change gear ratios in a 6.5L TD 4x4

[BIGTPM73]

Hello everyone. Does any body know whats involved in converting my gear ratios from 4.10 to 3.42. I want to keep the truck, but with fuel prices skyrocketing, I was interested possible switching the gear ratios. I have a K2500 4x4. I do occasionally tow a trailor, but not often enough to justify guzzling fuel when I am not. Thanks.

Tom

[JohnC]

If it's a 2500HD I have a rear axle you can buy and bolt in. You'll have to change the ring and pinion in the front axle. Plan on about $200 plus labor. then you have to adjust the VSSB so the speedometer reads correctly.

I towed 5-6000 lbs regularly with the 3.42 gears and a 5 speed. I found the gears were a little too far apart, but it should work fine with an auto for the same loads.

[DA BIG ONE]

If you are running stock tires keep the gears and spend on some alloy rims and larger diameter tires like say a 255/85/16 = 33.0" that would give you some clearance and change overall ratio. When towing go back to stock tire diameter.

[DennisG01]

Do some math and figure out how long it would take you to re-coup (in MPG savings) the cost of changing the axle ratio. I'm not saying to do it or not to do it, just do some calculations first. Depending on how long the time frame is, by then you may want the 4.10's back in if you've started to pull something heavier or more often.

[DA BIG ONE]

Do some math and figure out how long it would take you to re-coup (in MPG savings) the cost of changing the axle ratio. I'm not saying to do it or not to do it, just do some calculations first. Depending on how long the time frame is, by then you may want the 4.10's back in if you've started to pull something heavier or more often.

I had gone to 3.42's frt/back and feel the cost of gear change out is not worth the gains, or lack there of w/my use of Burb. Larger diameter tires and perhaps 19.5" rims too would have been better choice.

Height, rolling resistance (wide tires) will have a negative effect at higher speeds.

Fuel quality differs greatly herein my AO in the sub-tropics so mileage is effected.

Good luck with whatever you decide on!

[JohnC]

I went from 245/75's to 255/85's and it didn't make one iota of difference in the mileage. And, yes, I recalibrated the speedometer. The tire change was equal to about half the difference between 3.73 and 4.10 gears.

The photo in my avatar shows the truck with the bigger tires on it. It did look good, but I wore out the edge of the leather seat climbing in and out... ;)