Why replace diff and trans plugs?

elwesso · 03-08-2013, 07:13 PM

So I did some research and I ordered everything I needed for my spring maintenance, which is basically changing all the fluids (less brake fluid, it was done recently, so I'll wait till the next brake job)... Got everything from ECS tuning, seems like a good outfit with good pricing.

I did a lot of reading on the drain and fill plugs for the transmission and diff, and I saw lots of posts they were one-time use, but I didn't run across why they need to be replaced. I've never heard of one-time use plugs, especially if they're not plastic or something cheesy like that..

If there's a good reason to replace them I'll get them from BMW before I put the fluids in. I got the gaskets for all (4).

I apologize if this has been asked before, but again I don't see why anyone would replace the plugs if they're not damaged? Did you guys get in there and either wonder why you're replacing them, or glad you had them?

a_riddler · 03-08-2013, 08:32 PM

Built in o-rings, one time use. Play it safe, order new ones...

MFGJR · 03-09-2013, 06:13 AM

Trans plug is very soft aluminum--easy to damage/strip it just by lookng at it.

mike519 · 03-09-2013, 07:59 AM

Changing all fluids today..have all new plugs

Mirko · 03-09-2013, 08:06 AM

I have read on the other forums that they suck the fluid out via the fill hole and don't need to buy a new plug since they never touch it. That is what I plan to do

Quote:

Originally Posted by mike519

Changing all fluids today..have all new plugs

Good .. you are awake

bignosejim · 03-09-2013, 08:23 AM

I did my transmission fluid a couple of months ago. Soft Aluminium is definitely right! I had to use a vice to extract the plug from my hex socket. The new ones went in and took a lot of wiggling to get the hex bit out also. I'll replace those in the future as well.

elwesso · 03-09-2013, 01:09 PM

I guess that begs the question about replacing the plugs with more permanent ones?

MFGJR · 03-09-2013, 05:37 PM

Quote:

Originally Posted by elwesso

I guess that begs the question about replacing the plugs with more permanent ones?

I assume that the transmission case and plugs are all aluminum so that they have similar expansion properties as things heat up. Note that I'm an accountant and not an engineer... probably with good reason.

Finnegan · 03-09-2013, 05:56 PM

It's a reasonable assertion. That and I'm not aware of alternatives. IIRC these were pretty cheap, like under 30 bucks too.

a_riddler · 03-09-2013, 06:00 PM

I don't recall the part number, but I believe that you could get an e46 plug that has replaceable o-rings.

Finnegan · 03-09-2013, 06:13 PM

^hmm. Have to look at realoem later on PC.

mike519 · 03-09-2013, 07:15 PM

Diff plugs cost me $14 each, tranny plugs were $10 each but those are from the dealer. They are cheaper at ECS and Tischer.

O-cha · 03-09-2013, 07:19 PM

Quote:

Originally Posted by a_riddler

Built in o-rings, one time use. Play it safe, order new ones...

Quote:

Originally Posted by MFGJR

Trans plug is very soft aluminum--easy to damage/strip it just by lookng at it.

No and no.

Basically pretty much anything that could possibly be worn out is considered one time use. For instance, after 100k+ miles that O ring is probably going to be stiff, after breaking it loose it will not seal again. So, instead of writing out something complicated and open to interpretation like make sure the O ring is still soft and pliable BMW just says one time us replace it.

There's a lot of items like this.

Bolts are not really like this though.

StickMon · 03-12-2013, 06:32 PM

Given that the diff oil is about $80 a quart, do you really want to skimp on the plugs?
Whenever possible I try to buy all new hardware before a job. It's usually less than 10% of the total cost and since I keep the old stuff I now have lots of spare hardware.

And Oh.
Remove the fill plug first. I've read horror stories in here about the trans fill plug head stripping.
(Not me. I read the horror stories first, and got the proper 8mm shorty bit.)
If the fill plug is going to strip, you want that to happen before you've drained the fluid.

G80indy · 03-13-2013, 12:13 AM

You might consider getting the aftermarket magnetic plugs

elerner61 · 03-13-2013, 11:21 AM

Quote:

Originally Posted by bignosejim

I did my transmission fluid a couple of months ago. Soft Aluminium is definitely right! I had to use a vice to extract the plug from my hex socket. The new ones went in and took a lot of wiggling to get the hex bit out also. I'll replace those in the future as well.

