is it possible to add a sixth gear to my existing transmission or would i have to get a new one? i have a 5 speed manual, 4 cylinder, something like 2.5L engine, 97 cherokee. and im kinda new to this, so i'd have someone helping me with it. i just want to know if its possible and if it would better my high way mpg. and if adding a 6th gear isnt the way to go, could i change the gearing so i could cruise at a lower rpm at higher speeds?

 

you have a lot of learning to do. Now you cannot add a gear to a transmission. What size tires are you turning to want to lower you cruise rpm?

 

Unfortunately, without swapping the transmission (Which may or may not involve adapter plates and various shafts) you can't simply add a gear to the transmission.

If you're looking for mileage, or lower cruising RPM's, what you're after is gearing. For example, if you're rolling 4:15 gears, your cruising RPM in 5th will be around 3100-3800 (Estimating, may not be accurate) - The higher in gear you go - Example being 5:10 gears, the worse that will get.

So with higher number gears, you're getting worse fuel economy, but you're also getting a considerably more torquey response to the gas pedal - But you're also going to see a lower top speed (Which, on a Jeep isn't terribly important)

My suggestion would be, depending on the gears, lowering the ratio a bit. A lot of times you'll see AWD, fuel-economy minded cars (Such as the Toyota Matrix AWD) rocking something small like a 2:19 gear set, which has a low cruising RPM, as well as reasonable fuel economy.

 

A taller tire (not wider) will lower cruising rpm's.
But you will sacrifice acceleration.

 

You already have 6 gears.
5 forward.
1 reverse...... lol

 

An external overdrive might work, but your 4-cyl will probably bog-down making millage worse if you could shift into 6th.

 

Lower RPM does not always translate into better MPGs.

 

Lol even then the money you'd have to spend would completely nullify the gas savings.

 

www.addmesomemoregears.com

 

Are you sure it's a 4 cylinder?

 

X2 you're gonna use more fuel at 1,500rpm at 30-50% throttle vs 2,500rpm at 5-10% throttle.

 

Even with a transmission swap, or the expense and complexity of some other custom work, here's your better option:

For about the same money or less than what that project would cost you, go buy a used Honda Civic or Toyota Corolla, drive it, and save your XJ for wheeling on the weekends.

 

Well stated and true.

 

Also well stated and true.

 

Gear vendors has a overdrive unit that will double your gears.But for its price vs what little mileage you pick it up its not worth putting it in.Lets face it a jeep xj has the aerodynamic shape of a brick and its 4wd both kill mileage.My friends stock yj 4 cylinder 5 speed got 14mpg highway.Sad thing i have seen that kinda mileage out of a 1 ton 4x4 truck before.