blue project

[QUOTE=planman;2802716]3.73s in 3rd gear results in the about the same rpm on the highway as with 5.38s in 4th gear.

As a result, some people find 3.73s fine with 33s and taller tires with an automatic as long as they turn the overdrive off at highway speeds.

In fact, with the OD turned off, 3.73s are more bearable on the highway with 33s or larger than 4.10s, 4.56s, or 4.88s.


I couldn't be more confused at this point. Wouldn't turing off the OD make the rpms higher? Everytime I drive on the highway I seem to be above 3200 anytime I need a little extra power. I overheated my trans a few times with these conditions during the summer. I do tow in the summer, so now I'm wondering what now. Are 4.56's going to make things better or worse???

IKE2011

So is there a ProCAl available for the 2011 JKs???? I read a thread stating that is where the buck stopped. I have an '11 and am planning on moving to 35s, and would like some compensation other than regearing. One for price and two it is my DD. I was thinking about a cold air intake kit too as there is some gains.
The O.D. button isn't a big deal. A lot of trucks and SUVs don't recommend towing in high gear anyway. For Blue Project, you may want to look at getting a transmission cooler installed. Thanks

blue project

To the best of my knowledge the procal is avalible. Tuners like superchips are not.

IKE2011

Does the ProCal trick the computer or is there an actual performance boost like the chips?

nthinuf

You were over 3k rpm because you were dropping out of OD (4th gear) into 3rd gear, or possibly 2nd?. The basic set of numbers are pretty easy to understand, just by plugging them into the charts already mentioned. Also as already mentioned, there is no one-size-fits-all answer, it just makes more sense to me to see the numbers.


Assuming your current setup is -
Auto, 3.73, 31" (guessing at the actual height of your stock 32'),
you get :
= 1953 rpm @ 70 mph

(If your tires are shorter, the rpms go up a bit. Taller, they go down. Faster, they go up. Slower, they go down. Right?)

To get OD Off, you divide the rpm by .69. (hills, winds, lack of power, whatever)
1953 / .69
= 2830 rpm @ 70

(3200 rpm? Your speed was up around 80ish?)

Swapping to 5.38's, with no tire change, gives you :
= 2817 rpm @ 70


So what he is saying is that, right now, with OD Off, you are running about the same rpms as 5.38's with OD On. Moving to a taller tire lowers the rpms at a given speed, so turning OD Off is one way to get the rpm's/hp/torque back up to a usable level until you get around to re-gearing.

nthinuf

It 'programs' the new tire height and/or gear ratio so the computer knows what you have, instead of still thinking you have the stock height and ratio. No tricking to it.

blue project

Tires are a true 31"s tall. Will be going to a 32.8 or so. I'm still so confused. Will a 4.56 ratio be better or worse on and of the highway with a 32.8 tire? What about towing?

nthinuf

That is the mfg's spec, right? What is the actual mounted height under vehicle weight? 31.5ish? 32" if they run tall? It's not magic, just plug in the numbers and see what you come up with.

Assuming 32", 4.56's give:
= 2313 rpm @ 70

2313 / .69
= 3352 rpm @ 70, with OD Off


So right off the bat, you will be running about 360 rpm higher at 70 than you are right now. Is that enough rpm/hp/torque to keep you in OD without downshifts? 4.88's will give higher cruising rpm's, and will keep you in OD even longer before downshifts. Which is right for you is something that only you can answer.


With 35's measuring right around 33.5", I swapped from 3.73 to 5.13, then went on to 5.38 when I swapped the front axle. Whether I am up in colorado or down in texas, I much prefer the mid 2k range for my freeway time.

IKE2011

Ok that is pretty good. I like the Flexibiity there, Thanks. I haven't researched it yet.

catahoula

Alright goofy question. I don't know it this has been answered before, but a local shop I stopped at said if you were to run the ProCal or the SuperChip to adjust for tires then change back to stock when you go into a dealership for maintenance they could read that something has been hooked up or adjusted and that would void the warranty. Is this true?