3.73 vs. 4.10 Gear Ratios

[Kelly Hayes]

What advanatges does one gear ratio over the other?

Better MPG?

Better acceleration?

Better top end speed?

Better towing?

 

[Michael Cacioppo]

Kelly, what is important is the effective gear ratio. Given the same size tires, there is more torque available to the ground with a larger numerical rear end ration 4.10 vs 3.73. Given the same tire size the engine revolves fewer revolutions per mile with the lower numerical ratio and thus usually better gas mileage. The Trac overall ratio between a 4.10 set up and the 3.73 set up is almost identical since the tire sizes are different ( smaller diameter on the 3.73's (235/60/16) than on the 4.10's (255/60/16).



So with the same size tires:



For Better MPG use 3.73

Better acceleration use 4.10

Better towing 4.10

Top speed could either be the 4.10 or 3.73 depending on the horsepower required to drive the vehicle at that rate. If there is enough HP to reach the maximum allowable engine RPM, then the 3.73's will have a higher top end (assuming no speed limiter). It is possible that the 4.10's to affect a higher top speed if the 3.73's can't generate enough torque to reach the RPM limit. In general, however, the lower numerical rear will have the higher top speed.



I had a 1956 studerbaker silver hawk. I had the same top speed in third or second gear. In third I ran out of HP to accelerate and in second I ran out of engine rpm.

 

[Johnny O]

Put another way, the driveshaft spins 3.73 times for every 1 revolution of the tires or 4.1 times for every 1 revolution. But with the vehicle on the ground, then tire diameter enters into the equation. So you can see a 4.10 gearset exerts more leverage (torque) to the wheels, just like a lower gear on a bicycle.

 

[Tom Schindler]

Do a search on the MPG log. The 4.10 differential and the 3.73 differential show about the same MPG and in some cases, the 4.10 does better in MPG.





Tom

 

[Richard L]

I have had two Sport Tracs. The first one with the 3.73 and my current one with the 4.10.



With the 4.10 there is a noticable improvement in accelleration and pulling power. There appears to be no significant or noticable difference in fuel mileage. If there is a mileage difference it's less than 1 MPG a gained and hard to prove it's caused by the axle ratio. You could catch an extra stop light and loose any mileage difference gained by the 3.73 axle.



I would recommend that anyone get the 4.10 axle since the performance improvement way out weights the almost insignificant MPG loss,



...Rich

 

[2]

Like Richard L I haved owned two STs, the first with 3.73 and the second with 4.10.



I agree with him about the performance difference. I tracked my milage on both and I consistently had 1 MPG better with the 4.10.

 

[Todd Z]

With your foot on the right place the 4.10 are easier on the engine to get the heavy truck moving. The difference on the top end rpm is only a couple of hundred rpms...

Get the 4.10's....

Todd Z

 

[Eduardo Bailey]

Which rear end do you have now? What are your plans, towing, long hauls, hills? Do you have 2 or 4 wd? Will you be in snow or not? I discovered that the 4.10 needs good tires for winter use. Let me know and perhaps I can add to the excellent advice here.



Ed

 

[Heather inOC]

How do you find out what you have?



-Heather in OC

 

[Todd Z]

Heather.



Look for the code number on the drivers door jamb...



The axle codes:



46 — 3.73 non-limited slip

42 — 4.10 non-limited slip

D4 — 3.73 limited slip

D2 — 4.10 limited slip

Todd Z