9. Driveline DynamicsLook at an automotive driveshaft next to an injected Hemi or a cross-rammed big-block, then walk around back and check out those massive meats, and you've gotta wonder how that stick lives in between them. For the street driver, the driveshaft needs to be tough enough to take whatever level of abuse is tossed at it and smooth enough to be imperceptible on the road. Getting it right starts with having a level of beef that's up for the application. Most Mopars came with either 7260- or 7290-series U-joints, with the latter being the larger style used in factory H/D or HP cars. The smaller 7260 was generally used with six-cylinder or smaller and low-performance V8 applications. For performance applications, the 7290 is the one to use, since it handles more torque and lasts longer. Yokes are available for most rear-end and tranny applications to run the larger U-joint, if the vehicle wasn't originally so equipped. There was an even heavier duty U-joint used in some Hemi/Dana applications and with the Imperial "constant velocity" shafts, the 1330. Whatever joint type is used, the key here is to use only premium replacement joints, rather than be suckered in by the low price of weak imported units (your lack of towing bills in this area will more than make up the difference).
Beyond having U-joints up to the job, three other factors have to be correct: balance, phasing, and angle. Production balance was adequate for lower speed passenger-car duty. However, if performance modifications are done or higher driveline speeds are anticipated, it pays to have the driveshaft professionally dynamically balanced. Phasing is not an issue except in the actual construction of the shaft and relates to the alignment of the yoke eyes, and thus, the U-joints at each end. Getting smooth operation for road use relies on having the driveshaft (balance and phase) and the driven angles (the tranny and rear-end pinion centerlines, respectively) at specification. The factory service manuals for Mopar passenger cars have the specs. Adjustment is also outlined in the service manual, and remember that altering the angle for dragstrip use will come with a price in terms of open-road smoothness. Trick aftermarket aluminum and even carbon-fiber driveshafts can be bought, and they are often smoother at high speed than the stock steel shafts but are usually pricey.
10. BTU BlowoutHeat is the enemy of mechanical or hydraulic components, and it pays to dissipate heat, especially when specific modifications increase component heat loads. For example, a high-stall torque converter that generates more heat through increased slippage. Oil cooler systems are available to combat added heat, with the finest factory example being the late '70s B-Body Monaco and Fury Police Interceptors, which came rigged with rugged and efficient coolers for the trannys, the power steering, and the engine oil. Aftermarket sources can cover these applications as well and offer systems to cool high-winding rear axles. Do you need them? That depends on how the car is driven and what kind of modifications have been performed. Here's a B&M tranny cooler on a high-stall-equipped B-Body. For desert banzai runs, don't consider running without them.