We found the vibration!

[Aunt Bee]

We still had a vibration to fix on the Bee, and had it narrowed down the rear end. We pulled the 8 3/4 489 apart this weekend and found the problem. Thanks to this forum, we know we're supposed to have an adjustment on the passenger side axle. This is what happens when you don't...

 

[benno440]

i have just put mine back together eaton true trac 3:55 gears 30 spline axles new with 489 case all new, i just assembled and bolted up was not aware of any adjustments,care to explain?

 

[daredevil]

If your new axles have sealed bearings you are fine. Factory bearings have to be adjusted. Most aftermarket use sealed (green) bearings

 

[Aunt Bee]

True! The last ones installed in our Bee weren't green, and this axle has been doing some walking around...at least we know what the problem was now, and we'll do a couple of upgrades as we get it back together!

 

[Meep-Meep]

We still had a vibration to fix on the Bee, and had it narrowed down the rear end. We pulled the 8 3/4 489 apart this weekend and found the problem. Thanks to this forum, we know we're supposed to have an adjustment on the passenger side axle. This is what happens when you don't...

I'm glad you discovered the adjustment for the factory tapered roller bearings, but I don't see anything wrong in that axle spline pic.

 

[Meep-Meep]

i have just put mine back together eaton true trac 3:55 gears 30 spline axles new with 489 case all new, i just assembled and bolted up was not aware of any adjustments,care to explain?

If you are running the tapered roller bearings you will need to adjust axle end play using the castle looking nut in the axle retainer plate. I'm not sure about the true track, but if it's intended for use with factory axles and bearings it must have some kind of floating thrust button in the center of the carrier.

Let us know what you have for axle bearings and we'll be happy to go from there. Note: If you have a sealed ball bearing that is not stock, and as mentioned, requires no adjustment.

 

[benno440]

ahh sweet yeh its a new style green bearing so should be fine,
thanks

 

[Kernel Sanders]

Looks like that was cut wrong! or if it were cut right it was using a bent or deformed axle. Definately your vibration problem right there...glad you found it!

 

[Meep-Meep]

Looks like that was cut wrong! or if it were cut right it was using a bent or deformed axle. Definately your vibration problem right there...glad you found it!

I disagree. That is just the way it was machined at the factory and I bet that axle is fine. That small amount of mass displacement at that radius would never be detected.

 

[Cranky]

So long as the machined areas were machined concentric with the centers, then it should be fine but to really know for sure is to put it in a lathe (between centers) and spool it up to around 1000 rpm and see if it vibrates the lathe. If it were me, I'd start out at around 400 rpm and step it just in case it is out of balance etc.

 

[RustyRatRod]

I thought the axle looked fine, too. In fact, I've seen much worse.

 

[Supershafts]

We still had a vibration to fix on the Bee, and had it narrowed down the rear end. We pulled the 8 3/4 489 apart this weekend and found the problem. Thanks to this forum, we know we're supposed to have an adjustment on the passenger side axle. This is what happens when you don't...

If the axle adjustment wasn't right then you would have a issue because the entire wheel can move as the axle won't be held right and centered and have the ability to move in corners ect.

The splines look ok other than maybe what looks like wear at the very inside section of spline, which that won't cause a vibration at that section

 

[coloradodave]

Doesn't it look like the machined section near the splines is NOT concentric to the rest of the axle? Is it just the camera angle? What say you, original poster?

 

[snakeoil24]

You will never know for sure unit you spin the axel up like cranky said in a lathe. Mount it, center it and run a dial indicator first to check run out.

 

[Meep-Meep]

Yes, the spline is not concentric to the forging, but the spline and bearing seat are machined between centers in one operation so it's a non issue.

 

[Kernel Sanders]

I thought the axle looked fine, too. In fact, I've seen much worse.

Ok I will stand corrected lol

I've just never seen one like that and if I had one I personally wouldnt use it if I had disassembled looking for a vibration, however as was mentioned spinning it up on a lathe is a good idea for sure.

 

[Aunt Bee]

OK, thanks for all the input!!

The picture I posted shows what we're considering to be non-concentric wear, and on the opposite side (which I didn't get a clear picture of), the splines are scored and chipped. The driver's side axle doesn't show any wear.

We're confident that we found the issue. The answer for us is to install new axles, along with a Detroit Locker True Trac, and change the gear ratio while we're at it. This is the last part of the drivetrain that needs to be rebuilt, and we're looking forward to it!

 

[snakeoil24]

Hey you can always throw money at it, when you can't find the answer.

 

[Meep-Meep]

OK, thanks for all the input!!

The picture I posted shows what we're considering to be non-concentric wear, and on the opposite side (which I didn't get a clear picture of), the splines are scored and chipped. The driver's side axle doesn't show any wear.

We're confident that we found the issue. The answer for us is to install new axles, along with a Detroit Locker True Trac, and change the gear ratio while we're at it. This is the last part of the drivetrain that needs to be rebuilt, and we're looking forward to it!

What is shown in the pic is not wear! It can't possibly be wear because that part of the axle doesn't touch anything. The splines can wear at the point where they contact the side gear and maybe the very end where the thrust is taken up, but that's it. Those are tool marks from being cut on a lathe. It just so happens that when the center drill hole was put in the end it wasn't very concentric so all the other cuts were referenced off that point. Can't comment on the other side.

 

[Aunt Bee]

Hmmm...when we're back in the garage next weekend, we'll re-evaluate. Maybe there's more to the story, we'll let you know. Thanks again for the experience and opinions!