Gearing for a heavy GU on 35's

[BIGDAVET86]

I have searched but cant really get a definate answer on what im chasing.

I have a 04 GU coil cab on 35's with std gearing and std turbo setup. I am about the upgrade the turbo and intercooler hoping for about 110kw at the tyres. I am setup fairly heavy with 315l of fuel, steel tray with steel roofed/canvas canopy. I also tow a 1T boat. I live in the Pilbara and do a fair bit of highway/long dirt roads and want to get the whole show a bit more sorted. Without the boat into i like to do some decent wheeling and i am really feeling the pain on the beach at the moment, just lacks the punch down low.

now the questions: What R+P gear do i have now? I am assuming 4.1:1?? What do you reckon i should change to, 4.375 or 4.625? I dont want to lose all my top end cruising but i dont like the low down response now. Needs to sit at 100-120km hapily.

Which one is for me???

Cheers
Dave

[unmass]

Hey there, you need to look at the plate on the drivers side to see what gears u have without pulling diff apart if they are HG41 they are 4.11 ratio which is pretty common amongst diesel patrols with manual transmission, or 4.3 for rb30 patrols and so on.

My recommendation and the most common gear we sell is the 4.6 ratio gears which we have in stock I think they retail for 585 which we can also freight and install.

We run our previous 4.2 TD Gq patrol which had 4.11 ratio with 35 inch tyres daily with these 4.6 ratio gears we have never had a gear set come back and back our gears thoroughly and recommend this gear to rectify 35 inch tyres to standard or near enough to standard

Regards
Mitch
Mitch@mitchellbros4x4.com.au
02 9905 4764
I hope this helps

[turbo gu]

This always gets laughed at but never run 4.6s with a diesel and 35! L have learnt the hard way. 4.3s are the only way to go! The motor sits in the right part of the torque curve with them. In lite cars I would keep 4.1s.
My gu wagon regulary tows a gu ute and by changing back to 4.3s I improved my ecomomy by approx 8litres per hundred and the car is far better to drive.
Im shure ozy1 on here has had the same experience

[BIGDAVET86]

My concern is that 4.6's might be too short for long hauls. But the poor ute struggles to drag the boat out of the water up the ramp, with out slipping the clutch, unless i put it in low range.

Cheers
Dave

[thehanko]

You will have 4.11's

I feel your pain, i have upgraded turbo and pump and find the gearing on 35's lacking, normal driving i dont notice but off road .

Worth considering though 4.1 to 4.3 or 4.6 will be good onroad but I personally think it would still be too high for offroad. at $5-600 per gear set plus install its alot of coin.

I would personally prefer to get a set of crawler gears - similar money about $1200 plus install but wicked lowrange and pretty good high range.


I have the same truck but run 31's daily and tow alot as well, considering its better to roll in 4th than 5th when towing i dont think 35's would be so bad for towing on std gearing. especially when you get a bit more poke out of the power range with your upgrades.

A couple of times I have had steep hill starts towing big loads, i just use low range for these and drive in that until i get off what ever big slope was too steep to start on the go back to high range. e.g a boat ramp.

it might be a bit harder on your clutch to tow on 35's with std gearing but in low range your clutch wont get a work out at all.


Turbo GU - Holy crap. I didnt know it was possible to get a 4.2td to use 8L more than normal regardless what you do. I can tow a 3t trailer roughly the dimensions of a 5th wheeler and still only use 5 maybe 6L more than around town. and thats when i tell it it has to do the speed limit... everywhere I would never have guessed such a small gearing change could make so much difference.

Mine gets almost identical fuel ecconomy - maybe 5% more on 35's than on 31's by the time you take the change in odo % into account that is.

[gu town]

I'd say wait and see what your turbo and i/c upgrade does for your low end power. My 2000 gu 4.2td ute runs 35's with around 110rwkw on standard turbo, top mount i/c and standard 4.11 gears, i'm not gonna change them, I reckon theres plenty of low down power even in the sand (fraser island, moreton island, big and little deserts SA)

Here in the NT with the 130km/h speed limits my ute will happily sit on 117-120 @ 2500rpm all day and still consistantly get 1100km give or take 100k's to the standard 180-odd litres.

