I have an 8.1 w/ 4.10's now. I have the chance to by a D-max, same year. I have a Rancho lift right now. What are the consequences (if any) of swapping out the front/rear diffs w/ the 4.10's into the D-Max?

I'm 95% sure its the same

Let me rephrase that.....

What would the 4.10 gears do to the D-Max as far as power and mileage?

I think 285's would get you closer to the 3.73's. Depends on your driving, too. I think you'd tend to notice a little less mpg if you were doing a lot of highway. Around town, I question whether you'd even notice the deeper gear...

More grunt down low, too. I wish my work truck had 4.10's.

Let me rephrase that.....

What would the 4.10 gears do to the D-Max as far as power and mileage?Assuming that they would fit, the 4.10 gears should give you 9.9% more torque at the wheels for any particular engine speed. Also, your speedometer will read approx 9.9% higher than actual truck speed with the stock 245 tires & wheels. Theoretically, your mileage would suffer, but that would depend on how heavy a load you tow and how fast you drive.

On another note, you could also install 305/70-17 tires & wheels and your truck speed would be around 60.7 mph when the speedometer reads 60.0 mph; so you would only need approx +1.16% speedo correction with those tires and 4.10 gears. (For only 1.16% I would probably leave it alone - right now my stock speedometer reads 1.6% high)

Hope this helps.:)

Unless you are going to run something in the neighborhood of a 35" tire I wouldn't waste your time.

Let me rephrase that.....

What would the 4.10 gears do to the D-Max as far as power and mileage?

They would reduce top speed and increase RPS at any given speed unless you got larger tires.

For refrence, the higher the differential gearing number, the LOWER the gear ratio, meaning it takes MORE engine reveloutions to turn the same amount of tire reveloutions.

Don't do it.

John

I would be removing the Rancho lift and both diffs (4.10) from my 8.1 and reinstalling all of that into the D-Max, then install the 3.73 diffs into the 8.1. My 8.1 has 295/75's right now, so that would be the tire I would be running.

I would be removing the Rancho lift and both diffs (4.10) from my 8.1 and reinstalling all of that into the D-Max, then install the 3.73 diffs into the 8.1. My 8.1 has 295/75's right now, so that would be the tire I would be running.

They would reduce top speed and increase RPS at any given speed unless you got larger tires.

For refrence, the higher the differential gearing number, the LOWER the gear ratio, meaning it takes MORE engine reveloutions to turn the same amount of tire reveloutions.

Don't do it.

John

If Higher RPM's is what you are after, by all means do it. No matter what else you have on it, changing the gear ratio changes engine RPM at the same given speed.

John

On Edit: The DMax Allison combo is designed to run with 3.73 diff gears.

I see no problems at all with the swap, the larger tires cancel out the lower gears, speedo may be close to same... may have to reflash PCM due to it seeing different speeds than it's programmed for.

I would be removing the Rancho lift and both diffs (4.10) from my 8.1 and reinstalling all of that into the D-Max, then install the 3.73 diffs into the 8.1. My 8.1 has 295/75's right now, so that would be the tire I would be running.


Since you are going to do all the work it would probably be easier to do it that way anyways. I would think that would be a great tire to gear ratio.

I would be removing the Rancho lift and both diffs (4.10) from my 8.1 and reinstalling all of that into the D-Max, then install the 3.73 diffs into the 8.1. My 8.1 has 295/75's right now, so that would be the tire I would be running.Assuming those tires are on 16" wheels, using them with the 4.10 gears will only slightly change your speedometer readings. That combination would mean that when the speedometer reads 60.0mph, actual speed will be 59.8mph: (0.33% slower). Most people would say it's right on. The ECM and ABS wouldn't sense the difference.

I know that other members here have installed 4.10 gears with bigger tires and they seem to be happy with their setup.

Keep in mind that most people eperience reduced MPG when they install a lift kit and bigger tires.

Let us know how you come out. :)

Thanks everybody for your input. We'll see if I can land this D-Max or not. I'll keep you posted.

Just make sure you check all the mounting brackets, pinion U-joint, etc., before you remove anything to make sure they will swap without any issues.

Good luck!:)