Rear-End Differential Ratio. - Ford Mustang Forum

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post #1 of 1 (permalink) Old 07-10-2005 Thread Starter
yorgie's Avatar
Joined: May 2005
Location: Racine
Posts: 60
Rear-End Differential Ratio.

Hi everyone, I've recently joined and have been reading the tech for a couple of weeks now and have seen at least [and I'm not done yet] 3 or more queries on how to determine the "ratio" of the rear end. Here's a rock solid method if your tag is missing from the rear-end access plate or you think it's been changed and you don't know what it is. On an open differential,...jack up one side of the rear of the car on level ground [jack stand for safety], put the car in neutral, turn the wheel so the tire valves's at 12 o'clock, mark the drive shaft with chalk or white-out and turn the wheel all the way around to 12 o'clock again while counting how many turns the drive shaft takes making believe the mark is the hand of a clock. If you get approx. 3 and 3/4 turns, you have a 3:73-1 ratio, 4 turns and 6 minutes, you have a 4:10-1 ratio, etc., etc. If you have a locked rear-end jack up both sides and both wheels must turn the same. The pinion is a direct connection to the ring gear and this method is for them only and has no bearing on transmission ratios for the different ratios you see in the manual for shifting.

'95, white convertable, auto trans, under drive pulley, cai, 3:73 gear. Just enough snap for a 62 year old kid! (my wife's a blond so the top MUST be down, or she won't get in!!)
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