I have a v6 and was planing on changing the rear gears from stock to 3.75 or 4.10. I was wondering if anybody had tried that already and if there was any difference in acceleration. also is 4.10 a little too much...

 

tons of us have. i have 3.73s in mine personally.

yes you accelerate quicker

 

sweet then i'll get started on it by the way is a tract control device necessary in this setup

 

The best to have would be a Detroit TrueTrac:
http://www.detroitlocker.com/DT.htm

This device will allow your Mustang to free wheel around corners, giving you the maximum cornering force, while still locking up within a fraction of a second upon slippage by one wheel. Quite an ingenious invention from about 30 years ago, they never really fully caught-on due to their initial high price (around $2,000 back then!). Now, at about $525, they are relatively cheap. Be sure to use the stock Ford rear-end fluid with this, WITHOUT a friction modifier. That would be the Synthetic 75W-140 fluid. Pricy at $20 per quart, but you only need two quarts. If you use a fluid with a friction modifier, it will exacerbate the TrueTrac Shuffle, a railroad type noise noticeable on slow-down. With the correct Ford Fluid, it is just a pleasant clack that let's you know its back there. Perhaps best of all, the thing never wears out, and is very strong.

 

I have the Truetrac/ 3.73 gears combo in my car. I am entirely thrilled with the improvement and how it works.

I have my diff filled with Royal Purple Max-Gear 75W-140. I've never heard the "Truetrac Shuffle" nor even the "clack" described by Gearhead. It's dead quiet back there except for the sound of both tires chirping when I'm nailing it

 

Hi Paul,
So the Royal Purple stuff has no Friction Modifier? If so, that sounds like it works better than the stock Ford Fluid. The TrueTrac Shuffle only happens when you are slowing down (negative load). I believe you are the first I know of who has never heard it.
Thanks, Brian.

 

thx for the info gear head this has really been helpful!!!