1st Gear Too High

[BarnesBuilt]

G’Day all, new to this so please bear with me, I have a 05 GU4 with the factory intercooled and turbo charged 4.2 diesel; the exhaust has been changed to 3”. I tow a caravan and while once the car is rolling it has quite a lot of pull, taking off from a standing start can be an issue particularly on an uphill gradient (feels like first gear is too high). Can anyone suggest any inexpensive adjustments/modifications that can be done to improve the vehicles capacity to move off from the start under load without having to slip the clutch?.


BarnesBuilt

[4bye4]

Is that the original motor and what wheel size on it? Wondering if the diffs are incorrect ratio for towing a van.

[Winnie]

What size tyres do you have?
You could change the diff ratios, which will give you a bit more not only when taking off but right through the rev range in every gear. The engine will rev higher to achieve the same speeds though.

[mudski]

I think you will have 3.9's for diff ratio. Changing to 4.11's will help greatly, or even 4.3's but you will lose top end the higher you go. I went from 4.3's to 4.11's when I did my ZD to TD conversion as 1st was virtually non existant, pulled like a freight train but very annoying to drive in town.
Maybe getting a dyno done of the car to give you more bottom end go might help. As the TD's in stock form are lacking in bottom end go go. Cheaper than a diff swap, may help, it may not. But atleast your car will go better anyway with a dyno tune. I don't really think theres much you can do, on the cheap side of things, that will help.

[Robo]

Hi Mate.
I noticed the same problem on mine. To the extent one could dem it dangerous, trying to get going at a intersection.
That is now a thing of the past with new DC3 injection pump ( Diesel Central, in QLD).
Reco injectors.
GTX2863R Turbo.
3" exh.
lot of other bits n pieces, and a dyno tune the build your choice etc.
And 4" stainless snorkel and pod (Radius Fabrication in Qld also).
After fitting all bits, "except the snorkel & pod" then driven for a week,
the car performed heaps better with the new snork and pod pre dyno tune.
The std air box is a dud for the 4.2.

Our car is a completely different animal to drive now, touring pulling 22ft van is now a breeze.
including those long steep hills and hard take offs, up hill etc.
Fuel consumption down and torque up lots (when needed, it's all in the right boot).
Its a fair bit of coin but in my opinion worth every penny.
And don't worry, it's still Very street-able to drive every day.
My wife loves "her" car now, regularly telling me how well it goes up this and that hill now.
Cheers

Oh I did read some where, up till around 2003 manual box has a higher first gear , but your 2005 so thats covered.
Your compliance plate for axle should denote the ratio you have.

[MudRunnerTD]

If it's never been on a Dyno then expect to get up to a 30% gain drive in drive out. The TD42 is retarded out of the factory. Worth every cent. Beyond that I agree the cheapest upgrade by a lot would be a ratio change. It will provide you an immediate upgrade throughout the gearbox.

What Robo has described above would be AWESOME! But not cheap. I want one though!!

[Maxhead]

Geez, I would have thought the turboed 4.2 should pull the van with no issues. These motors have heaps of torque down low.
Sounds like a good tune is in order.

I tow a 2.7T van with my 3L and have no issues taking off but yeah it is a much better motor....LOL. What you reckon Westy :)

[mudski]

Geez, I would have thought the turboed 4.2 should pull the van with no issues. These motors have heaps of torque down low.
Sounds like a good tune is in order.

I tow a 2.7T van with my 3L and have no issues taking off but yeah it is a much better motor....LOL. What you reckon Westy :)
Out of the box Kris your ZD has more go in it than a stock TD42t/ Ti. They just need that little tickle to get them going.
For the op, like i said, the cheapest thing you can do is a dynotune. You may be surprised.

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[BigRAWesty]

Geez, I would have thought the turboed 4.2 should pull the van with no issues. These motors have heaps of torque down low.
Sounds like a good tune is in order.

I tow a 2.7T van with my 3L and have no issues taking off but yeah it is a much better motor....LOL. What you reckon Westy :)
I'm still on the fence lol

[nissannewby]

1st gear is taller in the gu box. Then for whatever reason nissan decided 3.9 ratios were good in the td42ti wagons. A tune will help a bit but a diff ratio change will get you closer to what you want to achieve.

[the evil twin]

If a TD42 is hard to get off the line don't ever try it in a ZD30.

I'd try and get a decent tuner to give it the once over as suggested

[happygu]

If a TD42 is hard to get off the line don't ever try it in a ZD30.

I'd try and get a decent tuner to give it the once over as suggested

Depending on the the load and temperature, the 4.2 can bog down and be hard to get off the line - just like the 3 Litre. I know as there were a few times in tricky spots I thought the 4.2 would never get moving, and I had to feather the clutch to try and get some flywheel momentum....

[BarnesBuilt]

Sorry for not getting back to everyone a little earlier and thank you all for responding to my query.
I have considered changing the diiff centers but am concerned about losing the top end as once the vehicle is under way it tows quite well as I had it put on a dyno to advance the timing and that alone did make a difference in overall performance but still have this problem taking off on a gradient under load.
Would be interested in hearing more about Robo's truck with the DC3 injection pump conversion and costings. Why does this pump offer greater power and approx costings?
Thanks again to everyone for their replies.

P.S. Wheels are the original 17" with BFG All-terrains that were the closest match in size to the original Bridgestones.

[MudRunnerTD]

changing the diff ratios won't have much top end loss mate, not the top end you are using anyway. It will increase your revs through out the gears and maybe add 200rpm at cruising why speed. This will mean that instead of sitting at 2100 rpm at 100km or so (just on boost) (The TD42T hates it here) you will be cruising down the road at maybe 2300rpm with solid boost.

The torque off the mark will be increased and the hill climbing will be well improved. I rate this upgrade for your money.

The type of upgrades that Robo has described start and $5000 but much closer to $10,000. It will be a Beast but it costs money.

[BarnesBuilt]

Thanks Mud Runner, you have obviously done your homework on this matter and will give this option some real consideration, do you have any idea of costings to change diff centers?
Stephen

[MudRunnerTD]

If you can find some second hand centres which should be fairly easy then you will probably be a Drive in Drive out fitting you might spend less than $1500. You could spend much less than that even to be honest. $1500 should be worst case.

[mudski]

If you can find some second hand centres which should be fairly easy then you will probably be a Drive in Drive out fitting you might spend less than $1500. You could spend much less than that even to be honest. $1500 should be worst case.
Yeah i paid $650 for two centres at 4.11 and then it was $800 i think for the fitment. I could have done this myself, as i have before, but laziness got the better of me back then.
So to the op, many would recommend 4.3 ratio. I had this and like i said, 1st was almost non existant. With 4.11s i can still take off quick in first im sitting on 2450rpm at 100clicks, give or take. Its right in the rev range so if i need to over take power is on tap straight away.
4.3s are dearer to buy too as everyone seems to prefer this ratio. Or even 4.6s. I love the 4.11s.

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[BarnesBuilt]

OK, MudRunner TD and Mudski have put up pretty convincing advice to change the diff ratios to 4.11, what part of the differential requires changing, is it the pinon and crown wheel?
Stephen

[MudRunnerTD]

OK, MudRunner TD and Mudski have put up pretty convincing advice to change the diff ratios to 4.11, what part of the differential requires changing, is it the pinon and crown wheel?
Stephen

Yes but just chase up a pair of complete centres, they will bolt straight in. Make sure you don't buy a H260 rear though as its too big for you and some Gus ran them.