If you do decide to change gearing IMO, go for the 4.3's you'll be revving too hard on the highway with 4.6's.

[thehanko]

I'd say wait and see what your turbo and i/c upgrade does for your low end power. My 2000 gu 4.2td ute runs 35's with around 110rwkw on standard turbo, top mount i/c and standard 4.11 gears, i'm not gonna change them, I reckon theres plenty of low down power even in the sand (fraser island, moreton island, big and little deserts SA)

Here in the NT with the 130km/h speed limits my ute will happily sit on 117-120 @ 2500rpm all day and still consistantly get 1100km give or take 100k's to the standard 180-odd litres.

If you do decide to change gearing IMO, go for the 4.3's you'll be revving too hard on the highway with 4.6's.

is your speedo corrected? as if not its stating 14% slower than it would have stock. due to the bigger tyres 4.6 changes gearing for 35's by about 12% basically back to stock. so 35s and 4.6's is basically stock gearing.

with 4.6's and 35's you would do 2450 at 100km/hr based on a speed with the same accuracy as stock. about 2700 at 110km/hr

peak torque is normally from around 2400rpm in a patrol so that looks about right to me. If it was 4.3's it would mean about 2270 at 100, IMO I would say thats a little low. but each to their own.

one thing about 4.6's is that it will mean you will be pretty much stuck with bigger tyres, so selling it or should your needs change and smaller tyres are needed then it will be harder. 4.3's would be better in this respect.


BTW as GU town said wait until after the mods are done is probably a good idea. In the soft sand up at stockton I had no issues whats so ever with 35's on. My only complaint is the lack of crawl ability with 35's either towing on steep starts - boat ramps / drive ways etc etc and rock work offroad.

[SIM79]

But the poor ute struggles to drag the boat out of the water up the ramp, with out slipping the clutch, unless i put it in low range.

Put it in low range problem solved.

[BIGDAVET86]

Put it in low range problem solved.

That was just one example. How come there are so many f*ckn smartarses on here.
Its quite obvious this is not the only drama im having. I do put it in low at the ramp, common sense not to kill the clutch, but as stated earlier it struggles on the highway as well. And it should be able to pull it up the ramp in 2H, did it with no drama before the tyres, and loading it up with all my gear. I just want to find out how to return the gearing to std after fitting the 35's, keeping in mind i regularly have the ute fully loaded, so being a bit tall in the gearing will be a pain.

cheers
Dave

[SIM79]

Put it in low range problem solved.

That was just one example. How come there are so many f*ckn smartarses on here.
Its quite obvious this is not the only drama im having. I do put it in low at the ramp, common sense not to kill the clutch, but as stated earlier it struggles on the highway as well. And it should be able to pull it up the ramp in 2H, did it with no drama before the tyres, and loading it up with all my gear. I just want to find out how to return the gearing to std after fitting the 35's, keeping in mind i regularly have the ute fully loaded, so being a bit tall in the gearing will be a pain.

I think the gearing has been sorted in the above threads 4.3s!

You just seemed to be making big deal about having to use L2 on the boat ramp, as far as I know using L2 on boat ram is common knowledge and practice with a 4x4.

Why would you use high range when you have low range?

[bushy555]

My 3 cents worth says that you will be slightly disapointed with 4.3 ratios.
I'd go with 4.625 or 4.66, especially with towing...

Normal usual thing for most people is 4.3 ratios for 33"s, 4.6 ratios for 35" tyres or 4.88 for 38" tyres when factory ratios are 4.1 for 31" or 7.50/R16 32" tyres...

[turbo gu]

Turbo GU - Holy crap. I didnt know it was possible to get a 4.2td to use 8L more than normal regardless what you do. I can tow a 3t trailer roughly the dimensions of a 5th wheeler and still only use 5 maybe 6L more than around town. and thats when i tell it it has to do the speed limit... everywhere I would never have guessed such a small gearing change could make so much difference.

Mine gets almost identical fuel ecconomy - maybe 5% more on 35's than on 31's by the time you take the change in odo % into account that is.

