Well, today, I adjusted my custom adjustable carrier bearing bracket to the proper location to get my U-joints within specs (no less than 1* and no more than 3*). Then I adjusted my pinion angle where it was 1* lower than the output propeller shaft just behind the carrier bearing.
So...everything looked great with the numbers.
Went for a test drive.....fricken made the vibration worse!!!!!!! I just dont get it!
Here's what I did:
I lowered the carrier bearing down from where it was set at to get the u-joint angles where they "should" be. Then, I added a 1* shim to the rear axle with the fat side facing the front.
The vibration was only noticed slightly under hard acceleration and at 65mph before any changes where made.
Here's my specs:
Tranny angle: 4.5* down
Front driveshaft angle: 2* down
Final driveshaft angle: 0* down
Pinion angle: 1* upward slope (with 1* shim). 2* upward without any shims

What went wrong???????
What do I need to do??? Add a 2 or 3* shim to the axle to push the nose of the diff downward more?
HELP! I'm very frustrated with this driveline stuff already.......
Any knowledgeable recommendations are highly needed!!!

Jim

 

is your driveshaft balanced?

 

Balanced? There was nothing that was wrong prior to lowering truck. This started immediatley after I lowered the rear of the truck.
If I raise the carrier bearing up higher, the vibration will lessen a lot, but it puts the tranny u-joint angles out of specs. Raising the carrier will bring the front DS section closer to 0*. Though the vibration tends to lessen.
The only thing I can think of is placing the pinion closer to a 0* angle. I just don't see it going the other way. Then again, nothing has been going right with this anyways.
It cannot be the balance, because the vibration was only noticed a little prior to todays adjustments.
Obviously I'm not doing something right.....I just dont know what.

Jim

 

I'd get it checked bro, but it's your call

 

Not a balance issue. It shudders at 15-20mph under light acceleration and shudders even more under hard acceleration.
This shudder wasn't there before today's changes. It only had a slight vibration at 64-68 mph.

Jim

 

I would still check the driveshaft, changing the angle may be only a band aid fix for the driveshaft being out of balance.

My stock drive shaft was horribly out of balance because the factory installed a u-joint off center creating a vibration. I added 4 degree shims and a carrier bearing relocator which fixed the problem.

I snapped the front u-joint and that was when I found out my driveshaft was out of balance.

 

I guess there is a misunderstanding here.
Guys, the truck had NO vibration issues until the day I lowered it.
I can't see why it would be out of balance in that case. The low speed shudder is definately not a vibration issue. It's an angle issue.

Jim

 

Your driveshaft angle is irrelevant unless you have a 2-piece driveshaft.

Your tranny output shaft and pinion angles need to be equal and opposite. If your tranny output shaft angle is 4.5* down, your pinion angle needs to be 4.5* up.

 

I have a question for you moregrip.
Does the tranny output angle need to be within 1/2-1* of the first driveshaft angle?
Reason I ask this, when you do a carrier bearing relocator, it dramatically changes the u-joint angles at the tranny. Does this pose as a problem?
I assume the u-joint angles aft the carrier bearing all the way to the pinion are the only ones that need to be within tolerance to have no vibration issues.
That's the only way I can see it when using a carrier bearing relocator.
What do you think?

Jim

 

To all moderators or anyone here that would know.
Who is an expert driveline person I can speak with about my problem?

Jim