3.25 LSD Diff overhaul question

[BMW3.0CSi]

Hi all,

I did some research on the forum, but could not exactly find if one of you have experience with surface rust on the crown wheel of the diff just by the fact that the diff was standing on the shelf for years?
We opened mine yesterday and it definitly needs new bearings, but the question is if it would be harmfull to take of the surface rust of the crown wheel by a copper brush and then put it back together. My specialist does not give any guarantee that it doesn't start 'crying' at idle speed afterwards. And I have some bad experience with crying diffs just by replacing stuff.

Personally I think it's not an issue, but before spending 1000+ euro's for a complete overhaul I would like to check some opinions here. My specialist did a few teeth already, but never experienced the amount of surface rust as with this one.

Thx!

 

[Fritzie]

How many kilometres/miles do you want to drive with car? 5000 / year or 100.000 / year?
I would give it a try. Cleaning looks nice enough. Cleaning with a copper brush.

 

[Arde]

On my E24 the differential had a bit of play and the mechanic replaced the gears inside, and while at it made it a bit shorter so it revs higher...Cleaned, resealed, like new.

 

[BMW3.0CSi]

How many kilometres/miles do you want to drive with car? 5000 / year or 100.000 / year?
I would give it a try. Cleaning looks nice enough. Cleaning with a copper brush.

I think 1000 kilometers per year max. But still, if the 'crying' is there it won't go away anymore is my experience no matter how many kilometers/miles you drive.
I know that it has to do with the pinion and crown wheel and how they are matched up to eachother. I read on the internet that the setup of the 2 in general is unique and therefore sensative for any adjustments or fixing play. But that is all based on what I read on the internet and my first diff overhaul, so I'm a bit careful in changing/replacing to much in the diff.

Thanks for your advice Fritzie.
@Arde, you didn't experience any 'crying' of the diff afterwards?

 

[Ian C]

I would think the rust must be removed or it will come off during use and go through the bearings

 

[Arde]

@Arde, you didn't experience any 'crying' of the diff afterwards?

My differential identifies as male, and men don't cry...
I can take a video next week, did not cry before or after. Had an annoying clank on acceleration.

 

[sfdon]

I see no pitting?

Is this an 8 or 10 bolt diff?

What ratio?

 

[Rouge]

I think this rust is really superficial and I don't think you'll get any extra noise.
Very nice bevel gear.

 

[BMW3.0CSi]

I see no pitting?

Is this an 8 or 10 bolt diff?

What ratio?

No pitting indeed, but according to my specialist it suffered enough based on below foto and the ‘blue’ line on the bearing rollers.
It’s an 8 bolt diff and 3.25 ratio.

 

[sfdon]

Final drive bearing set ( 6 bearings) including spacer for all models and years of production you need 1 for 1 car

Final drive bearing set ( 6 bearings) including spacer for all models and years of production you need 1 for 1 car

www.wallothnesch.com

 

[BMW3.0CSi]

Final drive bearing set ( 6 bearings) including spacer for all models and years of production you need 1 for 1 car

Final drive bearing set ( 6 bearings) including spacer for all models and years of production you need 1 for 1 car

www.wallothnesch.com

I know the set and the bearings will be replaced, but the whole point was my experience and fear for a crying diff based on previous overhaul. Was wondering if others also experienced that and to get a feeling on how critical the pinion-crown relation really is.

 

[sfdon]

If your guy is a diff specialist at a gear shop and he is good- listen to him.
i have a 3.25 open I could sell. In my personal car so I know it’s good.

 

[BMW3.0CSi]

If your guy is a diff specialist at a gear shop and he is good- listen to him.
i have a 3.25 open I could sell. In my personal car so I know it’s good.

I do, he does and has done many Getrag gearboxes and diffs, but did not have experience with the rust as he told me. Therefore I started this thread. He doesn’t give guarantee for the crying part (which I understand), thinks it’s not an issue, but before spending a 1000+ euros I wanted to check here if people have experience with this matter.

 

[sfdon]

Check with gear marking grease…..

Amazon.com