[dcay]

HI, I was getting ready to do my third drain and fill on my 2009 328i. I bought the car almost 5 years ago with about 132k miles and the first two times I simply drained and filled the transmission. I was being careful and ease into changing the fluid that had not been changed.

Now with almost 190k miles I want to drop the pan and change the filter, gasket and drain and fill plugs (o-ring seals) too. The drain plug is cheap but for some reason the hex fill plug is relatively expensive. My plug is in good shape and I just really want to replace the old o-ring on the fill plug. That o-ring is now 14 years old and deserves to be changed out. Does anyone know what size the o-ring on this Hex plug is? Has anyone ever replaced this plug and actually measured the OD and Thickness size of this o-ring?

Yes, if I have to I will spend the $30 for a new Fill Plug but I would prefer to be able to spend $2 and replace just the o-ring. Thanks for any help.

David

[mainbearing]

Unless the o-ring is damaged I have never replaced the o-ring or the plug for the '07 6L45. I am not sure if this is the same size and pitch as the ZF one, which is $4.25 plus shipping from CTSC. I have one of those on hand for our 6HP19 but never test fitted it in the 6L45.

https://www.thectsc.com/products/fil...32-181-10.html

[Bims328i]

I picked up the kit to do the transmission filter, drain and fill then internally questioned why I would need to replace the drain/fill plugs that came with it.

So long as the original ring is not flattened, you can likely just reuse it.

[e91Owner]

Originally Posted by Bims328i

I picked up the kit to do the transmission filter, drain and fill then internally questioned why I would need to replace the drain/fill plugs that came with it.

So long as the original ring is not flattened, you can likely just reuse it.

It’s because both are incredibly soft and get mangled on removal that most people replace them. And if you do, replace the fill plug with the GM plug as it’s a harder alloy and less prone to stripping.

[dcay]

I know many or most of the original o-rings on this car have failed and been replaced. It is about time for these. The groove in the bolt flange design does not allow for just tightening it to stop a leak.

The o-ring is the piece of the Fill Plug that would fail if it starts leaking. It should be reasonable to be able to replace just the o-ring. $30 for essentially 1 approximately 22mm o-ring is a bit much. I can gamble for the next 3 years/30k miles that it will not leak but would not like that.

[dcay]

Originally Posted by Bims328i

I picked up the kit to do the transmission filter, drain and fill then internally questioned why I would need to replace the drain/fill plugs that came with it.

So long as the original ring is not flattened, you can likely just reuse it.

Bims, if you still have the kit can you measure the Fill Plug o-ring od and thickness, or the old Fill Plug o-ring? It looks like the o-ring sits in the bolt groove fairly loose.

Thanks for anything you can do.

[Bims328i]

Originally Posted by dcay

Bims, if you still have the kit can you measure the Fill Plug o-ring od and thickness, or the old Fill Plug o-ring? It looks like the o-ring sits in the bolt groove fairly loose.

Thanks for anything you can do.

I don't actually have the o-ring to measure.

After doing the pan gasket and filter I simply installed the provided fill plug that came in the FCP Euro kit.

Perhaps you could message them about your specific plug o-ring request. I have a caliper and would check it for you if I didn't install it already.

[dcay]

Bims, I assume then that you did not keep the old plug after replacing it just in case something happened for which you needed it? I am bad about that and have many old replaced parts around my garage. If you did keep it you could measure the o-ring on that old fill plug.

I will try contacting FCPEuro just to see if they respond.

Thanks,

[mecheng77]

Trans fluid is easy on rubber, just re use, I haven’t heard it leaks from the full plug. If it does leak change after the fact, it’s not difficult

[dcay]

Well I finally replaced the filter and fluid on my 2009 328i with the GA6-L45R transmission. I bought an o-ring kit and use this to replace the o-ring on the fill plug. The existing o-ring was plenty flat and the new o-ring felt much better.

I wanted to report back to the forum the required o-ring size on the GA6-L45R transmission fill plug,

Best Fit:
JIS P18 Size O-ring = 17.8 mmID x 22.6 mmOD x 2.4 mmCSD

Alternative:
SAE AS568 115 Size O-ring = 17.5 mmID x 22.2 mmOD x 2.4 mmCSD

I used a Nitrile (NBR) rubber o-ring. Only changing the o-ring should cost only about $0.30 instead of the $32.59 for the whole plug. Just use a razor knife blade to pick the o-ring out of the fill plug hex head.

The plug felt good going together with the o-ring compression resistance felt before the plug head made contact with the transmission.

[gbalthrop]

Lots of Ink/ Electrons/ Time spent in this thread.
When you need an O-ring to finish the job correctly, here's HOW to have it ON HAND ALREADY:
https://www.amazon.com/s?k=o-ring+ki...f=nb_sb_noss_1

Here is size chart and general info:
https://www.allorings.com/o-ring-size-charts-index

There are DIFFERENT materials used in different applications (fluid used, e.g. Oil, Trans.Fluid, R-134a Refrigerant, pressure & temperature, etc.), so there are a LOT of DETAILS involved in some applications. Here is a link to general description of some of those Details:
https://www.globaloring.com/o-rings/

George