Diff ratios/engine compression/tyre size

I have had this happen as well Roachie, on quite a steep hill, all i did was apply a bit of handbreak and it stopped moving. At the same time as turning the key, released the handbreak and started back down with engine running.

So i don't think its a big deal, although you like to spend a few dollars now and then aye.

i have had my car slip in first low too (diesel) even fowards. It supprised me at first but it was a seriously steep hill. The fix? Handbrake seems to give it that little extra bit to stop the engine cranking. i am not sure this is the solution you were after tho.

Roachie,

The reverse stall recovery method is correct, but I don't take my foot of the brake completely.

Ease your foot up from the brake and at the same time watch the gear leaver.The leaver will move sideways to wards the driver if doing it in reverse.When the leaver has stopped moving that is where you leave you foot on the brake, no more pressure and no less. At this point the vehicle is held by the foot brake and engine compression. The motor should start with out any strain on the starter motor.

Having a little pressure on the brake will also stop a petrol taking off too quick and the driver is able to control the speed of the decent by applying more pressure on the brake.

If doing a forward stall recovery and the same method is used the gear leaver will move to wards the passenger side.

We also make sure that the ignition is turned off all the way after the vehicle has stopped and before we start to release the foot brake. The last thing we need is the ignition on and the vehicle creeps forward and starts the motor.

Wayne

Hi Roachie,

The poor low ratio of 2:1 on the Nissan GU is one of my biggest gripes with Nissans. IMHO the Nissan is more off road orientated than its competitors, yet it only has the 2:1 low range ratio, one of the poorest around. My old 1HZ 80 series had a 2.5:1 low ratio and even the VW Tourag has a 2.7:1 low range. Its not until you look at the old subaru's before you see worse low ranges like 1.6:1, but at least they never claimed to be a "proper" 4WD.

But if you do want to "fix" your vehicle, much better IMHO to put in the a better low range ratio than change your diffs. With the Marks Adaptors replacement (?), you get a 3.7:1 low range (I think) and do not affect your high range ratio.

Cheers

Captain

I am with Captain on this one. If you change diff gears you mess up High 2 gearing, and therefore road manners and economy. Change the transfercase gears and it will keep the same on road manners/economy. Changing low ratio will make it much better for slow off road work and for the quicker low ratio stuff you just use one gear higher. Unless of course you want better on road take off then go for the diff gears, but economy might suffer. JMHO.

Thats why tojos dont need handbrakes - we often have to park on underground mine dedeclines with slopes of 7-8 to1 you would be testing the walls and roo bars out constantly if they rolled against compression

You have not changed the tire size enough to worry the diffs.. If you go to 4.3 from 3.9, it will rev its tits off and go nowhere. maybe 4.1's if you must spend some cash.

They are around $1000 per diff + fitting on a Genuine Set of gears. Aftermarket ones, dont last very long as daily driver - or so a mate that sold them told me...

You are a hypochondriac on that car. Always lookin for things wrong with it..

You know the thing is massive... It's a 3 ton 4b.. crap final ratios, and massive tires..

Me thinks you are just lookin for an excuse to spend money.

... YMMV ...

Roachie,

I'm not sure what training exercise this was supposed to be but in the Vic. 4WD association training there is NEVER any intention in a reverse stall stop proceedure to have the vehicle hanging on engine compression braking only !
The intent of stall stop recoveries is to; a) secure the vehicle when in difficulty; and, b) to effect a safe retreat from the obstacle.
To do this we teach the use of all 3 braking systems; foot & hand brakes and engine compression. All three are used to secure the vehicle whilst the plan of recovery is developed and there should be no time during the preparation for the recovery that less than 2 braking systems are in use. eg. quickly operating the clutch to select reverse. Only when the driver is ready to back down are the handbrake and footbrake released as the starter is activated. The point when the footbrake is released [and the key turned] is only when the driver is prepared and ready to commence the recovery. There should be no reliance on engine compression braking alone to hold the vehicle at any point.
Just because the gearing of some Toyotas may hold them it is a very dangerous practice and totally negates the safety measures involved in a proper stall stop recovery.

