3rd gear and 4800RPM up hills.

[spenc938]

I have a 1998 2wd 2.5L 5SPD regular cab long bed ranger with the 3.73 rear end and 31 *10.5 tires. This is how I bought it, so I'm not sure what it was like with the stock tires, but how it is now it is incapable of getting up hills at anywhere near freeway speeds. Even slight grades on the freeway I have to downshift and slow down to about 60. Top speed (with maybe a slight tailwind ) is 75ish.

Now my question... IS this normal? Yeah it's a small, old motor trying to turn big tires, having to push a brick through the wind, but still... That brick only weighs 3000 lbs. I'm thinking about regearing if those on this board with more intelligence than I have think it will help. Is a 4.10 short enough? I don't want to destroy the gas mileage, but getting the truck so it's able to move is worth a hit at the pump. Travelling between home and anywhere outside of the valley I live in requires going through a canyon and going 40 at WOT with everyone else cruising by at 75 is a little pathetic.

One other thing I've noticed on my ultragauge is that when I am WOT trying to get up a hill the truck goes into open loop and stays that way until a few minutes after I let off . I'm pretty sure it shouldn't be doing this, and I'm thinking that it may have a small part to play in my problem above. And fyi, there are no check engine codes, pending or otherwise. I did have a pending code for a few minutes about a month ago but I can't remember what it was... I googled around and it had something to do with either the crankshaft position sensor or camshaft position sensor. Sorry, I can't remember which. But the light never came on and the pending code was only there for less than a day so I didn't think much of it.

Thanks in advance for any advice. If there is anything I left out or wasn't clear on, let me know.

Edit: I just went and checked the door tag to see what the stock tires were... 205/75r14. So it started with a 26" x 8" tire and now it has 31" x 10.5". This thing practically had bicycle tires on it.

Edit again: The below calculator says I need a 4.45 rear end ratio to get back to the stock actual ratio. Is there even anything available between the 4.10 and the 4.56? Because 4.56 seems awfully low.

 

[adsm08]

First lets address the WOT/OL issue. That is normal. When it hits a certain throttle position it goes into open loop, which basically means it starts ignoring the oxygen sensor and dumps fuel based only on the MAF input.

Now, next thing. I agree, the math suggests that a 4-cyl with 3.73 gears and 31" tires should be a dog, but are you sure the speedometer is accurate? Tire changes can mess with the speedo, if it hasn't been corrected the gauge is lying about how fast you are actually going. Verify your speedometer reading.

As for gears, 4.56 is not too terribly different from 4.45. It is certainly closer to the needed ratio than 4.10, and I would not want to drive a 4-banger with anything higher than 4.56. Lugging the engine that bad isn't helping you at the pump any either. 4 cylinder engines are meant to spin.

 

[spenc938]

First lets address the WOT/OL issue. That is normal. When it hits a certain throttle position it goes into open loop, which basically means it starts ignoring the oxygen sensor and dumps fuel based only on the MAF input.

Oh ok. That's good to know.

Now, next thing. I agree, the math suggests that a 4-cyl with 3.73 gears and 31" tires should be a dog, but are you sure the speedometer is accurate? Tire changes can mess with the speedo, if it hasn't been corrected the gauge is lying about how fast you are actually going. Verify your speedometer reading.

As for gears, 4.56 is not too terribly different from 4.45. It is certainly closer to the needed ratio than 4.10, and I would not want to drive a 4-banger with anything higher than 4.56. Lugging the engine that bad isn't helping you at the pump any either. 4 cylinder engines are meant to spin.

No, the speedometer is not correct. But my Ultragauge is accurate to about 1% (tested and calibrated with a GPS and a smartphone) and that's what I look at. The speedometer is WAY off, and not only that but the percentage that it's off by varies wildly.

So, what do you think would be better? Is 4.10 short enough? That would be the easier and cheaper route because I can get a junkyard axle assembly and then sell the old axle. 4.56 I would have to pay someone to install...

 

[adsm08]

4.10 will be better than what you have now, that's for sure. I used to have a 2.2L S-10 with 215/75/15 MT and 4.11 gears. It about matched my V6 Ranger with 3.45s and the same tires. I then put 3.73 gears in the Ranger.

Given my experience there which is about as close as I have for 1st hand, you will be happier with 4.56 gears.

 

[spenc938]

hmm. How bad do you think the gas mileage hit will be? The motor will be spinning a WHOLE lot faster, but it should also not be working quite as hard, so I don't know if that helps...

 

[adsm08]

I'm not nearly as familiar with the specific operating characteristics of the 4-cyl Ranger engines as I am with the V6's, so all I can do is generalize here.

The 2.9L hits max fuel economy around 2600 RPM, a smaller engine with fewer cylinders will generally peak higher in the RPM range. So you may actually see an improvement. And the engine shouldn't be spinning that much faster. There isn't really a huge difference between 3.73 and 4.10.

 

[spenc938]

Oh ok. I was thinking more with the 4.56. Theoretically (not accounting for the extra weight of the bigger tires) It should put me pretty close too stock mileage.

But, the 4.56 would be dependent on finding someone I could afford to put it in for me.

 

[adsm08]

Yeah, gears are expensive to get setup.

 

[scotts90ranger]

I ran 4.10's and 31's for a long time on my truck, did ok but 5th was somewhat useless at anything under 60 unless it was completely flat ground... It was livable though and my 2.3L was somewhat tired and your 2.5L is rated a bit better than a '89 2.3L was. That said, 3.73 to 4.10 isn't a big jump, if you are going to do it might as well do it once. Where are you located? Someone around here might have a suggestion on where to go...

 

[spenc938]

I ran 4.10's and 31's for a long time on my truck, did ok but 5th was somewhat useless at anything under 60 unless it was completely flat ground... It was livable though and my 2.3L was somewhat tired and your 2.5L is rated a bit better than a '89 2.3L was. That said, 3.73 to 4.10 isn't a big jump, if you are going to do it might as well do it once. Where are you located? Someone around here might have a suggestion on where to go...

I'm in Northern Utah, a town called Logan. But I travel between here and salt lake city fairly often.

Edit: jeez, the 4.56 ring and pinion sets are considerably more expensive.

 

[scotts90ranger]

not when you go HERE

 

[spenc938]

not when you go HERE

Thanks. bookmarked.

 

[Sunk]

I'd go 4.56 if you want to keep your tires. I have a similar truck with 4.10s and 225/75s and it's still gutless.

 

[scotts90ranger]

If you lose the link, just scroll up from here and hit the "Parts" button and attempt to apply logic from there

If you think that's low, my little Geo Tracker has 5.13:1 gears from the factory and came with little 205 75 15 tires on it, that's like 3500rpm or so at 75mph... but it gets 27ish MPG doing that...