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Diff and Axle troubleshooting

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Old 09-15-18, 04:46 PM
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Diff and Axle troubleshooting

Hey guys,

got some driveline questions for you folks. I was working on the car today, checking everything, and I came across two grease stripes along the underside of the car, where it had been flung out from where the axles attach to the diff (see pictures). Looks like leaks from seams and not from boots. I know I'm due for some driveline work, what would you guys recommend doing in this situation? This is my daily driver and only vehicle at the moment. It has to last me to the end of the year. Is it worth taking out the axles and rebuilding the CVs? There is minimal play in the axles from the diff to the hub.

The diff has some play in it where the axles bolt up to it. Those flanges have a little bit of play side to side. As far as play between driveshaft to axle, it equates to about 1/4" arc movement at the driveshaft bolt. Its an S4 Turbo diff. What would you guys recommend doing here? Bearings and spacers? Could that tighten things back up?

Driveshaft still seems good

Looking for advice as to what to maintain/fix, so I can keep this thing running (I know where the FSM is, and read through it).


Matt

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Old 09-15-18, 05:48 PM
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From your photos, the CV joint boots all look intact. From the first photo, it looks almost like the oil leak may have been from the half shaft seal. From the second photo, it's hard to tell where the oil leak may have came from. I think you need to dig deeper by dissembling and inspecting. Rather than rebuilding your CV joint, it would probably be a lot more cost effective to buy new half shafts. I don't have a TII, but I recall a recent thread about new TII half shafts being available from maybe Rockauto. I bought new half shafts for my NA from Rockauto for about $80 each.
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Old 09-15-18, 06:48 PM
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Probably not a bad idea on the shafts.

Looking at the manual, you replace those shaft seals from the outside pretty easily. That would be a cheap fix. I am just wondering if I should bother with the diff while I'm in the area (would give me an excuse to use my big micrometers...). It doesn't say how much wiggle those output shafts should have, just that they should be engaging the splines.
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Old 10-23-18, 09:19 PM
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To close this thread, the grease came from the CV joints. The stamped seals that seal the butt end of the diff-side CV joint leaked all my grease out. Boots weren't leaking, but would soon be in need of replacement. I replaced them with a new set of axles from ebay. $130/pair, nice machine work.
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Old 10-24-18, 02:03 PM
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Hope those workout for you. I brought a pair of rear axles for my S5 NA from Rockauto during summer 2017. They are SurTrack/TrakMotive p/n MZ-8028. Most of the new rear axles are made in China. Couple weeks ago, I took a 920 mile round trip road trip down to Charlotte NC. Had an annoying vibration at highway speeds (65+ mph) that was most pronounced when coasting. After returning home, I found that my rear axles have noticeable radial play at the inner CV joints. I believe that this is the source of my vibration. I've searched the web and found that some other folks have had problems with rear axle shafts that they bought from Rockauto. Apparently, they were made in China and the metallurgy maybe questionable at times. These new axle shafts were tight when I installed them. I have since picked up a used Mazda pair from another member of this forum. These axles have about 180k miles on them and no noticeable play at the CV joints. I'm hoping to put them in within the coming week or so. Hope that this will solve my vibration problem.

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