Some confusing groaning going on...

[ELVA164]

Hi all,

So I did a drivetrain fluid change recently (M1 0W-40, Redline MTL, M1 75-90LS) and all went well except I'm hearing some occasional groaning from the clutches in the diff. I double-checked that the oil I used had the additive package in it and I added the 1.9 quarts it needs, so I'm a bit confused. I thought maybe it might have to work into the clutches but it's been a little while. Anyone have opinions one way or the other about the Mobil 1 gear oil? I used AmsOil with additive before but didn't want to fool with it this time.

Thanks!

-Mike

[agent]

I've used M1 75-90 in several diffs. How many miles on it? Has it ever been serviced other than fluid changes?

[ELVA164]

I don't know the mileage for sure (bought and installed it used), but I'd guess in the mid 100s. I've never done service aside from oil changes. The thing that concerns me is the diff was quiet as far as the clutches go right up until I jacked it up and changed the oil. I mean, it's quiet probably 95% of the time but during tight turns it'll have the occasional "rrr" sound. Not chatter, more of a groan. If I'd used the additive like last time I would probably add a bit more, but I don't know if you can add that to oil with the additive built in. It's also curious if you say you've used it on other diffs without issue.

[TobyB]

I think it's that you used the 0-40 instead of the 15-50.
The 15-50 has the additive package you want...
...for your rockers and cam!!

heh

As to the diff, if it bugs you, change it. I have found that
'some works better than other' and that it's not entirely rational.

My experience was with Redline CV2, a good grease, that WOULD NOT
stay in the hubs of a 2002. Mobil 1 synthetic- no problems.
I've used CV2 in all other sorts of similar places with great results...

I use redline in the 4.11 LSD in the race car, and it behaves itself, and seems
to hold up fine despite getting damned close to 300f on a hot day when we're in
close traffic...

t

[ELVA164]

I think it's that you used the 0-40 instead of the 15-50.
The 15-50 has the additive package you want...
...for your rockers and cam!!

heh

As to the diff, if it bugs you, change it. I have found that
'some works better than other' and that it's not entirely rational.

My experience was with Redline CV2, a good grease, that WOULD NOT
stay in the hubs of a 2002. Mobil 1 synthetic- no problems.
I've used CV2 in all other sorts of similar places with great results...

I use redline in the 4.11 LSD in the race car, and it behaves itself, and seems
to hold up fine despite getting damned close to 300f on a hot day when we're in
close traffic...

t

I'll concede the 15W-50 has more ZDDP (1400ppm?), but the 1100ppm in the 0W-40 is enough for BMW so it's enough for me. Besides, the thickness of the heavier oil in cold starts up here is extremely noticeable and using the car every day in those conditions has to be worse than a bit less zinc, right?

....Right?

Regarding the diff oil, maybe it is just that simple. But you forum guys (and girls?) are supposed to have magical fixes so I don't need to jack the car up again! :p I did notice the diff was down half a quart or more from a slow leak at the drain plug; maybe it ran low for a bit too long and got hot?

[agent]

It could just be the first sign of a bearing giving up. Rotating the axle(s) while listening to the input and output shafts with a mechanic's stethoscope may give more insight.

[TobyB]

Hee- ok, fine, I run the 0-40 in all the M42-52-54's we have, too, so I can't
pick on you TOO much!

But if it was me, and IF it bugged me
(which it usually doesn't)
I'd try changing oil types. 1/2 qt low on a street car shouldn't have
caused any problems with the LSD, unless you were commuting a la Ken Block...

t

[ELVA164]

Hee- ok, fine, I run the 0-40 in all the M42-52-54's we have, too, so I can't
pick on you TOO much!

But if it was me, and IF it bugged me
(which it usually doesn't)
I'd try changing oil types. 1/2 qt low on a street car shouldn't have
caused any problems with the LSD, unless you were commuting a la Ken Block...

t

Who do you think taught him all that? ;D

I'm very touchy about noises and sensations when driving cars because I have an unhealthy amount of mechanical sympathy. Maybe I'll drive it around for a bit longer and see if anything changes.

Agent, I'm pretty positive it's the clutches in the limited slip, but it's not too tough to do as you suggested so I'll get to that either early next week or when we get back from COTA.