Ok so I am not a mechanic, but I like to work on things, and I love cars. So speak stupid to me. Lol I have an 89 mustang 5.0. It has drum brakes in the back and 3.73 gears. I also have a 95 mustang 3.8 that has the disc brakes that I want on my 89, and I want to keep my gear ratio. From what I understand as long as the spline count is the same on the two cars I can use everything except the pinion yoke. Anyone tried this before? Anyone know the spline count?

 

Doing a rear disk brake conversion on the Fox cars is pretty popular and there's a lot of documentation on it. Unfortunately, it's not the easiest thing in the world. I did the exact swap you're contemplating, brakes from a 95 onto an 89 GT.

You have a choice off the bat on axle length. The SN-95 axles are longer than the Fox axles. If you use the SN-95 axles you can use all the SN-95 bracketry with no problems but you will not be able to run wheels wider than 8" in the rear, at least not without some special offsets. You can use the Fox length axles, in 5-lug of course, but you will need special bracketry to mount the brakes.

You'll also need new e-brake cables (left and right) from a 93 cobra and an adjustable ebrake cable that hooks off the handle. You'll need to change the master cylinder, gut the stock proportioning valve and install a manual proportioning valve. You'll need to get adapters for the hard brake lines in the rear to go from the Fox threads to the SN-95 threads.

I researched the heck out of this here: http://home.comcast.net/~mjbobbitt/mustang/page1.html
Your specific question is here: http://home.comcast.net/~mjbobbitt/mustang/page8.html
And your axle length option is here: http://home.comcast.net/~mjbobbitt/mustang/page9.html

Maximummotorsports has master cylinders new and the hoses/adapters: http://www.maximummotorsports.com/st...ath=49_144_469
Plus they have great tech support.

Personally, I went with the SN-95 length axles knowing that I'd not be able to run the wide wheels. I just wanted the simplicity of using the stock Ford brackets. I do get rear wheel rubs on occasion though. I had help when doing mine and it took some time to finish. You'll be alright if you do your research and take your time. A friend of mine once described brakes as a "black art" and I totally believe him. Good luck.

EDIT: Stock axle spline count is 28 on Fox and SN-95

 

Awesome, thanks for all the info.

 

Just an fyi, those are two different size rears. The GT rear is a 8.8in and the V6 rear is a 7.5in so you dont want to use that whole axle. Though Im sure you can use the brakes as long as you do a 5 lug swap.

 

Ya, I decided that I'm just gonna rebuild the tranny on the 95 sell it and buy the 5 lug kit for my gt and do it the right way.