Why not replace the whole axle assembly???

I've been looking at replacing my stock gears and bearings AND then I saw where I should also consider the T-Lock due to miles (134,970 to be exact). Well, all these parts and install kits, not to mention labor, will ONLY cost about $100 less than a new stock rear axle assembly.

UPGRADE:
FMS 3.55 Gear Kit ($250.00)
FMS T-Lock ($240.00)
Complete Gear Install Kit ($110.00)
Still haven't replace axle shafts and other internals

TOTAL REPLACEMENT:
FMS stock axle assembly w/3.55 gears ($799.00)

Mustangs Unlimited has the new axle assembly:

http://www.mustangsunlimited.com/itemdy01.asp?T1=M4006B355+01&Category=Drivetrain&CatKey=74-01

Why shouldn't I do this on a car that will be totally street and probably never see a drag strip or road course??? I have no idea what the installation costs would be, but I'm going to call a few local reputable shops to find out.

Am I missing something here? I'm getting new Cobra brakes (front/rear) at the end of August, so maybe I should do that at the same time. Maybe add in FMS UCA and adjustable rear UCA, also.
 
well there are places you can shave some money off. 3.55 is a commen truck gear set and a lot of people switch them out for 4.10ish gears in there trucks. so you can usually pick up a set of 3.55 factory ford low milage gears for a dime a dozen on ebay. the t-lock doesnt need to be replaced. just rebuilt 50-80 dollars parts.

as for the install kit, thats about right, shave off some shopping around maybe but i personally dont think a mini kit is worth it b/c its well... incomplete. and actually im not sure. but isnt the $250 dollars for a fms gear kit. include the installation kit in the $250

but all in all, the hours to change the axle as a whole might be quite a bit less then setting up the old one. so i guess it dopends on the shop rate plus the satisfaction of getting more new parts.
 
I figured someone might have done a total swap. The more I think about it, I believe that I do want to just go ahead and replace the entire axle assembly. The stock rear will be just fine for my future mods, particularly for a street car.

Once I get an installation quote or two, I'll post those.

Thanks.