98 GT REAR AXLE RATIO, VERY CONFUSED

yellowgt98

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I'm not sure if I'm doing this correctly or wrong or if some previous owner swapped out the rear gears. I've been trying to determine the rear axle ratio on my 1998 GT. I raised the rear wheels off the ground marked the drive axle and the outside of the rear wheel rim. I rotated the rear wheel one complete turn and watched the axle for the number of rotations and the axle only rotated 1 and a little past 3/4 turns for one complete rotation of the wheel. I did this at least 5 times making new marks each time to see if something is wrong. If my calculations are correct. My rear axle is only about 1.90, is this correct or am I doing something wrong. The axle code on the door is ME but this does not even come close to my calculations. No wonder I can barely brake the tires free.
 

myk

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Did you look for the axle tag on the differential? It's been a long time since I've looked but I'm certain that the E in your door code represents a 3.27 ratio...

I have a 3.08. :rolleyes:

Also the ratio isn't necessarily why you can't do a burn out-the issue is how much torque your engine can produce. My '69 Charger with a 440 has a 2.73 axle ratio and it will smoke tires all day...
 

chris91

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Looking at the tag is basically useless unless you know for a fact the rear end hasnt been touched and with a Mustang that is pretty rare unless you buy a bone stock car and even then its kinda iffy. The way I have always done it and never had a problem deciphering is turn the tire 10 times and count how many times the driveshaft spins. 37 times = 3.73, 41 times 4.10 etc.
 

blackdemon007

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Sounds to me like you missed a rotation or two on the driveshaft.

Go slow and check again - my guess would be they are still stock at 2.73
 

lwarrior1016

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If I remember correctly; the 98's, 5 speed cars got 2.73 stock and automatic cars g0t 3.08 stock. My car was an auto and it had 3.08 when it was stock.
 
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yellowgt98

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Mine is an automatic and I hope your correct about missing a rotation, but I checked this at least 5 different times. I will check it again I'm very confused about all this. Thanks for the suggestions.
 
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yellowgt98

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O.K. Now it's 10 times I've checked it. I rotate the drivers side tire, one complete turn while watching the drive shaft rotate ONLY 1 complete turn and a little past 3/4 turn, so only 1.85 about. the driveshaft never completes 2 rotations for the wheels one rotation. I do not understand this at all. Is it possible to have a gear ratio like that installed. I'm not sure why anyone would want that type of gear. Any other ideas.
 
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yellowgt98

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I was just wondering if I did rotate the wheel twice, it would come out to around 3.27, but I would have to rotate it twice. Could that be possible, that I have to rotate it twice. Makes no sense to me.
 

RichV

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Leave one wheel on the ground, or have a buddy hold it still. Then do it again.
 
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yellowgt98

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O.K. Chris91, I did it your way. 10 complete turns of the wheel and count the complete turns of the axle, the axle turned 16 complete turns and about 1/4 more for the 10 complete turns of the wheel. That still give me about a 1.62 gear ratio. So I'm still very confused. I know that axle ratio is not anything that is standard and I just can't believe someone changed the gearing to that number.
 
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yellowgt98

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Rich, How is holding the other wheel going to help???. I haven't done it that way..
 

RichV

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That number is not even available. Stop one wheel from spinning.
 
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yellowgt98

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O.K. I just got out from under the car again with one wheel down and one wheel off the ground and the rotation was the same as before. I appreciate all the suggestions, but I think it's trans shop time. I was trying to figure out the ratio cause I was planning on installing a 3.73 gear, but now I have to find out what size gear is in this car. I've done this rotation thing many times before and have never found results like this. All I can figure is someone before I bought the car had the gear changed maybe trying to get better mileage. Thanks again
 
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yellowgt98

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The trans shop installs rear axles and gears, I know the trans has nothing to do with the axle gearing.
 

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