low Xfer gearing vs tall diff gearing, potential problems?

[CAP51Z]

i am just about to change my diff gears from 5.29 (hilux/bundy diffs) to some taller ones. My reasoning, its too low in 1st low (129:1), i want it slightly faster (105-110:1 range, it was previously @ 119:1 with a different gearbox which was also too low) & on road its revving @ 4150 rpm (1.8 diesel, atm NA) to do 100 kph, the motor originally designed to pull 110 kph in a gemini @ 2750 rpm.

To get the revs down to 3200 approx, i need to run 4.3s. This gives me a crawl of 105:1. My concern is that a couple of mates have told me a theory about having a significantly low xfer coming into a tall diff. That this will place huge load on the xfer, and greatly increase the likely hood of tearing it out. I have a Xfer ring in, that helps it distribute the load better. Running Calmini 6.5:1.

My other option is to use 4.55s, but this means im gonna be doing 3500 rpm @ 100 kph, with a CR of 111:1. This is acceptable, except id like the rpm lower.

I will also be adding a turbo soon. 4.88s are still too low, & 4.1s too tall. Even without the turbo, im confident the 4.3s will not be too sluggish on road. Any benefits in economy are just a bonus. Current tyres are 36"s.

[redzook]

you dont have a second gear?

i can swap you a 6:1 case

[Shorty40]

I have 4.55s in mine. I will swap you for the 5.29s.

[CAP51Z]

you dont have a second gear?

i can swap you a 6:1 case

2nd is good atm, its 75:1 & is a good 2nd option. Only thing is it gets driven to tracks & i want it to be able to sit on 100kph without labouring the motor so much, hence the need to change the diff gears. (already changed the box ratios)

If i change the Xfer gears, im still going to need to do diffs, as most 6:whatever gearsets are around the 20% reduction in high. Cheers anyway for the offer.

I have 4.55s in mine. I will swap you for the 5.29s.

i have access to 4.55s already if i decide to use them. Cheers anyway.

[OVERKILL ENG]

Your right the lower the ratio you can run in the diffs the less load on the transfer but unfortunately you cant have bothe. The diesel won't last too long reving at those sort of revs.
If you are planning on running a turbo i would just go with the 4.3 as the torque will easily make up for the decreesed gear ratio. Beeing a deisel it shoud be able to labour right down without stalling which will help in reducing shock load on the transfer and hopefully not tear it out.
SAM

[markil]

I voted 4.55's and 39's

[CAP51Z]

thanks for the replies & votes,

i took it for a run yesterday along a hwy & held it around 3500 rpm wherever i could. The motor still sounded good at these revs, with more to offer. Although, once it passed about 3700 rpm it started sounding different. By 4k it sounded not so good.

The only reason to go 4.3s is to sit on 100 kph while travelling. So ive decided to go 4.55s & sit on 90 kph. Once the turbo is on it will be a constant 90, so i can live with that.

& i will still have acceptable gearing should i choose to go bigger tyres later on.

[Snakezooki]

took it for a run yesterday along a hwy

How good was yesterday........

good pic of your car



bad pic of my car

[/img]

[Mud_Muncher]

Hey Snakezooki, are you a giant or is an optical illusion. Looks like you could push that zook back onto its wheels by yourself .

[Snakezooki]

its an illusion..........

Thats not me..

In that pic he looks big enough to catch it though.

[CAP51Z]

quite the illusion..

it was a good day. That pic makes it look real steep, i didnt think it was that bad. Next time when your not parked in the way i will try out my new gearing.

[christover1]

Hey Snakezooki, are you a giant or is an optical illusion. Looks like you could push that zook back onto its wheels by yourself .

[Snakezooki]

Thats awesome

[CAP51Z]

where was he yesterday, would have saved me finding a way around ya!!