4-speed transmission question - W123 240D - PeachParts Mercedes-Benz Forum

MagicBus · #1 10-06-2014, 09:59 AM

Hello, all

I have a 1983 240D that I bought in 2012 and have been re-habbing as time allows. What I thought would take 3 months is going on 2 and a half years, but I'm not complaining. I just finished the bodywork portion and have painted the car, though I still need to do a few touch-ups and wet sand then polish the new paint.

But, I ramble on... Now that I'm basically past the bodywork portion of the project, I'm going to be getting into the mechanical portion of the project. When I bought the car, the previous owner told me it needed a new clutch. So, that's on my to-do list.

Fast forward from 2012 to last summer (2013). I bought a '79 240D parts car, also 4-speed from the original owner. The seller told me he'd parked it with a new clutch and new tires (just what exactly constitutes "new" is unknown...) sometime around 2000. I got it running, and although the car looked OK-ish above the rockers, it was rotted out about as badly as I'd ever seen, so I opted to part the car out after I got it running.

Sorry... rambling again. So, I have the '79 engine and transmission still mated together. Supposedly, the '79 stuff had a fresh clutch. My plan, therefore, was to use that clutch (provided it really does look new-ish upon examination, that is...), but also to transplant in the '79 transmission.

The '83 has around 290,000 miles on it. The '79 had around 214,000, and appears to have been better-cared-for in its lifetime.

Now, my question(s). I THINK I read that the '79 transmission is actually a better unit, and was actually built by Mercedes. Is this true, and if so, what exactly makes it "better"?

I still have the shifter and shift rods from the '79, which I know I'll need. Is it reasonable to assume I have everything I need, and that everything should swap over without a problem?

t walgamuth · #2 10-06-2014, 10:11 AM

I'd not worry about which transmission is better. I'd use the one with lower miles unless something makes it look more worn. If you start with two cars between the two you should have all the parts needed to make the swap. I'd prolly pull the engine and tranny apart and look at the clutch though.

Stretch · #3 10-06-2014, 10:20 AM

The 83 is also potentially the uprated engine thought there's not that much difference in the published performance figures. Still pick the best of the rest of what's left!

MagicBus · #4 10-06-2014, 10:32 AM

Quote:

Originally Posted by t walgamuth

I'd not worry about which transmission is better. I'd use the one with lower miles unless something makes it look more worn. If you start with two cars between the two you should have all the parts needed to make the swap. I'd prolly pull the engine and tranny apart and look at the clutch though.

I do plan on separating the '79 engine and trans to have a look. Aside from that, I'm sure I saved everything I needed before I junked the shell of the '79.

The '79 transmission definitely has way lower miles on it. I have no reason to specifically distrust the higher-mileage '83 transmission, but as I said, I seem to remember reading that the '79 would have had a better overall transmission. Since I have two to choose from, and need to pull the '83 transmission to replace the clutch anyway, I'm just wondering if I should use the potentially better '79 transmission that I have handy.

Quote:

Originally Posted by Stretch

The 83 is also potentially the uprated engine thought there's not that much difference in the published performance figures. Still pick the best of the rest of what's left!

As for the engine, the native '83 engine is staying in place. The throttle linkage alone seems to be enough reason not to mess with things in that department.

Dan Stokes · #5 10-06-2014, 11:42 AM

As I understand it, the '79 clutch will not fit the '83 trans so that's not an option. I'm running the '83-style trans (I understand it's a Getrag) in my race truck and don't expect any issues. While the Mercedes-made trans is marginally stronger my understanding is that there isn't a LOT of difference between them. I mean, WHY would Mercedes install a trans that's too fragile behind their somewhat more powerful 616 engine? Unless you're doing a lot of drag strip racing I doubt there would be an issue.

Another thing to consider - I'm not sure that the transmissions are the same length so you may get into swapping driveshafts, crossmembers, replacing the rubber biscuits, etc. AND, the Mercedes trans is a TON heavier than the Gettrag which matters when you're shoving it up from under the car!

I'd buy a decent clutch for the '83 and fix what you have - I got my Sachs from Pelican parts. A consistent failure on these is the clutch slave cylinder so you may want to replace that while you're in there. It'll be a stinker to bleed but there is guidance on here for that.

Dan

leathermang · #6 10-06-2014, 11:58 AM

Quote:

Originally Posted by MagicBus

......The throttle linkage alone seems to be enough reason not to mess with things in that department.

AMEN. So many people find it a nightmare to get that fixed when dealing with two engines which are not Exactly the same.... which is hard to find... MB used a lot of different quirks over the years....

t walgamuth · #7 10-06-2014, 11:58 AM

I autocrossed with the aluminum case four speed with no issues.....running wide hoosier slicks with loads of traction and standing starts....

MagicBus · #8 10-06-2014, 02:11 PM

Quote:

Originally Posted by Dan Stokes

As I understand it, the '79 clutch will not fit the '83 trans so that's not an option. I'm running the '83-style trans (I understand it's a Getrag) in my race truck and don't expect any issues. While the Mercedes-made trans is marginally stronger my understanding is that there isn't a LOT of difference between them. I mean, WHY would Mercedes install a trans that's too fragile behind their somewhat more powerful 616 engine? Unless you're doing a lot of drag strip racing I doubt there would be an issue.

