Landcruiser Gears

Submitted: Thursday, Jan 31, 2013 at 13:01
ThreadID: 100277 Views:3991 Replies:3 FollowUps:2
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Has anyone fitted a Marks 4x4 overdrive gear to their v8 70 series cruiser and what about a Marks diff gears to achieve better fuel economy? And if you have is it worth the cash?
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Reply By: Ross M - Thursday, Jan 31, 2013 at 13:44

Thursday, Jan 31, 2013 at 13:44

Most vehicles don't give better fuel consumption figures with higher speed gearing.
The 5th is already an overdrive of around 0.87 :1 and increasing this to, for example 0.79 :1 may just cause you to be opening the throttle more to deliver more energy to overcome the taller gearing. So fuel consumption may actually rise.

Same may also occur if you change the diff ratios to a lower number ratio. ie 4.11 to 3.92.

The best thing to do is to find a friend who will lend you rims with bigger wheels of a known percentage increase and test run your originals, then run the bigger ones over a set distance and same loading/driving pattern to gauge results.

Your vehicle may be able to tolerate upping the gearing to some degree but until you evaluate it first the expensive tyre change 4 or 5 and or two diff gear sets + cost of the mechanical service to change them may not be cost effective.

The cost of bigger tyres or diffs may not give any great improvement and the cost of these for little gain may easily pay for the extra fuel you already use.

Is your vehicle in a top state of tune and injectors, valve clearances and timing adjusted properly?
Is your air cleaner clean and does your exhaust allow for free flow exit of gasses to maximize volumetric efficiency within the cylinder.

A $1000 of mod buys a lot of fuel if the intended advantages of the mod hardly do anything. Tread carefully, the theory is good, it just doesn't always work out well.

Ross M
AnswerID: 503698

Follow Up By: Member - Tony H (touring oz) - Thursday, Jan 31, 2013 at 13:56

Thursday, Jan 31, 2013 at 13:56
Hi Scoop,
I agree with Ross & his thoughts..... But if you do decide to go with any of the 'Marks Adaptor' products you are supporting a local manufacturer & keeping your $'s here..... oh & also buying a quality product.

Usual disclaimer .....NO association with the above company!
FollowupID: 780448

Follow Up By: Ross M - Thursday, Jan 31, 2013 at 14:54

Thursday, Jan 31, 2013 at 14:54
Nearly all fuel economy tests and runs ie Hans Tholstrup uses 4th gear direct drive and reduced speed to suit the beginning of the torque curve of the engine.
Possibly you don't want to sit in 4th at around 70 to 75kmh to get good economy anyway and like the rest of us the fuel consumption we get is a trade off from what is possible to achieve.

How wide are your tyres? It is common now to go wider and wider. Wider tyres use more fuel than the same diameter in a narrower tyre.
FollowupID: 780455

Reply By: Dennis Ellery - Thursday, Jan 31, 2013 at 15:26

Thursday, Jan 31, 2013 at 15:26
With the V8 Troopy 4 years ago - In the middle of the NT.
I did two 300 k test runs towing a 3 tonne caravan.
One in 4th and one in 5th at about 90Ks/hr – there was no measurable difference in fuel consumption.
5th gear towing with a Troopy causes wear problems - there are no benefits, only disadvantages.
AnswerID: 503704

Reply By: Scoop - Friday, Feb 01, 2013 at 09:05

Friday, Feb 01, 2013 at 09:05
Would fitting a 3 inch exhaust system improve the economy on the v8 cruiser
AnswerID: 503759

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