I towed the same GU ute behind my wagon on a very similar trailer 2 years in a row to Willowglen.
1st year with 4.6's it was around 28l per hundred, 2nd year was 4.3s and it was around 20l per hundred and alot faster with no other mods!
The difference is what rpm you can do at what speed in what gear. with the 4.6s it was in the wrong part of the torque curve so you were constantly changing gears to try and keep it going!
With the 4.3s it sits in the right part of the torque curve(no point reving over 3000rpm if its not making power).
I couldnt belive the difference!! It was also alot quicker trip as I could hold gears as opposed to swapping up and down gears! Mittagong bypass was a good 20km/h faster up the hill by being able to hold 3rd as opposed to swapping between 2nd and 3rd!!
4.6s are for 37s only!!!
My ute runs 4.1s with 37s and thats not so flash!! wouldn't tow a box trailer up a hill from a standing start! but onces its over come the tyres and its going it is quite good

[turbo gu]

from an open road driving point of view 4.6s DO NOT make it a very relaxed truck at speed!! Revs way too hard!! at 100km/h its alright but still a touch high but go to 120km/h and its really not happy!!!

Dont know if it can be done but the GQ gearbox has a better 1st gear but the box wont fit in the GU due to shifter location but if u can swap the guts into a GU housing that would your best outcome!

[thehanko]

Put it in low range problem solved.

That was just one example. How come there are so many f*ckn smartarses on here.
Its quite obvious this is not the only drama im having. I do put it in low at the ramp, common sense not to kill the clutch, but as stated earlier it struggles on the highway as well. And it should be able to pull it up the ramp in 2H, did it with no drama before the tyres, and loading it up with all my gear. I just want to find out how to return the gearing to std after fitting the 35's, keeping in mind i regularly have the ute fully loaded, so being a bit tall in the gearing will be a pain.

cheers
Dave

Mathematically if you want std gearing as requested then go for 4.6's end of story. Bushy is on the money.

your tyres have changed gearing buy 12.9%
35/31 = 112.9 %

So your diffs need to do the same to recover that
4.66/4.11 = 113.3 %
4.62/4.11 = 112.5 %

either option has you within half of a percent of original gearing

4.3 / 4.11 = 104.6% still 8% down on std gearing.


Big dave - once your turbo and ic are given a tickle dont worry so much about being about to cruise towing that will be more or less taken care of. The biggest problem I have towing is not speeding lol. But I tow on std gearing - equivalent to 4.6's on 35's.

Either option will improve it.

personally i would sort out your power and see how it feels. if its ok except for low range then tranfer gears, if it still needs more help everywhere then go for diff gears.



Turbo GU - You have some interesting experiences, However I don't agree at all. IMO std gearing in patrol is great for towing. and with that gearing i've never had 20l/100km or more consumption. those sort of figure should be reserved for petrol engines.

Each to their own.

[turbo gu]

4.1s are standard on a ute or a gq. Utes are geared slightly differently as they would be set up for the split rims which are bigger tyres. closer to 32/33inch so the tyres are already upgraded as such!
Wagons come with 31s and 3.9s. There is no difference in gear ratios in the gearboxs between the wagon and ute.

The wagon and ute combo is close to 6 ton and doing 100km/h its going to use fuel!! around town the wagon gets 12/14l/100. 20l/100 is the usual towing at 6ton!

Do what u want at the end of the day its your money. This is my experience with it and 4.6s arent the best IMHO!!

[thehanko]

First Ive heard of the wagons being different ratios to the utes, not saying its wrong, just not what i had heard.

Since the OP wants to return to stock gearing then it doesn't really matter as his is a ute so 4.11's.

By my factory manual both wagons and utes came out with the same tyre options 265/70r16 (31.6 inch) or 7.516C for both wagon and ute, the rims they came with was probably more to do with dx or st or ti.

as for the difference in tyres sizes, patrols never came out with 32/33 inch tyres if they did qlders wouldn't have so many issues. this is from http://www.1010tires.com/tiresizecalculator.asp

7.5r16 and 265/75/16 are both the same size about 31.6's



Yes more weight is more fuel but 6 tonnes from a 4.2 diesel should not use twice as much fuel as 2 x 4.2 diesels each with 3 tonnes. I'm not saying you didn't get those results but i am saying that a 7-8% change in gearing alone will not result in a 40% increase in fuel consumption from a diesel motor.

