In terms of performance and reliability, it’s no secret that automatic transmissions have evolved exponentially over the years. In many ways, they’ve surpassed their manually shifted brethren. However, it is also equally true that many individuals still like to get that adrenaline rush of banging through the gears and enjoying the feeling of being connected to the car beyond sliding a shifter into Drive. As with the automatic, the manual boxes have also evolved, and the efficiency of function has equally improved. If you’re a traditional muscle car or street rod fan and prefer a manual shift, then you’re probably familiar with the heavier feel some mechanical clutches deliver – and some prefer that feel. However, the benefits of a modern transmission coupled with a hydraulic-clutch system far outweigh an old-school mechanical setup.
If you’re basking in the warmth of being a traditionalist or are knee-deep into a nut and bolt restoration that requires a mechanical clutch and OEM transmission, an upgrade probably isn’t in your vocabulary. However, if you’re the type of individual that likes to stretch your vehicle’s legs, a modern hydraulic-clutch upgrade is clearly an option. As with things that require change, there are always pros and cons to take into consideration. To clear up some of the confusion, we reached out to the folks at Silver Sport Transmissions (SST) to get some advice.
In the SST catalog, you can find a wide range of transmission packages that have been designed to work with most car brands. Some of the more popular offerings are the TREMEC TKO, the T-56 LS/Magnum, and the all-new TKX. But, the SST systems encompass a wider palette of shifting options. While we will use the modern boxes to illustrate some of the procedures, it is worth keeping in mind that if you don’t want to swap out your existing old-school four-speed, you can nudge it into the 21st century by replacing the mechanical clutch with its modern hydraulic counterpart — a Concentric Slave Cylinder — more commonly referred to as a hydraulic throwout bearing.
The cost of doing one of these upgrades is always a factor to take into consideration. A full swap will place you at a much higher price point. However, the mechanical-to-hydraulic switch, while still requiring an initial investment upfront, is actually cost-effective. We asked Jeff Kaufman of SST for his input on the nuances of such an upgrade. He notes, “The only perceived downside is the initial cost, but there are far more plusses that negate that initial cost.”
So, the logical question is, why make the switch? Let’s look at what you have with a mechanical system. By virtue of its design, with regular use, mechanical systems require periodic adjustments as the clutch wears down. Also, all the hardware utilized (linkages) takes up more space. Another consideration includes the deterioration of those linkage pieces that wear with time, causing actuation to get loose.
With the assistance of the folks at SST, planning what to install will require very little homework as to what will be best suited for a given application. The biggest mistake to avoid is the idea of piecing together a hydraulic system from a variety of different manufacturers. This can be quite problematic because every component needs to be mechanically matched in order to work properly. A company like SST offers a selection of kits that they’ve designed and tested for a wide range of vehicles.
“There are a lot of companies out there that use aftermarket parts,” says Jeff. “There is a difference between those and original equipment parts (OEM). With OEM parts, there is a whole lot more engineering behind them for long term use. The company that makes our bearings is an OEM tier-1 supplier to a number of automobile manufacturers. These bearings are the same-quality bearings that you will find in a brand-new Camaro. Their OEM validation is 10 years or 150,000 miles before you should expect any need for service, so our bearings are made to last within those parameters. The bearing itself is actually rated at 300,000 miles or one million strokes. That is the testing and validation on the bearings that we use.”
The Heart Of The System
Buying a kit that has been pre-packaged is a sensible approach because all the leg work has been done for you. With the SST kits, Jeff points out, “The appeal of our hydraulic-clutch systems is the firewall mount. In order for them to work, you have to have a small master cylinder. The concept of it is exactly the same as brakes. The small master cylinder on the firewall pushes fluid through a hydraulic line to a hydraulic bearing, making it expand, and that is what pushes the clutch finger to release the clutch. A Camaro firewall is going to be different than a Corvette firewall, so we have engineered individual firewall mounts that are specific to a given car that allow it to be mounted at a proper angle and location. We do this so someone doesn’t have to mess around to find the correct pushrod angle and where to mount the master cylinder.”
He further adds, “Older cars with mechanical clutches have a rod attached to the clutch pedal that goes through the firewall. They are set at a particular angle. That is what we duplicate with our firewall mount. That mount will maintain the pedal ratio and a straight push into the master cylinder. You can’t have the rod going into the master cylinder off-center, because it will score the internal bore. As long as the owner maintains a straight push of around a 6:1 pedal ratio, then the pedal will be nice and soft with that straight push into the master cylinder.”
On a car originally equipped with a manual transmission, you’ll need to locate the clutch-pushrod hole. On a factory automatic car, this may be a hole with a rubber grommet or a small sheetmetal cover. Some vehicles may not have a factory hole in the firewall at all, but there should be a spot that is contoured for a hole. If you don’t have an existing hole, you’ll need to cut a 1-inch hole in the factory spot on the firewall.
Are there any downsides to a hydraulic system? We’ve mentioned the perceived up-front cost is actually a non-issue when factored with the longevity of the system, however, hydraulic systems aren’t bulletproof – nothing ever is. Maintaining a proper fluid level in the reservoir and keeping the system leak-free are key factors with a hydraulic system because it allows the clutch to self-adjust. Outside of that, it is maintenance-free.
Jeff does point out, “Typically, we don’t see any failures, but when we do, it usually occurs from the beginning, when there is a very specific set of procedures to have the bearing operate in a defined distance behind the clutch fingers. If a person skips those steps or doesn’t read the directions — or makes assumptions and the bearing is outside of that functioning range and it overextends — that’s when it can blow apart. If the directions are followed, there won’t be any issues.
Most guys we work with don’t do this every day, so they aren’t going to have an understanding of the nuances of these systems. If something is unclear, we have dedicated tech support. Jeff also points out that if you have a vehicle that is not a mainstream brand or model, SST has you covered as well. “We have a universal kit where you can adjust the pushrod length and the pushrod angle on the master cylinder, so it can be more universal.”
Doing the swap to a hydraulic clutch system isn’t very difficult, and is in many ways a cost-effective upgrade that will add enjoyment to your driving experience. The task can typically be accomplished in a day, with a few simple hand tools. ONce completed, you’ll be bangin’ gears in no time, and staving-off leg cramps from holding the pedal while in traffic. What’s not to like?