1990 Mustang LX T5 To C4 Conversion(Not Finished user contacted. rick)
I bought a 1990 Mustang LX V8 last year for a toy. It's a nice ride, had 105k on the clock, and was owned by a former KY State Trooper. It was bone stock when I bought it, with no modifications whatsoever.
Being the gearhead that I am, I can't leave anything alone for long. I installed a new set of FMS 4.10 gears in the rear, along with a new FMS 31 spline differential and a new set of Alloy USA 31 spline axles. Along with that went a FMS aluminum driveshaft, and a Hurst SST shifter for the T5. For the suspension, I went with a set of Strange coilovers in the front along with new caster/camber plates and lower a-arms. Tubular upper/lower control arms were installed on the rearend. A Bassani X-pipe going through Dynomax Super Turbos was used for the exhaust.
OK, now for the part that this thread was intended for: the C4 install.
Whoever owns this car gets credit for my wanting a C4 in my Fox Mustang.
I've always owned 4 & 5-speed cars, so I wanted to walk on the other side of the fence and see what a fast shifting automatic was all about.
I started doing some research and found that a C4 swap was relatively easy on a Fox-body Mustang. So I started ordering parts.
For #11, I found a local C4 on Craig's List. It is a 1972 trans, which is case filled and has a 26 spline input.
I was in possession of it for about 30 minutes as I dropped it off at my trans guy's shop (Wolford Transmission in Hodgenville, KY) right after I picked it up. He tore it down, cleaned it up, then assembled it with Alto clutches, extra wide bands, a new hardened input shaft, a reverse manual valve body, a billet servo, and a deep pan. My next step for the Mustang is to build a 408-410W, so I wanted a trans that would easily hold the power.
When I got it back, it looked like this:
With a butt-load of parts in front of me, I put the Mustang up on 4 ramps so I could easily get under it and work. I yanked out the T5, the bellhousing, clutch, and flywheel. (It still had the factory clutch in it and it didn't look half bad.) I then pulled the pilot bearing out, fixed a couple of oil pan drain plug leaks, and installed the new block plate and flexplate.
Out in front, the Flex-a-lite trans cooler went in pretty slick. Not sure about other years, but my Mustang has a front core support that vertically runs right down the middle of the condenser. It sits pretty close to the condenser as well, so I just mounted the trans cooler vertically on the passenger side of that support.
That cooler is roughly 7x15x3/4.
Up inside the car, the shifter went in. Holcomb Motorsport's adapter is meant to mount a Hurst Quarter Stick or B&M shifter in place of the factory 5-speed shifter without having to hack up the console. However, I had to do a lot of hacking on the shifter adapter. I ended up having to space the front of it up and notch the back of it so that it would sit without the shifter handle hitting the CD player. I ended up getting some good clearance, but I decided to move the CD player down a hole. I then cut the top 1/3 of the factory shifter boot off and tucked it down. I plan to have it professionally sewn later on.
I had to order a Hurst reverse switch as the shifter only had a neutral safety switch.
Here is where I had the most trouble. I had removed the clutch pedal completely and of course I wanted to keep the reverse lights working, along with the neutral safety switch so some moron couldn't start it in gear.
After doing MUCH research, I've found out that most people have no clue about what switches do what. To be brutally honest with you, I don't either. However, this is what I did and it works.
There are two switches that connect to the factory clutch pedal. One is a clutch safety switch and I believe the other disengages the cruise control so you don't stab the clutch while running down the interstate and cause the engine to bounce off the rev limiter.
Armed with some advice from a good buddy, a schematic, and a multi-meter, I got it working by doing this:
1. Jumpering both switches on the clutch pedal.
2. On the 4 prong switch in the trans tunnel, I connected the red/blue and white/pink wires in line with my neutral switch on the Hurst shifter.
3. On that same switch, I connected the black and purple/orange wires inline with my Hurst reverse switch.
4. There is a 2 prong switch under the car in the trans tunnel, but I haven't messed with it yet. I'm thinking it has to do with the cruise control, but we'll see when the car gets on the road.
5. I confirmed that the backup lights worked and the engine would bump over (starter has to be mounted and grounded solid).
Once all of that was done, it was time for the trans to go in.
I'm 5'6" and 140lbs totally sopping wet, but I managed to slide the transmission under the car, and up p on a floor jack. I put a quart of ATF in the converter and installed it on the trans. Up goes the jack, and the trans is mated to the engine.
As of right now, the trans is bolted up solid to the engine, the trans lines are connected, and the dipstick is in place. I called it quits for today, but I plan to finish up tomorrow. I still have to hook the shifter cable up, install the crossmember, put a final tighten on the converter nuts, fill the trans with fluid, put the exhaust system back in, and install the driveshaft. There was about 1/2 the slip yoke showing on the stock length aluminum driveshaft, so I ordered an 11/16" spacer to help out with that.
I'll update with final pics and info as I finish up.