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Discussion Starter · #1 ·
I drained my gear oil last feb and chunks of black gunk came out, so i refilled it and just this weekend i swaped out the fluid again only 6k later, once again i got black gunk but not nearly to the extend of the first time, even wrose this time i found what looked like a chipped tooth only about 3mm in dia but still it pissed me off.


SO the question is
How often do you guys change your diff fluid?


OOH btw I overfilled it by accident, the first time b/c the car wasnt level, this cause the weaker axle seal to blow giving me headcahes, but i replaced that seal when i did my rear suspension b/c you have to take the control arms off the knuckles which is a PITA job if you dont have the right tools.
 

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SO the question is
How often do you guys change your diff fluid?
On my 929, it's never been changed since I've owned it. Same with my Mercedes. My streetrod, with a '70's Nova 10-bolt rear was changed when I had to drain it to replace an axle seal. This has to be the most neglected maintenance item ever, but I can't say it has ever really caused me any grief, probably due to the rugged nature of the rear-end's internals (unless you race, which would get me interested in doing more changes/inspections).
The change interval for the '88 929 is 5 years or 60,000 miles.
 

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I will have to double check, but I thought the change interval on the 90 was at 100K for the first time, then 60K thereafter.

I have always changed my others at 100K, with no signs of any black rubber.

I wonder if its part of the seal that went bad? Maybe the seal was going bad long before you over filled it.

There is also a compression spacer that goes in the differential. I have not touched one, so I am not sure what its made of. From the manual, it looks like a piece that thats likely rubber or plastic that compresses when you put the gears all together, but that hold a space. I wonder if this thing is shreadding?
 

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Discussion Starter · #4 ·
i'm guessing the seal on the other side was broken because the other side was covered with oil when i first got the car, but i'm guessing that was replaced b/c that side doesnt leak oil..... after i over filled it the other side got covered with oil...... so i could have been a combo of both letting dirt inside the diff :unsure: , i'm just glad i caught this item before any real damage was done.


Yeah i'd imagine it is one of the most neglected items on rwd cars.
 

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is there a better an OEM diff oil that can be used ? will it make anyhting smoother ? I can say the futhest Ive gone is to have my diff oil level check and it appeared to be clean...
 

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Lucas oil recommends theirs, and there are synthetics, but if conventional will go 100K, I doubt they will make a difference. Just my opinion, though.
 

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Discussion Starter · #7 ·
i'm sure any synthetic blend will make things smoother and it supposebly runs longer, knowing most car manufacturers they tend to cut corners and oil seems like an easy place to do so. As far as gains i'm sure changing it front an old to a new fluid will transfer the power better esp with synthetic. It has been proven that car gain hp just from a complete oil change. That is trans, motor, and diff. Now grant it these gains are minimal, but they are gains.... and it'll keep your car running longer. From this recent "tune up" i gained a shitloada power, but that has very little to do with the diff fluid. I gained power b/c i tuned air intake temp and got rid of/weled up exhaust leaks. I can do burn outs :D, and that is on new tires which are v rated.

As far as synthetic running longer, that doesnt really concern me b/c i plan on changing out my diff fluid every 25k since that diff has 200k on it, but i did put it in this time.
 

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burn outs from a stop ? without braking ?
 

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Discussion Starter · #9 ·
hmm havent tried from a stop, i will later on tonight, but i did a massive burnout from 5 mph roll it kinda scared me b/c i just bought these tires, i'm pretty confident it'll do them from a stop tho
 

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I can do it rollin at 10 km in 1st gear, punch it and spinin the rears for a bit but It hasnt been able to do it lately, too many kms.
 

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Discussion Starter · #12 ·
i cant do it because the exhaust system i designed gave quite a bit of top end hp but down low it stayed stock i think, so when its rolling the engine is turning higher rpms thus creating more power. She is really fun on the h-way now and i do have to watch out on turn because i'll fishtail without a problem if i gun it too mutch :whistle:. I'm really trying to take it easy on her this time because i need her to last untill i have time to finish my sho, which shouldnt be too long but i dun know. I'm praying i have time because its starting to snow and i really wanted to avoid driving her thru this winter.
 

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I found keepin the gas tank full with full size spare tire gave me some decent snow traction, its a fun car to drive in snow even though Ive lost it a couple times, like on a freeway on ramp going sideways in 3rd.
 

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Discussion Starter · #17 ·
i just recently put synthetic in my diff case, and i also run synthetic in the trans althought i think all of the tranny fluid is synthetic, and i run regular 10w30 in the engine.

Weather you run synthetic or not doesnt really affect the life of a mechanism, its weather you warm up the mecahnism before use and oil change intervals that play the biggest roles.

I always try to warm up the car before driving because it allows the oil to reach the temperature where its viscousity is at a prime level, and ofcourse i always change my oil in the engine every 3k miles. What synthetics do is allow you to run the car for a longer period of time without an oil change, and that is just abuse of a car and plain stupid to begin with because overhauling an engine after throwing a rodbearing isnt fun at all.
 

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Discussion Starter · #19 ·
i agree that they flow better but cleaning? really? i never thought about that since if you just stick to changing the oil regularly all the gunk is just washed out with the old oil.
 
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