RPM on the highway - JeepForum.com

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post #1 of 16 Old 09-04-2011, 04:09 PM Thread Starter
wanabejeeper
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RPM on the highway

I'm thinking about regearing, whats a reasonable RPM while on the highway 65-70 mph with a 4.2 engine.


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It goes in that barrel you wheel out to the street once a week.

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post #2 of 16 Old 09-04-2011, 04:16 PM
oldtime_ironman
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Maybe its just me, but I've always tried to keep my cruise RPM's around 2500 no matter what kind of engine. That's why I'm so interested in the new 6-speeds. Low RPM's == longer life and better MPG's.

.
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post #3 of 16 Old 09-04-2011, 05:03 PM
Desert_Rampage
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^^ What Ironman said!

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post #4 of 16 Old 09-04-2011, 07:17 PM
mxmike480
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My 89 with 3.07s & P235/75s turns around 2100 @ 70mph.

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post #5 of 16 Old 09-04-2011, 07:26 PM
Yonco
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31 x 10.5 x 15's with stock 3.55's on my 4.0 run about 2500@ 65 mph. Which is where i keep it at when on the highway, or i run about 55 and take it easy. I couldnt even imagine having a closer ratio than this, i have enough power with these gears and its still high rpm on the highway.

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post #6 of 16 Old 09-04-2011, 07:32 PM
ClarkRCC
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My 90 has got the 4.2 ax15 and 3.07 with 31 10.50's and do 70 at 2000 rpm's and manage to pull 21 mpg

Just keep going till it sounds expensive
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post #7 of 16 Old 09-04-2011, 07:44 PM
notmyj
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Mine does 2200 at 65. 35's, 4.88, with an AW4 from an XJ.

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post #8 of 16 Old 09-04-2011, 08:10 PM Thread Starter
wanabejeeper
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So what I'm hearing is stick with the 3.07 gears even with my 33's? Wow just not what I would expect reading all the regear threads. How is your acceleration off the line? Wheeling performance is acceptable too?

87 YJ The Original!

Quote:
Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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post #9 of 16 Old 09-04-2011, 08:21 PM
oldtime_ironman
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Quote:
Originally Posted by wanabejeeper View Post
So what I'm hearing is stick with the 3.07 gears even with my 33's? Wow just not what I would expect reading all the regear threads. How is your acceleration off the line? Wheeling performance is acceptable too?
Even though I don't have one at the moment, I would imagine that the sheer torque from the 6-cylinder makes up for a lot of gears.

I would be more worried about eating up a lot of clutches with such a stiff gear ratio and engine torque.

.

Last edited by oldtime_ironman; 09-04-2011 at 08:24 PM. Reason: worries
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post #10 of 16 Old 09-05-2011, 03:21 AM
Tongie
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Quote:
Originally Posted by wanabejeeper View Post
So what I'm hearing is stick with the 3.07 gears even with my 33's? Wow just not what I would expect reading all the regear threads. How is your acceleration off the line? Wheeling performance is acceptable too?
I had 3:07 in my 4.0, 5 speed and when I went to 33 inch tires, it couldn't pull itself up a hill on the highway. Forget about and crawling or offroading. Went to 4:88's and couldn't be happier. Runs about 2500 rpm at 65 mph, 3000 rpm at 72 mph. Seems the 4.0 likes to run the best at 2500 rpm.
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post #11 of 16 Old 09-05-2011, 04:45 AM
Yonco
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When im on the trails i am in 4x4 low EVERYTIME. I am geared a little higher than you, but i can just crawl it at idle and it will climb up some really steep angles and i dont even have to gas it for more torque.

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post #12 of 16 Old 09-05-2011, 04:52 AM
badmax
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you do not want 3.07's with 33's.... it will be a dog.. i had 4.88's in my last jeep, it had an ax-15 & 33's. It turned 2500 at 65 mph. I would go no less than 4.56 gears. JMO and everyone has an opinion.
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post #13 of 16 Old 09-05-2011, 06:16 AM Thread Starter
wanabejeeper
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its interesting because the calculator i'm using http://www.grimmjeeper.com/gears.html shows my setup tf909, np203, 3.07 gears, turning 33's at 64mph at 2000 rpm mabe a tad low. going to 3.73's moves it to 53 at 2000 which is starting to get to high. Whats the final drive on that 5 speeed? I'll bet its less than the 1:1 I'll be using

Most of the rural roads near my house are 50-55 and I drive them at 60-65. Not to mention the higway.

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Quote:
Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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post #14 of 16 Old 09-05-2011, 06:48 AM
oldtime_ironman
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Quote:
Originally Posted by wanabejeeper View Post
its interesting because the calculator i'm using http://www.grimmjeeper.com/gears.html shows my setup tf909, np203, 3.07 gears, turning 33's at 64mph at 2000 rpm mabe a tad low. going to 3.73's moves it to 53 at 2000 which is starting to get to high. Whats the final drive on that 5 speeed? I'll bet its less than the 1:1 I'll be using

Most of the rural roads near my house are 50-55 and I drive them at 60-65. Not to mention the higway.
Final drive on the 5-speed is in the neighborhood of 0.72 to 1.

.
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post #15 of 16 Old 09-05-2011, 07:39 AM Thread Starter
wanabejeeper
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I'm thinking I could find a yj with a 30/35 combo with 3.54 gears and just bolt that in cheaper than re-gearing and have ust about the perfect setup for me.

87 YJ The Original!

Quote:
Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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