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I6 and 3000rpm cruise, any one live this life?

M

Mike H.

NAXJA Forum User
Location
phoenix az
situation... XJ, I6, ax-15, 4.56's and 31's...
Doing gears next week, and, had convinced myself that 4.56's were the way to go.
Had some folks question it, and ever since I've not been so confident.

What are folks opinions on 3000rpm cruise at 70mph with the I6.
 
I have an auto but it runs around 2900 at 75. Works great for me!

Much better than the lugging and hunting it did before.

Glen
 
Well, for me, 70mph is about 2600 with 4.56's and 35's, aw-4, and the jeep has no problems holdig 3k (which is about 80 or so for me). I say go for it, but I'm no expert, although I don't know if i'd reccomend 4.56's for 31's unless its just an around town, see no highway, trail mostly sorta jeep.
 
All day long, 1,000 miles at a time to Moab, JV etc. Even on the new stroker.

On straight road, I can cruise at 3100+ in the newish stroker. At a more modest 2800, I get 18 MPG, loaded, on flat ground.

Mike H. said:
situation... XJ, I6, ax-15, 4.56's and 31's...
Doing gears next week, and, had convinced myself that 4.56's were the way to go.
Had some folks question it, and ever since I've not been so confident.

What are folks opinions on 3000rpm cruise at 70mph with the I6.
Click to expand...
 
well thats probably too much gear for 31's. but you can always adjust the size of your tires to match the ratio. seems to me 3k rpm is high for the 4.0, as far as wear and tear, plus it is hard on gas mileage. 33's should be a good choice for 4.56, kind of depends on what brand of tire you get. which reminds me, why the hell can't tire companies just make the tires to be the advertised size? good thing they don't make bolts...
 
flexjay87 said:
seems to me 3k rpm is high for the 4.0, as far as wear and tear, plus it is hard on gas mileage.
Click to expand...

Why do you say this? The 4.0 is a short stroke motor, it is quite happy at high RPM, more so if you do some induction improvements.
 
don't fear 3k rpms for long periods.
 
I'll run 3K all day interstate or not.

Here's a real chart those of us with low gears have made and swear by even on the interstate.

Stock tires--4.10
31's--------4.56
32's--------4.56
33's--------4.88 My old setup
34's--------5.13
35's--------5.38 My new setup (4.88's and 35's suck)

Yes I have K&N FIPK, bored TB, Bosh 4 prong, wires, Banks header, full welded in exhaust.
 
I run 3000 rpms around 100 mph. I run 2300 rpms around 75 mph.

This is with the aw4, stock gears, and 29" diameter tires. I also installed a different speedo gear, so the numbers are fairly accurate.

I agree with Crash. The 4.0 is ok running 3000 rpms. The 4.0 makes excellent power at all rpms, but I wouldn't lug it below 1500 rpm or race it above 4000 rpm for any extended period of time. 3000 rpm is almost right in the middle of these two spectrums so your fine. For my purposes I try and keep the rpms hovering around 2000 because thats where I get the best mileage.

As far as engine wear is concerned, I don't think it would make a lot of difference between 2000 and 3000 rpms. If it were me, id just change the oil a little sooner.
 
j99xj said:
I run 3000 rpms around 100 mph. I run 2300 rpms around 75 mph.
Click to expand...


That must suck cause I know with 4.56s and 33s you are geard about 8% lower than stock and with that setup you'll run 2700 rpms at 70.
 
33's and 4:56 and leaving all my jeepin friends in the dust. Everyone tells me to slow down and the jeep is happy on cruise. 2800 RPM 80 MPH
 
I have 4:10's, 32" tires,and a 5 speed, he runs 2500 rpm at 70 mph in 5th and 3200 in 4th which is giving me 18 mpg. I would have to go up to a 33' tire before I went 4:56's. It seems to have all the power I need.
 
33's and 4.88's 2800 rpm all day long keeping up with traffic on the freeway.
 
ZachMan said:
That must suck cause I know with 4.56s and 33s you are geard about 8% lower than stock and with that setup you'll run 2700 rpms at 70.
Click to expand...

My performance is great. Even with the stock gearing and slightly bigger tires (29s). My 99 xj came stock with the good flowing heads (0630 model) AND the curved intake manifold. Most jeeps have either the crappy emissions heads (0331) with the new intake, or the good heads with the old intake.

So my Jeep was ahead of the curve in terms of performance stock. I have added even more performance when I opened up the intake and exhaust.

Even though 3000 rpms at 100 mph in overdrive is pretty tall, it still performs great. There is plenty of gas pedal left at 75 mph for plenty of overtaking power. Off road my Jeep has plenty of torque even in 4 wheel high.

A lot of people would say that I should upgrade to 4.10 gears. I don't see the need. I can put more torque to the wheel in 3rd gear with 3.55s than I could with 4th gear and 4.10s. So if I need "4.10" like power I would simply more the shifter down a notch. And if push comes to shove I could kick it down to 2nd gear. My second gear lasts all the way to 70 mph or so at about 4800 rpms. But like I said, I would never race the engine like that for an extended period of time.
 
Last edited:
bigwhitey said:
I'll run 3K all day interstate or not.

Here's a real chart those of us with low gears have made and swear by even on the interstate.

Stock tires--4.10
.
Click to expand...

Just wondering...why would someone want to run a 4.10 ratio with stock tires for daily commuting? With 3.07 and stock tires i get around 20mpg in town and 25mpg on the highway at 70-75mph.
 
johnlv6 said:
Just wondering...why would someone want to run a 4.10 ratio with stock tires for daily commuting? With 3.07 and stock tires i get around 20mpg in town and 25mpg on the highway at 70-75mph.
Click to expand...

You won't know until you do it.
 
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