On the left is the stock transmission for an X-11, specifically, an '81 X-11. on the right is the "Economy" geared transmission for an '84 Fiero coupe. As you can see, they share the same transmission casing, only the internal gears are different. The X-11 tranny has a differential gear of 3.65:1, 1st 3.31:1, 2nd 1.95:1, 3rd 1.24:1, and 4th 0.81:1. The Fiero "Econo" tranny has a differential gear of 3.32:1, 1st 3.53:1, 2nd 1.95:1, 3rd 1.24:1, 4th 0.73:1. As you can tell from the specs, the gears are taller on the "Econo" Fiero tranny, which makes it the best candidate to handle the low-end torque of the Cadillac V8. Also note that the clutch lever on the X-11 tranny has provisions for a clutch cable, whereas the fiero tranny has provisions for clutch slave cylinder.

Of course, it would have been simple enough to just take this tranny and install it on the caddy V8 engine, but I was bothered by the fact that this transmission was designed for a 4 cyl. engine, and I didn't feel the casing was up to the challenge of withstanding the monstrous torque of a V8. After much research and debate over in Pennock's Fiero forum, www.fiero.nl , I discovered that not all Fiero transmissions were created equal....

This is the casing from a 1985 v6 Fiero GT. Apparently GM had redesigned the transmission casing and bellhousing because of failures due to weak casing, so they added in many ribs to counteract this problem. The "Econo" gears inside the FieroV6 tranny casing will make a killer combination for a V8. Only the best for my X-11!!

Here is a shot of the inside of the transmission casing for the Fiero "econo" tranny. Note the yellow plastic gear on the differential for driving the Vehicle speed sensor's gear. This same gear is made of metal instead of plastic on the '81 X-11 transmission. One possible explanation for this is that the speedometer in citations is mechanically driven, rather than electronically driven as it is in the fieros. Either way, the caddy ECM requires a vehicle speed sensor, so this works out well for me.

This is the bellhousing for the Fiero "econo" tranny. Only one piece will be used off this, and that is the vehicle speed sensor(VSS), located in the red box.

When removing the gears from the Fiero "econo" tranny, it is very important to keep track of the order you take everything out, and then EXACTLY reverse the process when installing them into the '85 Fiero tranny casing, with the exception of the shift forks and levers, as the forks and levers from the '81 X-11 tranny will be used so that they mate with the shift cables currently in the vehicle.

Working on a transmission for the first time, it was helpful to have the guidance of an experienced hand. My uncle Salvatore provided much needed assistance throughout the duration of the swap, including painting the engine bay for me, since I have an aversion to painting.

After the entire contents of the Fiero "econo" tranny were moved to the heavier duty '85 Fiero tranny casing, a thin layer of high-temp silicone sealant was applied to the mating surfaces for the bellhousing and the transmission casing.

As mentioned earlier, the shift levers and forks were transplanted from the '81 X-11 tranny to retain the stock location for the shift cables. In this picture, I am holding the Fiero's shift levers for comparison. Because of the later revision of the tranny casing, a bolt-on mounting bracket for the shift cables will have to be pulled from an '84-'85 FWD GM car with the 4 speed muncie tranny, OR a custom bracket will have to be fabricated if one cannot be located.

Since the X-11 uses a clutch cable rather than a clutch slave cylinder, the X-11 tranny's mount for the clutch cable was moved over to the new casing.

Because the outside of the '85 Fiero tranny casing looked like multicolored hell, painting it a uniform flat black seemed like a wise choice. I chose flat black because it is different enough from the engine bay's gloss black color to stand out, but not enough to where it sticks out like a sore thumb.