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Discussion Starter #1
I’m in the process of doing my winter upgrades, one of which is installing my Wilwood rear discs and e-stopp. When I measured the axle offset on each side I measured on the front side of the axle flange not thinking two things of it. Both sides measure 2.50 for offset. When the kit finally showed up the driver side won’t bolt up properly, the caliper is so far off center it damn near physically hits the rotor. Thinking I had the wrong offset I ordered a 2.66 kit. This evening it was not sitting right with me so I put the passenger side on to verify, well it worked perfect. I set out to figure out what the problem was and think I found it. The bearing on the axle is sitting a 1/16th farther out on the rear than the front. The bearing appears to be fully seated on the axle itself and is square. The axle housing measures .70 from flange front to where the bearing seats. There is a small lip you can see in the picture on the bottom of the housing right near where the bearing would seat but it’s only on the bottom and shouldn’t force the bearing out on the rear and not the bottom. The 2.66 kit will be here tomorrow so I’m debating options:

1. Any thoughts on the issues? I can only think maybe the axle is bent but I don’t have an easy way to verify that. I don’t have an extra bearing laying around to set it in and see if that’s the problem but I’ll call around tomorrow and see if a parts store has one. The small ridge may be an issue but I don’t feel it is and I don‘t know a way to ream that out easily either.

2. If the 2.66 kit works on the driver side I could probably contact Wilwood and mix and match but that begs the question if the pads will engage properly. It does seem to measure the same all across the rear so I feel it would be minute and anything.

I’m leaning towards trying the 2.66 kit and seeing if I can shim it to center but I’m up firm ideas for sure.
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Master Chief, since the photo provides no depth perception, perhaps another photo, identical except 20° of the axis could be provided?
 

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1966 GT Fastback, 289, TKO 5-spd, EFI, 4-discs, TCP coilovers
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I am in the process of renovating the entire rear drivetrain and suspension, plus switching the third member from 3.00 to 3.55. My car already has the disc brake conversion and cable e-brake. From what I have read, there are two alignment issues to address; 1) the bearing has to seat fully into the differential housing, and 2) the axle splines have to go all the way into the third member. I read another post on this topic in VMF, where one Mustanger was able to get the axle on one side to fit and seat, but on the other side, the axle would not slide fully into the third member. This had to do with some kind of alignment setting with the drive splines and the positraction. Unfortunately, that's all the info that was available on the post, but I made a mental note because I will be dealing with the same situation when a get my axles and differential back from detailing / powder coat.

20200329_090224.jpg 20200329_092624.jpg 20200329_162446.jpg 20200329_162602.jpg

PS - Thank you for your service; all citizens owe you a debt of gratitude.
 

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Discussion Starter #4
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Here are a few different shots. The slight ridge I’m talking about is on the bottom but it’s also where the bearing is tapered so I’m not sure it matters. The axle itself has a weird line in the middle of the splines that was present when it was an open diff, I’ve been running this setup for about 3 years with this issue likely present the entire time and never noticed tire wear or braking issues with drums, really only noticed it due to the 2.50 offset setup not aligning properly. The end of the flange to the bearing surface is .70 all the way around but is it possible the flange itself is tweaked? Any other ideas? I’m open to about everything except replacing the housing, lol. The 2.6 will be here this afternoon so I’ll at least mock that and see where I’m at. And thank you for the gratitude.
 

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First of all - caution - I am not an expert by any means, but I have looked at a lot of stuff related to this topic, so ignore anything stupid.

Can you take a picture of the other axle, with the view like the photo second from the bottom? Maybe it is just an optical illusion in the picture, but it looks like the bearing is seated differently into the differential on the left and right hand sides; the left looks like it is in deeper . Can you use your calipers to measure the height of the bearing protrusion (it is supposed to stick out a little) on both the left and right hand sides, looking from the top. Also, is it possible that the bearing is not fully up against the stop on the axle - there's a gap. Is it possible the bearing moved a bit when you pulled it out?
 

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Discussion Starter #6
Soooo that is exactly what I'm asking and have described. I know the bearing isn't sitting flat, it's 1/16th out on the aft portion causing my issue. No the bearing hasn't moved or at least the best I can tell, it's sitting all the way down on the chamfer section like it should. The left side is where it's in 1/16th further and the caliper mounts to the rear, hence why I can't get the current 2.50 offset caliper to sit centered on the rotor. Now I'm just trying to figure out what could be causing it to sit 1/16th out on the right side. I'm going to try to run down an uninstalled bearing today and if I cannot I'll try and remove my existing bearing to make sure it seats properly but given that it measures .70 all the way around I'm more inclined to think it's either an issue related to the axle itself or that my housing is somehow canted at the end if that makes sense.
 

