Idiot question

Got a 99 XJ 4.0 AW4. Whats the best way to shift in town? Ive always left it in OD. I hear alot of people slide it into 3. Whats the diffrence? I know 3 only uses 3 gears. Does it shift diffrently? Will it eat up the tranny? Always wondered what they do.

Also, the older XJs had that tranny swich that you could set to power or comfort. Do the newer XJs have that (1999). Or is it built in somewhere.

In '99 there are no power or comfort buttons, its built into the engine.

No real need to use 3 unless you are around a lot of hills. It helps with engine braking and such.

Unless you are off road or in a low traction situation, you only use three transmission positions. Park, Drive, Reverse.

Follow the recommendations of your owners manual.

D - Drive
For all normal driving. Downshifts automatically as needed.

3
For driving in hilly areas, towing, and to have compression braking on hills, mud, or snow (and 4x4 trails).

I've found that when I'm driving 40-50 mph, my RPMs drop into the 1200-1800 range as I feel my AW4 slide into OD. It's a pain in the ass when I'm trying to accelerate on the highway. I lose all, and I mean all, torque! So I've started using only 3rd if I know I'm going to be at 40 to 50 mph on a particular road. My RPMs at that point are 1800-2300 (roughly). Is that bad? I was under the impression that if RPMs can stay around 2000+/-, it wears the engine less.

Am I wrong?

Would I be better off resetting my computer and driving like a madman as opposed to a granny so my tranny would not shift to OD so quickly as determined by my driving style?

Stock everything, 235/75r15 tires

rockjockphatts said:

I've found that when I'm driving 40-50 mph, my RPMs drop into the 1200-1800 range as I feel my AW4 slide into OD. It's a pain in the ass when I'm trying to accelerate on the highway. I lose all, and I mean all, torque! So I've started using only 3rd if I know I'm going to be at 40 to 50 mph on a particular road. My RPMs at that point are 1800-2300 (roughly). Is that bad? I was under the impression that if RPMs can stay around 2000+/-, it wears the engine less.

Am I wrong?




Would I be better off resetting my computer and driving like a madman as opposed to a granny so my tranny would not shift to OD so quickly as determined by my driving style?

Stock everything, 235/75r15 tires

Click to expand...

You are not really hurting much just eating a lot more gas

rockjockphatts said:

I've found that when I'm driving 40-50 mph, my RPMs drop into the 1200-1800 range as I feel my AW4 slide into OD. It's a pain in the ass when I'm trying to accelerate on the highway. I lose all, and I mean all, torque! So I've started using only 3rd if I know I'm going to be at 40 to 50 mph on a particular road. My RPMs at that point are 1800-2300 (roughly). Is that bad? I was under the impression that if RPMs can stay around 2000+/-, it wears the engine less.

Am I wrong?

Would I be better off resetting my computer and driving like a madman as opposed to a granny so my tranny would not shift to OD so quickly as determined by my driving style?

Stock everything, 235/75r15 tires

Click to expand...

actually your doing your motor/tranny a favor by driving like that. your motor will run more efficiently in the 1800-2500 rpm range where it makes the most power with the least amount of fuel. i've always gotten better gas mileage in my trucks by manually shifting in and out of overdrive to keep the engine rpm's in the 2k range then just putting it in od and run around town at 1200 rpm in 4th gear. it makes even my tweaked 350 sluggish and unresponsive so instead like i said i keep it in the 2k range and it reacts just like a tweaked out 350 should.

to put it this way the higher the gear your in makes your engine work harder at low rpm's. first gear at 1000 rpm's is like using a big lever to move a heavy object.....5th gear and 1000 rpm's is like using a toothpick to move a heavy object. something's gonna give eventually

as a side note i guess i should mention that that's been my experience with all the gm trucks i've owned but i see no reason why it shouldn't be the same with jeeps

I think it's pretty easy to test. Just hold the gas pedal at a steady position as you drive. If you downshift out of D (OD) into 3 and you speed up, you are improving your gas mileage. If you have to press down the gas pedal more to keep the same speed, you are decreasing gas mileage. My XJ does not have a mileage computer, but my other vehicles do. I have verified this with and without trailers. Whenever I've downshifted, even with a trailer load, instantaneous gas mileage goes way down.

Seems to be just a matter of comfort vs gas mileage.
I leave mine in D all the time, unless I'm towing up hill. Seems to work out fine for me.

shawnxj said:

actually your doing your motor/tranny a favor by driving like that. your motor will run more efficiently in the 1800-2500 rpm range where it makes the most power with the least amount of fuel. i've always gotten better gas mileage in my trucks by manually shifting in and out of overdrive to keep the engine rpm's in the 2k range then just putting it in od and run around town at 1200 rpm in 4th gear. it makes even my tweaked 350 sluggish and unresponsive so instead like i said i keep it in the 2k range and it reacts just like a tweaked out 350 should.

to put it this way the higher the gear your in makes your engine work harder at low rpm's. first gear at 1000 rpm's is like using a big lever to move a heavy object.....5th gear and 1000 rpm's is like using a toothpick to move a heavy object. something's gonna give eventually

as a side note i guess i should mention that that's been my experience with all the gm trucks i've owned but i see no reason why it shouldn't be the same with jeeps

Click to expand...

Actually, isn't that your TCC engaging...and if it is not disengaging when you try to accelerate, you might get that sluggish feeling...if you are at 40-50mph and you try to accelerate up to highway speeds...if you give it enough throttle, it should down shift to 3rd gear...

Forgot to add...others can chime in here, but isn't the 'kick down cable' from the throttle body down to the tranny adjustable? I was thinking it was...

I guess I was basing my decision to drive between 40 and 50 (not while trying to accelerate to faster speeds) on this like on go-jeep's site:

http://www.go.jeep-xj.info/HowtoSpeedoGears.htm

Though I am not regearing, I am trying to find myself in that range of RPM which will cause my engine not to lug or get bogged down becuase I know it's harder on my poor ol' 4L. It may or may not use more gas, I'm unsure. On one hand your RPMs will be higher-so more injector bursts of gas into each cylinder, but because the motor's turning 2000 times per minute instead of 1300, each firing requires less power produced to generate the energy needed to propel the vehicle. Thus, less gas is required for each cylinder's burn. There is, I'm sure, a break-even point where you'll burn more gas by running a lower gear, but I don't know what that is.

According to my graph (granted it's from my purchase brochure of my 98), at roughly 1200 RPM my 4L produces roughly 70 hp, at 2000, it's near 100 hp. More power available means the engine actually struggles less because it's working harder so the task is that much easier. That's how I look at it.