Hey guys I am looking to swap out the rear 3.73 and put in a 4.10 to help with towing and better acceleration. I have heard that you need to change the front to match the back and I have also heard you don't. Can someone help me out with the logistics of this project? I have a 8.8 rear diff with 3.73. It's a 1996 mazda b4000 with the 4r55e transmission. So the biggest questions are is the 4.10 the best middle ground for towing and decent gas mileage and if not what should I put in it. I do want better than the 3.73. Second do I have to change the front. I only use the 4wd offroading or in snow so i'm never going faster than 20 mph. Thanks!

 

Yes, in a 4WD both front and rear ratios need to be the same or transfer case will break when you engage 4WD
Ratio changes the drive shaft rotation and transfer case is connected to BOTH driveshafts when in 4WD so speed wouldn't matter, transfer case would break pretty fast, 100 yards maybe, unless a drive shaft broke first

I can't image anyone saying you don't have to match ratios, you also have to run same diameter tires on the front and back of a 4WD if you want to use the 4WD part, same as ratio thing

4.10 is a common ratio with trailer packages, it allows better low end pulling power, but.........................
You have an automatic, so you already have a infinite ratio "gear" in the torque converter
So not sure you really need to change from a 3.73 to 4.10
If you were running 31+ inch tires then maybe