1998 Cobra T56 Viper Transmission Swap

With help from fellow Primedian Randy Bolig, the 3550 is lowered, disengaged from the clutch, and removed from the Mustang. Two people can easily do this job--even flat-backing--as long as the car is high enough. Disconnect the starter and clutch fork/cable before unbolting the housing cover from the engine. If you haven't already done so, disconnect the battery as well since the cable leading to the starter is always hot and you don't want to weld a wrench to the starter. Be mindful that the housing-to-block bolts differ in length, so note where they go as you remove them.

Because of the differing spline count on the input shaft of the T56, you will have to replace the clutch disc (not the entire assembly, unless you need a fresh clutch) with a new disc with the proper 26-spline hub ($199). Unbolt the clutch cover--except for two or three bolts at the top--and slide the new clutch disc into place. Don't forget to use a clutch-disc alignment tool to get the disc centered before tightening the clutch-cover bolts.

While we could have heaved the entire T56 into place and jockeyed it around to engage the clutch hub and block dowels, we decided to yank the bell off the T56 and bolt it in place first. This allows easier access for installing the starter and getting the bell lined up with the block dowels.

The only real modification required to get the T56 (Viper or otherwise) into the Mustang is the relocation of the crossmember mounting brackets. On earlier Fox cars these are welded, but the SN-95 models feature a bolt-on bracket, as evidenced by the two holes in the framerail. The brackets on Editor Turner's Cobra had been relocated forward and welded when the Tremec TKO was installed. Now they need to be moved back. In a stock swap we would typically unbolt the brackets, relocate them, then drill two new holes and bolt them in (or weld them) to their new location. For now we'll cut the brackets off and then check fitment when the trans goes into place.

There's already a new release fork pivot stud on the front of the T56, so all you have to do is slide the fork and release bearing into place and seat it over the pivot stud. Some applications require a different fork, but the '96-'98 Cobra does not. Check your release bearing for smooth operation because now is the perfect time to replace it.

The Vehicle Speed Sensor and backup light switch are both located on the passenger side of the T56 as opposed to the driver's side on a stock transmission. Since the '98 Cobra uses an electric speedometer, it's a simple matter of relocating the transmission harness from the driver's side to the passenger's side of the transmission. We also installed the correct 20-tooth driven gear for Editor Turner's new 4.10 gears as well. Some applications, such as Fox cars, require longer speedometer cables and length-ening of some wires.