After my loaner T-5 failed on Friday afternoon of the October 2003 COM event, some frustrating miscommunication led to my buying a new T-5, even though I knew that this would not be adequate for my purposes if I am able to upgrade the engine at some point.
With its 330 ft-lb torque capacity, the Z-series T-5 would be adequate for my stock motor, but any reasonable upgrade (heads, intake manifold, injectors, etc.) would put the engine's output beyond the T-5's rating. I was glad I was able to finish the event, but upset because I felt I'd bought the wrong transmission.
The following Monday I called Mike Forte and arranged to return the slightly used T-5 in partial exchange for a Tremec 3550-2 road racing transmission, which Mike assured me was good for 525 ft-lb of torque and should be up to anything I ever hope to do with the Cobra. Mike helped me out as much as he could, but the exchange still cost me; essentially I paid a couple hundred dollars to "rent" the T-5 for the weekend.
However, I felt so awful after destroying the second transmission in two months! I just could not stand the idea of having yet another transmission failure at some point in the future. The succession of transmission failures made me feel like a failure myself.
Granted, the first T-5 had been faulty (it was a V-8 transmission which had been rebuilt with a countershaft from a 4 cylinder transmission, so the teeth didn't mesh properly) and the second was just plain wrong (it was from a 4 cylinder car and was not rated for the torque of even my stock V-8).
Even though I knew this, it still felt to me as though the failures indicated bad preparation or bad driving on my part. I also missed a considerable amount of track time each time a transmission failed. I was not willing to risk this happening again.
So despite my very tight budget, I decided to spend the money to get a Tremec. I opted for the 3550-2 road racing version, which added $250 to the price, but can handle 100 more ft-lb of torque and gives a useful .83 ratio 5th gear instead of the dreadfully tall .68 5th gear that comes with the standard 3550.
The .68 ratio is apparently targeted at drag racers who run really short rear end gears. I guess they never use 5th on the track, but because of their short differential gearing need a really tall 5th if they drive the car on the street.
On the other hand, my car, with its 3.27 gears, just reaches redline in 4th at most road courses. If I upgrade the engine, I'll need 5th on long straights, and the .68 would be useless. Also it's way too tall on the street. The .83 should be just right.
I hope to keep the Cobra for the rest of my life, and now I have a transmission that will hopefully also last for the rest of my life. Spending so much money on the Tremec (bottom line was over $2200 including bell housing and shifter) means I won't be able to afford an engine upgrade any time soon, but if and when I do, the transmission will be ready for it.
The Tremec required a new bell housing (it has a different bolt pattern than the T-5) but is supposed to otherwise be a direct replacement for the T-5. I decided to get a McLoed steel bell housing, which would protect my legs in the event of a clutch explosion.
Fitting the bell housing turned out to be a big job for me. I don't have a lift, so had to work from under the car while lying on the floor. The steel bell housing weighs 35 lb, and its "block plate" (a heavy steel plate that makes up the front surface of the bell housing) weighs another 20 or so. Neither of these were drilled properly to fit the dowel pins on the Ford engine, so I had to lift each one up, test it, lower it down, file the holes out a little, lift it up and test it again, and repeat the process until it finally went onto the dowel pins. Each lift had to be done with one hand so I could use the other hand to insert or remove a bolt to hold the part in place.
Another glitch was caused by my ignorance: there are two bolts at the top of the bell housing that can't be inserted from the rear; they must be inserted through the block plate from the front before the flywheel is installed. I didn't discover this until I'd already installed the block plate, flywheel, clutch, pressure plate, and had halfway installed the bell housing. I had to dismantle everything down to the block plate once more in order to insert the bolts.
I spread the effort over two days, but it still destroyed me; at the end of the process I was so wiped out that even though I still had over a week to go to finish the transmission install and prepare for Lime Rock, I barely made it.
A neighbor and fellow Cobra enthusiast, Tom Maher, kindly came over and helped me slot the Tremec into place. Then I discovered another fit issue: the Tremec isn't really an exact replacement fit for the T-5. It's about an inch longer from the bell housing mating surface to the rear transmission mounting pad, which meant that the rear transmission mount was hitting the frame and the transmission itself was also hitting the transmission mounting bracket on the frame. The FFR frame is designed for the T-5, and it didn't have clearance for the longer Tremec.
A few minutes with a sawzall took care of the bracket clearance problem, but the mount clearance was not so easily resolved. Some extra shimming helped by raising the rear of the transmission, and I also had to loosen the front motor mounts and slide the whole engine/transmission assembly as far forward as I could. Some fudging on the rear mount as I tightened the mounting bolts also helped.
Once I had the car back together, I took it for a ride. The transmission promptly popped out of 4th gear consistently whenever I backed off on the throttle. A consultation with Mike Forte indicated that the transmission was probably defective internally, which would have required removing it and replacing it with another.
However, Mike suggested trying one thing: removing the shift boot. I did so, and the transmission stayed in gear. After some analysis, I concluded that the boot was pulling on the lever enough to tug it out of gear whenever there was no drive load on the teeth.
For some reason, Transmission Technolgies Corporation ships their robust Tremec with an incredibly wimpy shifter. Its weak-kneed springs might be adequate for a stock Mustang with a stock short lever and perfectly placed shift boot, but it just doesn't do it for an FFR Cobra, with its longer Cobra-style laydown shift lever.
I did a careful relocation of the shift boot and was able to get the transmission to stay in gear, but with just a couple of ounces of pressure on the lever at neutral throttle, it would pop out of any gear from 1st through 4th. It was especially tender in 3rd and 5th.
Popping out of gear in a fast corner can make you lose control. At places like Lime Rock, where there are lots of fast corners with little or no runoff room, if the transmission pops out of gear at the wrong time it could kill you.
It was back to Forte's for a Pro 5.0 shifter (another $180 down the tubes!) and the top of the transmission tunnel came off one more time. The Pro 5.0 has much stronger detent springs, so shifts are much more positive and the lever isn't likely to pop out unexpectedly. Also it has adjustable stops, which completely eliminate the stock shifter's rubbery feel and make the shifts feel even more positive. It's snick-clunk instead of squish-wobble-squish - much nicer!
The transmission feels great with the Pro 5.0 shifter, and the shorter 3rd and 5th gears should work better on the track. It's certainly more pleasant on the street than the V-8 T-5 was with the latter's ridiculously tall .68 5th gear! Can't wait to see what it's like on the track.