Pops out of first gear

[wideminer]

My 1991 318is pops out of first gear when taking off. Only when the clutch is slipping. Once rolling with the clutch fully engaged it is perfectly normal. Any thoughts?

[Neohostus]

I'm guessing you mean that it begins to catch, enough that you begin to move, but when engine load reaches a certain point it gives way unless fully engaged...
Or do you have to engage while already in motion in order to avoid popping out of gear?
You could need new synchronizer rings, a new operating sleeve, and it's possible that your first gear dog teeth could be worn out...

Is your transmission re manufactured? It's possible that it could have been been improperly assembled...
You could just need to replace some worn bearings...

Any notable noises?
Does this happen every time you accelerate?
It could be a thrust clearance problem due to gears not fully contacting one another. If that's the case a rebuild would be necessary.

Honestly, I'm no expert; I'm just giving suggestions, but I don't really know if they are tips specific to the transmission of the M42. =]

[individualist]

Not saying this is your particular problem but when I bought my car 3 years ago it had the same symptoms. A new\used transmission fixed it.

[E30technik]

1st gear synchro's! Just get another used tranny unless you don't mind holding it in first gear.