Things have been progressing smoothly for Project Tiger’s Eye, our 1950 Chevrolet Fleetline that’s destined to look amazing when all is said and done. Up to now, we’ve partaken in important steps needed to get the car rolling again–from tackling a budget SBC rebuild with the help of L&R Engines to adjusting stance by way of TCI Engineering, things are starting to shape up for the fastback Bowtie.
In our latest stage of the rebuild, we’ve gotten concerned with how we’re going to make our 383ci stroker get power to the rearend. Over the course of our planning, we came up with several questions that needed answering before we proceeded, but the most important one was: which transmission is right for the car?
Beyond simply doing our due diligence, we were able to get some help from B&M Racing, who was there to lend a hand in more ways than one. In business for more than sixty years, the Santa Rosa, California-based company is definitely a great source for expertise in all things drivetrain-related.
Though most of B&M’s milestones have been related to drag racing, the company is nothing if not enthusiastic about hot rods, and were more than happy to advise and equip us properly as we continue our efforts on Tiger’s Eye. The list of parts included a street and strip TH700R4 transmission (PN 117101), a Tork Master 2,400 rpm stall converter (PN 70418), a converter lockup controller (PN 70244), and a transmission oil cooler (PN 70255).
Choose Wisely: Going Over Transmission Options
Were we to go true-blue with this project Fleetline, our setup would warrant a 216ci 3.5-liter straight-six motor paired with a three-speed manual (three on the tree) transmission. Though perfectly serviceable for the average Joe back in those postwar days, our 383ci stroker would not be well suited to such a limiting gearbox. As such, the options have to expand.
Viable choices include the Turbo-Hydramatic 350, Turbo-Hydramatic 400, 700R4/4L60, and 4L60E. All four could potentially work with our stout mill, but we wanted to have something that could meet all the checkboxes: smooth shifting, decent acceleration, and sensible gear selection for cruising around.
The TH350 was the mainstay gearbox for a number of years, having first arrived on the scene in 1969. It was the brainchild of Chevrolet and Buick’s engineers getting together to come up with an improvement to the two-speed Powerglide that was showing its age.
Simple, versatile, and tough, the TH350 earned its stripes in both cars and trucks as the standard option across GM’s brands. It became a star performer when the aftermarket came into the equation. Owing to its small dimensions, it also made for an ideal fit into 4WD Jeeps once the proper modifications were made.
As a rule of thumb, TH350s found behind larger motors like the 327ci and 350ci tended to have stronger specs. Some of the drawbacks of the TH350 were its excessive end-play between the pump and center support, which would mess with the direct clutch drum, as well as thin center support that would require a case saver kit for heavy-duty applications.
A step up from the Turbo 350 was the Turbo 400, which preceded the TH350 by five years when it came out in 1964. The bigger, older brother to the TH350, the TH400 found its way into just about every one of GM’s brands, and even made the leap into competitors’ vehicles–Jeep, Ferrari, and Jaguar, just to name a few.
Early versions (1965-67) of the Turbo 400 came with a highly sought-after torque converter featuring variable pitch. Variable pitch basically allowed the transmission to change up its stall speed during use, and was dependent on an electrical impulse sent from the carburetor or gas pedal. Later versions got rid of the variable pitch option and instead had a fixed-pitch converter.
Its advantages included Simpson-style gear sets, and a cast iron center support that joined the clutch assemblies to the gear train. The support would absorb a lot of the reactive force from shifting and made the gearboxes a big hit in racing applications back in the day.
Next up was the 700R4/4L60. This transmission was introduced in 1981 for 1982 model year vehicles. It was a shift from the preceding Turbo-Hydramatics in that it possessed an overdrive gear. This was in response to consumer demands for better fuel economy, which an O/D gear provides when cruising at highway speeds.
