Stiffening plate removal / reinstallation

[Ricky Bobby]

Does the oil that is dripping now smell like PS or is it mixed with actual engine oil leak?

And jesus those stiffening plate bolts went through the roof - even with discount about $14 per bolt, the nuts are cheap at $1.50 apiece I would definitely do those lol and do it right

[StephenVA]

If the block and under parts were not cleaned off after all the work was done you can count on any leak will refresh the gunk and bleed oil residue all over. Solution brake clean buy 4 cans when you pull the plate.
There are two versions of this plate and depending on your assembly date yours is either nice shiny aluminum or black painted steel.
Some time in 2003 they switched.

[wpoll]

I'm about to change my front diff fluid and so the plate has to come off. It's going to cost me nearly $200 to get new BMW OEM bolts, by the time I figure in the exchange rate and the freight.

I'm looking at generic zinc or nickel plated M10 x 1.5 x 55mm grade 10.9 bolts locally and can get six of them for about $20. While I REALLY want to replace these bolts and REALLY want to OEM bolts, each of those two "REALLY" desires is worth about $50, meaning I'd pay about $100 to replace them.

But $200....?

[oldskewel]

Originally Posted by wpoll

I'm about to change my front diff fluid and so the plate has to come off. It's going to cost me nearly $200 to get new BMW OEM bolts, by the time I figure in the exchange rate and the freight.

I'm looking at generic zinc or nickel plated M10 x 1.5 x 55mm grade 10.9 bolts locally and can get six of them for about $20. While I REALLY want to replace these bolts and REALLY want to OEM bolts, each of those two "REALLY" desires is worth about $50, meaning I'd pay about $100 to replace them.

But $200....?

There is nothing special about the bolts that I know, or that I know could be possible. Just bolts. M10 x 1.5 x 55mm class (not grade) 10.9. I'm assuming you got the numbers right there, I did not double check. They are not in any special shape to work with the TTY application here, unlike some TTY bolts.

Related to the nuts question - in a normal specially made TTY bolt, there would be a narrowed section that is purposely designed to yield first, leaving the actual thread-nut interface below yield stress. These BMW bolts are not like that, they're just regular bolts, with no narrowed stem. So it is likely that the nuts will have yielded (plastically deformed). So if you care about stuff like that and are replacing the bolts, it does make sense to replace the nuts as well. Both nuts and bolts are regular hardware (specs above).

I re-use mine carefully without worry. If you do re-use them the main thing is to definitely NOT follow the same torque procedure that is used for new hardware - you will be will be pushing deeper into the plastic deformation zone, closer to the failure point.

Also, my understanding is that the 4.4 engines are way tougher access-wise than the 3.0. I had no problems at all on my 3.0.

[Fifty150hs]

Loc-tite

[wpoll]

Originally Posted by Fifty150hs

Loc-tite

Yeah, nah. The torque to yield thing isn't about how tight the bolt is in order to stop it coming off, it's about how much clamping force is in play holding the plate in place. Loc-tite has no role to play here... in fact using Loc-tite would alter (lower) the torque spec that would be needed to achieve the correct bolt stretch.

But yeah, it would stop it coming undone.

[StephenVA]

In a Aussie world with import costs beyond reason, I would choose to use grade 8 (8.8) bolts, lock washers and nuts that were of stainless config and torque that sucker down. This solution will provide a level of clamping power within engineering acceptable ranges to ensure your safe and there is no flex in high load conditions.

Go for it.

[Ricky Bobby]

Ugh if only we could use VW subframe bolts, this one is too long though at 105mm

https://deutscheautoparts.com/n-908-235-01.html

[OptimusPriM5]

Did this twice, once by myself and then on Stephens (pan envy...mine was stainless) and its easier with 2 people of course but also helps if your a contortionist, at least it did for some of angles i needed to get into.

The tools needed were nothing special, couple box wrenches and sockets and a lot of patience, and of course if you havent figured it out that plate isnt lite. When doing it myself I wasnt thinking it and it landed square on my chest and neck.

Also, to your question I bought new nuts...the cost was immaterial and was just right thing to do.

[oldskewel]

Originally Posted by StephenVA

In a Aussie world with import costs beyond reason, I would choose to use grade 8 (8.8) bolts, lock washers and nuts that were of stainless config and torque that sucker down. This solution will provide a level of clamping power within engineering acceptable ranges to ensure your safe and there is no flex in high load conditions.

Go for it.

While I generally agree with what you're saying here, there are some specific issues that I'll point out for anyone who might do this. (again, I just re-use mine, but I feel knowledgeable enough to do it carefully; others might not)

Grade 8 is not the same as (8.8). Grade 8 is used for rating SAE bolts. The equivalent rating for Metric would be Class 10.9. "Class" for Metric, "Grade" for SAE. Class 10.9 is what these BMW overpriced bolts are rated at. Grade 5 SAE bolts are similar in strength to Class 8.8. Grade 8 SAE ~ Class 10.9.

I would just stick with M10 10.9 bolts. And make sure you get the right thread pitch too, since that affects the actual bolt stretch that occurs when you torque or TTY them down.

Stainless - no, don't do that. Stainless will be weaker, and it seems clear BMW was concerned with a specific strength rating here. If it says 10.9 on the bolt, it will be what you want. If it does not, keep looking. Besides, unless you have one of the 1% of x5's without a perpetually oil-coated stiffening plate, you don't need to worry about corrosion.

Lock washers - I would not change anything like that (I don't recall there being lock washers on there originally). If there were any original washers, they can be re-used. Nuts and bolts, try to buy Class 10.9 ones that match in every way, but without the 700% markup.