[vodadub]

I've noticed MANY 4 cylinders runnin' on BIG rubbers around here.

When I bought mine with the 33"x12.5"s , some told me the guy who mounted those was crazy. I know what they mean, and I've lived it, cuz the Jeep WON'T even reach 60mph on a highway! It's kinda frustrating. Not to mention on inclines!... 5th gear is USELESS!
... I'm not ranting 'bout the LOW though. () Jeep's got it going on LOW with no problem.


I would like to know what MODS u people have done to deal with this matter.

Smaller tires? Diff. ratios? Engine swaps? Forced induction?... other engine/drivetrain mods?


Cheers!

[TheRealOldjeep]

Lower gears will help, but so will reving the engine up where a 4cyl likes to live. I can pretty easily run 65-70 mph with 4:10's and 35" tires, but you have to be running 3500-4000 rpm - which is what a 4cyl likes to do.

[shaggyjim]

For the money the best thing you can do is to change your ring and pinion gear. The other thing is to not get in a hurry!

[vodadub]

Originally Posted by shaggyjim

For the money the best thing you can do is to change your ring and pinion gear. The other thing is to not get in a hurry!

Tranny or diff. ???

[TNG97]

Originally Posted by vodadub

Tranny or diff. ???

Your front and rear differentials

[shaggyjim]

Sorry Bro.... The ring and pinion gear is in your diff. If your running stock now you should have 4:10's and you can regain some of your power with a move to 4:88's I cant remember now if you can go into the 5's or not on a D30. By regearing your axles you will also move your engine higher into the powerband or higher RPM like Chuck said. You never know? You could get a set of junkyard axles and have them set up you could sell your 4:10's and recoup some of your cost.

[jonzjeepyj]

Your right shaggyjim, The Dana 30 up front wont hold anything larger then th 4.88's. It already has the largest carrier it can hold and the 4.88's are as tall as you can go if you want a matched set.

[GRN_BEAST95]

okay i got a 4 banger. i have a question. I looked at a ratio chart and im really confused. if im going 55 in 4th gear, im running at 2500 rpm. Now on the chart it looked like that was 4.56 gears but i always thought i had 4.10. can someone help clear up my confusion. Am i right or wrong about having 4.56's?

[jonzjeepyj]

There is no doubt that a 4.0 or a 4.2 is much better, let alone a V-8, but if your keeping your 2.5 there are a few low dollar mods you can do to give slight improvements. By far, the gear swap to 4.88's will be the best and put you back to stock power but there are arguments for this to.

To have someone swap out your gears is costly. With the cost of both gear sets and both install sets, it will run you 500-600 bucks in parts alone, with labor being between 250-350 per axle. It can easily add up to 1000-1300 to upgrade to 4.88's After its all done you have a very week Dana 35 with stock drum brakes to boot. The better option is to swap in a heaver axle with 4'88 gear ratios, the most common being a later model ford explorer which is a ford 8.8 axle. This not only gives you the benefit of upgrading your rear axle but you also switch to rear disc brakes. It is nearly a direct bolt on application with just relocating the spring perches. It also has the same wheel bolt pattern as your jeep being 5 on 4.5 so you can use your tires and rims.

There seems to be some arguments about the next few mods I'm going to tell you about. These I have personally done so I will give you my opinion.

1) Better air intake
2) More fuel
3) Better aspiration
4) Change to an electric colling fan

You can search and find out the how to's so I'll keep it simple

1) Remove the air restrictors in your air intake ans air cleaner box, and add an upgrade your Throttle Body to a 4.0L jeep TB. Also, bore out the intake to match the larger TB. This will allow for more air to be mixed for fuel burn.

2) Upgrade from stock 17lb injectors to Bosch/Ford design III 19lb injectors. It is a given fact that your ECU leans out your fuel delivery at higher RPM's By upgrading to the 19lb injectors, when you rev your 2.5 up where it likes to be in its power band , you will have more fuel to deliver. I can now pull through 5200 to 5500 RPM's without starving the motor for fuel. Before, it felt like my 2.5L didn't have any more to give after 3500 to 4000 RPM's

3) Open up your exhaust for better aspiration. A high flow cat and muffler will make a hugh difference for your engine to breath.

4) you can switch to an electric cooling fan. Remove your fan clutch and blade and install a thermostat controlled electric fan which will lighten up the drag/load on your 2.5L and free up 10-12 HP. A ford Taurus fan swap is the most popular swap with very little modifications to install.

All these can be found in your local U-Pull-It salvage yards at a relatively low cost.

Hope this helps,

John

[jonzjeepyj]

okay i got a 4 banger. i have a question. I looked at a ratio chart and I'm really
confused. if I'm going 55 in 4th gear, I'm running at 2500 rpm. Now on the chart it looked
like that was 4.56 gears but i always thought i had 4.10. can someone help clear up my
confusion. Am i right or wrong about having 4.56's?

This is you stock tire - 205/75R15 or 27" tall
You need to see what your doing RPM wise at 65 not 55 RPM's
What tire are you running?

This chart is an estimation of your engine's RPM while the transmission is in a 1:1 ratio at
65mph. A 1:1 ratio is the 4th gear on a 4-speed or 5-speed transmission.
Transmissions with five or more speeds will allow for lower RPMs than indicated
in the chart because they have overdrive.

here is a good link to use for you calculations....

Jeep Wrangler Gear Ratio Guide

[GRN_BEAST95]

im runniing over 3000 rpm while doing 65 in 4th gear

[ak_vaquero]

I have a 4banger with 33's, with the stock 3:73 gears it has been okay but its definately a struggle to keep up on the highway, as we speak its getting 4:88 gears, so I will tell you the difference soon!

[jonzjeepyj]

im runniing over 3000 rpm while doing 65 in 4th gear

With What Tire ?

205/75R/15's --- 27" tire --- 65Mph --- 4th gear --- 4.11's --- 3325 Rpm's
215/75R/15's --- 29" tire --- 65Mph --- 4th gear --- 4.11's --- 3095 Rpm's

There were 2 stock sizes for Jeep YJ's depending on Model

[jonzjeepyj]

ak_vaquero wrote: I have a 4banger with 33's, with the stock 3:73 gears it has been okay but
its definitely a struggle to keep up on the highway

What is your tranny? Not in your profile ? Auto or 5/Speed

All 2.5L 5/Speeds came "stock" with 4.11"s

[youngYJ95]

i have 3.73s and an auto so he must have an auto