FINALLY getting 3.73's for my 06 GT Auto!!!!

A few questions:
The shop where I'm going for installation said that I have my choice of differential fluid. He has Ams Oil, and Royal Purple. He told me that it really doesnt make much of a difference, but helikes Ams Oil. I've heard Royal Purple is great... what do you guys think?

He also said that bc my car has such low mileage (less than 7,000) I will not need to change the bearing... does this sound right to you guys??

I do trust him, he's worked on a lot of my buddies cars in the past, but I figured it doesnt hurt to ask.

While I'm at it.. he quoted me $275 for the work- I am supplying the FRPP gears... so its about $275+180= $455.... not bad right?

 

both of those are good products so it won't make much of a difference, price is decent

 

I have the RP in mine Vin, I also had them put Friction Modifier in, even though they claim it's in the RP already.........No issues with mine whatsoever. As far as the install, I had it done at Mustang Magic, install cost for the Labor was $180.

 

AMSOIL has been around forever and they are used in many race cars and they claim to be the first synethetic oil company out there from the website. Either one is great and make sure they add some friction modifier and there is no whine on accel or decel after insatllation of the gears! J

The quote is great and the bearing should be changed if there is wear but that you guys will know after you open the diff and check it out!

 

Ams or RP it doesn't really make much difference. Both of those companies have a good rep for a great product !!!

 

After doing some research, I have learned that a lot of people will replace the differential fluid after the break in period.... is this necessary? From what I understand, there could be some metal shavings inside the fluid once they break in (but didnt this happen from the factory too?)

How long is the recommended break in period??? I've heard different ranges of 100 to 500 miles.

 

Amsoil had an outside company do testing on 14 different types of 75W90 gear oil. Sorry to say, RP did not fair so well in that testing. I had posted those results in an earlier thread. https://mustangforums.com/m_4203730/tm.htm

As far as break -in and metal shavings, you bet, there is PLENTY of metal inside that rear end. I did mine at about 5000mi, and got a big surprise by how bad it was. Yeah, some people never do it. Their loss. When you take off that cover and the stench pours out (they all stink anyway) look inside, then stick your finger in a slot right below the ring gear. There is a small "pit" where larger stuff settles. NOT pretty. The gear oil itself will look like liquid etch-a-sketch as itpours out. Remember, the rear end will break in just like the engine, but without a filter.

If you use Amsoil, use their slip additive. I started out with their Severe Gear 75W90. It is suppose to have the additive already blended in. Within 2 days, it started howling around corners. Got some additive from Oreillys and poured it in. Within 2 weeks, the howling returned. I had to now resort to changing the whole thing again and used Amsoil slip additive. Silence has been the norm now for 4000 miles.