Reverse Gear Selection

[Lutz Kramer]

Need some help with the center shift gearbox of my AH 3000 Mk III.

After my journey of about 1500 miles from Germany to northern Italy I had some noises coming from the gearbox. After I had pulled the trans and taken it apart I had to replace the main ball bearings and all needle bearings as well as the main shaft. The wear wasn’t caused by the long trip but it accelarated the process.

When everything was done and the trans was back in the car it all of a sudden crossed my mind that I had forgotten to take care of a problem which already had lasted for while.
When the car ist not in motion and you shift into reverse gear you have to overcome a spring load which usuallly prevents shifting into reverse gear when you are rolling and want to shift from 1st to 2nd or back from 3rd to 2nd gear. This is managed by the reverse selector plunger and detent plunger (No 105 and 107 in the workshop manual) which are located on the striking fork inside the gear box.
So usually you have to push or pull (depends on LHD or RHD drive) the gear lever very hard to the left side to be able to shift into reverse gear.

Not so with my car. There is no more force to overcome when shifting into reverse gear. So I was pretty much sure that the plunger spring would have gone. With the trans mounted in the car I opened the gear box cover today and found that the reverse selector plunger is hanging when its pushed back by the selector lever, even the spring seems to work correctly.

Now here is my problem:
I believe there is no way to remove the plungers while the trans is in the car. Even when you remove all 3 securing screws of the striking forks, which enables you to move the forks all together at one time, you won’t find a position of the forks that let you pull out the reverse selector plunger to the right side to clean or machine it.
After having moved the plunger several times forth and back it suddenly did what it’s suppoded to, but after another few tries it started hanging again. The spring seems to be okay, because you need some force to overcome its resistance.

One more thing. I’m not pretty much sure, how the detent plunger works, that is located on the fork vertically. It could also be the reason, that the selector plunger gets stuck. Shouldn’t there be a steel ball or how is this plunger shaped so it can work together with the selector plunger without preventing it to move freely?

Now, is there any chance to fix this problem without pulling the trans again?

Does anybody know:
a) whether you can remove the reverse selector plunger,
b) whether you can remove the detent plunger (may be by moving the selector plunger out of its housing as far as the other forks give way)
whithout pulling the trans and if so, how?

 

[Lutz Kramer]

I should like to add something that may solve the problem of how to remove the selector plunger. When I looked through the spare part offers of Moss, Limora (Germany) and Bastuck (Germany) I found out that the forks they offer for the 3rd and 4th gear have no barrier on their right side, so that you can pull out the selector plunger together with the spring.
This is different to the fork I have which you can see from the following picture:



Perhaps I could cut off this little barrier if this doesn't weaken the stability of the fork. What do you all think about this idea?

Lutz

 

[Lutz Kramer]

Here is a progress report:

I found a way to pull the reverse selector plunger without removing the gearbox. First of all you have to remove the security screws that hold the 3 forks in their position on the shifter shafts. This way you are able to move all three forks at one time and even in one direction which is usually not possible.
Now here comes the trick!
Then you have to loosen the the reverse gear shaft by loosening the reverse shaft retaining screw. This will enable you to pull the gear shaft almost completely out so the reverse gear falls down on the bottom of the gearbox. This gives the reverse gear fork enough play to be moved so far to the front end of the gear box that you can pull out the reverse selector plunger with its spring to the right side.

I found, that the spring of the reverse selector plunger was weak and shortened. So I replaced it and everything seems to work now.

I'll let you know, when everything is reassembled and I done my first test ride.

Lutz