bent axle flange?

[WSSix]

I'm still fighting a vibration issue with my car. I've slowly been testing areas and making adjustments. Here's where I'm at now. I have new wheel adapters that center on what little bit of a hub I have. They fit great. They helped the vibrations but didn't eliminate them. The wheels and tires have been balanced using a road force machine. They were out and that helped again. Again, however, it didn't eliminate the vibrations. I had the driveshaft balance checked. It's good. While I had the car at the driveshaft shop, the tech noticed the passenger side rear wheel vibrated/wobbled/bounced around. So I've currently been concentrating my efforts there.

I've had the rear of the car up and have been checking that right rear axle. It's not the wheels as I can swap wheels side to side and the wobble is the same regardless of the wheel. I bought a dial indicator and am getting about 0.035" wobble on the outer rim lip. I've been able to trace this back to the axle flange itself. I've identified high and low, or in and out, using that same dial indicator. The difference is about 0.006". Can this be the issue? I can remove the wheel from the car and drive it up to about 30-35mph while on jack stands and there's no vibrations in the car like there is when the wheel is on. I can also see the rotor wobble as it rotates and it pushes the caliper in and out as well. There's definitely an issue with the flange and not the wheel balance that's vibrating the car. So it feels like this is the issue. But I don't feel any vibrations while driving the car until 60mph. I would think if it's the wheels I would feel something always. I wonder though if the shocks are able to control the vibrations until 60mph since it's not a serious wobble. Think that's plausible? I'm going to adjust them tomorrow and see if I can get the vibrations to change when they come in or something.

The concern I have is if this is the flange, how in the world did this happen? These axles are brand new, custom units from Moser with a few hundred miles at most on them. There's no way their tolerances are that lax. That's terribly out of round for a brand new machined part. The high and the low points on the axle flange are not 180* apart. It's more like 150*-160* at most. I've been fighting this issue since the rear end went into the car. I haven't hit a curb or anything. I just didn't expect it to be axle related since I was doing other work at the same time and these axles fit just fine without fighting them. I'm just not sure what's going on any more with this vibration issue. It's driving me bonkers.

Thanks

[TheJDMan]

Seems to me that you have answered your own question. You have a bent axle and if it is new you need to contact Moser about getting it replaced ASAP. Did you purchase the complete rear end from Moser or just the axles? Either way, it may have been damaged in shipment.

[WSSix]

that's what I was thinking, too, Steve. I just thought I run my tests and observations by others to see what they thought.

I'm not sure Moser will help. I had to take the axles to a machine shop in order to get the access hole drilled into the flange so I could bolt the axles in. I don't see how the machine shop could have damaged them, but I'm sure Moser will wash their hands of the situation since work was done to them after the fact.

I just got the axles from Moser.

Thanks

[WSSix]

Changing the shock settings didn't change anything in terms of the vibration.

I also spoke to Moser. They said 0.004-0.005 is typical but that it has to be measured on a lathe with the shaft between centers or on V-blocks in order to be accurate. This makes sense but at the same time, my wheel wobbles. I can take a video and show it wobbling. So if it's not the flange or axle shaft, what else could it be?

The person who welded the Ford bearing ends onto my housing used the alignment tool that puts the axles in line. Also, installing and removing the axles is easy as expected.

Thanks

[SSChef]

I had a similar situation and it turned out to be the wheel hub register to hub register. One axle was off by .015 and the wheel would not fit perfectly on the axle hub. It would be crooked when you tighten the wheel. I have read that you are running spacers. Are they hub concentric?

[WSSix]

Yes, that was the reason for needing new adapters. The new axles had very little hub protruding through the rotor so I needed an adapter that was squared on the backside so that it could engage the hub. The front side of the adapters fit the wheels well. The wheels haven't changed through any of this.

Unless anyone has some better ideas, I think what I'll do is have the wheels balanced one more time with emphasis on checking for rims being true and tires being good. I just had them balanced last time. I didn't specify anything beyond that. I'm expecting them to come back as being just fine.

Then, I'll swap axles side to side and see if the wobble follows. If so, I guess I'll have to order a new axle. While the axles are out, is there anything in particular I should do or look for to help determine a cause to the issue?

I hate throwing parts at a problem. I'd rather try to learn from the issue

Thanks!

[MillerBuilt]

Originally Posted by WSSix

I'm still fighting a vibration issue with my car. I've slowly been testing areas and making adjustments. Here's where I'm at now.
1) I have new wheel adapters that center on what little bit of a hub I have. They fit great.

2) I've had the rear of the car up and have been checking that right rear axle. It's not the wheels as I can swap wheels side to side and the wobble is the same regardless of the wheel. .