Ken

G'day Bill,
Just imagine if your truck was an automatic and you would need to hold the vehicle in reverse with the handbrake applied. As you commenced the descent, apply the throttle power gently until the vehicle drives against the handbrake. Control the descent by gentle throttle control. Complete the descent. You can apply the same proceedures if your compression won't hold the vehicle. Is the expense necessary for the number of times that you need compression to control your descent. The mpney you have saved can be deposited into my retirement account.
If you have the latest DTU Training Manual, it's explained in section 7-9.
I hope you will appreciate my omittance refering to an altenative vehicle. Sorry. I couldn't help myself. LOL

Roachie me mate

""At one point in the proceedure, you are required to have the vehicle in low-range, reverse gear (if pointing up the hill), engine stopped, release handbrake, and gradually release footbrake""

WHY?

Roachie,

Get with it, it's a Nissan so in the real world you wouldn't need to stop on the side of a dirty big hill, just drive to the top unless you have a yota in the road of course
lol.
Lower transfer gears are the go if you want my opinion.

Cheers Trevor.

Roachie
A few points:
As per a previous reply to one of your posts I told you which diff ratios would and would not fit your diffs. (H233 vs H260 diffs)
Marks are about to release a 40% lower low range gear to fit between the standard one and their 83% lower gear.

My stock as a rock GU with 3.9 diffs and 305/70/16 tyres towed a camper weighing nearly 1.5tonnes up and down some seriously steep and loose high country tracks last xmas (Twin Jeeps, Blue Rag, Brewery, etc).
2 petrol Prados with me (one was less than 2 months old) both cooked their brakes downhill so badly they have both had to replace the front rotors. Mine just wandered down held back by engine compression. Their campers weighed 1000 and 1200kgs

The "handing on the trans" thing should be a split second thing. Key start the motor as the footbrake is released.
As part of training its done for a bit longer to demonstrate that compression will hold it. Most petrols and some diesels will turn over. Older diesels can -*sometimes*- actually start and run backwards. Pretty scary.

Hi Roachie
Maybe the slipage was due to wear in the engine e.g. piston ring to cylinder bore gap?

Maybe she needs a rebuild ??

I have some info at work that gives all the Maths to work out what you require (I think) If I remember I will try to scan it and post it to the file swap

Regards

Richard

Roachie ! you and your fellow members of the 'Pink Nissan mafia' are the greatest wasters of time, money and cyberspace on this forum.

Now look what you have done - sucked me into your artfully conrtrived attempt to terminate all Toyota owners by boreing them to death with more 'eye witness' reports and experiences of what they already know, and that is:

Nissans should be renamed BLOWFLIES ( greatest pest known to mankind)

Ooh! Roachie, you make my day every time you let loose on this forum.

Surely reducing the weight of your vehicle to comply with the OEM GVM and replacing the tyres and/or with OEM specs would fix the perceived problem.

Far cheaper than d i c k i n g with the diff ratios and or transfer case whatevers, cause that may alter the 'engineering' somewhat and make it a un-roadworthy vehicle that can't be insured, and in turn possibly placing the operator of same at the mercy of the 'litigators'.

Bill,

Do you have any genuine parts left on your "vehicle"?

Maybe you need to call it a "Roach", rather than a "Patrol"
.

Hi Roachie have you got an E-mail address
the file is to big to put on swap file

if you want send it to me at work today or at home on

rdkovac@bigpond.net.au

Regards

Richard Kovac
Service Manager
Gerrard Hydraulics
Phone: 08 9455-2344
Fax: 08 9455-2045
Email: richard@gerrardhydraulics.com.au

Hi Roachie,

Just sent you a message re my Gearmasters (sorry hadn't read this post first). As mentioned the extra low range gears are desined for better control and handling in slow rough going situations. It is increases torque significantly and allows you to go slower at a higher engine rev which means you are on boost most/all the time, do not need to slip the clutch at all to keep revs up and have better use of the rev range. Engine braking is fantastic and can happily idle down a steep hill in 3rd gear without any brakes. With a camper itis 2nd and you still have another gear as backup.

Your situation would require a set of extra low range gears and not diff ratios in my opinion. Diff ratio's affect the car in both high and low range and are to bring the vehicle back to standard drivability after modifying wheels to a larger size or some sort of engine/driveline modification. Diff ratio's are all about having the vehicle go at a certain speen for a given rev and how they are matched when designing the vehicle. Extra low range gears only affect the car in low range and have no effect on high range at all.

