4.2 GU Patrol problems with uphill starts

Submitted: Saturday, Feb 04, 2006 at 20:14
ThreadID: 30421 Views:3841 Replies:6 FollowUps:8
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I have a 2000 model 4.2 GU Patrol and tow a trailer with a GVM in the order of 1 tonne. Total combined GVM is probably around 4 tonne. No problems except that on five or so occasions I have had to stop unexpectedly on short, steep inclines on sealed roads. It will simply not pull up the slope (from standstill) without excessive wearing of the clutch or dropping into 4WD low range. The 4WD solution is a worry because of wind up and matching the clutch and engine revs gives me a tender feeling in the wallet. Does anyone know if there of any mods available to reduce the ratio of (at least) first gear in the main box (the rock crawling transfer case option is not applicable) or will a change to the dif ratios solve the problem. Buying another vehicle is not an option -- General Manager Home Affairs has prohibited same.

mitch
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Reply By: Exploder - Saturday, Feb 04, 2006 at 20:49

Saturday, Feb 04, 2006 at 20:49
1. Turbo it.

2. put in 4L and don’t lock the hubs

3. just work the clutch and rev the chit out of it.

They must be steep hills.
AnswerID: 153004

Reply By: Member - Paul P (Bris) - Saturday, Feb 04, 2006 at 21:01

Saturday, Feb 04, 2006 at 21:01
G'day Mitch

If yours has auto hubs replace them with manual hubs (about $200.00). I replaced my auto's with manuals (AVM's). This allows use of low range in 2 wheel drive with no winde up. I have a steep driveway and also great in caravan/national parks when backing trailer on hard surfaces.

Regards

Paul
AnswerID: 153005

Follow Up By: rustytruck - Saturday, Feb 04, 2006 at 22:25

Saturday, Feb 04, 2006 at 22:25
Paul are these hubs from Nissan, or if not where are they available without having to part with my first born?
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FollowupID: 406900

Follow Up By: Member - Paul P (Bris) - Saturday, Feb 04, 2006 at 23:00

Saturday, Feb 04, 2006 at 23:00
Mitch

They are an ARB item ( AVM hubs). I paid a little over $200.00 supplied and fitted at my favourite ARB shop in Brissy. ( Probably around $300.00 now)

Regards

Paul
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FollowupID: 406906

Reply By: Member - Roachie (SA) - Sunday, Feb 05, 2006 at 00:03

Sunday, Feb 05, 2006 at 00:03
I know exactly what you're talking about Mitch.

Problem stems partly from the fact that most of us have fitted slightly larger tyres than "normal" (ie: most of us run 265/75R16 instead of the original 265/70R16). This would not normally be a problem except that the 4.2TD is also the only Patrol in the range to have been fitted with 3.9 diffs. Other ratios available are/have been, 4.1, 4.3, 4.6 and 4.8 (I think). If you log onto Marks Adaptors web site hwere they talk about the extra low-range gearsets they do, there is a comprehensive chart of the various gearing that each Patrol model has in it.

I recently looked into changing my diff ratios over to 4.1s and got as far as ordering and paying for a 2nd hand set for $950- (front and back diffs of course). However, then I started to sus out how much it was gunna cost to get the changeover done and it would have been an additional $1,700-. So I rang back the supplier in Adelaide and cancelled the order. They'd already had the parts freighted over from Melbourne, so I got back $80- less than what I'd paid. Expensive lesson, but I couldn't justify almost $3K just to change my diffs over. The result (if I'd gone ahead) would have been that the engine would have revved at about 2250rpm @ 100kph instead of the current 2050rpm. This would have made take-offs on slopes a bit easier, but trade off would have been in the engine wear and fuel economy. I also intended to fit 285/75R16s at next tyre change (if I'd gone ahead with the diff change-over) and I calculated that that would have made the gearing VERY close to the original gearing with the 265/70R16 tyres.

As it is now, I just have to live with it. I too have fitted the AVM hubs a few years ago (think they were about $160-) and can drive in 2wd-low range now without any wind-up.......just have to be mindful not to plant the right foot too hard or there could be issues for the back drive train I guess.

Hope this helps

Cheers

Roachie
AnswerID: 153040

Follow Up By: Mitch of Bleakheath - Sunday, Feb 05, 2006 at 10:44

Sunday, Feb 05, 2006 at 10:44
Thanks everyone. I should have said it was the ST model with the auto hubs. I thought there would be a simple sensible solution. I am certain I created some of the problem by switching to Cooper tyres (6% greater rolling distance). I have been revving chit out of the system and riding the clutch to get from idle to 1500 rpm+ to overcome the inertia. The problem has arisen in a number of different situations ranging from a 20m steep uphill pinch from a side road onto the main road in Lismore to the grade out of Tumut Ponds in the Snowies (stopped by unexpected roadworks last month). I didn't think I could replace the auto hubs so thanks everyone. Roachie, what sort of right foot issues do you possibly perceive for the rear drive chain from this mod? I have a sensitive right foot but the wife also drives. . . . .

