Drivetrain Swap Guide

Driveshaft angle

Up And Down
Driveshaft angle: Mounting the drivetrain lower in the frame helps cure extreme driveshaft angles caused by lots of lift or suspension travel; the closer the transfer case outputs are to being inline with the axles, the less severe the driveshaft angles.

Ground clearance: Even though lowering the drivetrain fixes driveshaft problems, it reduces ground clearance. This is especially true at the transfer case crossmember, but keep in mind that less severe driveshaft angles also mean a greater length of the driveshafts are closer to the ground. For this reason, we like to keep the drivetrain as high as practical.

Clearance to axle: As discussed in the "Fore and Aft" section, front-axle interference with the engine is also an issue. The higher you can mount the engine, the less of a concern this is.

Center of gravity: One disadvantage of mounting the engine high is that the 4x4's center of gravity is increased, thereby raising the possibility of rollover. However, given the 1- to 3-inch margin of up and down engine placement, we don't get too concerned about it.

Tunnel clearance

Tunnel clearance: Your biggest limitation to raising the drivetrain will be the transmission tunnel; don't forget to leave room for linkage, bolt access, and frame flex.

Driveshaft angle

Side To Side
Driveshaft angle: Most swappers prefer to have the rear transfer case output inline with the rear axle. Depending on your vehicle and the components used, that may not necessarily mean that the engine is centered in the chassis. Also, there may be other factors that prevent you from putting the rear output inline with the rear-axle pinion. In that case, the answer is either to get the rear axle custom-made to compensate, or to run the driveshaft crooked-that is, at an angle to the rearend as viewed from the top or bottom. Contrary to popular belief, it is possible to prevent the driveshaft from vibrating under this condition. See "All About Driveshaft Angles" (Sept. '97) or call Six States Distributors for help.

Front driveshaft clearance: It's common to have the front driveshaft on passenger-side-output applications smack either the trans-pan rail (on automatics) or the starter during full-suspension compression. If you can move the drivetrain to the driver side and let the driveshaft slope sideways a bit to the axle, it can help. Small-diameter driveshafts also help.

Steering-column clearance: It's common to see an engine offset a bit to the passenger side to clear the steering column. If this is absolutely required, it can be somewhat beneficial to run a 'case with driver-side offset. That way, the front-axle pumpkin will also be on the driver side; therefore, engine offset to the passenger side will help clear both the steering column and the front pumpkin. In the more common application with a passenger-side 'case output, it may be beneficial to leave the engine centered or offset a bit to the driver side to clear the pumpkin, then solve any steering-column interference with Borgeson U-joints to move the column out of the way.

Side-to-side

Tilt!
Side-to-side: The engine may be tilted in the chassis as viewed from the side or as viewed from the front although we couldn't think of any reason you'd want it tilted side-to-side as viewed from the front. Stage West used a level across the valvecovers to square the 350 in the frame.

Nose-to-tail: Tilting the drivetrain so it's a bit down at the rear output can often help solve problems with the rear driveshaft, but keep in mind that every degree of downward tilt at the rear 'case output equals a degree of upward tilt on the front output. Unless you have fulltime four-wheel drive, the front driveshaft rarely spins at high speeds, so the compromise to benefit rear-shaft angles may be worth it. However, lowering the rear of the drivetrain also reduces clearance at the 'case crossmember. It may also cause clearance problems with the distributor to the firewall or the bottom of the fan to the radiator.