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What are the signs of a bad Diff?

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Old 05-03-08, 05:38 PM
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What are the signs of a bad Diff?

Hey all, I am pulling the engine and trans and getting a J-spec trans to replace mine.

I figured i would take alook at the diff fluid while everythign was apart (I have had the car for 4 years and neverchecked it....in my defence it hasn't run in the last 3. Either way it should have been one of the regular maintenance items.


Getting back on topic. I pulled the drain plug and there was quite a bit of microscopic metal shavings on the magnetic plug. But how much is too much? How do you know you need a new diff?

The reason I ask is because I can get a low mileage TII diff shipped with my transmission and save $125 in freight, but I don't want to get it if I don't have to. Also the current diff is leaking at the pinion seal, so if I use the current diff that is on the car I will have to replace that seal.


Also, what lubes do you guys preffer? (brand/weight?) for diffs and trannies. Have any of you used Mobil 1?
Old 05-04-08, 12:38 AM
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Metal shavings are pretty common in the diff. If they are bigger than grains of sand, there may be a problem. Was there any howling coming from it while driving? Any clunking?

TII rear ends tend to hold for up a long time. Mobile 1 is a fine choice for oil. I prefer redline.
Old 05-04-08, 01:00 AM
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i use redline 75w90 with the added lsd stuff.

peace
Old 05-04-08, 02:52 AM
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I had this problem with my z28 before.
Listen for weird high-pitch huming noises coming from the dif while driving, it that happens then you already have a bad diff. one of the teeth is messed and is vibrating evertime it makes a revolution. i had no clue b4 so i thought it was nothing, later on the noise became louder and then one day BANG. and i lol i heard crunch then BANG BANG bang then car stoped moving.
sry for making a short story long but yea i was 17 so i didnt know anything about that ****. high pitch huming noises that come and go are a begining sign.
to many times i would fucken race off red lights, or floor it from stop.
now with my rx7 i wait till i get going and dont burn out as much then i drop the torque that these cars so elegantly provide
Old 05-04-08, 03:24 AM
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high pitch noise is ring and pinion

most diffs go bad by clutches wearing out.


ps i do have a brand new mazdaspeed 2 way lsd for sale, pm me if interested.

https://www.rx7club.com/showthread.php?t=748796
Old 05-04-08, 07:38 AM
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what does a clicking/clunking sound mean? my S4 TII will sometimes do this when making tight turns
Old 05-04-08, 11:37 AM
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the clicking and clunking means that one or more teeth are already bad, and the diff is already bad. the clicking turns to clunk then it gets louder , then the car wont move.
do you do alot of burnouts? : )
Old 05-04-08, 01:00 PM
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A clunck going around corners can also be a locking diff unlocking so the wheels can turn at different speeds.

Brian
Old 05-04-08, 04:03 PM
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When you hear a knocking sound on the rear of the car, definitively you have a differential problem.
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