[E7J3F3]

I took the car in today to have that done. 270k with no record of a previous change. Mechanic at the dealer said if they changed the fluids with those miles, it'd cause it to fail. What should I do?

[Tambohamilton]

No expertise on trans oil (assuming auto), but definitely change the diff oil. Makes no sense to me otherwise!

[E7J3F3]

Originally Posted by Tambohamilton

No expertise on trans oil (assuming auto), but definitely change the diff oil. Makes no sense to me otherwise!

It's a manual.

[Emilime75]

Change them.

[Tambohamilton]

If this...

Originally Posted by E7J3F3

It's a manual.

...then this...

Originally Posted by Emilime75

Change them.

[Efthreeoh]

Go to an independent BMW mechanic. That dealer is an idiot. No record of it doesn't mean the fluids haven't been changed (unless you know for sure...?). The manual trans and diffs in these cars are bullet proof. They need lube changes every 100,000. Get the juices changed.

[E90convert]

There’s no reason not to change them. I’m a transmission/axle engineer. But there also might not be any reason to change them. I’ve tested axles and transmissions that have gone through a entire “vehicle life” and had the oil analyzed and it was totally serviceable.

[niteshadesc2]

Change them. Pronto. This is cheapish easy maintenance that will save your transmissions/Differential for a lifetime.

I have an E90 328xi and the lifespan on the gear oil is about 100k KM.

Easy to do, on stands, but much easier on a hoist.
There is many a guide on youtube, and even to the uninitiated, it took me more time putting the car off the ground, than it took to do the job. I think in total it took me 1 hour. Have many rags handy. It's not super messy, but you will make a spilly.

Remember to replace the drain/fill plugs with new ones from BMW as they have non-replaceable seals on them. Also get their gear oil while there (don't waste your time trying to find aftermarket gear oil/ MT fluid, as everyone has their own opinion). I believe BMW MT- LT3 is what youll need.

Stuff 'n Things:
BMW Manual Transmission Drain/Fill Plug - Genuine BMW 23117531356
https://www.fcpeuro.com/products/bmw...ug-23117531356

BMW 75W80 MTF-LT-3 Manual Transmission Fluid (1 Liter) - Genuine BMW 83222339221
https://www.fcpeuro.com/products/bmw...ml-83222339221

BMW Differential Drain/Fill Plug - OEM Supplier 33117525064
https://www.fcpeuro.com/products/bmw...ial-drain-plug

Guides:
Manual Transmission Fluid Change:

Differential Fluid Change:

You'll need the Allen Hex Socket set to remove the drain plugs, and a standard socket to remove the bottom rear plastic cover from the bottom of your car.

Double check my part numbers, as I pulled them for the Xdrive model.

Niteshade

[Efthreeoh]

There is no need to buy new drain/fill plugs. Waist of money.

[niteshadesc2]

Originally Posted by Efthreeoh

There is no need to buy new drain/fill plugs. Waist of money.

I disagree. Considering how cheap they are, and the fact that your cannot change only the seal, it is a great deal of peace of mind knowing the job was completed properly, and will not leak due to a faulty seal as a result of negligence.

Niteshade

[Efthreeoh]

Originally Posted by niteshadesc2

I disagree. Considering how cheap they are, and the fact that your cannot change only the seal, it is a great deal of peace of mind knowing the job was completed properly, and will not leak due to a faulty seal as a result of negligence.

Niteshade

Well I probably have a lot more data on it than you do. Of the five (5) 3-series variants I've owned, three (3) of the cars still in the fleet which all use the same style of drain/fill plugs and that have a combined total milage of over 580,000 miles, none have ever leaked at the drain or fill plug. The E90 has had a minimum of 3 fluid changes on each diff and trans. The Z4 now at 100,000 has had two changes of each component fluid. The E46 just had it's first changes at 100,000. I just did the Z4 and E46 earlier this month. All cars mentioned are using their original factory-installed plugs; the oldest car is a 2005, the newest is 2008.

The trans and diff fill plugs have no fluid to hold back since the oil level sits at the bottom of the fill hole. Second, there is no internal pressure buildup in either component to force oil past the seal. Gravity will affect pressure on the trans drain plug, but the weight on the drain plug just a few pounds at worse and has to get past 15 thread turns before it reaches the seal. Replacing the plugs is overkill.

If you really are worried about leaks, use some Teflon tape on the plug threads. But again, the plug style of which you speak of that has the green rubber seal ring do not leak due to age or number of times they are opened/closed.

