W115 manual transmission syncro parts

[luketmarx]

Hi,


I have a '76 w115 240D, manual trans, about 200k miles. Problem is very livable, but I'm doing an OM617 swap and keeping my trans so am thinking of fixing while everything is out.


What happens is when shifting, usually from 1st to 2nd, can definitely feel a bit of grinding. If I shift slowly then usually pops right in and feels good. If I jamb it in, you can tell "Olga" isn't super happy. I did a trans fluid change to the recommended ATF. I think there was slight improvement. I did another change 5k miles later, no change.


Ok, my reckoning is the syncro is worn going into 2nd. I know a good trans shop as I'm assuming this isn't a great DIY project (unless someone tells me different, I'd love to try) but I'd like to supply parts, as I'm sure they're hard to come by...so where do I get them?


Looking for advice and recommendations.


Thanks!

[Stretch]

Originally Posted by luketmarx

Hi,


I have a '76 w115 240D, manual trans, about 200k miles. Problem is very livable, but I'm doing an OM617 swap and keeping my trans so am thinking of fixing while everything is out.


What happens is when shifting, usually from 1st to 2nd, can definitely feel a bit of grinding. If I shift slowly then usually pops right in and feels good. If I jamb it in, you can tell "Olga" isn't super happy. I did a trans fluid change to the recommended ATF. I think there was slight improvement. I did another change 5k miles later, no change.


Ok, my reckoning is the syncro is worn going into 2nd. I know a good trans shop as I'm assuming this isn't a great DIY project (unless someone tells me different, I'd love to try) but I'd like to supply parts, as I'm sure they're hard to come by...so where do I get them?


Looking for advice and recommendations.


Thanks!

Parts are mostly most easily found at the dealership - the synchros could be aproblem but I would check the rubber shifter linkages first and see if the shifter rods line up as they should when you put the pin through the set-up holes on the underside of the shifting mechanism


I believe these four speed gearboxes don't have the easier to disassemble tapered roller bearings so it ends up in the category of difficult / advanced DIY (if only for the disassembly and assembly)

[Frank Reiner]

Originally Posted by luketmarx

What happens is when shifting, usually from 1st to 2nd, can definitely feel a bit of grinding. If I shift slowly then usually pops right in and feels good. If I jamb it in, you can tell "Olga" isn't super happy. I did a trans fluid change to the recommended ATF. I think there was slight improvement. I did another change 5k miles later, no change.


Ok, my reckoning is the syncro is worn going into 2nd. I know a good trans shop as I'm assuming this isn't a great DIY project (unless someone tells me different, I'd love to try) but I'd like to supply parts, as I'm sure they're hard to come by...so where do I get them?


Looking for advice and recommendations.


Thanks!

Originally Posted by Stretch

Parts are mostly most easily found at the dealership - the synchros could be aproblem but I would check the rubber shifter linkages first and see if the shifter rods line up as they should when you put the pin through the set-up holes on the underside of the shifting mechanism


I believe these four speed gearboxes don't have the easier to disassemble tapered roller bearings so it ends up in the category of difficult / advanced DIY (if only for the disassembly and assembly)

ltm:

1) Does the 3-2 downshift also exhibit the same grinding as the 1-2 upshift?
2) The 2nd gear synchro ring wears more than the other three because there is a greater percentage change in shaft speeds during the 1-2 change than during the 2-3 or 3-4 changes.
3) If the decision is made to open the box, and new synchro rings are not available, the 1st and 2nd rings may be interchanged; the 1st gear ring is usually worn less than 2nd.
4) As Stretch has noted, these iron boxes are not the easiest to work on; a copy of the factory manual will be helpful.
5) Before doing anything else, try a fluid change to Type F ATF; Type F is free of the friction modifiers found in other ATF types, and will help the synchros to bite more aggressively.

[cth350]

I happened to notice that there was a transmission rebuild manual on ebay a few days ago. -CTH

[Mike D]

The grind between first and second can also be indicative of a worn clutch plate. The shift between second and third or into fourth is not of a as drastic change in rpm vs. road speed.

I imagine you are replacing the clutch disk and pressure plate assembly when you do the engine swap. Before I'd tear into the transmission I'd do the swap.

It's not hard to pull the transmission if the clutch replacement doesn't solve the problem.

Opening up a transmission with 200K or better miles can turn into an expensive and labor intensive can of worms. You might be better off sourcing a used gear box.

[Stretch]

Good point about the clutch Mike - if the mechanical side is OK sometimes a bleed helps - though bleeding a Mercedes hydraulic clutch can be a frustrating experience...

...I've found the best solution to be a pressure bleeder forcing fluid up through the system

@Frank - I like the idea about swapping the synchros

[luketmarx]

Thanks for all the replies and advice! Yes, I was planning on changing the clutch and pressure plate assy when doing swap. As you say, it's not that difficult to remove the trans so I think your suggestions of doing them separately are wise.