Reduction Gears

[Guest Close Guest]

Does anyone know where we can purchase reduction gears for transfer case Toyota 2002 GXL 3.4L prado (automatic). We tow an off road camper trailer and find the low range is inadequate on decents and better gearing in low range transfer case would improve handling. We have tried Marks Adaptors and BB motorsports but they do no do them for the 90 series Prado. We are looking at installing new grooved brake discs with Kevlar coated pads for improved braking which will fix brake fading.

Hope you can assist

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

Hi CP, welcome to pradopoint
An auto petrel 4WD will always run away from you down hill, Im not to sure if lower gears will give you that much benefit. One of the benefits of a manual diesel, I can walk my CT down the steapest of hills without even touching the brake pedel.
Would be interested to hear about the brake mods though, lets us know how you go.

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

Rather than lowering the gearing what about trying to minimize the auto runaway. If you could manually lock the torque converter clutch could you then have engine braking like a manual or does 1st gear have an overrun clutch.

Torque converter clutches mostly have an electrically controlled solenoid but also require an oil pressure source which the auto valve-body may only supply in top gear. Maybe a trip to an auto specialist would be worthwhile to see if it is possible to modify the box or valve body to get the pressure to the lock-up solenoid in 1st / all gears. I think it would be relatively easy after that to find a way to activate the solenoid.

There would be a few operating constraints, like a minimum engine rpm to maintain transmission oil pressure so it didn't drop out of gear, and probably not changing gears with the converter locked. Are there any auto gurus around on the forum that could give a more informed answer.

[watsea Member Find all posts View Profile Close watsea]

There have been significant threads on the 4wdmonthly forum about auto vs manuals and down hill descent with autos. Really good stuff. I see Trojan often posting there as well. I have an auto in my Prado. It is great in the sand.

[craig Member Find all posts View Profile Close craig]

What I have done in the past going down a steep decline is use the handbrake, but ensure you don't lock your back wheels.

[Guest Close Guest]

Usually I use the brake to control the descent but I would prefer to have a lower gear . This is also very helpful for controlled driving through rocks . I searched this issue and I found the the rockhopper kit is very interesting . Does anyone know if there is a version for LC90?

[xlr8_87 Advanced Member Find all posts View Profile Close xlr8_87]

Re: Reduction Gears

Digging up an old thread rather than starting a new one...

Has anyone looked any further into this? It's ridiculous how much I need to use the brakes to control speed downhill, especially here around the Vic high country.

Now surely reduction gears would prove to be of good benefit because when the vehicle is locked into LL the auto clutch is definately engaged?

If nothing comes of this, anyone know a good transmission place in Vic I could go talk to?

[dhula Member Find all posts View Profile Close dhula]

Re: Reduction Gears

AFAIK there are no reduction gears available for the Prado as the tcase reduction is made by using an epicyclic gear set so cost would be huge.

another option might be to look into hilux transfer case but again this could get expensive.

there is some discussion around the traps somewhere that i remember being part of, just can't remember where.

[Whitey1 Advanced Member Find all posts View Profile Close Whitey1]

Re: Reduction Gears

Hi guys,
I have also been thinking about lowering the gearing(or should that be raising the ratios?) on my 120 series man(6 speed) as I reckon its just geared too tall all round. Especially since picking up a camper trailer the other week. And with the bigger tyres it has made it worse. I was thinking of changing the diff ratios(and while I'm there a diff lock). Has anyone been down this path?

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

Re: Reduction Gears

Hi Whitey

I've changed front and rear diff ratios on my 90 series RV TD. The ratio's are 3.9's from the factory to suit the smaller tyres. I fitted 265/75 R16,s and changed the ratios to 4.3's. (90 series GXL TD's have 4.1's from the factory to suit 265/70 tyres).

I managed to get the diffs from a wrecker with about 70000k's on them for around a grand. They are easy to come by in 4.3 as most of the petrol 90 series run these and we all know how many petrol 90 series are around.

The end result is a Prado with fantastic low range and almost perfect gearing on the road. It is slightly undergeared ( 105kph on the speedo is 102kph on the GPS) but is especially good off road.

Cheers

Mark

[xlr8_87 Advanced Member Find all posts View Profile Close xlr8_87]

Re: Reduction Gears

Hi Whitey

I've changed front and rear diff ratios on my 90 series RV TD. The ratio's are 3.9's from the factory to suit the smaller tyres. I fitted 265/75 R16,s and changed the ratios to 4.3's. (90 series GXL TD's have 4.1's from the factory to suit 265/70 tyres).

I managed to get the diffs from a wrecker with about 70000k's on them for around a grand. They are easy to come by in 4.3 as most of the petrol 90 series run these and we all know how many petrol 90 series are around.

The end result is a Prado with fantastic low range and almost perfect gearing on the road. It is slightly undergeared ( 105kph on the speedo is 102kph on the GPS) but is especially good off road.

Cheers

Mark

Really? Because my petrol 90 has terrible low range... basically flies straight down the hills. Did all petrol 90's come with the 4.3's? If so, do you reckon I could raise my ratio without causing too much trouble?

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

Re: Reduction Gears

Yes..

TD RV 3.909
TD GXL,TX etc & Pet RV 4.100
Pet GXL,VX etc 4.300

The 4.300 is better for downhill, but its not enough to beat the TD compression in combination with the 4.100 - however 3.909 would be better for all of us

Cheers

[rptdprado Member Find all posts View Profile Close rptdprado]

Re: Reduction Gears

Hi,

Correct the GXL Petrol V6 Auto has the following:

Final Ratio or Crawl Ratio =Gear ratio (1ST) 2.804 x Transfer Case (low range) 2.566 x Diff Ratio 4.30 = 30.93

Just to compare with the new Prado 150.

Prado 150 TD 6 Speed Manual Crawl Ratio is 41.83
Prado 150 TD 5 Speed Auto Crawl Ratio is 33.66

So really the 150 Auto TD is not much better than the old V6 90 series petrol for steep downhill work, of course the diesel has inherently better engine braking.

Cheer

Rob
99 V6 GXL Melbounre

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

Re: Reduction Gears

You can also get 4.56, 4.88 and 5.29 ratio gears from the States. 35's anyone???

[xlr8_87 Advanced Member Find all posts View Profile Close xlr8_87]

Re: Reduction Gears

Sorry I don't know much about the numbers we're talking.

Am I correct in assuming the Higher the diff ratio (currently at 4.3 as you said), the slower it will crawl down a hill? Am I also correct in assuming that the bigger the tyres you run, the faster you crawl down a hill?

And one final question :P

If the diff ratios were changed to a higher ratio, would this impact on the installation of diff lockers?