I also don't know anyone who put 33's on their patrol and claimed better fuel economy than stock size tyres.

But our nattering isn't really helping the OP so I will leave it there he has all the info he can use.

OP for what its worth I have also towed less, about 1.5T with 35's and 4.11's with modded engine and didn't really have a problem with it. thats why i would try engine first, then decide on gears. but if you want stock gearing then go 4.6's.

[turbo gu]

All 4.2td GU wagons come with 3.9s as do 4.5 petrols. Early non turbo GU 4.2s might have 4.1s. Never checked one but every 4.2td I have seen has 3.9s!
Sorry but your comparo is flawed!!!! There is massive differences!! Your throttle is open alot more keeping 6ton going than 3 ton and thats without the wind resistance of the towed car affecting the airflow over the towing car eg more drag!! Plus the resistance of the trailer etc!!!
The difference in comsumption comes down to having to downshift and loosing speed up hills therefore on the hill for longer in a lower gear pulling more rpm and wide open throttle using more fuel!!

[Portal Pat]

Been reading this one with interest. The overall consideration seems to be how the truck will be on road-and at speed. I built my Datto for 4 wheelin'. It is an '06 4.2 coilcab with 5.0: 1 diffs. i.e. 4.11:1 diffs +1.22:1 hub reduction= 5.0:1, due to portals. Using 315/75x16s I am perfectly happy with my gearing on road,but then I rarely drive over 100 km/h. We carry a Trayon at times and that would be the heaviest load, approx. 550kg. So, where I am leading is, I strongly recommend 4.6s for 35s. It is a 4WD after all, and ya don't want to be slipping the clutch just to get moving in the scrub,eh? Anyway, Google auto maths. and you will find equations that will advise what you should fit.Cheers.

[turbo gu]

Been reading this one with interest. The overall consideration seems to be how the truck will be on road-and at speed. I built my Datto for 4 wheelin'. It is an '06 4.2 coilcab with 5.0: 1 diffs. i.e. 4.11:1 diffs +1.22:1 hub reduction= 5.0:1, due to portals. Using 315/75x16s I am perfectly happy with my gearing on road,but then I rarely drive over 100 km/h. We carry a Trayon at times and that would be the heaviest load, approx. 550kg. So, where I am leading is, I strongly recommend 4.6s for 35s. It is a 4WD after all, and ya don't want to be slipping the clutch just to get moving in the scrub,eh? Anyway, Google auto maths. and you will find equations that will advise what you should fit.Cheers.

He says he wants to do 120km/h and i would guess more considering where he lives plus not much of a chance of speed camera/highway patrol probably a bit more!
4.6s are not the gear of choice for high speed!

[BIGDAVET86]

Thanks everyone, seems like 4.3 is the way to go. We like to be able to do 120km/h all day, and at least 145 to over take, and sit on 130 at night. Next question would be, where to buy? i see marks adapters has them any others?

Cheers
Dave

[SIM79]

. Next question would be, where to buy? i see marks adapters has them any others?

Cheers
Dave

Brunswickdiesel have heaps or 4.3s and they need 4.1s! My mate paid around $550 for f + r delivered, when he replaced his 4.6s. You should get them cheaper if you send your 4.1s.

http://www.brunswickdiesels.com.au/new/index.php" onclick="window.open(this.href);return false;

[BIGDAVET86]

Just talked to brunswicks, got 4.3's, 800 for the pair. Gonna pick them up next week.

How am i best to store them? I was thinking i would cover them in oil, wrap them in some oiled ragsthen wrap that with plastic. Or is there a easier way?

[gu town]

I'd say wait and see what your turbo and i/c upgrade does for your low end power. My 2000 gu 4.2td ute runs 35's with around 110rwkw on standard turbo, top mount i/c and standard 4.11 gears, i'm not gonna change them, I reckon theres plenty of low down power even in the sand (fraser island, moreton island, big and little deserts SA)

Here in the NT with the 130km/h speed limits my ute will happily sit on 117-120 @ 2500rpm all day and still consistantly get 1100km give or take 100k's to the standard 180-odd litres.

