Still grinding going into reverse - PeachParts Mercedes-Benz Forum

fruitcakesa · #1 05-17-2010, 06:47 AM

Well, months after replacing the clutch slave {Clutch master was done a while before that as was trans fluid change}, reverse gear still grinds when engaging.
I do notice however, that it is worst when the car has sat long enough to cool off but it engages much more smoothly and quietly when the car has been driven a while. I also notice that the forward gears are "stiff" when the car is cold and loosen up when the car is warm.
Anybody have an idea about this?
Although my clutch pedal begins engaging while very close to the floor, I measured clutch wear and it still seemed within spec.

69shovlhed · #2 05-17-2010, 10:05 AM

you sure you got it completely bled?

barry123400 · #3 05-17-2010, 10:24 AM

It is pretty well obvious the clutch engagement close to the floor will have to be dealt with first. I have a couple of 240d manual transmission cars.

I notice I still take it easy going into reverse.The sensation of being on the edge of grinding is there in my opinion. I get no grinding though and the clutches of both cars seem well into the normal range. Personally I would try another bleeding system on the setup as there are more than one. I assume you have tried the bottom up bleeding method already? It seems to me that would be the preffered sytem of bleeding.

I also seem to remember there are two different throwout bearings. I wonder without knowing what the wrong one in there would cause. Someone else with more knowledge should be able to comment on this.

Stevo · #4 05-17-2010, 10:40 AM

I would defiantly try a re bleed as you have nothing too lose.

I installed the wrong throw out bearing in the "later" 240D a few years ago. It was drivable but the clutch was ingauging very close to the floor, I pulled the tranny a couple of times before I figured it out. Are you sure you got the right bearing??

fruitcakesa · #5 05-17-2010, 10:59 AM

AFAIK, the clutch and trans components are original.
I did a bottom up bleed 3 times with no observable air bubbles.
Clutch "feel" is unchanged since I have owned the car.

And having just returned from a drive, reverse engages with no grinding!

Stevo · #6 05-17-2010, 04:13 PM

Well good, your car might have just temporarily been infected with an evil spirit/virus, what ever.

The wrong bearing caused more than "grinding in reverse". I dont know about a case of a later bearing in an "early" 240, haven't done that yet

fruitcakesa · #7 05-17-2010, 04:29 PM

I don't think it is temporary insanity.
I think the next time I drive it will grind again.

Stevo · #8 05-17-2010, 05:07 PM

Your "R" shifter rod bushing (both ends) and arm are OK, I'm sure you checked that. If it was air in the system it would grind in first too, so if you've looked under the shifter boot and not found pennies and/or other debris stuck in the works maybe the problem is in the tranny itself

fruitcakesa · #9 05-17-2010, 07:41 PM

I actually have not checked the shifter bushings since the overall shifting action is good, no slop in the stick and this issue has been creeping up on me for months before actually grinding regularly like it does now.
I cleaned out the shift tunnel when I got the car so I know it doesn't have "clutter" in there.
The shifter bushings are accessed from under the car?

Stevo · #10 05-17-2010, 10:41 PM

Quote:

Originally Posted by fruitcakesa

I actually have not checked the shifter bushings since the overall shifting action is good, no slop in the stick and this issue has been creeping up on me for months before actually grinding regularly like it does now.
I cleaned out the shift tunnel when I got the car so I know it doesn't have "clutter" in there.
The shifter bushings are accessed from under the car?

The bushings are easy to check when the car is safely jacked up. You can see if the rod ends are not supported securely at both ends and if there is slop when you move the rods back and forth. Good bushings=no slop in the shift rods. Its worth checking

Beagle · #11 05-18-2010, 02:15 AM

Quote:

Originally Posted by fruitcakesa

I do notice however, that it is worst when the car has sat long enough to cool off but it engages much more smoothly and quietly when the car has been driven a while. I also notice that the forward gears are "stiff" when the car is cold and loosen up when the car is warm.

Since the problem disappears when warm this could be a gummed up pilot bearing not releasing the input shaft - the grease dries out eventually and heat will ease it. You should hear the input shaft stop turning when the pedal is fully depressed in neutral. Clutch dragging would likely occur hot or cold and this should not affect 1st either way as it is synchro.

The later (long) self centering release bearing MA 000 250 68 15 is 5.5mm longer than the old and this translates into 11mm of slave piston travel.

fruitcakesa · #12 05-18-2010, 07:33 AM

Quote:

Originally Posted by Beagle

Since the problem disappears when warm this could be a gummed up pilot bearing not releasing the input shaft - the grease dries out eventually and heat will ease it. You should hear the input shaft stop turning when the pedal is fully depressed in neutral. Clutch dragging would likely occur hot or cold and this should not affect 1st either way as it is synchro.

The later (long) self centering release bearing MA 000 250 68 15 is 5.5mm longer than the old and this translates into 11mm of slave piston travel.

I assume this would necessitate dropping the tranny to check and repair.

nhdoc · #13 05-18-2010, 07:44 AM

Yes, to fix a sticky pilot or throwout bearing you would need to remove the transmission - which, at that point you might as well put a new clutch in if yours is original. Or, you could just live with it. One trick you can learn is put the car in reverse BEFORE you start the engine and just keep your foot on the clutch when you start it in cases where you know you will be putting it into reverse right afterwards (like backing out of a parking space). At some point it might get so bad that will be the only way to get it into reverse, so it is not a bad habit to pick up. Frankly, if the only problem you have is a little grinding going into reverse that's not that bad...when it is really sticky you will start to feel it going into forward gears too, especially if you have the typical weak syncros.

fruitcakesa · #14 05-18-2010, 08:59 AM

I have been doing "the put er in reverse first".
And, yes I will live with it till it gets too bad and then do a complete clutch job.

JB3 · #15 05-18-2010, 09:06 AM

Quote:

Originally Posted by Beagle

Since the problem disappears when warm this could be a gummed up pilot bearing not releasing the input shaft - the grease dries out eventually and heat will ease it. You should hear the input shaft stop turning when the pedal is fully depressed in neutral. Clutch dragging would likely occur hot or cold and this should not affect 1st either way as it is synchro.

The later (long) self centering release bearing MA 000 250 68 15 is 5.5mm longer than the old and this translates into 11mm of slave piston travel.

I 2nd this theory. It took me almost 20 minuted to remove a release bearing from the input shaft cover plate sleeve because it had seized up on it through lack of lubrication.
Eventually had to use a puller and slide hammer to get it off. If its getting sticky, it could be causing issues and occasionally binding. Heres a picture of how corroded it was compared to a new one