Crown wheel and Pinion swap

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

Curious if anyone has swapped there diff ratios in their 90 series prado? I plan to change mine from 3.9 to 4.3 when I go up to 265/75 tyres on my 2002 RV TD.

Still researching the most cost effective way to do it. Can import the gears from the USA or perhaps try wreckers for parts. The gears I need are standard on manual petrol 95 series prados so they are common enough.

Has anyone done it?

Thanks

Mark

[KZJ90 Member Find all posts View Profile Close KZJ90]

I think it´s wasting your money. The overall ratio will be fine, I think. Try first with bigger tires, until you make your decision.

I also think that you´ve read about gearing from US-forums. It´s more significant thing if you´ve gasoline engine, because those have less torque particulaly at normal driving rpm. Diesel rules!

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

Sorry I can't answer your question, but I'd also suggest that the gearing would be fine. 265/75 R16 isn't much different from standard - I hardly notice the gearing change using 285/75R16.

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

265/75 R16 is a pretty big jump up from standard on an RV prado. Standard sise tyres on the RV are 750mm, but 265/75's are around 810mm. This is an 8% increase in gearing which is pretty noticable especially if you are towing something. Anyone with a GXL or up Prado doesn't need to worry much because it is only a 3% change for you guys.

The reason is that the diff ratio's in the RV TD's are 3.9 but the GXL's get 4.1's so it makes a difference which model you drive.

Regards

Mark

[Dieselman Member Find all posts View Profile Close Dieselman]

Hey Mark,

Have you thought about using 245/75's or are you wanting to go to a taller tyre?? These are roughly the same size as the original 265/70's found on the GXL's. Have you picked a brand yet??

Cheers Ben

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

Hi Ben

Re tyre sise, I want to go to 265/75 for the extra off road ability. Providing I can do the ratios at a reasonable cost. Otherwise it will be 245/75.

I have decided on Goodyear silent armours to go on those Kimberley alloys I picked up a while back :wink:

Cheers

Mark

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

Pretty disappointing response all round Mark, seems no one has done it. I have 265/75 BFG muddies on my RV TD and have contemplated one day swapping ratios just like you.

However it'll probably never happen (probably couldnt afford it) and to be perfectly honest, it doesnt seem to have made that much difference to the vehicles performance.

I used to swap the BFGs back to the original tiny tyres when I took the vehicle to Toyota for servicing in case they said something about it and refused any warranty claims.

The smaller tyres generally stayed on for about a week or two before I got round to swapping them back and apart from taking off a bit faster they seemed to make very little difference performance wise.

I guess you get up to the 2000 rpm range where the 1KZTE engine really shines a bit quicker, but its never going to be a rocket. Fuel economy drops a bit, but nothing startling (from memory).

My wife is a real leadfoot and she never noticed any difference in performance. She can generally tell when I put more air in her cars tyres so she does have some awareness of what is happening to a vehicle.

The larger wheels certainly made a difference in on and off road performance. We have a camper trailer, and took it down south not long after getting the Prado and it was a nightmare steering through the winding south west roads.

It felt like the trailer was pushing me off the line I was taking and a couple of times the old bum was going "sixpence, half a crown" as we went round some sharp bends.

I managed to get bogged on the beach near Nanarup with a rising swell, and that along with the "trailer effect" resulted in SWMBO giving specific instructions to upgrade the wheels/tyres as soon as we got back to Perth. Reluctantly I had to comply.

Now I dont bother changing the wheels when Toyota service it (still under used car warranty) and I still get bogged on the beach (see attached at Wilbinga) but I'm happy. I'm just not sure who the fat old bugger in the Bundy shirt is trying to dig me out.

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

I've considered doing a diff ratio change for my previous Surf. It seemed to make a lot of difference in that one when I went to 33" tyres (I can't remember what the original size was), but that was with an underpowered, tired 2.4TD.

Since they're common, as you say, try wreckers, or watch the 'drive train bits for sale' section of something like outerlimits4x4.com.

[KZJ90 Member Find all posts View Profile Close KZJ90]

Do you have different gear rations there? In Europe models they are:
4.10, when 215/80R16
4.30, when 265/70R16

I have now 4.30 and 285/75R16 tires, and I think the overall ratio could still be lower. Now it´s about 2400 rpm at 100 km/h. Something like 2200 rpm would be better for fuel economy, it goes so easily.

