Quote:
The driveshaft does not have to be straight back, or parallel to anything (body, crank...). The point is the crankshaft (and tranny input) and the pinion shaft should be parallel, but not necessarily in a line.
Lou
Yes, precisely-- sorry if I wasn't clear. Driveshaft angles can be a couple of degrees without any problem. Off-roaders tend to go a lot more than that, if the body is lifted.
In fact, according to a Dana/Spicer manual I read, the U-Joints
should have some slight angle, not zero, in order to keep them moving and lubricated.
From an engineering design perspective, it helps to think of a drivetrain as three distinct pieces (assuming a single-piece driveshaft)--
you've got the engine -> driveshaft -> pinion shaft. The first and third pieces must be parallel to each other. That fact is never mentioned in any of the numerous auto repair manuals, because it is assumed that the manufacturer built it that way in the first place. But when you're customizing a new engine placement into a hot rod, you learn about all sorts of assumptions. It doesn't take much lateral shift-- front motor mounts 1/4" too far right, tranny tail mount 1/4" too far left-- to cause the engine to be not parallel to the rear axle pinion, and the whole car to feel like it's dancing the hokey-pokey.
When those first and third pieces don't line up parallel to each other (regardless of the angle of the middle piece), the rotational velocity of the shaft is
always changing during the course of every revolution. I still can't understand why the driveshaft shudder is
most pronounced between 2-10 mph, and then quiets down dramatically between 10-40 mph until of course it becomes obvious again at highway speeds. But that pattern is well-documented online, and it was what caused me to actually measure the engine position in order to discover the problem.
Didn't want anyone else to have to learn it the hard way.
- Erik
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Dually Clubcab needs a injector pump
