My 94 250 has 3.55's. It does not pull a hill very well at all. Has good power 1-3 but sometimes dropping down to 4th isn't enough. I do have 35" or 315's on it. I want to swap to 3.73 or 4.10's as I know it would help power, but drive the truck everyday and don't want to lose to much mpgs. What do you guys think?

 

Don't waste your time with 3.73's. With 35's I'd go with 4.10's

 

If the OP's truck has a 5.8L engine I would seriously consider 4.56s....

 

too late.return to stock tires if you want your economy.35" are performance and economy killers.
if you can live with the economy reduction of large meats,then consider 4.30 - 4.56 ring and pinion to restore the performance.

 

Yep. The MPG's are gone already. With those tires your only option is to get the power back. 4.56 gears are what you want.

 

It's a manual with the 5.8l. I am not trying to restore performance or mileage. I just want to know opinions on how much worse or better changing the gears would be. I am fine driving the truck as is as long as I don't row anything and the mileage does t seem too bad right now lol. I just want alittle more power but it's gonna be easier to do the gears.

 

4:10's will help some and are the easiest and cheapest to acquire, the JY's are full of them. Just buy a front diff assy and a complete rear end and you are set. 4:56's would be better for power but doubtful they will be a JY find and will cost considerably more. Either gears may actually improve your mileage because the engine isn't working as hard and not requiring as much fuel up to, say, 55MPH. After that, well, good luck!

 

What?!?!?!? How can everyone miss the logical mistake here. A gear change only effects the extreme high and extreme low, if you need more RPM to pull a hill you gear down in the transmission. A axle gear change may leave you in a higher gear in the transmission but you won't pull the hill any faster.


The only reason for a gear change like suggested would be if you've found that you're never going fast enough to get the engine in the high RPM range in OD gear, and/or you'd like to stay in OD on the hwy all the time and can't currently, and/or if you've found that low won't give enough grunt, and/or having to start in low vs. 1st too often is a pain in the ****.


However for the issue as described it sounds like what you need is engine work instead.

 

Well he SAID it ran good. "Has good power" is the exact quote. If it was said on the internet it has to be true, right?

 

I have changed gears in my mustangs and know the results. Just wondering what you guys thought on the 250. The truck runs great has plenty of power until I hit a hill in 4th or OD. I know that I want/ need more power but I am not messing with the motor until something is wrong with it. A gear change will be perfect with the bigger tires I just wasn't sure if I wanted 3.73's or 4.10s for 2 reasons.

 

Gears also affect the total mechanical advantage of the final drive combo(R&P, ring gear diameter, tire size), so lower gears will put more torque to the ground and improve performance across the board.

 

that's the most important factor when it comes to gears right there.the rpm differences between the ratios are just a small side effect compared to this statement.
(those who have done a gear swap in their truck/car know this very well.)

well if it's between 3.73 or 4.10 that's a very simply decision.the 4.10's win for two reasons.the 4.10's would be the bare min with large tires,plus it's a factory option.
3.73 isn't a factory option so no used axles to keep costs down like the 4.10.if you had to spend the $ on aftermarket parts anyway then you would go with at least 4.30 imho.

 

I've used this site to calculate tire/gear changes.
Gear Ratio Calculator
I'm currently working on changing from 3.55 to 4.10s to get the engine RPMs back up to stock. We'll have to see what difference it makes for power/economy.

 

Very unlikely to find a 4.10 TTB, but true, 4.10s would be the cheaper option as you can get a complete 4.10 10.25 easy and rather cheap.






If you want to change gears then change gears, IMO the same money put in the engine is a better use but to each their own. 4.10 vs. 3.73 is a minor difference that comes down to your driving style, uses, etc. Only advise I can offer there is said above by eakermeld and myself, that 4.10s would be cheaper, and rather might as well, as 3.55 vs. 3.73 isn't much either.

 

A what?


Ring gear diameter? All 10.25 ring gears are the same diameter whether 2.73s or 5.38s.


Yes a higher(numerically) gear ratio will take torque stress off the drivetrain in between the input shaft of the transmission and the pinion. However this isn't much of a concern with a ZF5 and 10.25 with 35s. Nor does the OP mention it as a reason.


Other then that as said it only effects final drive ratios at the top and bottom as mentioned. In between it only effects shift points.


Lower gears only "put more torque to the ground" in low, again, as mentioned. Do the math with the gears, it's not hard.


Recommendations would be different if the truck was an automatic, gear changes have more effect in automatics as they tend to be in(and have) higher gears using the converter more.


Wow that's a heck of a calculator, thanks for posting that.