[GQ Toy]

Has anyone replaced 5th gear with the Marks overdrive gear. http://www.marks4wd.com/products/gearma ... -gears.htm I am looking to run 4.6 diffs in a CRD with 33's - because that is what I have lying around - but don't want to be running in excess of 3k revs to do 110.
I am very disappointed in the initial take off of the CRD, especially when towing and in heavy conditions so was looking at using the 4.6s to gear down for this. Currently I am running 4.1s and 33's so I am not helping myself much .
The approx 10% reduction in gearing with the 4.6's would be offset in 5th by the 10% increase with the Marks overdrive.
As I see it I would achieve lower gearing for take off and going through the box but would get back to approx factory setting once in 5th.

I could of course run 35" tyres but that would not help with the initial take off.

 

[ringo]

I have a set in my 4.8 GU, done approx. 30k no problems at all.

 

[bennoGU28]

Why dont you want to run >3k for 110?

 

[GQ Toy]

Why dont you want to run >3k for 110?

Cos I will keep looking for the next gear all the time, I would have thought it is more wear and tear on the motor running at higher revs for lomg periods, and it is noisy.

However, using this on line calculator Gear Ratio Calculator indicates that I will be less than that anyway. Might just have to put diff gears in and see how I go

 

[bennoGU28]

Cos I will keep looking for the next gear all the time, I would have thought it is more wear and tear on the motor running at higher revs for lomg periods, and it is noisy.

As it will be producing less internal pressure as it is firing more often it will result in far less wear than running at a lower engine speed. After the redline is when you need to start worrying about accelerated internal wear as a result of engine vibration as it is over speed.

As for wanting an extra gear thats in your head.

As for noise turn the stereo up a bit.

 

[landy]

I don't know about that Ben..less RPM doesn't always mean less wear.
If your are labouring your motor it can be detrimental - more fuel coming in and less air, more heat and stress to move the vehicle. The motor wants to breathe when loaded. Watch EGT's sky rocket when loaded up in too higher gear.

I would be getting the truck on the dyno and have a look at your torque curve to determine what revs you need a what RPM.

All about the torque!

 

[bennoGU28]

Im arguing to to run it at a higher rpm not a lower one. It would have to produce a greater internal pressures if it is firing less often.

 

[landy]

I misread - whoops.
carry on.

 

[GQ Toy]

As it will be producing less internal pressure as it is firing more often it will result in far less wear than running at a lower engine speed. After the redline is when you need to start worrying about accelerated internal wear as a result of engine vibration as it is over speed.

As for wanting an extra gear thats in your head.

As for noise turn the stereo up a bit.

Hmm food for thought. Max power is 3000-3200 revs, max torque is 2000-2400, Road test in 5th today with std gearing and worn 285's at 100km/hr I was at 2400 revs. If my calculations are right I will be at 2700 with 4.625 diffs

I wonder what the torque curve is like for these motors.

I hear you about lugging around at low revs

 

[BRAHMAN]

G'day GQ TOY, mate i agree with you on this one. Marks 5th gear is a must on many diesel motors with a 5th speed box. Reving at 3000 @ 110 is bulls##t. A six speed box like Land Rover Defenders is the smart way. Many on this forum, is that they haven't experienced driving at those speed continuously for hours on end, like driving round oz or the nullabor. It's palin physics, it wears any motor quicker. To say, it's in ur head, or turn up stereo, is plain juvenile. Many acclaimed motors to reach a million k's are those that are not over reved. If a motor is labouring, drop in down a gear. Simple. Many think diesels are indestructable, and dont wear till it's reached 500,000k's. Many die at around 200,000 just like petrol. Don't listen, and just do it. It's worth every cent, and will save ur motor and ur pocket THOUSANDS. Rebuild motors up to $10,000. Marks 5th gear, around $1,000. Simple job too. I've done it and wish i had done it earlier. :angryfir:

 

[bennoGU28]

G'day GQ TOY, mate i agree with you on this one. Marks 5th gear is a must on many diesel motors with a 5th speed box. Reving at 3000 @ 110 is bulls##t. A six speed box like Land Rover Defenders is the smart way. Many on this forum, is that they haven't experienced driving at those speed continuously for hours on end, like driving round oz or the nullabor. It's palin physics, it wears any motor quicker. To say, it's in ur head, or turn up stereo, is plain juvenile. Many acclaimed motors to reach a million k's are those that are not over reved. If a motor is labouring, drop in down a gear. Simple. Many think diesels are indestructable, and dont wear till it's reached 500,000k's. Many die at around 200,000 just like petrol. Don't listen, and just do it. It's worth every cent, and will save ur motor and ur pocket THOUSANDS. Rebuild motors up to $10,000. Marks 5th gear, around $1,000. Simple job too. I've done it and wish i had done it earlier. :angryfir:

Engineering degree?

 

[GQ COILY]

G'day GQ TOY, mate i agree with you on this one. Marks 5th gear is a must on many diesel motors with a 5th speed box. Reving at 3000 @ 110 is bulls##t. A six speed box like Land Rover Defenders is the smart way. Many on this forum, is that they haven't experienced driving at those speed continuously for hours on end, like driving round oz or the nullabor. It's palin physics, it wears any motor quicker. To say, it's in ur head, or turn up stereo, is plain juvenile. Many acclaimed motors to reach a million k's are those that are not over reved. If a motor is labouring, drop in down a gear. Simple. Many think diesels are indestructable, and dont wear till it's reached 500,000k's. Many die at around 200,000 just like petrol. Don't listen, and just do it. It's worth every cent, and will save ur motor and ur pocket THOUSANDS. Rebuild motors up to $10,000. Marks 5th gear, around $1,000. Simple job too. I've done it and wish i had done it earlier. :angryfir:

I'm with you mate. I don't even like reving my TD42 over 3000rpm whilst going up through the gears let alone sit on it all day for hours on end. I am currently running 35s with 4.1 diffs and am tossing up between 4.3 gears for $2000 supplied not fitted or swapping my 4.1s with a mates 4.6s as he is only running 33" tyres and it wouldn't cost either of us a cent. This way I can also just change the ratios in 5th gear.