mitch
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FollowupID: 406978

Follow Up By: Member - Roachie (SA) - Sunday, Feb 05, 2006 at 19:01

Sunday, Feb 05, 2006 at 19:01
Mitch,
I'm not sure what would break, but you've just gotta remember that low range is meant to be used in conjunction with 4 wheel drive.......so I'd imagine the consequences of too much right foot, with all that additional torque being directed only to the rear wheels, 'could' be a twisted tail shaft, broken uni joint etc. Other blokes who are more mechanically-minded than me (don't forget, I'm just a dumb bank johnnie) might be able to elaborate on what 'could' break. However, having said that, the Patrol DOES HAVE one of the strongest drive trains in the business, so you'd have to do something really stupid to break it!!!! hahahaha;-))
Cheers
Roachie
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FollowupID: 407090

Reply By: Member - Collyn R (WA) - Sunday, Feb 05, 2006 at 16:18

Sunday, Feb 05, 2006 at 16:18
This will only help occasionally - where there's ample space. But then it works very well.

If you reverse a metre or two and stop with the trailer at an angle to the car the first metre or so of subsequent forward movement will simply pull the trailer into a straight line. This hugely lessen the initial load. With luck the clutch can be fully engaged and the engine on song before the trailer and car are in a straight line.

I know the above is not the answer you seek - but short of smaller diameter tyres or fitting ute diff ratio (if the diffs fit) there's not a great deal more you can do - except add a supercharger (these give a bag of torque at very low revs but will increase consumption) - but a turbo is not the answer here - it may even worsen the problem.
Collyn Rivers
AnswerID: 153152

Reply By: desert - Sunday, Feb 05, 2006 at 21:17

Sunday, Feb 05, 2006 at 21:17
By far the cheapest and easiest option is as others have stated; fit the AVM manual hubs leave them unlocked and shift to Low 4x4, 2nd gear is the next one down from High first.
Another option is changing the gearbox for the one fitted in the following vehicles:
Naturally aspirated coil cab ute; Naturally aspirated Leaf sprung ute or the turbo leaf DX ute. This gearbox has a lower first,second and third gear and (I think) is also the gearbox used in early GQ, although they would be getting on in mileage by now. This option ain't cheap, but is your only choice if you wish to retain factory auto hubs etc.
AnswerID: 153208

Reply By: DesC - Monday, Feb 06, 2006 at 16:44

Monday, Feb 06, 2006 at 16:44
try getting your injection timing checked and adjust the screw on your aneroid valve diaphragm to give you more fuel down low. (hope i spelt that right).
AnswerID: 153376

Follow Up By: Member - Duncs - Monday, Feb 06, 2006 at 18:34

Monday, Feb 06, 2006 at 18:34
Des,

I'm not a mechanic but I'd be careful with adjusting fuel settings myself. The GU 4.2 has a tendency to overheat, right Roachie, and overfueling is a major cause of overheating in any diesel.

You can select lowrange even with the auto hubs. Provided the distance isn't great and you keep it straight line it won't wind up. Wind up only occurs when one wheel travels a greater distance than another. That only occurs when going around corners.

Duncs
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FollowupID: 407332

Follow Up By: DesC - Tuesday, Feb 07, 2006 at 11:03

Tuesday, Feb 07, 2006 at 11:03
only adjusting the delivery screw that limits the diaphragm movement for fuel at low rpm. not adjusting fuel ratio. I should know being a diesel fitter. Also windup can happen in a straight line with different rolling radius tyres front to rear which can be caused by tyre pressures/load etc
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FollowupID: 407477

Follow Up By: Member - Duncs - Tuesday, Feb 07, 2006 at 16:29

Tuesday, Feb 07, 2006 at 16:29
Des,

Not meaning to argue, and I guess if you are a diesel fitter it would be ok for you. My point is that it is very easy to stuff things up on a diesel pump and make things worse rather than better. I am not a mechanic so I leave things like that alone. I have done a lot of the work on my vehicles, including rear main oil seals, clutches and head replacements and I take an active interest in what my mechanic does. Oil changes, belts, brake pad replacement and the like I am happy to do but when something requires fine adjustment and more than basic mechanical knowledge I leave it to the man. My comments were just a caution to Joe Average to be careful with what he may not fully understand.

As for wind up in a staight line you are right but is it likely to be significant if you keep the distance travelled short.

The other night I travelled from Ivanhoe to Menindee. 212km of dirt and it rained so I slipped it in to 4H. Near the Menindee end of the trip, where it was dry again, there are a number of bridges which have a sealed surface for about 100m to 200m. I simply kept it straight and drove across, no problems that I can see. I did this sort of thing often in both my previous 4wd's with no problems. The GQ had 385,000km on the clock when I sold it and it never had a transmission problem.

If you need low range for a short steep climb say <100m on a sealed surface and you can keep it straight I don't see a problem with using the GU as is in 4L. I would not use 4L to back the trailer up a steep windy driveway for example because that may cause probs.

Duncs
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FollowupID: 407528

Follow Up By: DesC - Tuesday, Feb 07, 2006 at 17:04

Tuesday, Feb 07, 2006 at 17:04
I don't recall saying that using 4wd in that situation was a problem, all i said is to adjust the aneroid valve to give himself more torque at idle as those turbo 4.2's when they came out were fairly ordinary down there until they were adjusted.
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FollowupID: 407542

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