3) I can also see the rotor wobble as it rotates and it pushes the caliper in and out as well. There's definitely an issue with the flange and not the wheel balance that's vibrating the car.
Thanks

Based on your previous statements above I have a few comments. The one I have labeled #3 though stands out the most to me. I would start here since that is not normal. For this wobble to occur a few things could be causing this. Axle flange face may not be "true and 90" with the shaft, assuming you run a two piece rotor, your rotor hat may not be "true", or rotor may not be "true". If you run a 1 piece rotor it also may not be true. Then there are the adaptors you are running, are those true in thickness when checked in multiple areas?

Then,,,,, if you are super unlucky, it could be a combination of all the above in what's called "tolerance stacking". 005", .005", .005", 005" starts to add up and wobbles will occur that also translate into vibrations. If you think about the above and the motion it would create if these components are not true and of consistent thickness, it absolutely would create an increasing vibration as the near hub center issue works its way up through the heavy, large o.d of the wheel/tire combo...

I would like to see that video of the rotor wobbling and pushing back on the caliper piston. Also curious what brake package?

Hope this helps.

Jay

[WSSix]

Thanks Jay. My reasoning for removing each component and working my way back to the axle flange was in an attempt to eliminate tolerance stacking and ensure it wasn't multiple issues. I also was checking for flushing fitting between components as I assembled and disassembled.

My adapters came from Motorsport Tech. They are a good company. I haven't measured them beyond putting the dial indicator on them. What I did find is that the wobble is approximately the same 0.006 and in the same high and low locations as the axle flange.

Brakes are C5's so rotor is one piece. Brake kit is from Kore 3 though I supplied the rotors and calipers. I had these same brakes and calipers on the last rear end with a different company's kit. No issues there. I don't really have a way to check the rotor hat for flatness. The rotor does lay flat and not wobble when set on the floor or other "flat" surface.

One other thing I haven't mentioned is I have gone through and cleaned all the mating surfaces and inspected them to make sure I don't have any mate up issues that could some how create a stacking issue. I've sanded down the back of the wheel with a sanding pad and 320 grit for instance just to see if there were any high spots. I noticed nothing out of the ordinary. The high and low spots from the axle flange translates out to the rim edge.

I'm about to go out side and start working on swapping the axles. I'll see about getting a video when I do that. I'll have to remove the brake kit which I think this will give me a better view of the axle flange to determine is the face is simply not true or if the shaft is bent which is throwing off the flange.

Thanks!

[MillerBuilt]

No doubt you are taking a very thorough approach to solve this issue, and all your parts selections are solid too. I feel for you on this. I hate problems like these. Everything sure does seem to point in the axles direction though..

I take it you have a 12 bolt since you are swapping axles. This will certainly prove it out if the wobble now presents itself on the opposite side that you change it to.

Let us know what you find.

Jay

[WSSix]

At this point, I don't know how else to solve this issue without being thorough in my methods. Nothing is obviously the culprit. I'm also still concerned I may have more than one problem.

I played around with the car today but didn't swap axles yet. With the new tires on the car, the wobble and vibrations weren't as pronounced. So I decided to swap wheels front to rear instead of just going straight to swapping axles. The low speed vibrations at 30 mph are pretty much gone with the front wheels on the back now. I decided I better try 65 to see how it felt there considering that's where I get the vibrations when driving the car and not just sitting on jack stands. I was only going to 30-35 on jack stands because that's all I needed in order to get the vibrations.

The vibrations are definitely there at 65. 55 feels ok but 65 is very different. I got the vibrations with the wheels on or off the car. This leaves me confused in all honesty. My thoughts at this point are to pull the axles and run the car up to 65 with just the differential in place. If I get vibrations, it's in the driveshaft/pinion angle. If not, axles. I have a Detroit TruTrac differential. I'm going to read the manual as well, but does anyone know if running it without axles in place will cause a problem?

I've gone through 6 degrees of sweep with the pinion angle in 2 degree increments previously. Nothing changed one way or the other from what I could tell. If it's driveshaft/pinion related, I'm going to be more lost than I am now, lol.

Jay, I have a modified 8.5" 10 bolt with Torino bearing ends welded on.

Also, before I pull the axles, I'll most likely go drive the car with the wheels swapped front to rear. I want to see if the vibrations also move. While I had the wheels and tires checked and they told me the wheels are good. I'm not sure why I don't get the vibration with the front wheels but I do with the rear wheels.

The one good thing from today is that I've determined I can indeed run a 9.5" rim and 275 tire on the front without too much trouble. Yes, minor inner fender work and lip rolling will be needed but I already planned on that anyway. I'll start the hunt for some factory 9.5 rims soon.

Thanks