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Ever since I bought my 2006 M Roadster last year I've been dissatisfied with the shifting action. I know that's it's a Z4M think that in order to shift smoothly you need to shift fast, but this was also requiring much more force than one would expect, especially when cold and especially going 2nd to 3rd.

BMW schedule has the transmission fluid change at inspection 2, which at circa 100k kms is still 18k kms from where I'm at now. So I decided to change the transmission fluid early, along with the diff fluid. After much deliberation and research (detailed here) I replaced the MTF-LT2 fluid with MTF-LT3 on the weekend.

The fluid that came out was definitely less than ideal. Still very clear but a lot of fine black sediment in it that settled in the bottom of the drain container. I forgot to grab a pic

Man what a difference it has made! Cold shifting is way easier and in general far less force is required to engage a gear. You still have to shift quickly to avoid the car jerking during shifts, but that's the engine/flywheel characteristics rather than the gearbox. As far as I know this car hasn't had a hard life (I know one of the previous owners), so this is just more proof that BMW fluid change intervals are questionably long!

I also had my transmission fluid replaced when i took ownership of my M at 104000km's... the new oil made a world of a difference.

I contacted Opie oils to see which Millers oil I should use and I was advised to use Millers TRX 70W80 GL5 and if my gear change was stiff to mix it 50/50 with ATF DM. I have never heard of mixing gear box oils but might be worth a try seeing as they're the experts?. I had a T5 gear box in my Cossie engined TVR which used ATF so it's not uncommon.

Das882 wrote:I contacted Opie oils to see which Millers oil I should use and I was advised to use Millers TRX 70W80 GL5 and if my gear change was stiff to mix it 50/50 with ATF DM. I have never heard of mixing gear box oils but might be worth a try seeing as they're the experts?. I had a T5 gear box in my Cossie engined TVR which used ATF so it's not uncommon.

I too have heard that suggestion but I didn't really feel like experimenting with it. Although simply changing the fluid helped, I do think that there is more room for improvement!

ZAR4MC wrote:I also had my transmission fluid replaced when i took ownership of my M at 104000km's... the new oil made a world of a difference.

Completely agree - I had it changed as part of a 60k mileage refresh of a lot of parts and fluids. The whole car feels even more together and smooth, definitely recommended (engine oil, transmission, diff and brake fluids as well as a full front suspension refresh).

I had mine all done at 10k even then then difference as massive
I'm buying vibra engine mounts soon and shall swap diff and box oils
Some recommend redline oil for box but can't remember the spec

RedLine MTL 70W-80.

Made a world of difference too!

Argenta wrote:RedLine MTL 70W-80.

Made a world of difference too!

Thanks buddy

Morning All, I'm about to order 2 US Quarts of MTL 70W-80 for my Z4m gear box.

is it a DIY job or a garage job?

from here

https://www.ebay.co.uk/itm/Red-Line-MTL ... SwSdFbPPZ6

Just found this!

:viewtopic.php?t=76508

Well this is what came out of the gearbox of mine when it had its first Insp 2 at 77K miles!

When I was doing 25,000 miles, 3-4 trackdays and 2-3 Ring trips a year, I did mine annually as an Inspection I-andabit

The only thing I didn't do was spark plugs - did those every 2nd inspection to turn it into a full Insp II.

Just a word of warning: before you drain the gearbox oil, make sure that you can remove the fill plug, otherwise you'll be in trouble.

Can't say I noticed a difference in the gear change after the oil was changed. Happily there has always been a nice smooth solid action on mine , even from cold.

Even from 1st and 2nd Buzyg?