5-speed manual
 

Former Mercedshop forum member here, looking for some input.
I'm preparing to switch the Otto-matic out of my 1985 300 turbo, and swap for a manual out of a retired euro-market 300d NA. The manual is a 5 speed, the plate says "Teil nr. 123-260-2001 aggregate /80 024 716. This transmission has 200k miles on it, but works fine. It does have an odd fault. Engine running, in neutral, with clutch engaged, the transmission makes a "clanking" noise, sort of like the sound that a bad throw-out bearing would make when the clutch was disengaged. I've been told that this is a problem with a layshaft (for reverse gear?), the layshaft runs in bushings in the case, and get end play and make the noise. That's what I've been told, anyway. Some people say it's not a problem, others that it will cause trans failure, either way it's not a nice noise.
So, does anyone know about this problem? Is it easy to fix? I've heard about re-bushing, or boring a larger hole and installing a ball bearing. Do you know of anyone who works on these, or where parts are available. I'm in Maine.
I've been told that this is the same transmission as was found in some 280E gasoline cars of the same age. Was it ever imported to the US by Mercedes, and do they have parts for it? Lots of questions.
Thanks very much in advance for any feedback or advice.

SEO

Parts are available. I don't think it was ever imported directly by mb but there are some around. The tranny is notoriously noisy when in neutral, that said if it sounds like something is tearing itself to bits there may be a problem.

I've had a couple of these rare 5 speeds and they are lovely.

Greazzer has three now I think, one which I used to own.

Good luck on your swap Beware of the flywheel issue. Search for 617 manual conversions and flywheel threads there are several.

Hi Walgamuth, thanks for the reply. Can you tell me more about the "flywheel issue?" I know that I have to get new stretch bolts for flywheel/crank bolting, and have been told that MB has them. The local race engine builder says that if I bring the "old" automatic flex plate and torque converter that they will check its balance, and then balance the "new" flywheel so that it's the same. Seemed logical, and simple compared to tearing the engine down to dynamic balance the crank + flywheel assembly!
SEO

Make matchmarks on the flex plate and crankshaft before removing it. When balanced, make a corresponding mark on the flywheel that you can match w/ the shaft.

Sounds like you are on your way. Post #4 makes a good point as well.

I'm still hoping to find the best source for parts, and if there's anyone around who has particular experience with these transmissions. Also, is this an overdrive transmission? My guess is that it is, because in the manual where it shows speed in gears it actually shows the car going faster in 4th. If that's the case, and I put this transmission into a car that had an automatic, will the speedo be wrong. No, stupid question. The smart question is whether both the automatic and the 5 speed cars had the same differential ratio.

Almost certainly different differential ratios. You'll probably be happier with the diff from the euro car as well. Swap in the speedo from the euro (which is geared to match the diff) and you're golden.

I definitely wouldn't swap in the euro diff, that would be 3.46:1 or something crazy. You have the 2.88:1 in that car right now -- I would install the tranny with that and see how you like it. If you don't like it, go with a 3.07 out of a 300D Turbo made before 1985 or a 300SD made before 1985 (1985 is the only year that got the 2.88). The rear end out of the Euro would be higher than you need, though... remember, the turbo makes ~35 more HP than the NA. The 3.46 would just have running higher RPMs than necessary and that would increase your noise and engine wear and decrease your fuel mileage.

And yes, it's OD. I think 4th is 1:1 and 5th is 0.81:1.

I honestly can't say whether or not one needs to worry about the speedo, but since I've never seen any 4-speed swap threads dealing with it, I'm guessing its a non-issue. If somehow you do run into speedo inaccuracies, here is DeliveryValve's method for dealing with it:

http://www.peachparts.com/shopforum/diesel-discussion/238488-backyard-speedometer-adjustment.html

Charlie would know whether the speedo is a concern or not :).

Also, if you do swap out the diff, the 2.88:1 diff and speedo together are worth some $$, since they were only made for one year...

I've never had any issues with speedo accuracy swapping to 4speed in a 123, or 5 speed in a 124. As long as the diff matched the speedo.

The Mercedes of this era use the same differential ratio whether automatic or stick. The overdrive ratio is between 17 and 18% IIRC.

Thanks, all, for the input. I'm pretty sure that the clutch, pressure plate, throw out and cylinders are different for a 5 speed. Any advice on who might stock grey-market parts like that?
Thanks,
SEO

They are the same as a 4 speed, or at least that is what is most commonly used.

Not crazy at all; 3.46(final drive ratio) x .81(overdrive ratio) = 2.80 (engine speed to wheel speed ratio), right where it should be.

2.88x.81=2.33; too tall, even for a mighty 300TD.

A 2:88 and a 4-spd is almost too tall. On the flat land it is ok, but trying to start on a steep hill and get her rolling and get the rpm`s up w/o pumping and slipping the clutch is a challenge.

Now a disclaimer: I have driven 4-spds, 5-spds with 2 spd rear ends, 10 spd road Rangers, 13 speeds etc... for a good 40 years, so kind of have an idea how to shift and use the clutch.

On the majority of hills on the HWY`s it is ok. I had to get up a very steep drive way one time and she almost would not pull it.
Could have used a lower first and a few gears in between. In this situation a 3:46 would have been good.
A 2 speed rear end in our 123`s would help. :D Though most would know how to shift one. :(

A 2:88 on the Hwy is perfect.
A 3:07 would be good if there is mostly hilly terrain.
A 3:46 is good for low end start up, but will have the engine RPM`s running pretty high at 65mph.

I agree with Frank Reiner, a 2:88 in too tall with a 5-spd OD.
The engine will be straining to keep her up to speed, and the MPG will most likely drop.

Charlie