Before I did my fluids I read a post that talked about all Xmm hex sockets not being exactly Xmm (I forgot the specific size) and that using one that was smaller could strip the plug and get you in a world of trouble. Sure enough I took my micrometer to the hex that I had and it measured smaller. I picked up some stubbies on Ebay from a seller named ZDMAK and they measured true.

bignosejim · 03-13-2013, 08:23 PM

My hex socket was also exactly 8mm. It went in with absolutely no slop. I think maybe the socket has a very slight taper so that it is wider at the base than the tip.

Either way I'd much rather be trying to pry the fill/drain plug off my hex socket than trying to get a rounded plug out of my transmission.

elwesso · 03-13-2013, 08:25 PM

Quote:

Originally Posted by 330indy

You might consider getting the aftermarket magnetic plugs

Are the factory plugs not magnetic...? Any info where you got yours?

XMetal · 03-13-2013, 09:32 PM

The OE plugs are not magnetized.

elerner61 · 03-13-2013, 10:53 PM

Quote:

Originally Posted by bignosejim

Either way I'd much rather be trying to pry the fill/drain plug off my hex socket than trying to get a rounded plug out of my transmission.

Amen to that.

vachss · 03-13-2013, 11:04 PM

On the 3.0si there is no diff drain plug, and you have to suck the fluid out via the fill plug - and yes, I reused mine. The 3.0si tranny is the same 6sp as in other Z4s and has the same pair of plugs. That drain plug I replaced.

aerobod · 03-13-2013, 11:21 PM

Quote:

Originally Posted by elerner61

Before I did my fluids I read a post that talked about all Xmm hex sockets not being exactly Xmm (I forgot the specific size) and that using one that was smaller could strip the plug and get you in a world of trouble. Sure enough I took my micrometer to the hex that I had and it measured smaller. I picked up some stubbies on Ebay from a seller named ZDMAK and they measured true.

There is a tendency of some vendors to interchange certain metric and imperial tool sizes from an economy perspective with the philosophy that "near enough is good enough" In the case of an 8mm hex allen socket, 5/16" labelled as 8mm would only be 7.9375mm and may cause a problem. Some other near, but not exact sizes that I've seen "interchangeable" tools for are

14mm - 9/16" (14.2875mm)
16mm - 5/8" (15.8750mm)
19mm - 3/4" (19.0500mm)
22mm - 7/8" (22.2250mm)
24mm - 15/16" (23.8125mm)

