Viridian

Okay, I have a '02 GT automatic, 4.10s, and a Predator tuner.

I'm running the factory HP tune right now with some modified parameters. I went to change the axle ratio to 4.10 the other day to correct the speedometer, but it doesn't seem to have worked.

I've read some other threads on here about some people having the same problems, but what corrected it? I already tried reinstalling the stock tune and trying the new settings over, but I'm still off by quite a bit. It reads 45 when going 35, 55 when going 45, 67 when going 55, etc.

Any suggestions?

StangMan04

ditch the predator and get a xcal, xcal>predator. you cna change ALOT more things with the xcal. if u want a xcal hit me up I have one. I have had no problems in my 04 Auto GT with it.

BicketyBam

Crap - and I'm the bum who sold you that Predator

That is really weird. It worked when I corrected mine to my 3.90's. Are you sure that once you modified the parameters that it was saved (as opposed to backing out of the menu)? Anything that you change in the performance tune will have a * next to it. Check that out.

Viridian

Ed, I'm really happy with the tuner so far. I've made a whole bunch of other changes that have taken effect already, and I've watched them all flash the computer successfully.

I did some more research on Stangnet, and evidently when you only run the factory HP tune, it's unable to correct the speedometer. If you actually install the pre-loaded Diablo tune, it will work with new gears. As of last October, they said they would correct this problem with a future update. I know that updates 50a, 50b, and 50c haven't been successful, but I noticed they were up to 50d. I haven't checked my predator to see if it's the most recent version, but it's worth a shot.

I don't really want to run the Diablo performance tune with gas prices the way they are. I'm sure with some more research, I could find a way to retard the timing to run 89 octane gas instead of 93, but it's a lot circumventing for a simple problem like a speedometer change.

04BlueGT

If you're worried about gas prices, why did you put in the 4.10s? If you don't tune it, you'll regret it. Buy the gas and enjoy it. Higher octane fuel gets better gas milage, so it will even out or you'll actually get better milage. My '04 is supposed to run 87, but I buy 93 anyway. My milage improved, so it offset the cost increase.

nanaki

ummm.. buying higher octane won't improve your mileage. just a waste of money. getting 4.10s won't ruin your gas mileage either.

Viridian

That's what I thought. I heard that running 93 without advanced timing will gum up your engine over time. I do most of my driving in town, and I haven't noticed much of a change in mileage in that rpm range.

Anyway, we have three options here at the gas station: 87, 89 (with 10% ethanol), and 91. 89 is the cheapest, 87 is $.10 more than 89, and 91 is $.20 more than 89. I put 89 in my car, and it runs fine.

04BlueGT

I've read the reports, too, and I get better mileage on 93 vs. 87. And I didn't say 4.10 would ruin your mileage.

However, do the math. A higher gear ratio will require the motor to turn at higher rpms to maintain the same speed. In city driving, there will be little noticeable difference, as you can simply go up a gear, but driving the interstates will lower mileage.

Do what you will.

Viridian

Well, Diablo Sport has been very good to me. They offered to give me a custom tune free of charge to correct this whole thing.

Now I just have to figure out who to talk to about getting my custom tune...

mustangrob

Hey Viridian. I had the same problem when I installed 4.10s in my 04 gt auto. The only way the speedo error was corrected was when I installed the predator tune and 4.10 axle ratio tune. Just go ahead and install the predator tune, it will correct your speedo error and give you a nice boost in power.