I own a 1998 base Dakota with the 2.5L engine with tire size P235/75 R15 and a gear ratio of 3.5 my question is this I want more power out of my truck yes it’s under powered I know will changing my gear ratio to a 4.10:1 help get me some power back at all or what other gear ratio can I use/get available on the market.

I have wanted taller tires also but think that will suck my power so not sure on that?

I use my truck mainly on the road city driving so I’m looking at city drivability and economy not off-roading but get as much power out of my small 2.5L engine.

Other suggestions are welcome

 

Well if you increase your tire size you will be "decreasing" your gear ratio. AKA you will run at a lower RPM. and increase your gear ratio won't add power it just makes you run through the RPM faster which puts you in your powerband faster and therefore making you accelerate fast. If I'm correct

 

Thanks that helps a bit but still confused on this subject

thanks URBANRDNECK

 

if there's a dyno sheet for the 2.5, that's what will help best. I've read that the best power/economy balance is if you gear so that a majority of your driving takes place just under the torque peak of the engine.

 

That sounds right I think I need to take it to a good tire shop or two or three and ask questions.

Thanks magnethead

Ever wonder why I use a big font on the forum Im as blind as a bat my eyes suck wish I could buy a new set of eyes.

 

per wikipedia

Throttle body injection (TBI) 117 hp (87 kW) at 5,000 135 lb·ft (183 N·m) at 3,500
Multi-point fuel injection (MPFI) 120 hp (89 kW) at 5,250 139 lb·ft (188 N·m) at 3,250

I can't see running at 29-3000 RPM all day. That said, the 3.55's can't be working in favor of the 4 cylinder. What are your RPM's right now at the speed you typically drive at? If your cruising RPM is 1600 RPM right now with the 3.55's, 4.10's would put you at 1850 RPM.

 

I dont have a tack just the stock light that flashes if over the top in rpm's or under saying shift idiot or engine will blow.

I dont think Im using to much rpm's as I drive just kind of sloggy boggy lets go truck feeling all to often I saw a chart here with suggestions on tire size gear ratio to power so I got to thinking maybe I can improve things!!!

Chart here http://www.jeep4x4center.com/jeep-ti...atio-chart.htm

So i came up with changing my gear ratio.

 

So on the scale my tire size is 29 my gear ratio is 3.55 that says economy so I want to slide the scale to the 4.11 that shows better power to wheels.

Is this scale Crap or right on?

This is something I have no knowledge about help help help me mister wizard I want to go Home.

 

that chart says it's at assumed 1:1 at 65 MPH. I think 4.11 is the best general best-of-both-worlds gear. That table says I should be in the 4.56 range, but I'm going to 4.10 just to keep a trace of fuel mileage.

 

Sounds good to me, that or the 3.91 ratio not sure thats available so I get some improvement dont want to over do it.


Thanks for the help magnethead