Transmission options with M30B35

[Mike72]

I recently purchased a 1989 325i with an M30B35 and G260/6. I bought the car as is as it had a fuel pump issue and hadn’t been driven in several years. I got the engine running but immediately noticed issues with the transmission. Difficult to get into first and reverse and very notchy up shifting. Decided to remove the transmission to assess everything while the car is away for the winter. Definitely some work to be done to properly align the shifter and I will put a new clutch in before it goes back in.

I took a quick look inside the transmission and looks like the synchros are corroded. They are coated in what looks to be a green/white film. I am guessing this is the result of humidity in there or maybe someone ran GL5 in it at some point.

Now I need to decided what to do before putting this thing back in. I am much less confident the new clutch and fixed up shifter bushings and alignment are going to solve this issue. I started looking for used g260/6 transmissions but there sure isn’t much out there. Any other options that could potentially get me back up and running?

[82eye]

getrag 240/5 will bolt up. the m10 and m30 share bolt patterns. those are the only ones that will bolt up.

[Mike72]

Thanks for the feedback. I had read that the 240/5 is quite a bit weaker than the 260/6 and would also require a change to the length of the driveshaft.

any transmission experts have any feedback on the cause of the synchro turning a green color? And if there is any chance of the shifting improving if I get some miles on the car?

[packratbimmer]

Getrag 265 will bolt up, but they are expensive and you will need all the external parts to make it work.

[Mike72]

Do you know if the existing clutch will work with a g265? It currently has a stock e34 535 dual mass flywheel and clutch

[rturbo 930]

Is it just a bit of surface rust? If so I would think it should wear off with a bit of use. I have a jeep that was rusted into gear when I got it, after freeing it up, it shifts fine now, and that was much more severely rusted than yours is. Your trans may have other problems though.

[packratbimmer]

Do you know if the existing clutch will work with a g265? It currently has a stock e34 535 dual mass flywheel and clutch

Should work, but don't know about the throwout bearing.

[Mike72]

Is it just a bit of surface rust? If so I would think it should wear off with a bit of use. I have a jeep that was rusted into gear when I got it, after freeing it up, it shifts fine now, and that was much more severely rusted than yours is. Your trans may have other problems though.

It’s hard to say what the extent of the corrosion is. I would think that if they are turning green it’s likely pretty bad. And in even worse news….It looks like a bit more than just surface rust on the gear teeth. I definitely see some pitting.

[e30davie]

I wouldn't think the gears themselves would effect how it shifts, as they are meshed all the time anyway. Anything to do with actual shifting is selector rods or selector forks, if it goes into gear without grinding then the Synchro and fork is working.

Based only on your description id suspect the selector rods themselves are jamming and just slowing the whole shifting show up.

G260 is inherintly difficult to disassemble, not sure if you can partially disassemble the end to get access to the selector rod and have a look?

https://www.reddit.com/r/E30/comments/gb8nkh/mild_getrag_260_refresh_guess_whos_getting_a_new/

first photo I found is about where you'd need to get to if my theory is correct. but I haven't tried it, but apparently its a right pain in the ass to split the case. I had a dodgy box yrs ago and every shop I rung wouldn't touch it for fear of breaking it.

[Mike72]

I wouldn't think the gears themselves would effect how it shifts, as they are meshed all the time anyway. Anything to do with actual shifting is selector rods or selector forks, if it goes into gear without grinding then the Synchro and fork is working.

Based only on your description id suspect the selector rods themselves are jamming and just slowing the whole shifting show up.

G260 is inherintly difficult to disassemble, not sure if you can partially disassemble the end to get access to the selector rod and have a look?

https://www.reddit.com/r/E30/comments/gb8nkh/mild_getrag_260_refresh_guess_whos_getting_a_new/

first photo I found is about where you'd need to get to if my theory is correct. but I haven't tried it, but apparently its a right pain in the ass to split the case. I had a dodgy box yrs ago and every shop I rung wouldn't touch it for fear of breaking it.

It seems to shift perfectly when the car isn’t running which is why I am leaning towards the problem being either the terribly misaligned shifter setup as seen in this photo, or the corrosion on the synchros.

[e30davie]

hmm yer. Well one of those is alot easier to fix than the other. so id start by cleaning up the shifter and see if it helps. nothing stands out as too misaligned in your photo?

There are lots of rubber bits holding that all together though, so if they are all stuffed it will be a bit...floppy.

looks like your selector shaft seal is leaking too.

[Mike72]

hmm yer. Well one of those is alot easier to fix than the other. so id start by cleaning up the shifter and see if it helps. nothing stands out as too misaligned in your photo?

There are lots of rubber bits holding that all together though, so if they are all stuffed it will be a bit...floppy.

looks like your selector shaft seal is leaking too.

I will clean up the shifter setup by replacing the worn bushings and see if that improves anything. If it doesn’t I’m afraid it’s likely the internals causing the issue. I may have found a G265 available and will see about purchasing that as a possible replacement.