I want to change the rear gears on my 85gt for just street driving is the 7.5 good enough with better gears or should I swap to a 8.8? I do no want to change gears then have to get another rear end anyway if mine is weak. Are my stock gears 2.73's?
more than likely they're 2.73's. 3.27's came as an option though. i've been wondering the same thing, but i think it would be worth it to swap an 8.8 instead of just doing gears because if you are going to want more power, the 7.5 will eventually give out on you. anyone else have something to say?
Do the 87-88 T-Bird Turbo Coupe rear end swap and get it all: 8.8, gears and disc brakes
Auto trans Turbo Coupes come with 3.73 gears and manual Turbo Coupes come with 3.55 gears. I choose 3.55 since I do more highway driving.
It takes 2 guys the first day to get the old rear end out and the new one bolted in place. It takes 1 guy another whole day to do the brakes.
You will need a several sets of fittings, I recommend that you get them from Matt90GT's website, http://www.svo73mm.cjb.net/. Read Matt's instructions thoroughly, everything you need to know about the brakes is all there. You need to be patient and follow all the internal links, and there are many of them. You will need 2 fittings in the rear to adapt your old brake tubing to the TC disk brakes. The fittings go between the steel tube and the caliper brake hose. You will need another set of fittings to make a 2 port to 3 port adapter. To make life simpler, just buy the kits from Matt. You could piece them together, but it's not worth the time unless you work at an auto parts store with all the fittings ever made. You will need to drill the quad shock mounting holes 2” below the holes drilled for the Turbo Coupe mounting points. The bolts are metric, so don’t loose them or the nuts. A 15/32” drill should be about the right size unless you have access to metric sized drill bits. Going without quad shocks is not an option unless you have aftermarket parts to soak up the wheel hop.
You will need a proportioning valve, Summit has one for $40 + shipping.
You will need a kit (FMS makes the part) to gut the stock proportioning valve, Summit also has that, about $10.
You will need a new master cylinder, see Matt's site and make you choice. I used a 94-95 Mustang master cylinder. Note that rebuilt 94-95 Mustang master cylinders do not come with a reservoir. That means a trip to the junkyard and some more money spent.
Your brake pedal may be very hard and almost impossible to lock up the brakes. I had to replace the front calipers with 73 mm calipers from a 91 Lincoln Mark 8 to get the braking performance up to par.
Bleeding the brakes will require 2 people and some coordinated effort. I don’t recommend using you wife or girlfriend to pump the pedal – they get offended when you yell at them. I used a homemade power brake bleeder constructed from a garden sprayer and some fittings from Home Depot. It cost about $25 and was worth every penny.
See http://www.mustangcentral.net/tech/brake.html for help with the emergency brake - the stock setup tends to lock up and not release properly.
All in all I have been very pleased with the results.
Honestly, I'd look around for an 8.8. Take this opportunity to upgrade while you were planning on doing it. You should be able to pick one up pretty cheap if you search around. The 7.5 would probably hold up for a while but if you upgrade the gears you'll probably be wanting to get on it a little harder . I've already had to rebuild the 7.5 in my 4-cyl daily driver. I would go for the 8.8 if time and funds are available.
To change to the T-bird rear you also need to change master cylinder no?? How long will stock last with no more than 300hp and pretty mild driving? If I do swap to the 3.73's will I notice an EXTREME increase in quickness?? I know 4.11++ would do more but I like the highway too.
Let's keep it simple.... Do it right the first time. Throw that 7.5 in the garbage and slap an 8.8 in your Stang. No question about it. It's that simple and straight forward.