Differential Bolt Hole Fix Gone Wrong

[sapote]

I did use loctite, but I think I just tapped it wrong from the start and that's what caused all my issues. I used a drill press when doing the M20 bolt, just to make sure everything was square..

Agree that it's easier to drill and tap with the diff removed off the car, as there is not much space around for the drill gun to do it safe. When I drilled and tapped and Timesert all 14 head bolt threaded holes on the engine block (M54 325i) it's not easy with the tilted engine in the car but I had the space though. All went well except one that I was careless and didn't tap straight, but caught it early and fixed the problem. Needed to Timesert because engine was overheated so bad that 5 of the 14 head bolts pulled threads off the aluminum block.

[heinzboehmer]

Pretty much exactly what I wanted to hear. Did you use any loctite on the inserts when you tried a timesert by any chance?

Also, do you recall the length of that bolt by any chance?

Thanks

Yep, 65 mm is correct.

I did use loctite, but I think I just tapped it wrong from the start and that's what caused all my issues. I used a drill press when doing the M20 bolt, just to make sure everything was square.

[evanr614]

Thanks everyone. Gonna throw a M20x2.5 in there as I think the hole is too big already for an M18.

[Stilt]

65 mm, that’s the length of the oem bolt.


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[evanr614]

I have an M20 bolt in my diff. Has been through lots of abuse and it's still fine: https://nam3forum.com/forums/forum/m...8088#post68088

Pretty much exactly what I wanted to hear. Did you use any loctite on the inserts when you tried a timesert by any chance?

Also, do you recall the length of that bolt by any chance?

Thanks

[heinzboehmer]

I have an M20 bolt in my diff. Has been through lots of abuse and it's still fine: https://nam3forum.com/forums/forum/m...8088#post68088

[evanr614]

Sapote knows that the rogue kit upsizes the bolt. What he's getting at is asking if you drilled out the threads before you tapped the diff housing to accept the larger bolt that comes in the Rogue kit.

You could get another tap, larger than the rogue one, drill out the threads that are there ( the new and original, since you said that it didn't thread all the way), and then tap the housing with the new, larger one.


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Yes I drilled the old threads. I hadn’t considered upsizing again to an M18. I don’t have the diff out of the car to measure but I’m not sure if there is enough metal there to do it without comprising its structure or not. I will consider it

[Stilt]

Yes, the Rogue Engineering kit upsizes to an M16x2

Sapote knows that the rogue kit upsizes the bolt. What he's getting at is asking if you drilled out the threads before you tapped the diff housing to accept the larger bolt that comes in the Rogue kit.

You could get another tap, larger than the rogue one, drill out the threads that are there ( the new and original, since you said that it didn't thread all the way), and then tap the housing with the new, larger one.


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[evanr614]

Did you drill out the old damaged threads before tapping?

Do you want tapping for next larger bolt or Timesert?

Yes, the Rogue Engineering kit upsizes to an M16x2

[sapote]

Did you drill out the old damaged threads before tapping?

Do you want tapping for next larger bolt or Timesert?

[evanr614]

Anyone ever fudge up re-tapping their diff hole? I used the RE kit. This happened months ago and never got around to asking for some opinions/fully fixing it on my car. Was very careless when starting the tap, being such a coarse thread it cut well and felt like it was going in straight but didn’t take long to realize it wasn’t. The bolt still threads in 3-4 turns but you can tell it’s crooked and didn’t cut threads into the entire hole.

Aside from a new diff housing, the only thing I can think of is a super expensive Time Sert kit, however haven’t taken measurements to see if an insert will work there or not yet. Any ideas?