Another Diff ratio question!

[GUEEY]

i have a GU TD42T Wagon.

it currently runs 3.9 ratios, i want to run my 35 radial Claws all the time.
if i had 4.1 my obvoius choice would be 4.6s
but because i have 3.9 should i be installing 4.3s
i am also planing some turbo upgrades.
i am worried that 4.6s might be a bit short in the gearing for highway driving.
i am buying gears very soon , i need some advise please.

Thanks Grant

[Vulcanised]

i know a guy with a Mav/GQ who runs 35's on his... he poked 4.65's in his and it brought the speedo back to normal, and drives ok. I plan on the same ratios for my GQ running 35" tyres as well. Ther 35's will run ok on the 3.9's... but you will chew a fair bit of fuel doing it. i ran them ok with the 4.2 donk, but got about 26 litres per hundred..... the V8 runs about 18/100 i think.

[Fozdick]

Is this an auto or a manual?

[MyGQ]

I at the moment run 35's offroad on 3.9:1 diff ratios and i find that the downhill is a bit faster than when i ran 33's but the extra diff clearance is great

To that end i have got hold of some 4.1:1 diff's for my GQ and am planing on swapping them out to give it a bit more power when running the 35's as well as slow the downhill movement.

[GUEEY]

Is this an auto or a manual?

It is a Manual!

[Fozdick]

is it a big diff or a little one eg h260 hb233
as 4.375 is common on GUs with the 260 diff (eg 3l diesel), but not sure if 4.625 is available maybe only on hb233?

[MyGQ]

Best idea i found (would have loved to have done it but oh well) is to look for a damaged 2.8L TD Patrol. they run the 4.6 ratios as standard. This will just bolt in front and back if you can get the full lot

[Darren Bell]

Hay i had a rd28 in my GU and when it gave up the gost i fitted a TD42 from an 03 GU and i still run the 4.6 gears and i run 35/12.5/15 pro comps and the speedo is about 4km/h out at 100ks, i could run slightly bigger tyres if i wanted and this would bring the gearing back to standard for the 4.2.
Revs sit at 2650rpm at 100km/h

[GUEEY]

does anyone know what rpm i would be doing at 100ks in 5th gear with 4.3 and 4.6s
just worried about it reving its nuts off on the hwy

my truck is manual and currently 3.9s on 35 claws.

[Fozdick]

from my calculations you have increased your tire diameter by about 9%
this is approx 35/32 (1.09)
a change to 4.375 gearing would give you a 12% increase in gearing
this is approx 4.375/3.9 (1.12)

this would retain your spedo accuracy to within specs . EG +-3%

going to 4.6 gears would be a 19% increase ,(more revs than stock on highway) which may not be needed if you have Rock hoppers for low range and turbo boost for highway.

P.S did you work out which rear axel type as this may be important.

Shaun.

[GUEEY]

from my calculations you have increased your tire diameter by about 9%
this is approx 35/32 (1.09)
a change to 4.375 gearing would give you a 12% increase in gearing
this is approx 4.375/3.9 (1.12)

this would retain your spedo accuracy to within specs . EG +-3%

going to 4.6 gears would be a 19% increase ,(more revs than stock on highway) which may not be needed if you have Rock hoppers for low range and turbo boost for highway.

P.S did you work out which rear axel type as this may be important.

Shaun.

It is the smaller diff not the large diff.
The info in my avitar is from my old Gu which has the rockhoppers and it was a petrol.
My new Gu deisel will not be getting the rockhoppers so i am trying to make the right diff gears selection.

Grant

[MyGQ]

does anyone know what rpm i would be doing at 100ks in 5th gear with 4.3 and 4.6s
just worried about it reving its nuts off on the hwy

my truck is manual and currently 3.9s on 35 claws.

U would be doing the same RPM as if it were running standard tyres

Remember running 3.9:1 ratios with 35's will put your speedo out, so doing 100K's on the speedo might be around 115K's on the cops radar gun

going to 35's with the longer diff gears will give you same RPM as running standard ratio's and standard tyres, its if you go to smaller tyres with the bigger ratios you will rev the nuts out of the engine to do the same speed, as you would need to do around 120K's on the speedo to be sitting 100K's on the radar gun

[InSanE]

i have a td42 with stock diffs and 36" peede's and when im doing 100 on my gps my speedo reads like 82 im not sure what diff gear ratio's a stock td42 has

[GQ Toy]

i have a td42 with stock diffs and 36" peede's and when im doing 100 on my gps my speedo reads like 82 im not sure what diff gear ratio's a stock td42 has

4.11's as a rule.


For those wanting genuine 4.3 or 4.6 ratio's try Brunswick Diesels in WA. I bought some 4.6s the other day for a really good price and you buy the complete centre. The guy said they have quite a few all the time.

[j-top paj]

get some 4.88s you know you wanna

mine sits on 2550 at 110kmh (havnt checked it with the gps yet, but i was told that 4.6s would bring me back to standard with 35s) so im thinking that at 110kph on the speedo i would be doing 100-105 on the gps.
it all depends on the type of driving your going to be doing.... if its mostly on road with a few C or B grade trips here and there then 4.3s would be the go, or if your doing harder stuff more often then id say go the 4.6s or even better the 4.88s

also im not sure if the box is the same as yours.. we may have different ratios???

[MyGQ]

i have a td42 with stock diffs and 36" peede's and when im doing 100 on my gps my speedo reads like 82 im not sure what diff gear ratio's a stock td42 has

All TD42 Manuals have 4.1:1 ratios, Dunno about the Auto's as there are too few to really get an idea

I am swapping my Ford Mav's 3.9's out to 4.1's to gain a bit more power, I run 33's on road and 35's off. so i am gaining power in both areas.

[turbo gu]

your build plate tells you what ratio you have factory.eg hg39 is a 3.9:1 diff,hg41 is 4.1:1. mannells sell the full range aswell.

[Jimbo]

Try here

http://members.optusnet.com.au/%7Ezerosin/gearcalc.html


Jimmy