03-08-2013, 07:13 PM	#1
elwesso Second Lieutenant 25 Rep 299 Posts Drives: Z4 M Coupe Join Date: Dec 2012 Location: Indiana iTrader: (1)	Why replace diff and trans plugs? So I did some research and I ordered everything I needed for my spring maintenance, which is basically changing all the fluids (less brake fluid, it was done recently, so I'll wait till the next brake job)... Got everything from ECS tuning, seems like a good outfit with good pricing. I did a lot of reading on the drain and fill plugs for the transmission and diff, and I saw lots of posts they were one-time use, but I didn't run across why they need to be replaced. I've never heard of one-time use plugs, especially if they're not plastic or something cheesy like that.. If there's a good reason to replace them I'll get them from BMW before I put the fluids in. I got the gaskets for all (4). I apologize if this has been asked before, but again I don't see why anyone would replace the plugs if they're not damaged? Did you guys get in there and either wonder why you're replacing them, or glad you had them? __________________ - Wes 2007 BMW M Coupe 2016 VW GTI
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03-08-2013, 08:32 PM	#2
a_riddler Bimmer Noob 30 Rep 566 Posts Drives: 08 Z4MC;08 MBZ E350 4Matic Join Date: May 2010 Location: Seattle, WA iTrader: (6)	Built in o-rings, one time use. Play it safe, order new ones... __________________ 08 Z4MC /// DKF Exhaust, Stoptech 6/4 BBK, TCK Coilovers, Strong-Strut, Apex EC-7's, APR Splitter/Wing, AFE Intake, Underdrive pulleys, AS SSK, Jaffster, UUC Tranny Mounts, Matte Grill, RPI Scoop, CF Badges
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03-09-2013, 06:13 AM	#3
MFGJR First Lieutenant 27 Rep 341 Posts Drives: 2007 Z4 M Coupe Join Date: Sep 2008 Location: Richmond, VA iTrader: (0)	Trans plug is very soft aluminum--easy to damage/strip it just by lookng at it. __________________
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03-09-2013, 07:59 AM	#4
mike519 Captain 130 Rep 832 Posts Drives: 2018 M240i Join Date: Apr 2012 Location: Waterloo, Ontario iTrader: (0)	Changing all fluids today..have all new plugs
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03-09-2013, 08:23 AM	#6
bignosejim Lieutenant 43 Rep 400 Posts Drives: 2007 IB M Coupe Join Date: Oct 2011 Location: DFW iTrader: (0)	I did my transmission fluid a couple of months ago. Soft Aluminium is definitely right! I had to use a vice to extract the plug from my hex socket. The new ones went in and took a lot of wiggling to get the hex bit out also. I'll replace those in the future as well.
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03-09-2013, 01:09 PM	#7
elwesso Second Lieutenant 25 Rep 299 Posts Drives: Z4 M Coupe Join Date: Dec 2012 Location: Indiana iTrader: (1)	I guess that begs the question about replacing the plugs with more permanent ones?
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03-09-2013, 05:56 PM	#9
Finnegan Dog Listener 703 Rep 7,850 Posts Drives: Z4M/. Z3M, E36/46 M3 Join Date: Oct 2008 Location: Teaching the dog to slalom iTrader: (22)	It's a reasonable assertion. That and I'm not aware of alternatives. IIRC these were pretty cheap, like under 30 bucks too.
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03-09-2013, 06:00 PM	#10
a_riddler Bimmer Noob 30 Rep 566 Posts Drives: 08 Z4MC;08 MBZ E350 4Matic Join Date: May 2010 Location: Seattle, WA iTrader: (6)	I don't recall the part number, but I believe that you could get an e46 plug that has replaceable o-rings. __________________ 08 Z4MC /// DKF Exhaust, Stoptech 6/4 BBK, TCK Coilovers, Strong-Strut, Apex EC-7's, APR Splitter/Wing, AFE Intake, Underdrive pulleys, AS SSK, Jaffster, UUC Tranny Mounts, Matte Grill, RPI Scoop, CF Badges
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03-09-2013, 06:13 PM	#11
Finnegan Dog Listener 703 Rep 7,850 Posts Drives: Z4M/. Z3M, E36/46 M3 Join Date: Oct 2008 Location: Teaching the dog to slalom iTrader: (22)	^hmm. Have to look at realoem later on PC.
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03-09-2013, 07:15 PM	#12
mike519 Captain 130 Rep 832 Posts Drives: 2018 M240i Join Date: Apr 2012 Location: Waterloo, Ontario iTrader: (0)	Diff plugs cost me $14 each, tranny plugs were $10 each but those are from the dealer. They are cheaper at ECS and Tischer.
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03-12-2013, 06:32 PM	#14
StickMon My other car is on Mars 636 Rep 3,124 Posts Drives: 2006 MR Join Date: Feb 2011 Location: Lo-Cal iTrader: (1)	Given that the diff oil is about $80 a quart, do you really want to skimp on the plugs? Whenever possible I try to buy all new hardware before a job. It's usually less than 10% of the total cost and since I keep the old stuff I now have lots of spare hardware. And Oh. Remove the fill plug first. I've read horror stories in here about the trans fill plug head stripping. (Not me. I read the horror stories first, and got the proper 8mm shorty bit.) If the fill plug is going to strip, you want that to happen before you've drained the fluid. Last edited by StickMon; 03-12-2013 at 07:27 PM..
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03-13-2013, 12:13 AM	#15
G80indy Save the Manuals 1714 Rep 2,937 Posts Drives: Z3, E46, G80 Join Date: May 2005 Location: Indy iTrader: (0)	You might consider getting the aftermarket magnetic plugs __________________ 2023 G80 6MT, CCBs 2002 330i Dinan, 5MT 2000 Z3 Conforti, 5MT
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03-13-2013, 08:23 PM	#17
bignosejim Lieutenant 43 Rep 400 Posts Drives: 2007 IB M Coupe Join Date: Oct 2011 Location: DFW iTrader: (0)	My hex socket was also exactly 8mm. It went in with absolutely no slop. I think maybe the socket has a very slight taper so that it is wider at the base than the tip. Either way I'd much rather be trying to pry the fill/drain plug off my hex socket than trying to get a rounded plug out of my transmission.
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03-13-2013, 09:32 PM	#19
XMetal Colonel 1136 Rep 2,867 Posts Drives: Anything Join Date: Apr 2010 Location: SoCal iTrader: (0) Garage List 2008 Z4M Coupe [10.00] 2018 Audi S3 [0.00] 2004 X5 [8.50]	The OE plugs are not magnetized.
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03-13-2013, 11:04 PM	#21
vachss Captain 55 Rep 815 Posts Drives: Z4 Coupe Join Date: Jan 2008 Location: Ventura County, CA iTrader: (1)	On the 3.0si there is no diff drain plug, and you have to suck the fluid out via the fill plug - and yes, I reused mine. The 3.0si tranny is the same 6sp as in other Z4s and has the same pair of plugs. That drain plug I replaced.
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