[TheCoder]

So It is very possible that I over tightened the input flange nut! I heared a whiz . Just yesterday I took it for an alignment and after I left it got pretty bad. The guys at the shop showed me some play at the input flange!

After I left the shop, I could hear a strong sound from the diff , especially when I am decelerating (either by using the brakes or just letting it cruise to a stop).

So the question is

1. is this a sign that the pinion is toast !

2. if that is indeed the case, am I just better off getting another diff (heck, maybe it's a sign from the heavens it's time for a 4.10)

To be clear, I want this fixed without spending unneeded extra cash. Having said that, if I am going to blow above +$1000 , then I'll start considering a diff upgrade.

Thanks,

[cowboyM3]

idk man. Where'd you go for the alignment?

I feel SWB or Sin City you're 500+ anyway looking at it.

[TheCoder]

Originally Posted by cowboyM3

idk man. Where'd you go for the alignment?

I feel SWB or Sin City you're 500+ anyway looking at it.

Went to Arrow. They actually showed me the play at the input flange. I am highly certain it has something to do with me over / or under tightening that input flange nut. The question is, what are the signs of a damaged pinion ?

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[whips333]

What's your mileage? It might just be time for a rebuild.

[TheCoder]

Originally Posted by whips333

What's your mileage? It might just be time for a rebuild.

Its only 99k. What is normally the "time to rebuild" ? I dont think its 99k...

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[duracellttu]

When I had diff issues I did a ton of research and found that people experience with getting the diff rebuilt at local shops varied WIDELY. I ended up ordering a new diff through Turner Motorsports who gets them directly from Dan at diffsonline. Dan is arguably the most knowledgeable guy out there on BMW diffs and can customize them any way you want. My new diff with upgraded REM polished 3.91 gears and replaced the Mvariable LSD with a traditional 3 clutch pack was pricey but I've had zero issues. You are paying for peace of mind. If you want a rebuilt stock unit it will be less expensive of course. Sometimes it pays to make a larger investment to get it done properly at a shop with a known reputation. Sorry to hear you are having so many issues. Just my 2 cents...

[TheCoder]

Originally Posted by duracellttu

When I had diff issues I did a ton of research and found that people experience with getting the diff rebuilt at local shops varied WIDELY. I ended up ordering a new diff through Turner Motorsports who gets them directly from Dan at diffsonline. Dan is arguably the most knowledgeable guy out there on BMW diffs and can customize them any way you want. My new diff with upgraded REM polished 3.91 gears and replaced the Mvariable LSD with a traditional 3 clutch pack was pricey but I've had zero issues. You are paying for peace of mind. If you want a rebuilt stock unit it will be less expensive of course. Sometimes it pays to make a larger investment to get it done properly at a shop with a known reputation. Sorry to hear you are having so many issues. Just my 2 cents...

Ive called 4 shops (3 are diff shops) here just for fun. All 4 said they cant rebuild an m3 diff, so i see your point about variance in outcome.

I didnt do anything yet, but im preparing for the worst. However, just like your case, I'm taking this as a sign from the heavens that i need a 4.1 ( or 3.91).

Let me inspect the diff first, but if i end up needing a replacement, then i might just upgrade.

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[Rontgen]

If you under tightened it, you may be able to tighten it back up - you did mark the position of the pinion nut before you loosened it, right? The idea is to put the nut back on to the same relative position as it was originally - it's not torqued to a specific torque spec. If you didn't mark the nut before removal, this will be a crap-shoot at best.

If it's over tightened, you've over-crushed the crush sleeve and you're totally screwed. There's no fixing it besides pulling the diff and completely disassembling it, replacing the crush sleeve (and anything else worth replacing while you're at it).

In either case, there's a high probability it's time for a rebuilt diff. Good Luck!

[TheCoder]

Originally Posted by Rontgen

If you under tightened it, you may be able to tighten it back up - you did mark the position of the pinion nut before you loosened it, right? The idea is to put the nut back on to the same relative position as it was originally - it's not torqued to a specific torque spec. If you didn't mark the nut before removal, this will be a crap-shoot at best.

If it's over tightened, you've over-crushed the crush sleeve and you're totally screwed. There's no fixing it besides pulling the diff and completely disassembling it, replacing the crush sleeve (and anything else worth replacing while you're at it).

In either case, there's a high probability it's time for a rebuilt diff. Good Luck!

So I don't know yet if I under or over tightened it. Honestly, I'm a bit demoralized after this. But as soon as I get under the car I think It will be clear what happened. However, something in my mind tells me I didn't put the retaining plate back, so I hope the end result was that I under tightened it. I did mark it , but I can't recall the revolutions!

Anyway, I am shopping around and I came across a 4.1 diff by Fall-Line motor sports for a decent price. Are they a reputable shop when it comes to diff rebuilding ?

[AndresC]

Hey TheCoder! Sorry to hear that happened. Just curious, what were you doing on your diff?