If you do decide to change gearing IMO, go for the 4.3's you'll be revving too hard on the highway with 4.6's.

is your speedo corrected? as if not its stating 14% slower than it would have stock. due to the bigger tyres 4.6 changes gearing for 35's by about 12% basically back to stock. so 35s and 4.6's is basically stock gearing.
.

Yeah thats off a gps. it shows about 7-8 kays slow on the speedo.

Just talked to brunswicks, got 4.3's, 800 for the pair. Gonna pick them up next week.

How am i best to store them? I was thinking i would cover them in oil, wrap them in some oiled ragsthen wrap that with plastic. Or is there a easier way?

Glad you went with the 4.3's.

Thats how i'd store them. I'm no expert though.

post up some speed/RPM, l/100 and speedo accuracy when ya can.

[thehanko]

glad you got the info you needed to make your decision. hope its everything you want.

good luck.

leaving them oily and wrapping them up should be fine. just needs to stop moisture which the oil will do. I have diff parts oiled then covered in glad wrap as it kind of seals against itself though not fully. the rags would help stop the teeth ripping the plastic.

[twodiffs]

4.3's on 35's are a good choice, there's plenty of threads on Patrol forum where guys say they have changed from 4.6's to 4.3's - purely because of the highway speeds and revs etc.

I drive around a lot of hills daily for work and use 31's, the 4.3's give me plenty of room for torque just at the right time and gear. My speedo is also
10kmph UNDER with 31's.

With 35's (BFG KM's) my speedo is spot on with the gps AND roadside speed checks etc. I did loads of reading about gearing and decided 4.3's...best mod yet for me mate!

[twodiffs]

Bear in mind 4.375's are closer to actually being 4.4's.

[turbo gu]

My 4.2td GU wagon on 4.3s with 315/75/16 mtrs
100km/h 2250rpm
110km/h 2450rpm
120km/h 2650rpm
give or take a small%
Speeds are off the speedo which is approx 2km/h fast

[simcoe]

[quote="turbo gu"]All 4.2td GU wagons come with 3.9s as do 4.5 petrols. Early non turbo GU 4.2s might have 4.1s. Never checked one but every 4.2td I have seen has 3.9s!

not all 4.5's came with 3.9's, i think only the auto's did.
my manual wagon 4.5(v8 now) has 4.1's with big diff.

[love ke70]

My concern is that 4.6's might be too short for long hauls. But the poor ute struggles to drag the boat out of the water up the ramp, with out slipping the clutch, unless i put it in low range.

Cheers
Dave

then put it in low range!
thats what its for.

my ute weighs 3.1 as it sits, then i have a 1 tonne car trailer, and put the 1 tonne car on, so thats over 5 tonne. and it doesnt struggle on 35s with 4.1s
on 31s ive towed my trailer full of wet dirt up the highway 40km, 4 times in a day. estimated weight of trailer was a minimum of 4 tonne. (4.5m x 2.4 trailer bed) it struggled with that, but when your towing weight, you dont it in 5th, so the 4.1 ratio is perfect.

[BIGDAVET86]

then put it in low range!
thats what its for.

my ute weighs 3.1 as it sits, then i have a 1 tonne car trailer, and put the 1 tonne car on, so thats over 5 tonne. and it doesnt struggle on 35s with 4.1s
on 31s ive towed my trailer full of wet dirt up the highway 40km, 4 times in a day. estimated weight of trailer was a minimum of 4 tonne. (4.5m x 2.4 trailer bed) it struggled with that, but when your towing weight, you dont it in 5th, so the 4.1 ratio is perfect.

Like i said before i do put it in low range, FFS!!!!! but before i didnt have to. That was my point of reference for how much gearing i had lost. I estimate my ute will have about 1t in the tray most of the time plus the weight of the tray itself, its starting to get right up there. Then the boat 1t dry, about 1.3t with fuel and all the gear, plus trailer..... I have a feeling i dont want to visit the weighbridge as it might be a touch over GCM.

As for towing 4+t of wet dirt, your an idiot. Doing it on a main road with heaps of other around, even worse. things have ratings for a reason, both vehicle pulling and trailer/s behind.

Cheers
Dave