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Re: Drive Train Gearing Bible

PostPosted: Thu, 22 Sep 2016 9:12 +0000
by VMN
I'm RodW. There is no issue running Nitro in the back and Prado in the rear. Works for me.
If you want to save money get your mates and a 27 spline flange.
Otherwise the 29 spline is stronger but I don't think it is the weakest link so not really an advantage in practice.

Re: Drive Train Gearing Bible

PostPosted: Tue, 27 Sep 2016 6:15 +0000
by FAIL
Thanks Rod,

So it's a straight fit up like the 29 or is there more to be done with it?

Re: Drive Train Gearing Bible

PostPosted: Sun, 05 Nov 2017 6:33 +0000
by Blackdelux
hi all
can some one let me know if we can use 150 series prado diffs?
thanks in adavance

Re: Drive Train Gearing Bible

PostPosted: Sun, 18 Feb 2018 6:16 +0000
by kevinreid89
Can anyone confirm the Prado 120 series front and rear diffs are a straight swap with a 2012 SR Hilux diffs and nothing else to worry about?

Re: Drive Train Gearing Bible

PostPosted: Sun, 18 Feb 2018 6:33 +0000
by VMN
kevinreid89 wrote:Can anyone confirm the Prado 120 series front and rear diffs are a straight swap with a 2012 SR Hilux diffs and nothing else to worry about?


This is what I did years ago.

The front diff housing will work but keep your axle tube.

The rear will work but I think some of the bearings are different which might surprise a diff shop if you break something and they have to rebuild it.... Of course I've never broken a single diff... it has been 3!....

Re: Drive Train Gearing Bible

PostPosted: Sun, 18 Feb 2018 6:47 +0000
by kevinreid89
I was trying to avoid swapping axle tubes will the prado axle tube not work? As in I was hoping it was a straight forward swap including the axle tube and without opening the diff?

Re: Drive Train Gearing Bible

PostPosted: Sun, 18 Feb 2018 7:06 +0000
by VMN
The tube is a different part number. It probably also has ADD attached which the SR does not have. Its held on by 4 bolts so its not hard.

Re: Drive Train Gearing Bible

PostPosted: Mon, 28 May 2018 2:02 +0000
by Blackdelux
Hi all
looking for advice .

im thinking of puuting 3,9s into my existing hilux that runs 3.7s Diese 4 spd auto
i run 265 70 17 wheels just under 32 inch

can anyone advise if this would be enough?
was thinking 4.11 might make me run to high in rev range im a tourer and do a bit of towing
dont want a roar or noisey car

has anyone gone 3.9s in 4speed auto??

i am i being too conservative? i do have lock up torque coverter.
i have checked first page of ratios and would suggest 4.11

looking for real world feedback

thanks in advance

Re: Drive Train Gearing Bible

PostPosted: Mon, 28 May 2018 3:05 +0000
by VMN
I think I would stick to the 4.1's. Since I wrote the original post, I made up a table that does not lend itself to be published on the forum which I've always had on the VMN web site
See https://www.vehiclemods.net.au/page/hil ... 2005-2015/

Also there is now a nice complete package for 4.1 gears available which we order in on request (allow about 2 weeks).
https://www.vehiclemods.net.au/toyota-h ... regear-kit

We also supply the Harrop Elockers (You need the 3.73 and down) for the gear set above.
https://www.vehiclemods.net.au/spare-pa ... tion-aids/

With 3.9's there is no easy package and if you are not careful you'll end up buying gears from Toyota.

As far as real world experience, I've done a lot ot towing for a 1800kg caravan on 265/75 R16's and 4.1 gears. They are similar size to your proposed size.

Just drop it into third (as per the manual) and it will chug along all day. I could never get it to idle along in 4th gear even on flat ground around Broken Hill. I used to sit on about 92 km/hr (100km on the speedo). In 110 km speed zones, I'd sit on 100km/hr which is 110 km on the dial. It was also still fine at 110 km/hr if I had to get somewhere but hey a caravan implies a holiday! :)

Re: Drive Train Gearing Bible

PostPosted: Mon, 28 May 2018 3:33 +0000
by Blackdelux
thanks Rod
great reply thanks for the time
im assuming those revs on your table are in 3rd gear auto as im sitting at 1900-2000 rpm in 4th at 100
and 2500 in 3rd.
i tow in 4th with it locked up thru converter switch, in 3rd feels like its revving too high already
but i am a lead foot. maybe i need to slow down.
i have killed an auto already, why im looking to re gear.
if im going to hold it in 3rd im leaning toward 3.9s

Re: Drive Train Gearing Bible

PostPosted: Mon, 28 May 2018 3:48 +0000
by VMN
No, the table is in top gear at 100 km per hour based on nominal tyre circumference and allowing for all t/case and diff gearing. Towing was not a consideration.

Depending on the trailer weight, tow in 4th at your own peril. As you know, gearboxes are expensive to repair. Its a diesel motor. I think from memory it was 2700 rpm in 3rd at 92 km per hour which felt comfortable for the weight behind. Note that I joined this forum 5 years before you did and my Auto is still going strong and I hammer it except when towing.

Good luck finding 3.9's. If you are going to regear, don't be half arsed. Do it right or don't bother at all otherwise the expense is not warranted. The only guy I can remember who went with 3.9's had a manual and got it done at Toyota when he bought the truck. I think it broke half way across the Simpson. 4.1's are a better match for the auto.

Re: Drive Train Gearing Bible

PostPosted: Tue, 29 May 2018 6:37 +0000
by Blackdelux
thanks again Rod

Re: Drive Train Gearing Bible

PostPosted: Tue, 29 May 2018 7:54 +0000
by hiluxxury
I just found this youtube on another site - some real dyno numbers on HP and torque reduction with larger tyres

https://youtu.be/l1ULmPulZck