Outer Limits 4x4 Board

4.2L with 35's running 4.6 ratios is 10klms under what the Speedo is saying....so does that mean that the correct ratio should be 4.3s to get the correct Speedo reading??? Everybody always says it's 4.6s.....not so!

Just putting it up there. I don't care either way but would like to put the hassle free ratio set in so I don't lose any more points and retain some power.

was your original ratio 3.9's? Mine were, and I have the same problems. The easy way to fix it is to get some 36 - 37" tyres, thats what I'm doing

WAS THIS A MANUAL OR AUTO RIG. NISSAN OR FORD........

Formula for determining gear ratios

1) Effective Gear Ratio:
The effective gear ratio illustrates the changes that occur when larger tires are installed. For example, by replacing 29 inch tires with 33 inch tires, your 3.54:1 axle ratio will perform like a 3.11:1.
Divide the old tire diameter by the new tire diameter, then multiply by the original ratio. This will equal the effective ratio of the new combination.

2) Equivalent Ratio:
This formula is used to find the axle ratio needed to bring the overall tire/axle ratio gearing back to an approximation of stock after you have installed larger tires.
divide new tire diameter by the old tire diameter then multiply by the old ratio. This will equal the new gear ratio.

giantracing wrote:WAS THIS A MANUAL OR AUTO RIG. NISSAN OR FORD........

I don't see how that makes a difinative difference.....

My first GQ was a 89 nissan TB42 auto, with 3.9's
My mate had a 90 nissan TB42 manual, with 3.9's
my new GQ is a 92 TB42e auto nissan, with 3.9's

so I havn't been able to work out which ratios went where....

i love the way u think CRUSHU

badger wrote:i love the way u think CRUSHU

I'm just sore 'cause all my GQ's had the shit ratio...... unless I was installing a 8 litre Chev.

The overall ratio when you change to 4.6's, if you originally had 4.1's is slightly lower than standard. I find my speedo is correct when the 35's are new, then reads a couple of km/h under as they wear down.

Nick

Mine is a 98 gq cab chassis with 4.2 diesel, 5 spd, 4.6:1 ratio and on my 35" road tyres the speedo is spot on.

DR Frankenstine wrote:Mine is a 98 gq cab chassis with 4.2 diesel, 5 spd, 4.6:1 ratio and on my 35" road tyres the speedo is spot on.

What ratio was it standard? I'm tipping it was 4.1 if your speedo is 100%

The truck I'm talking about had 3.9's as standard (auto 4.2) and went to 4.6's with 35's, this producing a speedo reading 10klms over real speed. Mines got 4.1's as standard being a DX(manual 4.2) and I'm putting 35's back on. I don't want the same problem how ever now that I think about it, he should have gone 4.3s when I should go 4.6's.

Why not just change the $30 plastic gear on the gearbox end?

Hey bogged do you know if you can get these gears to replace and restore speedo readings to accurate.

I have 4.6's and only 33's on road and my speedo reads about 20kms too slow!!!! lol

Also sorry for hijack but does anyone know how to fix the odometers in these pieces of shit when they stop working? Mine is fucked sometimes works sometimes not. Wouldn't worry me but it is clicking sometimes.

Once again sorry for hijack I will Tonka in new topic if people worried.

Cheers
Brian

hey brian, bring it over one day i fix for you................

to fix the odometer, pull the dial console out and clean the plastic gears behind the odometer, its gets dust and gunge in there and stops working... cleaned mine 6 months ago when it stopped and its been fine since.
shouldn't take anymore than an hour tops to do it.

bogged wrote:Why not just change the $30 plastic gear on the gearbox end?

It's a power thing, I don't have alot to turn 35's and I'm not doing the turbo thing yet..

i was aware of the Patrol tb42 auto being 3.9, the tb42 manual being 4.1 except for the Maverick XL 4.2 manual.... they are 3.9 as well. A couple of people i know that are running 35's have gone to 4.65 and their speedo is spot on. Gives you your driveablility back as well. Even with the V8 in mine, 4.65s will make a huge difference on the highway and to fuel economy.

CRUSHU wrote:I don't see how that makes a difinative difference.....

My first GQ was a 89 nissan TB42 auto, with 3.9's
My mate had a 90 nissan TB42 manual, with 3.9's
my new GQ is a 92 TB42e auto nissan, with 3.9's

so I havn't been able to work out which ratios went where....

All these cars were Nissans, No Mavericks, and all TB42's and all 3.9 gears.

CRUSHU wrote:

DR Frankenstine wrote:Mine is a 98 gq cab chassis with 4.2 diesel, 5 spd, 4.6:1 ratio and on my 35" road tyres the speedo is spot on.

What ratio was it standard? I'm tipping it was 4.1 if your speedo is 100%

Not sure I bought it like it

check the ID tags, it should say in the axle section.

Seems to differ with some vehicles further; I was running 33's and 4.1 and speedo as checked by GPS was spot on. Put 4.3s in and speedo was reading 10% higher than actual - this was for a td42 ute with 4.1 std.

Just bought a tb42e manual and has 4.1 standard, not yet checked by GPS, changing to 4.6's and 35's.

Hijack - Sorry
For those with 3.9's still in a centre who want to sell them maybe try Brunswick diesels as they put 3.9s in for the v8 diesels.

fatassgq wrote:
I have 4.6's and only 33's on road and my speedo reads about 20kms too slow!!!! lol

Cheers
Brian

I've got tb42e manual patrol with 4.1 ratio and i run 35's off road, 31's on.

I want to change to 4.6 but can't afford a set of 35's for on-road. What's it like driving 33's with 4.6 ratio diffs? Aside from speedo issue

Thanks

I imagine 33s with 4.6s would rev its head off, in top gear. My GQ has 285x75x16 BFGATs with 4.3 diffs and it is quite driveable, but sometimes could do with a 6th gear. The GPS says that the speedo is less than 10% out - it shows that we are going faster than we really are, of course.