There are tons of threads on which gears, charts, and even calculators, but I am more curious to hear about those who regeared and do 75-80 on the highway.

I want to get truetracs front and rear, but i might as well regear. I currently have 33s and 3.73 gears, but want to move up to 35s. I live on the coast so its relatively flat, but I tow 2 jetskis and a 5x10 utility trailer now and then. I think 4.10 is almost useless to regear, but 4.56 would put me at 3k doing 80mph.

My question is who is running thier pentastar at 3k on the highway? I know the Rubicon with stock tires run almost 3k at 80mph.

Also anyone running 33s with 4.56?

I read somewhere that the pentastar's oil pump doesn't raise the pressure until 3500 rpm, so whats the highest rpm you can run on the highway without adverse effects?

 

There is a recent thread out there in which I commented on both my 2013 with 4.56s and my 2014 with 4.10s. Same 34" Duratracs. In summary, the 4.56s and the 34s were great. yes it ran right at 3K RPMs at 80mph. No issues with it at all. I really liked it. The 4.10s are adequate on my new one, but given the choice, I would pick the 4.56s. Now, 33s and 4.56s? I would say no way.

 

I did see your post on the other thread and even participated in it. Just trying to gather more data on engine longevity with running the motor above 3k. Why would you not run 4.56 with 33s, the RPM would only be 200 more than the rubicon with stock tires or 35s with 4.56. It would not be permanent, just until I upgrade to bigger tires (mostly likely the Duratracs).

Stock tires(31") with 4.10s is 2951rpm @ 80mph
33s(32") with 4.56 is 3179rpm @ 80 mph
35s(34") with 4.56 is 3k @ 80mph

 

Driving on the highway with hills at 75 I felt 4.56 was too much gear for 35's. I think it's perfect for me with 37's.

 

What do you mean by feels too much? You did not like the RPM that high, I noticed there is little difference in engine tone from 2500-3k.

Edit: I also noticed you have a 6 speed so your 6th gear would put you at an even lower RPM then those with the 5 speed.

 

I could stay in 6th at 75 going up a 10% grade. I would hit 6th at about 55 mph. I was at about 3k rpm in 6th at 75. Too much gear for my needs.

 

How were you at 3K doing 75 in 6th gear with 35s, did they measure 31"? If that were the case I could see how you would say it was too much gear, but based on the calculations you should have been around 2670rpm @75MPH in 6th gear. At 80mph you should only be around 2850rpm.

 

You also start reaching and exceeding the upper rpm limits of driveshafts. Most shafts max around 3000 rpm constant speed (partly because most aren't balanced past that). Some of the max is determined by driveline angle - the more angle, the lower the max constant speed. Rough math at 3000 rpm, is driveshaft spinning 3500 rpm.

 

may have been somewhere closer to 2700-2800. Closer to 3000 than 2400 where it cruises comfortably now at 75. Regardless 4.56 is way too much gear for 33's

If you move to 35's and tow regularly 4.56 will be fine. But I wouldn't touch the gears until you go bigger.

 

Does anyone have any information or data on continuously running the pentastar at 3000-3200 RPM?

The torque curve does not really flatten out until 2000 RPM and stays pretty flat up until 4000 rpm. I know modern engines are made to rev much higher and can sustain higher revs, like I said previously I read the pentastar oil pump does not even boost the pressure until 3500 rpm. I am not so concerned about MPG as anything over 65 the wind resistance is really what kills mileage. Changing tires from stock to 33s dropped my MPG about .5 then, the lift dropped it another .5mpg. Speed was the most determining factor not RPM.