I had 4.10 and 33x10.50 in my ex-4Runner (1KZ-T) and it was very optimal combination. So (32/33)x4.10=3.97, which is very near of 3.90. That´s why I think that gear changing is unnecessary in this case.

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

Hi Rainman

Love the look of your Prado with those big muddies. I fish up at Wilbinga a fair bit and that sort of scenario is the main reason I want/need the sise increase. Can be hell boggy on some of those beaches even with deflated tyres. I'll keep looking into the diff swap and start contacting some wreckers. I tried one a while back but they were only interested in selling me the entire diff and axle assemblies :roll: I can get 4.56 ratios from the states pretty cheap but they would make the car under geared unless I run 33's. 4.3's will be great with 32's I reckon.

Cheers and stay tuned.

Mark

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

I fish up at Wilbinga a fair bit and that sort of scenario is the main reason I want/need the sise increase. Can be hell boggy on some of those beaches even with deflated tyres.

I was fishing up there a couple of years ago on a 40 odd degree day and had to rescue (almost) a bloke in an old 40 series.

I saw him drive off into the dunes in the distance and about an hour later he suddenly appeared at my shoulder asking for help to get him out.

I drove up and he had a trolley jack under the vehicle and was trying to jack it up in the sand and as the jack sunk, he kept digging and had dug a massive hole under his vehicle.

He had no recovery gear and fully inflated tyres. I let his tyres down, attached a snatch rope to his tow ball (against my better judgement) and told him to hit the go pedal as he felt the slack taken up.

He jumped in and drove out in reverse before I had even taken off, he hadnt even tried to reverse out before I got there.

I caught no fish (as usual) and burnt the tops of my feet to a crisp, but at least his girlfriend had a bikini on

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

I fished Wilbinga last night and got stuck 3 times in various places even with the tyres down to around 15psi. Some of the holes going up some of the dunes are getting really deep. An extra couple of inches in tyre diameter would have made all the difference.

Fishing was quiet apart from a 1.5kilo 57cm tailor that I managed to get past the weed. :lol:

[big al Junior Member Find all posts View Profile Close big al]

Ratio not a big beach bog issue.

Hi fellows.Im a beach regular,and a tip for the people who seem to get bogged in sand now follows;4x4 come in all shapes and sizes with all different degrees of gear and diff ratios yet I see all of these at different times on the beaches,some get bogged and some dont.The main reason some get bogged is not being able to read the sand,for example ,is the sand dry or is it wet,is it corse or is it fine.This has a bearing in which take of gear to choose or which range or gear to run along the beach in,but that said the most important thing to get right is the tyre preasures. eg.Very dry sand=very soft tyres,about 10 psi... Very dry corse sand go even softer,7 psi... Just after rain the sand is wet and 15 to 20 psi is fine.Very fine wet sand can be hard and require only the normal tyre preasures.Beware of very cause pebbly sand,wet or dry as this sand does not hold the water.Driving on virgin inter tidle zones is asking for trouble.Of all the 20 or so vehicles I have helped rescue from the beach I have only ever snatched two out,the rest were rescued by letting the tyres down to the correct preasures. For rescues I very soft 5 to 7 psi depending on the sand.All of these bogged 4x4s had their tyres to hard for the type of sand they were on to begin with.Hope this helps....... :idea:

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

I fully agree with Big Al, most people get stuck either due to the wrong tire pressure, poor driving skills, or a combination of both. We should trust the engineers who designed these vehicles to get out of the situations you are describing. Unless you are doing extraordinary off roading work, these vehicles will get you out of most situations simply by using the appropriate tire pressure.

My most recent foray in the ridiculously soft sand was on New Year's eve where others were shocked how I got through without deflating; it can also be about knowing how and when to use the throtle and watching your approach speed.

Cheers.

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

Ok after a bit of hunting around I have located a front diff assembly and rear diff centre from a wrecked V6 Prado in 4.3 ratio. I intend to pick them up next week and drop them to my mechanic in readiness for my next service when I will get him to do the diff swap. I works out heaps easier and cheaper to swap the whole front diff and rear complete diff centre than stuff around pulling the diffs apart and changing CW & Pinions.

Stay tuned for the rest of the story once the diff swap is complete and the big wheels are fitted :lol: