How To Improve MPG & Performance With An Overdrive Transmission - CHP How It Works

Going Broke Filling Up Your Hot Rod? Here’s How to Improve MPG and Performance With an Overdrive Trans

Stephen Kim Jun 15, 2011 0 Comment(s)
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NonElectronic Overdrives

Zack Farah: Both the 200-4R and 700-R4 are excellent choices for those who want to upgrade to an overdrive without having to deal with electronics. In some applications a 200-4R is the better fit, as its dimensions are more slender, while other applications are better suited for the more durable 700-R4. In a car like an early Nova, a 200-4R would fit better than a 700-R4. Both transmissions operate with hydraulic logic via a throttle pressure cable to mechanically measure the throttle position from the carburetor to the transmission control valvebody assembly. This controls the shift timing, shift quality, and line pressure rise. There are no electronics involved, and converter lockup is controlled by a 12V wire that energizes the lockup solenoid once a vehicle reaches highway cruising speed.

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Stan Poff: The 700-R4 and 200-4R are popular swap candidates because they offer the benefits of an overdrive transmission without the hassle of electronics. Both transmissions can be built to handle more than double what GM designed for them from the factory. The 200-4R transmission is an easy replacement for the TH350. To upgrade from a TH350 to a 200-4R, all that’s required is changing the shifter. Most of the time, even the original driveshaft can be retained. With fewer replacement parts made for the 200-4R, when it comes to horsepower capacity, the upper hand goes to the 700-R4. TCI has developed a constant pressure valvebody for both of these transmissions. This innovation eliminates the problematic TV cable gremlin. With this valvebody the cable is now mainly used to set the shifting speed and no longer controls the pressure. It’s still important to get the shift speeds correct, but at least destroying the transmission is less likely.

Achilles Thomas: The 700-R4 and 200-4R are both extremely popular units for overdrive conversion, and each has their benefits. Regarding durability, the 200-4R was never put into a high-horsepower or heavy-duty truck application and was often found in midsize cars. On the other hand, the 700-R4 was pretty much used in everything from a V-6 Camaro to a fullsize truck. That being said, right from the factory the 700-R4 was deemed to be more durable, and now in today’s market, there is a vast amount of aftermarket upgrades available for the 700-R4 that make it the favored choice for overdrive conversions. In regards to price, the 700-R4 and 200-4R models that Monster Transmission carries are very similar, typically within $100-$200.

In terms of size, the 700-R4 is just over 30 inches in length from front to back, and the 200-4R is about 3 inches shorter at 2711/16 inches from front to back. So if you were converting from a TH350 with a 9-inch tailhousing, the 700-R4 would be a direct swap with no change in driveshaft length. A TH350 with a 6-inch tailhousing would be an easy swap for the 200-4R, again with no driveshaft mods required. In terms of weight differences, a typical 700-R4 weighs in the neighborhood of 135 pounds versus roughly 125 pounds for the 200-4R. These weights can vary depending on fluid capacity. An aftermarket heavy-duty aluminum pan will obviously add some weight in comparison to the factory steel pan.


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