearing from Marks Adapters
2. An Atlas/Klune Combo
3. A Lefty with 4.7:1 crawler gears
4. A Lefty with a 2.28:1 Crawl box in front of it
5. A Crawl box with 2.28:1 gears in front of the stock Hilux T/Case
6. A Crawl Box with 4.7 Crawler gears in front of the stock T/case and run the risk of blown output shafts

Now if you have the Auto Diesel like me, you might take the risk on option 6 as I calulated the torque to be about 30% lower than the Tacoma's 1880 because of the different gearbox ratios between the Hilux and the Tacoma and go easy on the right foot under pressure.

Personally, I think a good solution would be Option 5 as you could choose to engage one set of low gears or both. Engaging both low gears gives a low-low ratio of 5.83:1.

However, an extreme soluton would have to be option 4 which would give you a choice of 1:1, 2.28:1. 4.7:1 and a low-low of 10.72:1

So anyway guys, I think if you take on board this info and the driveline stuff about diff ratios if your pockets are deep anough, you will be able to build an awesome truck, Are you listening Bull?


I also obtained some quotes from Inchworm which I posted in the same thread and worked out landed costs (including freight, tarrifs and GST)at the going exchnge rate.

rodw wrote:Anyway, Back to Crawler Gears. I emailed Inchworm Gear a couple of times and they came back with some prices.

Crawl box
As far as I understand your talking about a 2007 Hilux with an automatic, 4 speed tranny and looking to add a crawler box infront of the transfer case you've got. In situation you'll want our Tacoma Double Case Setup (see link below). The good news is that we just lowered the price! http://www.inchwormgear.com/store/produ ... ucts_id=71.

Crawler box and adapters $1,450 with 23 Spline, Stock Gear Ratio of 2.28:1.
Shipping around $650.


Build Your Own Crawl Box
Crawl Box Parts- (will need a gear driven transfer case)
Tacoma Transmission Adapter: $399
Tacoma Double Case Adapter: $625 (comes with our double case adapter)
23 Spline Input Shaft: $165
Shipping Estimate via UPS: $520
Shipping Estimate via USPS: $290


Built Lefty
Tacoma Transmission Adapter: $399
Built Lefty: $1,995
Speed Sensor Adapter: $100
Shipping Estimate via UPS: $790
Shipping Estimate via USPS: not an option


or... build the Lefty yourself- (will need a gear driven transfer case)
Tacoma Transmission Adapter: $399
Lefty Adapter: $799
4.7 Gearset: $399
Chromoly Output Shaft: $280
Speed Sensor Adapter: $100
Quad Flanges (2): $39each
Shipping Estimate via UPS: $645
Shipping Estimate via USPS: $405


We can get the shipping estimates more accurate if you give me a full address.

Here is a link to our warranty and shipping instructions: http://www.inchwormgear.com/store/shipping.php; please note we only accept international payment via wire transfer.


I have not had time to think about this or add up the prices, but thought you'd like to see the costs guys.


And the landed costs:

rodw wrote:So at an exchange rate of 0.7696, and allowing for Customs duties and GST with UPS freight, these prices work out to:

Code: Select all
Built Lefty     AUD $4,872
DIY Lefty       AUD $4,006
Built Crawl Box AUD $3,105
DIY Crawl Box   AUD $2,580

If you go either of the DIY options you will need to also source a gear driven transfer case from an older model Hilux.
These are based on the Auto transmision, not sure how the manual affects these prices as it needs a different tranny adaper..

In addition to these costs, you would probably end up with a bill from a right forwarding agent who looks after the customs clearance.

There is probably not much benefit to be gained from going the DIY option by the time you buy an old t/case and get it built up if you can't do it all yourself.



The other thread of note is this one:
viewtopic.php?f=12&t=3222
In this, Max got some pricing on some options as well.

Inchworm Gear Special Pricing for NewHilux.net members

Finally, it is worth mentioning that I shared these threads with Inchworm to sort out the technical stuff to quote accurate pricing above and they wrote to me in May 2009 and advised that they would be prepared to look at some sort of group buy (to get the shipping costs down) and offer New Hilux Members a better price break. So if anybody is interested, send me a PM and I'll dig up the details.

Re: Drive Chain Gearing Bible - Draft

PostPosted: Thu, 07 May 2009 1:04 +0000
by 9W6VX
Changed to sticky thread....... :mrgreen: :mrgreen:

Re: Drive Chain Gearing Bible - Draft

PostPosted: Thu, 07 May 2009 1:20 +0000
by rodw
9W6VX wrote:Changed to sticky thread....... :mrgreen: :mrgreen:


Thanks mate, now no longer draft status :D :D
Enjoy everybody

Re: Drive Train Gearing Bible

PostPosted: Thu, 07 May 2009 1:32 +0000
by McSumWay
Excellent work Rod. The gearing bible is complete

Re: Drive Train Gearing Bible

PostPosted: Thu, 07 May 2009 2:19 +0000
by Batman
Rodw,

This is an excellent document, just a quick observation and not meant to be critical at all but it may help to clear up something that may cause confusion e.g.