[niteshadesc2]

1. Firstly, I have been working on cars for over 24 years (since I was 20). Don't make assumptions about my knowledge base or experience, as I have not made assumptions based upon yours.

2. There is a reason the manufacturers of nearly every vehicle state to replace the plugs and or gaskets on any drain bolt that is used (either for increased profit margins, or because they want to guarantee a no-leak repair - you pick). I think a bit of both is true.

3. You are willing to assume some risk, based upon your quoted experiences.

4. I am not willing to accept this risk as mentioned in #3 above. I like to guarantee that any drips in my driveway are not as a result of my negligence, but are in fact because of a problem on my 3 vehicles (which then get immediate attention). So far no drips is the best kind.

5. We do not know what level of risk, or thoroughness, the OP will assume. I am voicing my opinion, based upon my experience, as are you. Clearly they are looking for transmission/diff longevity. Doing the Fluid Re/Re correctly will accomplish this.

6. You disagree with my point, as I disagree with yours. No biggy. Let the OP make his decisions, as fortunately, we both have given him/her lots of viewpoints to think about.

Thanks! Niteshade

[Efthreeoh]

Originally Posted by niteshadesc2

1. Firstly, I have been working on cars for over 24 years (since I was 20). Don't make assumptions about my knowledge base or experience, as I have not made assumptions based upon yours.

2. There is a reason the manufacturers of nearly every vehicle state to replace the plugs and or gaskets on any drain bolt that is used (either for increased profit margins, or because they want to guarantee a no-leak repair - you pick). I think a bit of both is true.

3. You are willing to assume some risk, based upon your quoted experiences.

4. I am not willing to accept this risk as mentioned in #3 above. I like to guarantee that any drips in my driveway are not as a result of my negligence, but are in fact because of a problem on my 3 vehicles (which then get immediate attention). So far no drips is the best kind.

5. We do not know what level of risk, or thoroughness, the OP will assume. I am voicing my opinion, based upon my experience, as are you. Clearly they are looking for transmission/diff longevity. Doing the Fluid Re/Re correctly will accomplish this.

6. You disagree with my point, as I disagree with yours. No biggy. Let the OP make his decisions, as fortunately, we both have given him/her lots of viewpoints to think about.

Thanks! Niteshade

I was specifically speaking to BMW drain plugs on late model 3-series variants based on my extensive BMW ownership/wrenching experience that goes back 30 years. I've never had a plug leak. Never.

[niteshadesc2]

Good for you. I still would not accept that level of risk, for such a cheap, and easy to replace part.

Originally Posted by Efthreeoh

I was specifically speaking to BMW drain plugs on late model 3-series variants based on my extensive BMW ownership/wrenching experience that goes back 30 years. I've never had a plug leak. Never.

[Efthreeoh]

Originally Posted by niteshadesc2

Good for you. I still would not accept that level of risk, for such a cheap, and easy to replace part.

So I lied; well really a memory failure. Checking my service notes this morning, I've changed the driveline fluids in the E90 four (4) times, not three like thought. So finding the trans drain plugs on line at Tischer for $11.20 each and the diff plugs for $5.74 (the E46 takes 2ea.), based on the number of changes I've discussed above, I've saved $192.52 on drain and fill plugs.

So yeah, good for me; pissing away $193 is stupid.

[Tambohamilton]

You better not replace those drain/fill plugs, OP, it's illegal!

[tcphoto]

It's like going to the dentist and the person cleaning you teeth says, don't worry about flossing.

[E7J3F3]

Originally Posted by Tambohamilton

You better not replace those drain/fill plugs, OP, it's illegal!

I welded all mine shut, just to be safe.

[E92William]

Manual transmissions are lubricated the same way a differential is, splash lubrication. Old fluid with metal particles from ages of wear is not exactly the best lubricant. Change both of them.

On automatic transmission some shithead mechanics will say changing the fluid on high mileage ones will cause them to fail and argue thick worn fluid helps keeps them engaging the worn clutches, this is obviously clueless. Most people dont know anything about how an automatic works. Never have I had a failed automatic because of that or at all. It's old folks tale.

The fact that you made it to 270k is because you have a manual lol. Change the diff and tranny and you'll be good for more miles of fun.

[Efthreeoh]

Originally Posted by E7J3F3

I welded all mine shut, just to be safe.

What welding method did you use for the transmission? It might have been cheaper to just get new plugs.

[E92William]

Just serviced front and rear differentials in my car and good thing I did because the front was a bit low. Car is fine