Drive Train Gearing Bible

[StevenS]

I'm thinking of giving myself a project for over the holidays and thought I'd give this a try but I'm getting a bit confused with all the info present.

I'd be chasing 3.9s (running 31.5 tyres) for my 05 single cab diesel manual. I'm looking at the following front/rear combo
front:
http://www.ebay.com.au/itm/TOYOTA-PRADO ... 656&_uhb=1

rear:
http://www.ebay.com.au/itm/TOYOTA-PRADO ... a5d&_uhb=1

So basically, will these suit the Hilux and can I just remove my factory centers and replace them with these myself at home with standard tools? (I do have a torque wrench).

[4sullima]

Same boat as you stevenS,I'm also keen to know

[StevenS]

Same boat as you stevenS,I'm also keen to know

Hands off I saw em first. Least that's my belief and I'm sticking to it

[4sullima]

Haha mate I'm not after that parts, just interested in the choice of ratios and the self install as I have a manual D4D with same tyre size

[StevenS]

Anyone?

I should clarify I'm only wanting to know whether I can just swap the centers between these diffs and my factory diffs with basic tools, ie no need to get everything rebuilt at a diff shop (funds aren't plentiful afterall)

[calis101]

I have successfully swapped the front on an sr. By the sounds of things you just need to take the axle tube off for sr5. As for back I can't help sorry...

[Hilux Max]

I'm thinking of giving myself a project for over the holidays and thought I'd give this a try but I'm getting a bit confused with all the info present.

I'd be chasing 3.9s (running 31.5 tyres) for my 05 single cab diesel manual. I'm looking at the following front/rear combo
front:
http://www.ebay.com.au/itm/TOYOTA-PRADO ... 656&_uhb=1

rear:
http://www.ebay.com.au/itm/TOYOTA-PRADO ... a5d&_uhb=1

So basically, will these suit the Hilux and can I just remove my factory centers and replace them with these myself at home with standard tools? (I do have a torque wrench).

Prado has ADD diff, so will be fine for front of SR5 but if going into SR then you'll need to swap the diff side housing/tube section with the factory SR one.

yes you can swap all this yourself at home, if your handy on the tools.

[StevenS]

Sounds like a goer then - was concerned only diffs from the 150 series Prado fit too but obviously that's not the case.

Just hope Mr. postman can get them to me before the new year

[calis101]

:s does the front end out of a 150 series fit as well max? Or is it just the 120 series?

Cheers Simon.

[Hilux Max]

:s does the front end out of a 150 series fit as well max? Or is it just the 120 series?

Cheers Simon.

Simon,

The diff housing assemblies of the Prado 150 and 120 are exactly the same.

Same part number.

The 1KD in the Prado 150 both 5 speed auto and 6 speed manual run 3.9:1 ratio.

The 1GR in the Prado (only 6 speed auto), runs 3.7:1

[calis101]

Cheers mate dont suppose the rear is the same as our so we just go get front and n bolt it straight in without the need for a rebuild?

[hailbou]

Ok after reading all this and taking the 2 panadol , if I run 4.56 gears in my manual with 33.10.5 15 tyres would it rev to high ? And what would the be? Cause it would be great to have a lower crawl ratio . Ps I already have lockers for my standard riffs installed

[Hilux Max]

Would rev too high.

Look at it this way......(prepare the extra panadol)

Manual stock diff ratio is 3.5:1

Your running 33" diameter.

Standard hilux tyre diameter is 29"

Therefore: (3.5) divided by 29" multiplied by 33" = 3.96

So a 3.9 ratio would be better suited. 33/10.5x15 is actually slightly smaller than a true 33 so 3.9's would be perfect and give you stock crawl ratio in low range.

Downside is that you cannot fit 3.9's to your 3.7 and below lockers. In order to get the same revs at stock wwith a manual and 4.5 ratio you would need to run 37" tyres. so you can imagine how much more 33's would rev.


I would suggest if possible getting a Prado120 airlocker for the front and fitting a set of 3.9 gears to it.

Then sell your current locker/front center to recoup some costs in the excercise.

[hailbou]

Thanks max , will 3.9 be easer to find than 4.1 ?

[Muldz]

I have brand new 4.1s with overhaul kits for sale if you are interested...

[hailbou]

Muldz what price have you got on them?

[joffaute]

I want to get 4.1's installed in my d4d manual ute, it's already got twin lockers installed a couple of years ago. according to the arb application chart down the bottom of the page they seem to think all known aftermarket ring and pinion sets should fit the rd121 front locker. anyone know if this is actually the case?

i called arb thomastown and the bloke on the phone wasn't very helpful.

http://www.arb.com.au/media/products/ai ... _chart.pdf

i'm waiting to hear back from marks 4wd adapters to see if their gears will fit.

cheers.

[greg thomas]

Hi joffaute, thought i would chuck in my 2 cents worth, ive just been through the exercise of putting 4.1 gears in my manual 2012 lux, to my knowledge there is no 4.1s that will fit ur rd 121.i bought genuine gears having worked for the local toyota dealer in cairns i got a pretty good deal $1135 for fr and rr gears.i like u had fr and rr lockers but had to buy a rd 111 front locker $1100.00, i had no problem selling my old rd 121 locker for $700.00. i run 30.6" tyres and it does 2360 at 100 kph, now looking at running 265/75 16s hope this helps u out.

[joffaute]

Is there any reason why I can't run the 3.909 diff gears front and rear without changing the carrier?

The 3.9 gears and up are "offset" more than the 3.7 and 3.5 gearsets.

hence the different cariers required.

Hence 2 different part numbers for ARB airlockers for the front.

Hence why you can use a thick cut 4.5 for the front to take up the difference of this offset in the 3.7 and lower carrier due to the wider design.

i wonder if it's possible to machine up a spacer plate to fit a standard thickness gear?

[GeeBung]

I've never really thought about re-gearing but after reading this it sounds like the way to go. However i have a couple of questions that can hopefully be answered.

So my current situation is I have manual running 265/75 R16 MTZ's which is twin locked with an RD121 in the front. So questions i have are:

There seems to be two different views of which ratios to get for 32's, some say 3.9 some say 4.1 so which one should i get?

Secondly, i understand it's not ideal, but would going to a 3.7 make enough difference to offset the cost of having to buy another locker?

My lockers don't even have 5000km on them so just floating some ideas. Wish i had of known this before i got them!!