The STD SR5 tyre is stated at 739mm (or 29") for a 255 70 R15. A replacement Mickey Thompson tyre (for example only) at 30x9.5R15 is about 744mm or 29.3" dia, 31x10R15 is about 770 or 30.3" dia, 285 75R16 is about 835mm or 32.9" dia.

The point I make is that you need to check what the actual diameter is of the tyre being fitted and not just go off the tyre size as designated by the manufacturer because they do vary from tyre model to tyre model and from brand to brand for example a Bridgstone D673 in 285 75 R16 is 840mm dia and a Cooper ST 285 75R16is 833mm dia.

So your article is spot on but you must use the tyre size in the tables and compare them to tyres diameters stated by the manufacturer.

If you think this is not relevant then get Brendan to delete.

Cheers,

Steve.

Re: Drive Train Gearing Bible

PostPosted: Thu, 07 May 2009 3:20 +0000
by Hilux Max
Batman,

what you say is correct, and usually its something the owner of thevehicle does already when purchasing larger tyres....usually, when purchasing tyres 33" and bigger, the owner of the vehicle looks for the exact measurement just to make sure that it will fit....


I say in reference to 33" and bigger tyres because thats is usually when the owner will be considering a regear, yes some with 32's may feel they need to aswell but it is only an example.

The differences between the sidewall stated size and the actual size is negligible in comparison to working out the correct ratio.

32.8" diamter stated on the sidewall as a 285/75x16 compared to the actual size of 33.1" is only a .3" difference and not going to make bugger all difference when deciding between a 4.1 ratio or a 4.3 ratio.

Rod,

well done on a professional presented and well resourced document that Im sure is bound to help many people by educating them on all things drivetrain relating to the hilux. Im sure it wont be the last of such "Bible's" we will see from you.

Gee, you must have either alot of time on your hands, or are very committed to the hilux cause....or have a very reliable and knowledgable source of information...... ;)

or all the above.... :lol: :mrgreen:

great stuff mate....keep em coming. 8-)

Re: Drive Train Gearing Bible

PostPosted: Tue, 12 May 2009 5:42 +0000
by Skog07
A very well presented article Rod.
After a fair bit of extensive reaseach in conjunction with Mmaaxx and Rod. ARB Artarmon (Traction4), Wade and McSumway. It looks as though the ARB Prado airlocker and Prado diff carriers will fit into the Hilux housing giving us all the option of regearing to lower ratios from 3.9's upwards.
Earlier on tonight was lucky enough to be able to compare a brand spanking new Prado front diff to a Hilux front diff. A big thankyou to (Dave) ARB Traction4 and Wade's dad for allowing us to have a squizzy and throw a tape measure over the diff and compare its measurements to the Hilux diff.
It appears as though the diffs are identical externally. Even down to the way they are mounted to the chassis. The crossmember is a little different but diff still mounts in the exactly the same way. The part no.s for the housing are identical.
Mmaaxx has also found out the main difference between the Prado and the front diffs are the driveshafts out to the CV's. They have different part no. but there internal spining is Dia 30mm and 30 splines. This fits into either carrier. Geniune Prado, Hilux and Air locker Both Prado and Hilux
The external splining for the hub is different hence the difference in part no. and we found this out from an old thread where Doug67 could not fit a longer Prado Cv into his lux.
Also found out the reason why the 3.9 and upwards carriers are different. The reason is the front diff requires a slightly different offset. You can put a RD 121 Airlocker on a 3.9 gearset but there isnt enough adjustment left in the bearings to get the correct backlash. Hence the RD 111 has a different offset to the RD121 to allow this.
Will post up some more info when it comes to hand.
Cheers
Skog

Re: Drive Train Gearing Bible

PostPosted: Tue, 12 May 2009 6:20 +0000
by Hilux Max
Yep, it has been some pretty hardcore investigating and researching in the last week amongst us guys, but we finally have nailed the differences between the hilux and prado.....pretty sure no one else has figured this out so well done fella's.

we searched high and low and the results will be shared by everyone for everyones benefit.

The Prado outer driveshaft and hub are what is different along with the offset front diff carrier.

Re: Drive Train Gearing Bible

PostPosted: Wed, 13 May 2009 6:00 +0000
by Skog07
Mmaaxx.
Got the call from ARB this afternoon. The head engineer, the one who designed the Hilux and Prado new generation lockers said that the RD121 (Hilux front locker) 3.727:1 ratios and down can be interchanged to the RD111 (Prado front locker) to get ratios above 3.9:1's. The only difference between the carriers is offset to accomodate the lower ratio gears.
Even the genuine Prado carriers can be used in the hilux front diff as well for those who dont want to run a front locker....
Cheers
Skog

Re: Drive Train Gearing Bible

PostPosted: Wed, 13 May 2009 8:55 +0000
by Hilux Max
Skog,

I need some clarification here mate.....You are saying that my Hilux front locker, RD121 to suit gear ratios 3.7 and below will accomadate Prado 3.9 and up diff gears?

