I just bought a 1999 GT. I am disappointed it doesn't have a posi rear end...I'm new to Mustangs. This summer, I want to have a posi unit installed and new gears. What are my factory gears now? What do you guys recommend? This is for a daily driver, I drive on the highway alot....just want to wake it up a bit..nothing too extreme. Also, any recommendations on a posi unit? How much can I expect to spend on all of this(parts and labor)? Also, will I notice better acceleration? Thanks

 

3.27 stock gears.

If you are an auto, most recommend 4.10's. Manual, most recommend 3.73's, but you can get 4.10's as well.

Because of the highway, Might want to think 3.73's if you are an auto, but most say 4.10's aren't that bad on the highway.

Also, FRPP Gears are highly recommended and installed by a professional. Cost of install varies from 200-500. Look around, but I personally wouldn't pay more than 300.

 

Stock gear ratio is 3.27...I would recommend some 4.10's even if you do a lot of highway drving. I got 4.10's and a blower, and its not that bad on gas ( as long as I stay out of boost ). Posi you can use Eaton, Detriot True-Trac, or a 03-04 cobra differential. All depends on your budget. Dont forget your axles as well. You are looking at a pretty penny for all of the parts and labor. More than 1K. I'm on the process of getting my rear end done. Spending about 1K in total. Parts and labor.

 

Your car has a posi stock, it could be worn though and just need a simple rebuild (40bucks in parts). If your not gonna drag race it on sticky tires then there is no need to upgrade the posi or axles. Just get the gear installer to do a rebuild of the stock posi which shouldnt cost much as its a very fast and simple job to do. Since your on the highway alot I would lean more towards 3.73's but if your gonna stay n/a 4.10's are really the gear of choice in a 2v GT like yours.

 

cant decide between 3.73s or 4.10s?

get 3.90s!

 

Do all 99 GT's come with the posi rear end from the factory? Or, was it an option? My car has the 1 wheel peel. I've never taken the cover off to inspect inside(just bought the car). If it does have a posi that is worn, what do I need to fix it...and how hard of a job?

 

Since you're going to have work done on the rear, Id go ahead and upgrade everything. Moser 31 spline axles with 03-04 cobra posi or Eaton. Id also buy the bearing kit that they sell here on americanmuscle.com

 

I believe every GT on the planet has a posi.

 

All GT's have the Trac-Lok differential (Posi) Your clutches might be gone. Not hard to do if you are Mechanically Inclined, otherwise, leave it to the pros and save the headache later.

 

Does anyone have instructions on replacing the clutches in the posi-unit?

 

I don't have them saved on my computer but if you , you can find them.

 

Like he said search google there are a few pages on it on the net. Its really just the oppisite of taking it apart, thats it. very simple to do.

 

Is there any way I can verify that my posi isnt working, without driving the car? My car is off the road now. Can I jack up one rear tire and see if it turns with the other on the ground? If the posi is good, it shouldnt turn, right?

 

For the rebuild kits, do you guys recommend the Kevlar ones or the "regular" ones?

 

jack the car up and spin one wheel. the other one should spin the other way.

as for the rebuild, just get the regular. you dont seem like you are into too heavy into drag racing your car or anything.

 

You answered it yourself. If you are doing a one wheel burnout w/ a posi, your clutches are shot.

 

are you comfortable with pulling the axles, removing your driveshaft, and pulling your carier housing? i doubt you are if you are asking this question. you have to have someone who knows what they are doing, to fix it.