Jump to content

Another newbie M5 trans. question: falling out of gear


Sean Jackson
 Share

Go to solution Solved by James_Douglas,

Recommended Posts

So I’ve got the electrical side of my M5 gearbox working as it should again with very little effort thanks to you guys, but now I’ve discovered a new problem (and hopefully the cause and solution). 
 

In short: is it possible for low oil level in the transmission to let the car fall into a “neutral” state while driving in high range?


I went for a test drive to see how the solenoid circuit was working and it passed the test. However, upon coming back up the road I noticed this:

The car shifted just fine up into 4th at first, but a few moments later it seemed to drop into a neutral state. The engine would race without any of the power reaching the wheels. I pulled over and it went back into 3rd just fine, but then after taking off again it didn’t want to upshift (classic low oil symptom, right?) 

As soon as I got home I checked the level of the oil through the filler cap and found that it is definitely low. Obviously the next step is to top it off with proper SAE 10W, but my question is if this dropping to neutral behavior is a normal symptom of low oil pressure behind the direct drive piston?

As I visualize it by looking at the diagrams, the oil pressure is all that’s holding the piston in place and keeping the shift fork forward when driving- and if the oil pressure is too low the pressure of the spring on the front of the piston could overcome it and let it push backwards. 
Is there enough room between the gears for this to happen? Or am I dealing with a more mechanical issue here? I’m visualizing the drive gear just spinning in the gap between the 3rd and the direct drive gears. 
 

I know the obvious answer is to top it off and try again, which I’ll do soon, but I just want to see if my issue is a common symptom or if I need to prepare for some more serious repairs. 

Thanks for your patience, I’m slowly learning how this thing is supposed to work!

-Sean

 

Link to comment
Share on other sites

  • Solution

The way this thing works is that once the load of off the trans AND the piston is pushed back by the spring due to the fluid dumping OR a lack of fluid it will drop out of gear. make sure it is filed up and NEVER drive a M5/M6 without full fluid.

 

Go over to the Imperial Club and read over all the service booklets on the trans...

Link to comment
Share on other sites

44 minutes ago, James_Douglas said:

The way this thing works is that once the load of off the trans AND the piston is pushed back by the spring due to the fluid dumping OR a lack of fluid it will drop out of gear. make sure it is filed up and NEVER drive a M5/M6 without full fluid.

 

Go over to the Imperial Club and read over all the service booklets on the trans...

Thanks James. 
I won’t move the car until I’ve found some 10W for it. I’ve only put about ten miles on it in my ownership, but hopefully it wasn’t driven for too long BEFORE me with low oil. 

Link to comment
Share on other sites

19 minutes ago, chrysler1941 said:

There are other possibilities other than oil level I'll explain but first a question, do you experience the same situation with 1 and 2 ?

I haven’t experienced it in 1 and 2, although it seems a little more hesitant to shift from 1 to 2 when I’m on an incline. On level ground it does the 1/2 shift just fine. I haven’t driven it much in low range. 

Link to comment
Share on other sites

  • 2 weeks later...

The clue was going up a hill and popping back into third.

Low oil level...oil pump sucking air.

The trans won't burn up low on oil...reason is the car isn't really drivable maxing out at 25 mph in 3rd.

People park the car until the trans issue is fixed.

Glad you filled it up and it upshifts and stays in 4th.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use