A friend of mine is getting ready to buy a new F-150 and they offer 3.55,3.73, and 4.10 non limited slip axle and they also offer them in limited slip. They come standard with a 3.55 non limited slip axle. Could someone please explain the differences in these different axles. Anything other than a 3.55 is $300 more.
Which does he want? If he's not towing very much weight (under 5,000 lb.) or not towing very often, get the 3.55 If he's towing moderate weight (5,000-7500) get the 3.73, and retain some fuel savings over a 4.10. If he's towing heavy (7500-9500, or whatever is max for that truck) get the 4.10. If he's thinking of bigger tires, get the 4.10. The limited slip is a seperate issue, traction. It sends torque to the wheel with most traction, versus an open-differential which sends torque to the wheel with the least traction. Worth the cost if any driving offroad or in the snow is predicted. KB
The 4.10 is only available with the heavy suspension package, or 4x4. The 3.73 worked out good for me.
The lower gear (higher number) allows the engine to run at a higher RPM at a given road speed and, importantly, to gain RPM quicker when starting off. I other words, when you are driving 55 mph, the engine RPM will be higher with a 3.73 than with a 3.55, and evev higher with a 4.10. This higher engine speed lets the engine operate in it's power range, rather than 'lugging' at low RPM where it can't develop power. Starting from a standstill, the lower gear lets the engine rev quicker to it's power range and lets you get moving easier and quicker. Since the engine is running faster with lower gearing, it uses more fuel. "Lugging' (straining, or over working an engine at low RPM) will also cause an engine to use more fuel.
If you overload a 3.55 auto the trans can take up the slack but it will get hot. If you overload a 3.55 manual, and have to stop on a hill, you can really damage a clutch, in a smoky, stinky way.
