Baystate Jeepers

Yesterday was the first time since I installed the SYE/CV Shaft that I had a chance to drive the jeep on the highway. Well when I hit 60mph I believe you could feel slight driveshaft vibrations but not 100% that is the issue. The feeling was like driving on a road that has a rough surface, much like driving on a road where they just removed a layer of tar.

Does this sound like driveline vibrations?

If it didn't do it prior to the install, it's probably the angle of the rear yolk. Adjust the rear yolk 1-2* below the output of the transfercase. This compensates for axle twist during acceleration.

Who made the rear diveshaft? It is possible that it could be out of balance, although I doubt it if it's new. Check your angles and see if it helps.
You can buy a magnetic angle finder in most hardware stores. They're like $5-$10.

Not sure who made the ds, but i did Have the shaft balanced before I installed it. I guess i am going to have to remeasure the angle, just wish I could locate a better photo showing where to measure.

So as the RPM's increase, the angle changes?

It's more of a case of angles changing with more load.
Typically under heavy acceleration and or high traction the pinion gear will try to "climb" up the ring gear changing it's operating angle.
Higher speeds can make things be felt more.
The best spot to measure yoke angles in on the flats of the yokes with the drive shaft removed

Chris wrote:So as the RPM's increase, the angle changes?

The angle can change with applied load. However, increasing RPM's can add harmonics. The whole point of a double cardon driveshaft is that the front two u-joints cancel out each others ocillations. Remember that at an angle, a u-joint binds slightly and then releases. It does this very rapidly at speed. If the u-joint at the axle end is off too much, it will not have another joint to counter these harmonics - and then you get some bad vibes. We set the rear yolk to point 1-2* down from the optimal 0*, to compensate for axle twist under hard acceleration. Typically at normal cruising, 1-2* is not enough to cause a vibe.

I went Pinion nut to the TC yoke Nut Then drop it down 3 degrees my shaft is 19.5 inches long The longer the shaft the more it will move under full power

Well looks like I will have to tear into this when I get back in town, next week. However I am going to try to snap a couple photos to capture the current angle/measuring points for a reference.

Just measured and both are at 17deg, looks like I am going to have to adjust. BTW the output yoke (side with the clamps) is not 100% flat, which makes it kinda hard to adjust the angle.

Chris wrote:Just measured and both are at 17deg, looks like I am going to have to adjust. BTW the output yoke (side with the clamps) is not 100% flat, which makes it kinda hard to adjust the angle.

Glad you found it.

Found this, but it doesn't say anything about being 2degs less for the pinion.

http://www.4x4xplor.com/SYE-CV3.html

If the guy doesn't have any vibes, then he's lucky. Trust us on the 1-2*.

Yesterday I adjusted the angle and still have vibes starting at 65mph.

Any more suggestions? It happens at 65mph exactly!!

Dunno, drive 64????

O.K. kidding aside, does the vibe get worse the faster you go? Happen only within a "sweet spot"?
Is it a harsh vibe, or just a little shudder?
Could be the shaft wasn't balanced right, or the joints were not in alignment when it was welded up.

Doesn't get worse, just that little vibe. God I hope I don't have to make another trip to the dl shop.

Might be a dumb question, can you drive at 65mph in 4hi?