When I converted my 2.8Tdi to a 4.2T, I had to drive the car with 4.88 diffs installed (I upgraded the standard 4.6's to 4.88's when it was a 2.8), for a few weeks before I swapped back to 4.11's (3.9's are standard on a 4.2T GU but as I run 285's / 33's, I worked out 4.11's were what I needed to bring standard driveability back). The car was a DREAM to drive around town and could blow of any other 4wd at the lights no worries. However on the highway at 100km/hr, the engine would rev at 2650 RPM which is around 300-400 RPM higher than standard - this is not good for fuel economy.

With regards to prices - the Gearmaster gears were purchased as a show special for $1200 and I proceeded to do the installation myself (this is dead easy and took a bit over half a day). However to convert diffs, it costs a lot more. To convert to the 4.88's it cost me $1400 for F&R C&P sets. To fit the things was anywhere from $800 to $1200 and needs to be properly done so that backlash etc can be setup.

After the 4.2T conversion I tracked down F&R sets of 4.11's for $150 the lot. I would stay away from 4.3's as they are 1 to high for your tire size and 2 rare and expensive in 2nd hand form (forget new). 4.11's are a dime a dozen and were available in the GQ's and GU's (mine were from a GQ ute) and with the amount of people who upgrade their 4.2 (non turbo) GQ's you could probable get a complete set for a couple of slabs - you can hardly give them away. I ended up getting the guy who did my engine converions to do the ratio swap for $400 which was the best I could expect. Have done around 20k with them and everything is still smooth as silk.

So there you have it. Hope some of this helps.

Regards
David

Hi Roachie,

Off subject I know but I thought it the best way to get direct to you.

I've noticed all along your dramas with overheating and while interesting reading I have not had the problem, that is until now.

Mine is a 2002 GU 4.2 turbo diesel cab chassis with only basic mods including the 3 inch dump pipe and full flow exhaust etc. I've only just started towing a camper and this is were the problems have started. Never had the drama even with a very heavy tray back camper. Now I have a canopy with gear in the back and also tow a camper, a pioneer camper which is much lighter than yours, approx 750kg all up.

When travelling on the highway at 110kph, outside temps approx 38-40 dec C, air con on, towing trailer etc on a flat road the temp gauge is getting close to 3/4. Normal temp without towing is under half. Get to a hill and try and maintain speed and temp gauge goes to, HOT, needle is right on the line going to the red. Even at 100kph and same conditions and temp is just as hot. A/C doesn't shut down I've got to turn it off to help.

Was heading to Blackdown Table Lands in CQ so thought the slow crawl up the hill might be ok. But no way, the climb is very steep and so put it into low range 2nd and 3rd gear, outside temps similar and coolant temp just as hot as above. Only time it went into the red was when I stopped to let it cool down and at idle it went into the red so just increased rpm and temp started to drop.

Can you tell me is this what you had?? Did your temp gauge get this high??

Bit of a worry so need to do something as I'm going on leave for 6mths next year and don't want dramas.

Any help appreciated.

Roachie, I've had some discussions with Mark Hardman from Hardman Bros Engineering here in Melb. His company is the gear manufacturer who supplies Marks 4x4 for all their Gearmaster low range conversions.
He told me the 44% reduction gears were due out this month (December) and in his view were a more realistic reduction set than the previous 83% reduction gears. The 83% ones were more suited to rock crawling in according to him. I know a few people running the 83% ones but their complaints lie in the fact they simply run out of low range gearing too soon. Low range 1st down hill is unbelieveable and even the auto petrols go down much slower than a standard geared diesel to the extent that a diesel patrol following a petrol auto Patrol with these gears had to apply the brakes constantly to keep more of a gap between the 2 cars.
I'm going to go for a set of 44% gears myself when they are released for my auto petrol GQ, I think this will be the ideal setup for me. The 44% reduction gears give an effective low range gearing of 2.9:1 the 83% ones are 3.66:1
Unfortunately, Hardmans only sell these gearsets through Marks and not direct from them.
Regards Andrew.