Another thing to consider - I'm not sure that the transmissions are the same length so you may get into swapping driveshafts, crossmembers, replacing the rubber biscuits, etc. AND, the Mercedes trans is a TON heavier than the Gettrag which matters when you're shoving it up from under the car!

I'd buy a decent clutch for the '83 and fix what you have - I got my Sachs from Pelican parts. A consistent failure on these is the clutch slave cylinder so you may want to replace that while you're in there. It'll be a stinker to bleed but there is guidance on here for that.

Dan

From what I've seen, (and I've only done the bare minimum of research so far) there's only one clutch available (well, more than one brand, but I'm not seeing an early or a late version). I am seeing differences in the throwout bearing, though. If you're right, that's good info to have. As for swapping other parts, I'd have to remove the driveshaft anyway, and have all the parts from the '79, so that wouldn't pose a problem. I'm also planning on replacing the flexdiscs and center support/bearing while I'm doing all of this.

As luck would have it, when I bought the car, only the downpipe from the engine was installed, and the rest of the exhaust was off. The seller included a brand new, never-installed exhaust, but I've held off installing it until after I have the clutch/driveshaft stuff done. So, that won't be in my way.

As for the weight, I hadn't considered that the difference would be that large. It's not too big an issue. I do have a flat-topped transmission jack. But, it's still good to know.

Quote:

Originally Posted by t walgamuth

I autocrossed with the aluminum case four speed with no issues.....running wide hoosier slicks with loads of traction and standing starts....

Hmmm.... so, it sounds like there's no long-term design problems with the aluminum case transmission. Good to know.

Assuming the following is true...:

the '79 clutch actually is compatible with the '83 transmission
the '79 clutch does indeed seem to be in like-new condition

I wonder if it would make sense to save a few hundred dollars and swap those over to the '83. I realize a clutch is a wear item, but if it really was just about new when parked, could it potentially cause a problem to use that?

And yes, I very much am trying to be as cheap as I can with this project. I'm putting a formerly junkyard-grade car back on the road, and am interested in doing quality work as cheaply as I can. The hard part (bodywork) is basically done.

t walgamuth · #9 10-06-2014, 06:06 PM

you'll just have to look at the thickness of the clutch wearing material and the wear on the pressure plate fingers. If it is like new you should be good. are you certain the clutches are different between 79 and 83? if so it is surprising.

Stevo · #10 10-06-2014, 07:39 PM

The only difference in the clutches is the throw out bearing and clutch slave. The throw out bearings look very much alike so make sure you use the right one or you'll have to pull the tranny again

, don't ask how I know

Like Tom said, dont worry about which is better, their both fine boxs.

MagicBus · #11 10-06-2014, 07:45 PM

Quote:

Originally Posted by t walgamuth

you'll just have to look at the thickness of the clutch wearing material and the wear on the pressure plate fingers. If it is like new you should be good. are you certain the clutches are different between 79 and 83? if so it is surprising.

That's generally the idea. Of course, if I separate the '79 engine and transmission only to find that the seller had lied or remembered wrong, then I just buy a new clutch. End of story on that. As far as I'd heard, the clutches should be the same.

Quote:

Originally Posted by Stevo

The only difference in the clutches is the throw out bearing and clutch slave. The throw out bearings look very much alike so make sure you use the right one or you'll have to pull the tranny again

, don't ask how I know

Like Tom said, dont worry about which is better, their both fine boxs.

That matches what I'd seen so far.

If the clutch and pressure plate really do seem to be close to new on the '79 assembly, then I'll likely use them, and from what I've heard here, I'll probably use the '83 transmission, too (with new flex discs, center bearing support, new shift linkage bushings, etc), rather than lift the heavier '79 assembly into place. I'd buy a new pilot bearing, throwout bearing, slave and master cylinders anyway.

Thanks for the input so far, everyone.

Frank Reiner · #12 10-06-2014, 08:30 PM

Magic:

One thing that may complicate, but not prevent, a trans swap, is the centering method for the clutch housing to intermediate plate. The earlier (pre-Getrag) design has a circular, peripheral centering ring between the clutch housing and the intermediate plate. The Getrag uses two dowels between the one piece trans/clutch housing, and the intermediate plate. To use the earlier trans would require also swapping the intermediate plates, which entails flywheel R&R.

MagicBus · #13 10-06-2014, 10:16 PM

Quote:

Originally Posted by Frank Reiner

Magic:

One thing that may complicate, but not prevent, a trans swap, is the centering method for the clutch housing to intermediate plate. The earlier (pre-Getrag) design has a circular, peripheral centering ring between the clutch housing and the intermediate plate. The Getrag uses two dowels between the one piece trans/clutch housing, and the intermediate plate. To use the earlier trans would require also swapping the intermediate plates, which entails flywheel R&R.

Hmmm... sounds like it's probably more trouble than it's worth, anyway. Thanks for the info.