Porsche 930 Powerhouse - This tough 4-speed trans was designed by German engineers, and with certain upgrades it makes for a great sand car gear box.

As seen in Sand Sports Magazine
By Michael Sommer

Lately, we've had the opportunity to showcase several different types of transaxles built For sand cars here in Sand Sports magazine. Our goal is to feature the different options that are available, and leave it up to perspective car builders and owners to make the decision which drive train system is best suited for their needs. For this issue, we'll be taking a look at the Porsche 930 transaxle, which is a super strong 4-speed gear box that definitely is a viable option for use in hi-performance sand cars. It is currently available through Mechtech Motorsports, located in Escondido, CA, and recently we had the opportunity to visit with shop owner, Jim McFarland, to learn a little more about the technicals of this trans, and shoot some detailed pictures for readers that are interested in a new transaxle option.

In speaking with Jim McFarland, he told us that the reason why the Porsche 930 gear box was chosen is that it is the strongest model that Porsche has built. Also, being a 4-speed transaxle, it is better suited for sand and off-road cars because most recreational cars do not need more than four forward gears. For the most part, 5-speed transaxles are generally intended for street use where fuel economy is a factor in overall performance. The 930 transaxle is also about 35% stronger than any other transaxle that Porsche built for their production cars. McFarland also added that he believes the Porsche factory torque ratings for the 930 trans is rated at well over 500 ft.-lbs. of torque and about 500hp in stock condition. Keep in mind that this trans was used in the Porsche 930 turbo and 911 vehicles between the years of 1978 and 1989, which is when Porsche began using a 5-speed trans. So needless to say, quite a few of these transaxles were produced by the factory and sold here in the U.S., and it's fairly easy to locate them for custom built off-road.

Aside from the stout construction, another good feature of this gear box is the strong internal components. The ring and pinion section is ever bit as strong of the other hybrid transaxles on the market today, not to mention the physical characteristics of the drive gears. Compare the width of the Porsche gear with that of the late model Type 2 VW gears, such as the 091 versions, and you'll see that the Porsche gears are nearly twice as wide. This means the gears are much stronger during engagement, and they also have a better synchro design than VW transaxles and aftermarket transaxles that use VW-style gears. Other features of the 930 trans are the size of the synchro hubs, and the way that the gears are splined onto the main shaft, as opposed to being machined from a one-piece bar stock such as the VW design. It's also important to note that gear strength is very important but there have been instances where, if the gears don't break in a VW transaxle, oftentimes the synchro, hubs will actually twist or split into two pieces. Porsche was able to find a cure for this weak link.

Almost anyone who has run a Type 2 VW trans with extreme horsepower has probably experienced some sort of failure associated with the gears and/or synchros. This is what prompted McFarland to begin looking for an alternative type of transaxle. For him, the answer came in the form of this Porsche 930 trans. Two of the most positive design features were that the gears are splined onto to main shaft, and the synchros design than VW transaxles and aftermarket transaxles that use VW-style gears. Other features of the 930 trans are the size of the synchro hubs, and the way that the gears are splined onto the main shaft, as opposed to being machined from a one-piece bar stock such as the VW design. It's also important to note that gear strength is very important but there have been instances where, if the gears don't break in a VW transaxle, oftentimes the synchro, hubs will actually twist or split into two pieces. Porsche was able to find a cure for this weak link.

There are several ring and pinion options available for this trans. Some of the ratios are stock Porsche parts, and others are aftermarket units made by private manufacturers. The most popular stock ratio in this particular gear box is a 4.22:1 ratio. Mechtech also offers ratios such as 4.62, 4.87, 5.12, and they have a 4.0: 1, which is obviously something that you would not want for use in a sand car. In most cases, with the 4.22:1 ring and pinion very strong part in stock form, coupled with an unlimited amount of gear ratios to choose from, this is optimum for most sand car applications. The aftermarket gears are made here in America, and there are about 120 different gear combinations to choose from between first and fourth. Basically, it's possible to obtain any ratio that a car owner needs.

Another aspect about this trans that makes it more practical is that all the gears are totally usable. Often you will see that car owners with a Type 2 VW gear box rarely use the first gear, aside from loading the car back onto the trailer. This would be with the typical ratio of 3.70 or 3.50 1 st gear ratio. With the Porsche 930, they can supply you with a 2.25:1 first gear, which is a little lower than what would normally be used in a VW for second gear, but it's still taller than a common VW I st gear. That combination ends up working out pretty good for high torque, large displacement engines such as a V6- or a V8 powered buggy. These engines can easily pull a taller first gear.However, if it were a smaller displacement VW engine, or a Rotary, you may want to lower that gear ratio slightly.

Generally, what Mechtech has been doing up to this point is leaving the ring and pinion ratio stock and then selecting the best first through fourth gear ratio stack to suit the demands of the engine's torque and powerband. The reason why some of the gear ratios need to be changed is that the stock trans was designed for a Porsche 911 that was capable of running well over 150mph. Mechtech is simply re-gearing the trans so that the car owner can effectively use all the gears. And in the end they can supply the customer with a usable 4th gear that can also double as an overdrive gear. In this case, even though you wouldn't necessarily dune in 4th gear, you can still use that gear when cruising through the flats, across sand highway, as well as other terrain such as hard-packed desert off-road recreation areas.

Retrofitting this Porsche box into a car that currently uses a VW-style trans, or a gear box with a bellhousing that has a VW bolt pattern, would be fairly simple. The same engine adapter that they are currently using (if applicable) would bolt right up. All you would need to do is buy a new clutch and flywheel, and fabricate new brackets to mount the trans in the frame. The reason for this is the front pad mount is completely different than other transaxles, and the shifter shaft is in a completely different location. Actually, these are two really good features of the Porsche 930 transaxle. Not only does it have a super strong and sturdy mounting design, it also has a precision shifter which operates very smooth. We should also note that there are three different stages of clutches available for this trans, which are rated in terms of engine horsepower. The interesting feature about these clutches, as compared to traditional VW-style clutches, is that this is a puller-type clutch. You'll find these clutches on most of the new high horsepower cars built today, such as the Corvette, Toyota Supra, and many other performance automobiles. And the reason for this puller configuration is that it provides for a much stronger design without having excessive pedal travel and pressure.

While we understand that people are generally not experiencing problems with ring and pinion failures, or breaking the cases of most aftermarket hybrid transaxles, the units that are equipped with VW gears can potentially have a weak link that needs to be addressed. That's where Jim McFarland feels that the Porsche 930 Powerhouse trans fills a void for certain applications. Even with the upgraded aftermarket gears, this transmission is still less expensive than many of the aftermarket units being built today. The availability is good, there are a wide variety of gears ratios to choose, lubrication properties are excellent, the bearings are much larger than what you'll find in most gear boxes, and the synchros are a whole lot stronger than those in other transaxles. If this sounds like something of interest and you would like to obtain more information about this transaxle option, you can call Jim McFarland at (760) 432-0555, or log onto his web-site at www.mechtech-ms.com.

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