The first gear had a 3.06:1 ratio, lower than the 2.48:1 ratio found in the TH400 or the 2.52:1 ratio found in the TH350. This made it better for getting off the line quicker with enhanced acceleration, although the earlier versions (1981-86) were revealed to be problematic, so 1987 and newer versions are generally considered a safer bet.
In 1990, General Motors went through a stage of nomenclature revisions and changed the 700R4 to 4L60. It was a change in name only, and designated that the gearbox was four-speed, longitudinally positioned, with a GVW rating of 6,000 pounds. Mechanically, the transmission was the same and underwent no alterations.
So, which of these options makes the most sense for Project Tiger’s Eye? We envision our Fleetline as a cruiser that’s at home driving through downtown L.A. as much as it is going 70 mph up and down the Interstate 15. With that in mind, an overdrive gear would definitely come in handy, and thus the 700R4/4L60–and one built by B&M, no less–will be our transmission of choice.
Putting It Together
B&M’s Frank Marra chatted with us and explained what all made these parts a wise selection for Project Tiger’s Eye. Starting with the 700R4/4L60 (PN 117101), B&M approaches the product from an enthusiast’s standpoint, which treasures reliability because, after all, it’s about making a nearly 70-year-old car capable of moving on its own again.
The transmission is suitable for engines making up to 450 pound-feet of torque, and has a recalibrated valve body to optimize fluid flow. “For a car like Tiger’s Eye, the street and strip 700R4/4L60 makes great sense,” said Marra. “The clutch uses red style material for the friction plates, and everything packed inside the transmission just needs regular intervals of maintenance to keep going strong. We recommend users adhere to the GM-prescribed schedule for instructions on that, but if there’s a lot of hot and heavy usage going on, we’d recommend every 8,000 to 10,000 miles for servicing.”
The Tork Master 2,400 rpm torque converter (PN 70418), meanwhile, would make for a fine mate to the transmission. “It has a high stall performance at a great value,” said Marra. “Higher stall helps with acceleration and idle quality with larger camshafts.”
B&M’s quality control ensures the part doesn’t leave the facility without meeting stringent requirements, so only the tip-top products wind up in the customer’s hands. “When a B&M converter is built, it is put on a turn table assembly that spins at a low speed and is welded at the same time,” explained Marra. “Then it gets balanced on another machine. We send it underwater and apply air pressure to it and check for leaks, and then on to paint and packaging.”
The converter lockup controller (PN 70244)would give us that most treasured of qualities in a part: command. With it equipped to Tiger’s Eye, it will make for a console-mounted companion that will come in handy at highway speeds, when overdrive comes into effect. It will reduce the slippage between the input and output of the converter; in effect, it adds another gear to use and hence reducesheat and wear to the drivetrain
Last but not least, we would be ill-suited to take our hot rod for a ride without a way to keep hot things cooled as time goes on. That’s why we went for the SuperCooler transmission oil cooler (PN 70265), based on a stacked-plate design that channels lubricant through cooling air for a longer period of time than fan-and-tube units.
“Our coolers are more of a heat exchanger, which can radiate the heat out without a lot of airflow,” said Marra. “A tube and fin requires a lot of airflow in order for it to work correctly. The Supercooler has 27 rows for the oil to flow through, greatly increasing the time spent cooling the oil and making the system more long-lasting and efficient.”
Where We Go From Here
The time spent getting Project Tiger’s Eye from a barebones chassis to a full-blown stunner has been laborious yet intriguing. Getting to see every little upgrade get installed onto the ride makes our anticipation grow ever larger as the weeks tick by.
To paraphrase the great self-help book from the comedy What About Bob?, no project done right is done all at once; it’s done in baby steps. Our Fleetline will most assuredly come together soon, and when it’s all said and done, we can rest easy knowing that companies like B&M and others have helped us make great strides.
Stay tuned to our continued development of Project Tiger’s Eye right here on Rod Authority, and be sure to check out B&M and its top-notch drivetrain products on its website as well. While you’re at it, don’t forget to Like B&M on Facebook too.