But if the Prado centres are offset to fit 3.9 and up gears and the hilux one arent how will say a 4.1 diff gear fit the hilux?

If this is the case, then I may get me a set of genuine 4.1 prado gears...

another note, this information will be huge on the US scene as on their forums they are all led to beleive that you need the different arb locker or centre for the different gears.

Skog, can you get this on paper from this engineer?

How could arb develope 2 lockers if the hilux one fits in the prado housing? they could just use one across the board.

Re: Drive Train Gearing Bible

PostPosted: Wed, 13 May 2009 10:44 +0000
by Skog07
No Max
Sorry for the confusion,
RD 121 wil only suit from 3.727 down. (on the front diff)
And RD 111 are used for 3.9's upward. (on the front diff)
Stock Prado front carriers can be used as well to achieve ratios from 3:9's upwards on the front. ie (open front diffs).
Cant really offer any support from ARB but....
Now Im only guessing here..... And only guessing again
And again
and again...
The flange that holds the crown wheel on would be a bolt on part and possibly the only difference between the makes of airlockers... To allow the differences between crown and pinion wheels.....
You should have got an exploded view of your front locker when you purchased it..... I reckon this could be the difference between the makes. ie RD 121 and RD111
Sorry my Borg Warner experience shines through yet again....
Hopefully right.... :? :?
Cheers
Skog

Re: Drive Train Gearing Bible

PostPosted: Thu, 14 May 2009 4:42 +0000
by Hilux Max
keep us updated mate, you doing well.

Re: Drive Train Gearing Bible

PostPosted: Thu, 14 May 2009 4:53 +0000
by rodw
Mark, Max,

Looks like you are rediscovering things guys. What you are saying is covered on ARB lockers in my first bible post which was sourced from the ARB catalog. Both lockers are listed in the ARB catalog for the Hilux and the Prado.

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 7:22 +0000
by Smithyworld
After some clarification.

I am running 265/75/R16 MTZS (32") on my manual diesel SR5. So look at the table I should be switching to a gear ratio of 3.95?

Assuming I got that right the front diff part is
3.909 43:11 Toyota 4120180177 Fits standard Hilux Carrier
and the rear would be
3.909 43:11 Toyota 4120180195 Requires Prado Carrier

If I want a ARB locker then I would be looking at
3.91:1 and up RD111

Have I go this right?

Some current problems I have with my gear is low down starts on hills for example the engine labors a little. If I am towing the camper which is only about 700kgs loaded and I am on a reasonable steep hill, the vehicle may not take off in high first.

Also on Freeway she is revving over 200rpm at about 105kms/h. Anything over 100km/h kills the fuel economy.

Would changing my gears fix these problems? If not what changes would I see?

Thanks gurus! :D

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 7:34 +0000
by Hilux Max
Smithy,

You are better off going the 4.1 : 1 ratio diff gear not the 3.9's...but you will need the Prado carrier at the front either way, unless going a front locker...... 4.1's suit the 32's much better.

For the rear, you do not need to change any sort of carrier, they are standard Hilux 8" diff.....this part is easy.....the front diff has the different design requiring the different carrier.

If fitting a front locker with 4.1 gears you will need the Prado locker - RD121

hope that helps.

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 7:54 +0000
by Smithyworld
Yeah thanks Max. I am thinking towards putting a locker in and would change the gears at the same time. 4.1's would allow me to go to 33 too wouldn't they.

Would it resolve the problems I mentioned above?

Cheers

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 7:57 +0000
by Hilux Max
yes and yes...4.1's would help with 33's later on

go hard smithy..... :mrgreen:

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 10:27 +0000
by rodw
Smithy

I just checked your profile and see you have a manual diesel truck. I did up another table that I have not published that shows with 4.1's your truck will be revving 9 rpm slower at 100 km per hour than a truck with stock rubber on it. You are currently running 242 RPM slower.

4.1's are also the best match if you upgrade to 255/85 16's in the future (33.5") in which case you would run at 123 rpm slower. This is almost identical to the gearing on the TRD which with 30.5" tyres comes in at 127 RPM slower than stock.

3.9's are best for 30-31" tyres. I would be looking for a set of Prado 120 diff centres from the wrecker and maybe slip some lockers in the centres while you have them out. I'd have the centres checked out to make sure they don't need lapping etc before you fitted them. You should also be able to sell your diff centres to recoup some cost.

I am seriously considering this mod as soon as I can as I think the fuel savings will pay for them in under two years...

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 10:39 +0000
by Hilux Max
You will need to find the diff centres from an early 120 series Prado V6 with the 5 speed manual in it.....NOT the 6 speed manual version as these run 3.73's the same as our current hilux ones......

Re: Drive Train Gearing Bible

PostPosted: Fri, 17 Jul 2009 10:47 +0000
by rodw
mmaaxx wrote:You will need to find the diff centres from an early 120 series Prado V6 with the 5 speed manual in it.....NOT the 6 speed manual version as these run 3.73's the same as our current hilux ones......


Good feedback Max, just count the teeth and compare with the data in the bible to be sure....