Speedo is off...could I have upgraded gears?

FireMedic90 · May 29, 2009

Hi guys. I've been away awhile since I sold my 2005 GT, but I recently bought a 97 GT and on the trip home, I noticed something.

I was following my wife home and thought she was going pretty fast. I called her and asked her why she was doing 90. She said she was only doing 75. The tires are all 275/40R17's. But 1st gear also seems pretty short. Is it possible that the previous owner put some gears in this car? Is there any way to tell?

Thanks and good to be back!

squeak93 · May 29, 2009

Jack up the rear, turn the wheels 1 revolution and count how many times the d/s turns. That will tell you.

Good chance you have gears and they didn't put the speedo gear in.

FireMedic90 · May 29, 2009

squeak93 said:
Jack up the rear, turn the wheels 1 revolution and count how many times the d/s turns. That will tell you.

Good chance you have gears and they didn't put the speedo gear in.

What will the 1 turn ratio be? If I turn the rear wheels 4 times then should the D/S turn 10 times for 4.10's? Or is that not how it works? Forgive my ignorance here...

If it's the case that I DO have gears, is there a way to correct the speedo problem? Will a tuner do the trick or will it need to have the speedo gear inserted regardless of the tuner?

squeak93 · May 29, 2009

Your will be looking for ratio's like 3.27:1 3.73:1 4.10:1 4.30:1.... Stuff like that. And yes. YOu only need to figure out what ratio you have then call someone like Latemodelrestoration for the correct speedo gear. Real simple to swap.

squeak93 · May 29, 2009

Just re read ur ? there... If the wheel turns 1 time the d/s will turn 3 and 3/4 if u have 3.73s, little less for 3.55's or more for 4.10s or 4.30s.

FireMedic90 · May 29, 2009

squeak93 said:
Just re read ur ? there... If the wheel turns 1 time the d/s will turn 3 and 3/4 if u have 3.73s, little less for 3.55's or more for 4.10s or 4.30s.

Ok that makes sense. Thanks for the help!

d98gt · May 29, 2009

Likely have 3.73s but that will be my guess for now

FireMedic90 · May 29, 2009

d98gt said:
Likely have 3.73s but that will be my guess for now

If I could ask, what makes you think that?

d98gt · May 29, 2009

My car has been down for quite some time though I didn't replace my speedo gear and am going off of just memory--though I believe when driving 65-70, the speedo said 80 or in that area. I am basically just throwing out a guess

5 speed car? Any other mods that are visible/audible?

FireMedic90 · May 29, 2009

d98gt said:
My car has been down for quite some time though I didn't replace my speedo gear and am going off of just memory--though I believe when driving 65-70, the speedo said 80 or in that area. I am basically just throwing out a guess

5 speed car? Any other mods that are visible/audible?

Yea its a 5 speed. No other mods that I'm aware of. But I've only had it about 3 days. I'm about to put on a new tensioner pulley to replace the squeakin one I got. Bought it from here...

Spencer Performance Inc.

JPstealth · May 30, 2009

yea sounds like gears. I had the same problem when I bought my car. Even the previous owner had no idea and brought it to the dealer who then replaced the entire gauge cluster fools

With 4.10 i was about 10-15mph over about that speed so when it read 90 I was going about 75ish if my memory serves right. Your best bet is to do what was already said or buy yourself a tuner and play trial and error until the speedo reads right. A tuner is a good investment anyway if you plan on doing anything. I love my predator.

AUTOBAHN · May 30, 2009

You can't use a Tuner on a 97 GT to fix it. You either need the correct speedo gear or a speed cal.
Of course you need to figger out what gears you have first.

Mike

JPstealth · May 30, 2009

AUTOBAHN said:
You can't use a Tuner on a 97 GT to fix it. You either need the correct speedo gear or a speed cal.
Of course you need to figger out what gears you have first.

Mike

hmm, never knew that 99-04 FTW

FireMedic90 · May 30, 2009

Well 4.10's would definately explain why my gas mileage sucks! Even if it could be fixed with a tuner, I'd like to know whats in it.

But aside from the speedo, a tuner will work on a 97 right? I was thinking of one in the future. (lots of other stuff to do first!)

98bluevert · May 30, 2009

FireMedic90 said:
Well 4.10's would definately explain why my gas mileage sucks! Even if it could be fixed with a tuner, I'd like to know whats in it.

But aside from the speedo, a tuner will work on a 97 right? I was thinking of one in the future. (lots of other stuff to do first!)

yes a tuner will work on your car for tuning it. Just won't correct the speedo. you will need a speedcal for that.

squeak93 · Jun 1, 2009

You CAN'T tune a 97 with a handheld tuner. You need a speedo gear to correct it.

d98gt · Jun 1, 2009

I think squeak is over thinking it You can "tune" the car all you want with a programmer---just not correct the speedo as previously stated

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