More like a transformational makeover! However, let’s learn where we came from, first.
When I purchased #2060 in 2002 it had a close ratio Ford Toploader 4-speed and a 4.57 Trak-Loc differential. Not what you’d call comfortable for freeway cruising! Fun, nonetheless, on the street…and thirsty!
So, after 18 years of drivin’ around Southern California, I decided to upgrade to a 5-speed. I made the decision, in part, because of the 4.57 differential and because the Ford Toploader was getting tired. Mainshaft bearings were experiencing the ‘death rattle’ in neutral; second gear downshifts were becoming increasingly more notchy. Then I noticed the clutch would intermittently fail to fully release because the input shaft bearing was evidently sticking. The handwriting was on the wall.
I researched a variety of 5-speed purveyors and landed on Silver Sport Transmissions (www.shiftsst.com) in Rockford, Tennessee.
Why SST? Silver Sport Transmissions, an Elite Distributor of TREMEC® Transmissions, is the industry leader in the research and development of TREMEC conversion kits to modernize the drivetrain of classic cars, trucks, and street rods. I found SST’s Tremec TKO 600 and installation kit superior in fit, appearance, warranty (36 months) and most importantly, completeness: everything needed comes with the installation kit to fit my specific vehicle, right down to transmission oil. That’s nuts, bolts, brackets, templates, switches, wire connectors, trans crossmember…EVERYTHING!
Further, I reasoned, since the trans is coming out, why not replace everything from the flywheel to the differential. This was my opportunity to get the correct rear gear, a 3.89, into the Shelby. So, I opted to literally modernize the drivetrain: new billet steel flywheel, clutch and pressure plate, hydraulic clutch actuator & throw-out bearing, billet aluminum reservoir, and an all-new custom aluminum driveshaft. Knowing now that the differential would be a 3.89, I opted for an 0.82 overdrive ratio for fifth gear (rather than 0.64). The Shelby’s 289 engine has a Le Mans cam and is just coming up on the cam around 2,500 RPM. Using a 0.62 overdrive would have the engine at (roughly) 2,000 RPM at 60MPH…too much of a drop and too little power. The Shelby cruises at 60MPH at 2,500 RPM, right where power and torque begin to build and continue to 7,000 RPM. Making for a nice, wide powerband.
A word about the new differential. It’s a 3.89 (stock for all ’65 ~ ’66 Shelbys). I had it built with a Detroit Truetrac, replacing the previous Trac-Lok, as below.
The Truetrac is a helical-gear limited-slip (worm differential) and is the modern replacement for the classic clutch-type posi. Under normal light throttle driving conditions, a Truetrac operates much like a standard open differential, allowing the rear wheels to rotate at slightly different speeds for smooth cornering. However, when accelerating (torque applied), the six helical gears inside the unit smoothly and quietly engage, applying torque to both rear wheels equally, maximizing traction (think two equal length black stripes, aka darkies!). Unlike a traditional clutch-type posi, a Truetrac requires no special oil additive or maintenance. With silky-smooth positive operation and no components to wear out, the Truetrac maintains day-one performance for the life of the unit.
Once I configured the entire kit, I focused on a few transmission options to enhance performance: carbon fiber-lined synchronizer blocker rings (these provide better grip compared to stock brass rings with no friction lining); bronze shift fork pads, more durable compared to stock Nylon pads; SST’s 2~3 shift upgrade provides 7,000 RPM shifts, lower shift effort, and faster shifting.
And here's the only visual clue from Toploader to Tremec TKO600...
I even added a 1966 Shelby shift lever for that stock appearance…until you look a bit closer at the shift knob.
Who would do the install? I chose Cambra Motorsports, Inc. (dba, Cambra Speed Shop) in Orange, California (www.cambraspeedshop.com).
Great reputation for hot rods, show cars, and muscle cars, and highly recommended. Turns out it was a great choice.
I first met with the principal, Ron Cambra, to get to know him and his crew and set my expectations for the project. Ron listened carefully and confirmed the numerous requests and outcomes I’d outlined. I dropped off the Shelby with confidence (and a few trepidations…I usually don’t let the Shelby out of my sight, let alone my care). Any concerns I might have had melted away as Ron kept me informed on the progress of the project. Of course, it took some time. We had to pause for about two weeks after the full trans install to carefully measure for the new aluminum driveshaft, place the order, then get the new aluminum driveshaft back for the install.
Let’s describe the outcomes of the extreme drivetrain makeover. Everything we expected with the Silver Sport package, improvements, and installation package worked smoothly and perfectly. In other words, everything fit. The driveshaft was the only ‘thing’ left to finish the job. When we knew the expected arrival date for the custom driveshaft, we anxiously arranged for pickup and delivery of the rehabilitated 1966 Shelby G.T. 350!
Worth The Wait!
My 54-year-old Shelby G.T. 350 has been transformed with the changes and upgrades! Amazing what an extra transmission gear can do to an already sweet drivetrain! It’s much more like a late-model cruiser; however, it fully retains the visceral feelings and sounds just like back in the day…only better! In a word, the transmission and it’s gear shifts are BUTTERY. And, I’m thrilled!
Credits:
Silver Sport Transmissions — Jack | Gene | Jeff Cambra Speed Shop — Ron | Chris | Joey
Postscript
I’ve got just over a thousand miles on the new Tremec TKO600 transmission. I’ve changed the break-in oil and the trans is even sweeter as time and shifts go on.
I had Cambra re-build the Ford Toploader transmission that we removed. It will live on, however. I’ve gifted the newly-built Toploader to my nephew, Patrick, who’s continuing to build a Group Two-styled Mustang Coupe. Better watch out!
