CJ7nvrstk

How are the shift pints affected? Does it shift at a higher RPM much like installing a shift kit in old school slush box or what?

BTW, just got off the hypertech website and their programmer adjusts the shift points. I know there are several programers that just adjust for tire/gears so it would appear that one like the hypertech would make the difference but a simple one that only corrects for tire size and gears wouldn't do anything like that.

Now that makes sense.

Esspecially when combined with the power gains from the programmer as listed here http://www.hypertech.com/media/dynocharts/aa/52001_2007-2008%20jeep%20wrangler,%20chrysler%20pacifica,%202 0.pdf

Not to mention that I have read several posts on here of people that have only done the reflash for correct tire size and they posted that they had no performance gains.

Rattler

I founbd a couple people who will do it and will know

HappyCurmudgeon

Did these people you read posts from have standards? What you are saying makes perfect sense to me in that case. Simply changing the tire size in that instance wont do anything for performance. If they had automatics, then all i can say is I must have gotten lucky. I did not have a "reflash" to correct for my tire size. I used the AccuPro to manually set it, and i can say beyond any shadow of a doubt it made a HUGE difference in the way mine shifted and drove. Before i set the correct tire size it was stumbling badly, and i mean BADLY between second and third gear, especially on long grades, it couldnt decide which one it wanted to be in, it was upshifting and downshifting rapidly and erratically.

After setting the proper tire size, It GAINED leaps and bounds in the power department.
Now, I am NOT saying it increased my engines power, but it did effect the shift points to make the available power more useful when it was needed. Before the change, It seriously lacked power (or probably more correctly, lacked proper use of what it had) crossing the bridges near where i live. I cross those bridges 4 times each day, so I am very aware of the before/after effects of doing so. After the reprogramming, instead of having to drop it into second, it goes up and over without a whimper and isnt shifting up/down/up/down/up/down.

When I questioned the tech at the dealer about adjusting the tire size in the computer, he went into a long explanation of how the computer reads rpm, tire size, load on the transmission, wheel speed, etc. etc. and does the math and then tells the transmission when to shift. I do not know how the Hypertech handles all of that, I do not have one, and dont want one as for my use it would be a waste of money. Someone more familiar with that could answer your question far better than I.

Now, was the tech bullshitting me? Maybe, i wouldnt know if he was. I didnt get that read from him, he had nothing whatsoever to gain by it if he was. He didnt try to get me to make an appt or anything, and basically said it was wise to get the right tire size in the computer, and that was that. I dont know how that computer works in conjunction with the transmission beyond what i was told in that conversation. I am NO expert on that and make no claim to be, I was simply relaying the information as it was presented to me, so chose to believe whatever you will.


Bottom line for me, it was falling on it's face badly before i changed it. After the change it is back to where it was before i swapped the tires. Simple as that.

If for some reason it loses it's programming and goes back to default, i will be on the phone to get an Accupro back at my house as fast as possible.

deconstructionist

Well the tech was not BS'n ya entirely-- as stated the computer is programed to have the auto shift at point XXXXX, if you change either/or/both wheels/gears then the the ACTUAL speed and load is different than what the computer is reading....whether its now XXXX+yyy or XXXX-yyy

If you got the accupro then you're set-- it can/does correct for the programing...or maybe better put- overwrites the original data with the correct specs & parameters of the new combo.

I DO think he was BS'n ya' in saying that the computer "reads all the data" or however you put it...... I COULD be wrong but ABS sensors dont feed *Performance* data....only a on/off, yes/no, binary 1/2 combo if the wheel is spiining or not.........

RedneckJeep

I ain't seen anybody answer it yet, so here it is. The difference between 5.13 and 4.88 gears is 0.25.

HappyCurmudgeon

you could well be right about the ABS data, i dont know how that would factor in, unless an overspeed of one or two wheels was somehow a parameter of some cacculation in the black box?

All i do know for a fact out of all of it, is it shifts and drives 1000% better after setting the proper tire size, and if you changed tire size, i would recommend getting the right numbers in the computer.

HappyCurmudgeon

LMAO!

and, that, as they say, is all there is to that.





I didnt realise this was one of those stupid Algebra word questions, no wonder i nearly failed that damn class....

...to funny

chuck45

A big AMEN to that. Having the speedo recalibrated makes a huge difference. I bought the Hypertech speedo recalibrator and it worked great.

chuck45

What size tires are you running? If you've got 35's and they install 5.13's and not something else your rpm at 75 mph will be 2600.

If you truly don't trust the shop don't have themn do the work. You could ask them to show you the gears before installing. The box will have the ration on it and it is stamped into the gears too.

More on calibrating the speedo by changing the gear ratio and tire size in the computer. My wife hated driving the JK as it felt sluggish and aweful to her. After calibrating the speedo she said it drove better than stock. It makes a huge difference.