i changed from the stock 185 80R 13's on my 84 2m4 to 215 55R 16's from a grand am (about 1/2 inch taller). will this make my VSS malfunction and the ECM give off a code 24?

longjonsilver

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Im the original owner of a white 84 2M4 purchased Dec 10, 1983. "It is better to remain quiet and have people think you are a fool, than to speak and remove all doubt" - Abe Lincoln

It shouldn't affect the ecm but your speedometer will be showing a slower than actual speed.

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so can i assume that i should replace the VSS? thanx

longjonsilver

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Im the original owner of a white 84 2M4 purchased Dec 10, 1983. "It is better to remain quiet and have people think you are a fool, than to speak and remove all doubt" - Abe Lincoln

You dont have to change the VSS, you have to change the gear that turns it. This is called the driven gear. They are usually color coded by the number of teeth they have or have the number stamped on them. I dont have experience in this with Fiero trannys but I have done this to a TH700R4. I changed transmissions from a car with a different gear set and I had to change the driven gear. If the ratio change or tire size is dramatically different then you will probably have to change the drive gear located on the trans output shaft. If the change is small like in your case, you can probably get away with just changing the driven gear as they are nylon and there is some slop built into the way they mesh. I went to a local tranny shop and thay had the gear i needed. I would try a tranny shop, they should be able to help you.

I don't know why people have such a big concern with having a perfect speedometer reading when changing tires. With most changes you won't have more than 1-5 MPH difference (unless you put 28" slicks!). As long as you know that difference why bother changing gears and tranny stuff? What it will give you? Anyway it will still have some error. GMs speedos are the most accurate (R&T or Car Driver test) but still not perfect. If speed limit is 25MPH and your error is 2MPH then you add or subtract that according to your error. Just my opinion

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Alex4mula
:) 3.4 Red Original Owner
& NO2 Yellow F/X (:

common guys, im trying to solve the code 24, VSS, and i couldnt care less if my speedo is off a little bit - i can calculate the error in any case like you have suggested, but what i really need is to solve my code 24 - can i drive with a code 24 and for how long before damage????????

longjonsilver

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Im the original owner of a white 84 2M4 purchased Dec 10, 1983. "It is better to remain quiet and have people think you are a fool, than to speak and remove all doubt" - Abe Lincoln

The VSS, ECM, etc don't know/care anything about what tires are on it. (Other than the fact they won't be reading the actual speed of the car...)

If the speedometer is working, and you are getting a 24, then the problem is likely the dash or the ECM. The VSS feeds the dash. the dash divides the VSS by 2 and feeds that signal out to the ECM. (VSS = 4000 pulses per mile, ECM is fed 2000ppm.)

You can verify the VSS feed to the ECM with an ECM scanner.

You can use the miata net calculator to figure the error caused by the tires.... (link is in my cave.) A couple % error isn't to big a deal but a large error can be.

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11-Sept-01, The day the world as we knew it ended.

Sorry but from your post it was not clear that you were getting a code 24. If that's the case then theogre directed you.