[Morfius]

Three months ago I ordered a Quaife QDF17N LSD for my 2016 BMW M235i from Schmiedmann in Denmark.
I paid $1,400 for the differential.

As many BMW owners know, the OEM ring gear on the M235i is welded to the carrier and must be machined off and transferred to the Quaife unit. I followed the official instructions exactly and had a machine shop properly machine and fit the ring gear.

When we attempted installation, we immediately ran into a serious issue:

• The left-side bearing would not seat fully
• The carrier measured approximately 0.3–0.5mm taller
• The diff would not sit correctly in the housing

I documented everything:
• Measurements
• Photos
• Bearing/shim verification
• Part number confirmation (7599411 stamped)
• Bearing journal measurement (~6.063” per spec)

Schmiedmann insisted the product could not be wrong and suggested installation error.

For context: I have 20 years of mechanical experience.

To eliminate doubt, I sent the entire differential to a BMW-certified shop here in Ohio.

They had the exact same issue.

Schmiedmann’s position remained:
If I believed there was a defect, I could ship it back to Europe at my expense (around $600+ shipping), and only if they later approved it would anything be considered.

⸻

The Fix

The BMW shop suggested installing a RacingDiff BMW backlash adjustment snap ring kit.

I purchased:
• Snap ring kit – $390
• Assembly labor – $480

After installing the kit, the differential seated correctly.
Backlash was properly measured and confirmed.
I’ve driven 1,000+ miles with zero issues.

The diff now works perfectly.

This means additional compensation was required that was never disclosed on the product page. It is advertised as a direct-fit replacement.

Nowhere does it state that an additional $400 kit may be required.

⸻

Request for Compensation

I asked Schmiedmann only to reimburse the $390 snap ring kit (I did NOT request the $480 labor).

They refused, stating they are “only the seller” and cannot cover additional expenses.

⸻

Warranty Concern

After I informed them that I would be sharing my experience publicly, I was told that because the repair was done without their approval, my warranty may be revoked.

To be clear:

• I attempted to resolve this directly with them for months
• I provided documentation and measurements
• A BMW-certified shop confirmed the issue
• Shipping it overseas was financially unreasonable

The only way to make the differential usable was to purchase the adjustment kit.

Now I’m being told that fixing the issue locally — after they declined responsibility — may void my warranty.

⸻

Why I’m Sharing This

This is not about attacking a company.

It’s about transparency and accountability.

If a product sometimes requires additional components to function properly, that should be clearly stated before purchase.

Instead, I experienced:
• Months of delay
• Nearly $900 in additional expense
• Repeated suggestions that I installed it incorrectly
• Refusal to assist beyond “ship it back at your cost”
• And now possible warranty revocation for making it work

The differential performs great now.

But the customer service experience was extremely disappointing.

BMW owners deserve full transparency before spending $1,400+ on drivetrain components.

I got all the conversations with them Anyone interested in it I can send it out.

[Coupsoup]

I went with a wavetrac, purchased the unit fully built from diffsonline. I wanted to build the differential myself but after shipping the diff around the country and having the machine work done I was going to end up with no warrantee and be only $400 cheaper than just buying the thing from diffsonline.

To anyone wanting to avoid this, I'd suggest emailing the crew at Diffsonline, I've found Richard to be a little terse but generally helpful and knowledgeable. Well worth the extra money for the piece of mind and warrantee.

Glad OP got his diff all sorted out in the end.

[LA1Z24]

Originally Posted by Coupsoup

I went with a wavetrac, purchased the unit fully built from diffsonline. I wanted to build the differential myself but after shipping the diff around the country and having the machine work done I was going to end up with no warrantee and be only $400 cheaper than just buying the thing from diffsonline.

To anyone wanting to avoid this, I'd suggest emailing the crew at Diffsonline, I've found Richard to be a little terse but generally helpful and knowledgeable. Well worth the extra money for the piece of mind and warrantee.

Glad OP got his diff all sorted out in the end.

Do they cut the ring gear and attach it to the diff for you? thats what the machine shop is needed for. I thought diffsonline only sells the center section with no ring gear.
\Birds quoted me 3k to my door with upgraded bearings and NO CORE. The cheapest I can get from diffsonline is 3400 without tax and shipping, PLUS 500 core.

[Kernel Kurtz]

Originally Posted by Morfius

After I informed them that I would be sharing my experience publicly, I was told that because the repair was done without their approval, my warranty may be revoked.

That seems particularly douchey.

[Coupsoup]

Originally Posted by LA1Z24

Do they cut the ring gear and attach it to the diff for you? thats what the machine shop is needed for. I thought diffsonline only sells the center section with no ring gear.
\Birds quoted me 3k to my door with upgraded bearings and NO CORE. The cheapest I can get from diffsonline is 3400 without tax and shipping, PLUS 500 core.

Yeah diffsonline just ships you one they have, then you send them the core back. They don't build yours.

[who is this noob]

Good post. Thanks for sharing.

Why not buy the OEM M Performance LSD?