Reduction Gears Test

Submitted: Wednesday, Nov 17, 2010 at 13:13
ThreadID: 82547 Views:4483 Replies:7 FollowUps:10
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This really is 1/2 a test of the gears and 1/2 a test of ones judgement.

In a recent post I lamented just how hopeless my new 4800 GU petrol Patrol
was on downhill descents, compared to my manual petrol Patrol.
It wasn't just lacking it was bordering on unsafe and a serious concern as most of our driving is in Vic high country.
We take a dim view of fundamental issues with cars so no point stuffing around and moved quickly to get 43% reduction Marks adaptor gears fitted friday just in time for the severe weather to descend on Melbourne.

We headed off early saturday in heavy rain with both Patrols to our 4wding property 100km north of Melbourne to relatively dry conditions.

Marks has 3 different ratio gear sets you could choose for the transfer case and I choose the middle range which gave the car an overall ratio the same as my manual so the low range reduction goes from about 2:1 to about 2.8 to 1.
This means the car still does 85kmh redlined in low but more importantly only does around 2000 rpm when loping thru the dunes at 35kmh.
The gears are straight cut and hence a little noiser and hopefully more efficent than stock.

So the testing began with a 25 degree downslope and the car held at 2500rpm in 1st on this slope which is adequate for now.
We then proceeded to a wet grass hill sloping down 15 degrees and accelerated to 30 and slammed on the brakes whereapon the cars ABS obviously came into play but the whole system stopped in a reasonable
enough distance and in a straight line.

In both the above tests we were then able to do something I have found hard to accomplish in the past.
That is to reverse smoothly up both hills with no sudden jerks breaking traction.

We began to set up for more difficult tests when the phone call came "Dad where's the winch extension strap we are stuck".

Image Could Not Be Found

The kids had recently stuck the Prado badly and were showing off with the Patrol which could go anywhere and promptly got it stuck in exactly the same place in the same stinking mud-ooze swamp that they had bogged the Prado in.

The kids know everything and so just banged in both lockers and proceeded to move precisely 6 inches.
But the 6 inches was all straight down !

It would be embrassing to call dad up from the next paddock so they then dragged out the winch rope, tied it to another car and tried to pull the Patrol out.
After this the winch wouldn't free spool any more.
I informed them that the extension rope was under the seat they were sitting on then hung up and set off to assist.

Image Could Not Be Found

Well the winch still pulled and soon the car was free and a mess, but it wasn't the kids fault as I was quickly informed, it was mine because knowing they were to drive the car I removed the muddies and fitted all terrains for the wet weather.

We had to leave then and went back to load up my RTI ramp to take back to Melbourne for suspension tests.
As I grabbed the side of the ramp I felt a sharp sting, dropped it and the kids had a good look
and found 15 redback spiders living on the underside.

This day was deteriorating, my first aid qualification had just expired so I sat down without guilt and had a Barcardi and coke.
Apart from feeling a little wosey, everything seemed okay so we headed back to town.

The rest of the tests will have to wait for another day, but my conclusion so far is that the reduction gears were the right choice and a useful and significant improvement to the cars downhill ability, turning it from unacceptable to just poor.
However this change will give breathing space while we work on the torque converter and perhaps more driver training and also hunt down Redback spiders.

We then left for Melbounre even trailing a little dust, but soon crossed the divide and it was raining again as we came to a winding wet bitumen road near Dixons creek on dusk.

We saw someone with a slow down sign putting flares on the road and 500m later came across at least a dozen emergency vehicles.
As we shuffled past the scene I could see rescue people struggling with stretchers near a crumpled wreck in a deep gully.

You often wonder what might have been, but I figured I could live with the blame for the bogging and with repairing a stuffed winch.

Image Could Not Be Found


Robin Miller

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Reply By: TerraFirma - Wednesday, Nov 17, 2010 at 13:55

Wednesday, Nov 17, 2010 at 13:55
Hi Robin, Was waiting for the run down. After reading this felt like I was there.! Good to hear that the gearing mods worked well. Wow you had it all, the weather, the kids, broken winches, red back spiders and accidents. How did you feel after the Red back bite?, never been bitten myself. Did you hear what happened at the accident scene?
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Follow Up By: Robin Miller - Wednesday, Nov 17, 2010 at 16:05

Wednesday, Nov 17, 2010 at 16:05
Hi Terra

Yep another fun weekend for some.

I know nothing about Red back bites maybe someone else could help out here.

But I suspect I didn't get bitten properly , I may have just squashed one as I gripped the edge and it gave me a glancing bite.

It just stung at first and sort of tingled a little and it went away.

The mossies bites I got 1/2 hour earlier at least came up in a small lump, and they got away.

No more knowledge of accident , I was there about 7pm saturday at Dixons creek -maybe someone knows more.
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Follow Up By: get outmore - Thursday, Nov 18, 2010 at 10:39

Thursday, Nov 18, 2010 at 10:39
red back bites arnt painfull at first but creep up on you, the pain can migrate from the bite to other areas (in my case my testes!) the pan lasted for a good few hours and the bite sites (there were3) sweaed for a week
---------- and that was a small one
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Reply By: Member - Captain (WA) - Wednesday, Nov 17, 2010 at 15:07

Wednesday, Nov 17, 2010 at 15:07
Hi Robin,

Great report, as we have come to expect :)

Would be interesting to see how the Marks equipped Patrol compares to a 200TTD. Reckon the 2.8:1 would about equal the 2.6:1 plus the V8 braking of the cruiser. Then would be interesting to see Descent Control compared to the front diff lock thrown in. One day maybe...