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Soooo that is exactly what I'm asking and have described. I know the bearing isn't sitting flat, it's 1/16th out on the aft portion causing my issue. No the bearing hasn't moved or at least the best I can tell, it's sitting all the way down on the chamfer section like it should. The left side is where it's in 1/16th further and the caliper mounts to the rear, hence why I can't get the current 2.50 offset caliper to sit centered on the rotor. Now I'm just trying to figure out what could be causing it to sit 1/16th out on the right side. I'm going to try to run down an uninstalled bearing today and if I cannot I'll try and remove my existing bearing to make sure it seats properly but given that it measures .70 all the way around I'm more inclined to think it's either an issue related to the axle itself or that my housing is somehow canted at the end if that makes sense.
It is really unusual for the bearing to go in like that. And it really seems unlikely that it is the bearing itself, because they are normally made so precisely with virtually no side-to-side latitude or deformation possible. Also, it seems unlikely that the differential cavity that accepts the bearing could be as unsymmetrical as that (one side deeper than the other). My opinion is that the right hand edge of the bearing is being prevented from seating into the differential all the way (it would not take a lot of roughness to stop the bearing from seating all the way), and there now is enough clearance around the bearing (albeit really small) that the bearing is being allowed to sit in the cavity crooked. Can you remove the axle and the bearing and take a really close look at what is going on? For my money, the problem resides in the side wall or base of the differential cavity. Maybe a machine shop could chase the cavity and fix the problem.
 

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Discussion Starter #8
Yes I can remove the axle and bearing but that's where I'm at, with a 1/16th difference it'll be nearly impossible to see the problem on the axle. The cavity where the bearing sits is symmetrical, I've provided the measurements showing that. I'm super happy someone responding but I'm chuckling as you are really just reiterating what I've already identified. My goal with the stand alone bearing is that will tell me if there is something wrong with the cavity immediately and then I can focus on the axle issue or just screw it and remove the housing and install a 9 inch :D At this point I hate to throw an axle at it and find out that's not the problem, I was able to find a bearing though so part of me wants to put that in by itself and if it works go ahead and have that one pressed on and see if it still a problem. Realistically is there a way to tell that my carrier isn't the problem? Just spit balling now.
 

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Discussion Starter #9
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Current situation. The bearing by itself seats just fine and the measurement on the axle from the bearing to the big ridge you see is the same all the way around. Spent some time on the phone with Quick Performance today and we think either the axle is bent or the flange is off. They said they would be willing to send me an axle and if the axle isn’t the issue if I order a 9 inch from them they will send it with just one axle so I’m not paying twice. In chatting he said I’m on borrowed time with my 8 inch and have really beat the crap out of it over the years so now to decide to attempt an axle or just go ahead and do the entire 9 inch that I know will last. Time for a beer and decisions :)
 

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I was going to ask if the car has ever been hit hard on that side that you know of
 

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Discussion Starter #11
No I don’t know for sure, I’ve only had it for about 9 years so prior to me is a crap shoot. Good thinking though, I didn’t even consider that!
 

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Yes I can remove the axle and bearing but that's where I'm at, with a 1/16th difference it'll be nearly impossible to see the problem on the axle. The cavity where the bearing sits is symmetrical, I've provided the measurements showing that. I'm super happy someone responding but I'm chuckling as you are really just reiterating what I've already identified. My goal with the stand alone bearing is that will tell me if there is something wrong with the cavity immediately and then I can focus on the axle issue or just screw it and remove the housing and install a 9 inch :D At this point I hate to throw an axle at it and find out that's not the problem, I was able to find a bearing though so part of me wants to put that in by itself and if it works go ahead and have that one pressed on and see if it still a problem. Realistically is there a way to tell that my carrier isn't the problem? Just spit balling now.
Here is a possible definitive test for the source of the issue - if the axle / bearing combination is still installed and you have your 1/16" additional height on the right side (as in your picture), great. Pull the axle and then put it back in with the axle rotated 180 degrees (bearing doesn't matter). If the problem moves to the left side, it is the axle and it probably is bent. If the extra height still stays on the right, it is the differential housing.
 

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Here is a possible definitive test for the source of the issue - if the axle / bearing combination is still installed and you have your 1/16" additional height on the right side (as in your picture), great. Pull the axle and then put it back in with the axle rotated 180 degrees (bearing doesn't matter). If the problem moves to the left side, it is the axle and it probably is bent. If the extra height still stays on the right, it is the differential housing.
PS - I forgot to compliment you on your jack stand carpentry - very well made, straight, square, finished edges - nice job. I built a set similar, and even put casters on the bottom so I could still push the car around.
 

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Set up a couple of sawhorses and place the axle on them 1 horse just inside the splines and 1 horse past the step down area where the bearing is pressed on. roll the axle on the sawhorses and if it is bent you will see the flange wobble. It does look like the axle is bent looking at the overhead shot looking down on the axle inserted into the housing.
 
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