bent axle flange?

[WSSix]

New tires didn't help. That's one more thing checked off the list. Next, I'll swap axles around in a day or two.

[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

[SSLance]

Man I feel your pain chasing down vibrations...been there done that. I'm sure you have but just in case, make sure there isn't any play in your rear axle bearings. I've found pushing straight up and down on the raised off the ground tire with your hand is the best way to feel if there is any play at all. A very small movement of the bearing will vibrate..believe me...

Sweet about the 9.5s on the front, been there done that too!!

[WSSix]

Thanks Lance. There is very minor play in the axle bearing. A few thousandths at best. It's if I twist side to side though while grabbing the outside of the tires. I can't get any up or down movement. No in or out movement either.

[WSSix]

Well, it appears it is in the drive shaft or pinion. I get the vibration at 65 with no axles in the car. After this happened I decided to get under there and really be specific about what I felt and could move. I get a little slop in the u joint. It's so minor that I don't see how it could be the issue but I have a new u joint on order all the same. I'll get it put in today I hope. This is annoying, lol.

[WSSix]

How much does 3 in lbs matter?

When I built the rearend and set up the gears, I crushed the sleeve and went over the spec by 3-4 in lbs. Could this have anything to do with my vibration?

I ask because I could hear a noise in the rearend at the front under the pinion and it did feel rough. However, the pinion doesn't have any play. I also have no metal shavings or anything in the gear oil. I drained it last week when working on the car to check. This roughness and noise happens with speed. At idle in first gear, I hear or feel nothing. At idle in fourth gear, I hear and feel it. This is with the rear off the ground so the tires can spin freely.

I'm just looking at everything since I'm not getting far with this vibration issue. I've determined that it's definitely in the driveshaft and pinion area. I still got the vibration with no axles in the car and only the driveshaft in place.

New u joint didn't change anything.

Thanks

[WSSix]

Well, I've found something new that might be an issue. I have too much delta at the u-joints. It's 5* at the front u-joint and a little over 4* at the rear u-joint. The transmission is lower than the rear end so I'm going to raise it with shims to see if that will flatten out the angles at the u-joints. Might need to pull a shim out of the rear end too but that's no big deal either.

I don't see how this could be the issue necessarily though. Before I did the suspension work, the rear sat lower than it does now due to the worn out factory springs. That would have made the angles worse. Yet, I had no vibrations then.

[light bulb!] As I'm typing this I just remembered the front end used to sit higher too though. I've brought the front end down with the coil overs compared to worn out factory coil springs. That could be the reason I didn't have the issue when I first did the engine and transmission swap. Yep, going to raise the tail of the transmission.

Oh, and I have 1-1/2 inches of yoke shaft sticking out of the transmission currently. I still have plenty of engagement with the tail shaft. Could this be too much though?

Thanks