Cheers mate

Captain
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Follow Up By: Robin Miller - Wednesday, Nov 17, 2010 at 17:33

Wednesday, Nov 17, 2010 at 17:33
Hi Captain

No chance , I think cruiser would have significantly more braking still , certainly mine does not yet have the braking of the 3lt Nissan diesel.

One day if your over I will certainly do all I can to rig the results so that the Patrol looks better than the 200 series - mind you I was doing well recently with my homemade KDSS experiment on the Patrol until the hydraulic cylinder blew apart dumping its oil all over the underneath of the car.
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Follow Up By: Member - Captain (WA) - Wednesday, Nov 17, 2010 at 21:15

Wednesday, Nov 17, 2010 at 21:15
Ahh... a homemade KDSS. Now that is a report I am looking forward to :)

Cheers

Captain
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Reply By: Trevor R (QLD) - Wednesday, Nov 17, 2010 at 15:15

Wednesday, Nov 17, 2010 at 15:15
Robin,

I got the 2.8 ratio in my green 4.2's transfer case and reckon it is on the top of the list of best mods (not that I have done a lot of mods but still). Allows one to drive so much more controlled through situations it is not funny. The 2.8 ratio required a shaving of the inside of the transfer case where the higher ratios do not so there is a bit more involved for the lower gear.

Have fun, Trevor.
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Follow Up By: Robin Miller - Wednesday, Nov 17, 2010 at 21:38

Wednesday, Nov 17, 2010 at 21:38
Hi Trevour

I reckon you would have to push your car downhill now - I thought they were already pretty good.
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Follow Up By: Trevor R (QLD) - Thursday, Nov 18, 2010 at 09:56

Thursday, Nov 18, 2010 at 09:56
Yeah originally pretty good.... now bloody awesome. Don't know about needing to push it down hill but it can climb some hills with me standing on the sidesteps on the outside of the vehicle (no input by me apart from steering it).

Trevor.
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Reply By: roberttbruce - Wednesday, Nov 17, 2010 at 16:29

Wednesday, Nov 17, 2010 at 16:29
A darn nice read Robin...
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Reply By: Kimba10 - Wednesday, Nov 17, 2010 at 16:52

Wednesday, Nov 17, 2010 at 16:52
Hi Robin, are they 2 different spots they got stuck in ?? One spot looks awefully thick goo the other pic not as bad, or is just the angle of the pics ?? Regards Steve
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Follow Up By: Robin Miller - Wednesday, Nov 17, 2010 at 19:37

Wednesday, Nov 17, 2010 at 19:37
Same place Kim

I think the first one is as winch is pulling it out and carrying water with it , as front wheel is much further out than the rear.

Its actually a trough in the ground where water has carried sand and stilt into for some years making in about 1m deep before it becomes solid , and its across a wide area with no ruts , just quicksand like slop that we send newbies into if they get to clever.
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Reply By: Member - Darren & Janella (WA) - Wednesday, Nov 17, 2010 at 23:19

Wednesday, Nov 17, 2010 at 23:19
Hi Robin,

Thanks for the report on the reduction gears. These are on my "soon to be done" mods list.

What speed would you say you were doing down the 25 degree slope in 1st@2500rpm?

Would you think that the 85% reduction gears would be un-managable loping around in the bush? I tend to stay in low range most of the day out in the bush as usually I find that if I stop and put it back into 4H that 30 metres down the track I'm needing 4L again - haha!!

I look forward to hearing about the more difficult tests you have planned.

Cheers,
Darren

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Follow Up By: Robin Miller - Thursday, Nov 18, 2010 at 09:25

Thursday, Nov 18, 2010 at 09:25
Hi Darren

The gearbox ratio in the auto 4800 is 4.25:1 so at 2500RPM in low 1st I would be doing 9-10kmh.


Other 4800 owners live with the 88% reduction gears ok particularly in rocky areas.

Its a tricky choice but there is no lack of go in this car , even a couple of weeks ago on Stockton beach before the reduction, low range was enough for me , my entire reason for this is simply downhill engine braking and for reasonable economy it needs to lope along at normal track speeds in the bush and the 43% gears I choose clearly allow that.

I also did much driving up a steep rocky climb we have and the car would do it in high range first but I felt the auto was working to hard, and low range was more than enough for me to pick a line , make a mistake and still stop and engage the front locker , then take off uphill smoothly.

I feel confident that I have made the right reduction % choice but understand why the rock crawlers would choose lower.


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Follow Up By: Member - Darren & Janella (WA) - Thursday, Nov 18, 2010 at 10:04

Thursday, Nov 18, 2010 at 10:04
Hi Robin,

Thanks very much for the feedback. It looks like 43% reduction gears will be the go for me. My main reason for getting them would be the same as you, downhill engine braking.

Look forward to your further reports.

Cheers,
Darren
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Reply By: Member - Toby R (WA) - Friday, Nov 19, 2010 at 13:22

Friday, Nov 19, 2010 at 13:22
Hi Robin

I also went the 43% reduction gears and reckon there money well spent right up there with lockers great for down hill braking and not to low to effect you when you need momentum beach driving. I found them really helpful for dragging my 3.4t overloaded patrol up long steep inclines where the old 4.2td used to really struggle no problems now.
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Follow Up By: Robin Miller - Friday, Nov 19, 2010 at 16:11

Friday, Nov 19, 2010 at 16:11
Sounds like you have a good fix also Toby.

43% in my car is the difference between 1st & 2nd gear so I get a whole gear more as well and it seems as if most , except the rock crawlers would find this the best selection.


I have just found out that the automatic is this petrol patrol does not disconnect itself or upchange in first when revs get high so its seems reasonable to expect the car to now perform as good as the manual in this respect.

I still have a long way to go to overcome the auto's inherrent defietcies but there is light ahead now.






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