Has Anyone Changed their rear gears?

[Riverholic]

Just wondering if anyone has swapped their stock 3.73's in the differential to anything else? My local shop told me that swapping the stock 3.73's out for 4.10's would make very little difference and in their opinion isn't worth the cost. Any thoughts??

[More Power]

This axle is offered with 4.10's when getting the gas engine, but 3.73's are all you can get with the diesel.

In reality, 3.73's are probably a better choice for the diesel because you'll be running closer to the torque peak at highway speeds. With 4.10's, you'll be another 200 rpm higher - and farther away from the torque peak.

The 8.1L gas engine's torque peak is (if I remember correctly) at about 2800, which would be a better fit for 4.10's.

However, all theoreticals aside, no one has tried 4.10 gearing in a 2500HD/3500 Duramax, so it would be hard to know for sure.

I do have a little experience with the Duramax and 3.42 gears. 1800 rpm equals 75-mph or therabouts with the tires I'm running (31" tall). This would be too few rpms when pulling at typical loaded speeds. Makes a great Interstate cruiser though...... Also saw 22-mpg in the Project truck for the first quick fuel economy evaluation.

MP

[DA BIG ONE]

I went from 4.10:1 to 3.42:1 on my 99 2500 HD SUB, Broward Power Power Train in Ft. Lauderdale did the switch over.

The fuel mileage went to hell until I corrected the settings on my VSSB, then a top dead center learn, now getting 23mpg @ 70mph. Best $1,500. I spent so far on this rig!


The best milage before the change was 17mpg @ 70mph.

[1996-Burb]

Can you please explain what a VSSB is and a top dead center learn. You've stumped me.

[BassinRVer]

I replaced the 3.73 to 4.10 (front and back) to compensate for running 315/75/16 tires. I am very close to the 3.73 gear ratio now. It cost me 2000 with the new gears. I went with aftermarket 4.10 gears.

[Riverholic]

Hey bassin' what is the change in fuel milage with the new gears? Also are you happy with the swap? I am running 37" tires and noticed that when I went to the 37's the tranny temp went from 190 to 205-210. That's why I thought that changing the gears would bring the temp down a little. Thanks!

[BassinRVer]

I did not notice a change in MPG or tempature differences when I made the change. I still get crappy mileage, most likely from a heavy right foot.

[motovet]

Rob, those 4.10's still gonna make the Montana gig?

[BassinRVer]

Motovet,
I will not be able to make it this time. I just switched jobs and I have no vacation time. Shoot me an e-mail, I need to ask you something - ConnerRJ@c-b.com