Stuck in a mystery gear

[Dillon]

a M20 bmw engine spins clockwise [emoji4]

stuck in reverse seems to be the case

when you get it apart see if the shift selector rod (the thing poking out of box your gearshift connects to) have any visable damage.

or if you can see any mechanism out of place.

the selector rod has to interact with multiple different shift forks to handle the 5f+1r gear; trace the path of connection between them and should find what is broken

Hmmm... Ok that makes sense. Thank you. :) I'm not really getting how this thing comes apart. I've been looking at my manual and it's not really very much help on how you get the case apart in the first place. It tells me I need multiple special tools but I'm pretty sure you can get away without them. But how I don't know. Any help? I found a video of a guy splitting the case but it didn't give much info on how he did it. I'll have to pull off the output shaft flange and unscrew the bolts to the back cover. But I'm confused after that.

[Wanganstyle]

Hmmm... Ok that makes sense. Thank you. :) I'm not really getting how this thing comes apart. I've been looking at my manual and it's not really very much help on how you get the case apart in the first place. It tells me I need multiple special tools but I'm pretty sure you can get away without them. But how I don't know. Any help? I found a video of a guy splitting the case but it didn't give much info on how he did it. I'll have to pull off the output shaft flange and unscrew the bolts to the back cover. But I'm confused after that.

You need to find the bmw service manual for the g260; try looking in the e28 era of technical data as the 528e also came with a g260 same as e30’s

Basically...... it’s not that easy. But does come apart

Special tools are for extracting the front bellhousing part to extract the double race’ed front main Bearing; and gear 4/5 as they are pressed in


The getrag units centrally base around the middle of the transmission.

So the front and back parts will extract first ; the main/layshaft will be held in place as they are pressed in to place and ride on bearings

[TobyB]

if you haven't opened the case yet,
figure out which way the reverse idler goes to
disengage reverse (forward, I recall, but I've worked on too many
different boxes to be sure)
Assuming forward, set a pair of 4x4 chunks up so you can sit the bell
on them. The goal here is to NOT hit the input shaft on the floor.

Because you're now going to lift the transmission about an inch, and drop it on its bell.

Maybe several times.

Crap. I'm doubting myself on which way the reverse idler slides.
Wangan, help me out, here, 'cause the internet sux at this-
which way does the idler slide to engage reverse on a 260? I have h55f stuck in brain.
The short version is, bump the trans in the direction the idler moves to disengage

Anyway:
What happens (on several 245s, in my case) is that the trans gets bumped hard from
behind. The interlock pins aren't engaged in neutral, so the heavy reverse idler
on a long lever overcomes its detent, and slides into gear, but the selector isn't
in the slot for reverse. So you are stuck.

Try this, a few times. If you are careful not to damage the input, you will do no harm.
On a more sensible box, you'd just pull the top or side cover, move
the gear or selector, and bolt it back up. But BMW and sensible aren't always such good bedfellows...

hth, Byron taught me this one.

t

[AndrewBird]

You move the shift lever forward (towards the engine) when shifting into reverse, so that means the selector rod on the tranny moves out, away from the engine. So dropping it on the bell housing would move it the correct way to disengage it.

[Dillon]

if you haven't opened the case yet,
figure out which way the reverse idler goes to
disengage reverse (forward, I recall, but I've worked on too many
different boxes to be sure)
Assuming forward, set a pair of 4x4 chunks up so you can sit the bell
on them. The goal here is to NOT hit the input shaft on the floor.

Because you're now going to lift the transmission about an inch, and drop it on its bell.

Maybe several times.

Crap. I'm doubting myself on which way the reverse idler slides.
Wangan, help me out, here, 'cause the internet sux at this-
which way does the idler slide to engage reverse on a 260? I have h55f stuck in brain.
The short version is, bump the trans in the direction the idler moves to disengage

Anyway:
What happens (on several 245s, in my case) is that the trans gets bumped hard from
behind. The interlock pins aren't engaged in neutral, so the heavy reverse idler
on a long lever overcomes its detent, and slides into gear, but the selector isn't
in the slot for reverse. So you are stuck.

Try this, a few times. If you are careful not to damage the input, you will do no harm.
On a more sensible box, you'd just pull the top or side cover, move
the gear or selector, and bolt it back up. But BMW and sensible aren't always such good bedfellows...

hth, Byron taught me this one.

t

Well I tried this last night. No luck at all. I pulled off the cover with the detents inside and took a look. I took the detents out and tried to move the shifter but none of the selector rods moved. (whether that was a bad idea I don't know, but I did it anyways lol) So I'm going to Lowes today and finding some plumbing parts to make my own puller and hopefully I'll split the case tonight. (if homework is done. lol)

Seriously though guys, thanks for the help so far. I'm more determined to figure it out than ever.

[Dillon]

Oh, quick note. I also noticed that one of the springs holding the detent in was shorter than the other ones. Which I thought was strange...

[Wanganstyle]

Oh, quick note. I also noticed that one of the springs holding the detent in was shorter than the other ones. Which I thought was strange...

Sounds like a fun puzzle to me

Industrial or farm equipment pullers work as well for breaking down these units

[e30davie]

Good to see you having a go.

keep the updates coming on how you pull it appart, as one day if i get very enthusiastic might try and pull my dud one apart.

[LowR3V'in]

Oh, quick note. I also noticed that one of the springs holding the detent in was shorter than the other ones. Which I thought was strange...

That's normal

[TobyB]

Try the bell thing again, with the detents out.

The worms are hard to get back into the can with these transmissions...

t

[Dillon]

Well guys I started pulling apart the trans last night. (School has been crazy). I used a tool that was made from plumbing parts and it worked brilliantly. I'll post pictures tonight. But I ran into a problem. The case split as it should but it only would come apart about an inch or so. I have a manual and I missed that you have to take out a cap, spring and locking pin that are in the trans. But I cant for the life of me get the locking pin out. The spring and cap came off easily. But I can't seem to get the pin out. I'm afraid that it bent or something as I was splitting the case and now it's stuck in its little hole. Little bastard. Any ideas? I'll post pictures soon so you can see what I'm on about.

[Dillon]

OK, so I've talked to a mechanic friend of mine and he was looking at it and he thinks that this locking pin located in the side of the transmission is bent ever so slightly. We couldn't pull it out so I'm think I bent it whilst attempting to get the trans split. I can't really think of a solution now except for give up and save for a new tranny. What a disappointment.

[e30davie]

Well all you can do is keep trying to remove that pin. throw all your tools at it. you have nothing to lose now.

[Dillon]

What I ended up doing was sourcing one from a guy a couple hours away. I would one day like to take apart one so I'm gonna keep this thread for reference. It's been a big help.