Auto to manual swap advice
 

Ok. So I'm back after a long absence. I got side tracked on a BMW e21 resoration and have been ignoring my mercs now for about a year. The BMW is in pretty good shape now. it started out as I was going to buy it to restore and flip to make money to fix my 240. But then I drove it and kind of got hooked. ;)

Any ways long story short I am now back to working on my mercs. Specifically I am sitting on all the parts to do a manual 4 speed swap. My big question is regarding flywheels and crankshafts. As I understand it for a w123 the two are dynamically balanced together. Not statically balanced separately. Is this true? Will swapping them cause problems? I have searched the forums and this question has been asked over and over but I'm curious to hear of any real world experiences with folks who made the swap without pulling the crank and having it balanced to the flywheel. Specifically any noise issues or shorter wear life on the crank. I only want to do this job once. And I plan to drive the car till I'm dead. Should I pull the crank and balance it to the new manual flywheel from another car? The other option is I also have the engine that the manual flywheel came from in my garage on an engine stand and could conceivably pull the matching crank. Or just rebuild that engine and just replace the whole thing. I do know that engine used a lot of oil. A lot of options here but would be interested to here the current thinking regarding the crank flywheel balancing issue.

Well I did just what you are looking to do and came out 100% satisfied. If I would do another I would do it the same way. I pulled the 240D and put the clutch and flywheel on with zero orientation. None! The 240 had disintegrated and who knew what. I live out of town and to run around to get these things balanced is a lot of work. Now, if you see a well defined "Check Mark" on the flywheel, then I would take additional precautions. But if there is no check mark, put it on!

NC:

There are quite a few threads on this subject on the forum.
The short, condensed version is:

1) Some individual engines may have flywheels (either auto or manual) that are neutral, i.e., no imbalance, and other individual engines may have flywheels that are imbalanced.

2) Before removing the departing flywheel from the engine, either verify that the flywheel and crankshaft have match marks (orientation marks), or make your own.

3) Check the departing flywheel for balance, either neutral or imbalanced.

4) If neutral, the incoming flywheel must also be neutral. If imbalanced, the incoming flywheel must also be imbalanced in the same amount, and, in the same orientation (that's what the match mark is for).

OK, Frank did a good job of the overview...
The other item it would be worth splurging on .... is the part on manual trans cars front of the driveshaft just past the trans.... is it designed to reduce vibrations...

balancing
 

I have done this swap before and I personally don't think its worth the risk to just take a random flywheel, throw it on the engine, and hope it all works out.
I marked my old flexplate's orientation on the crankshaft and brought both it and the new flywheel to the machine shop. I'm glad I did because the guy had to do a bit of drilling on my flywheel to make it all balance out, but when I started up the engine after it was all put together, It ran super smooth at all revolutions. In the end the choice is up to you, but if your planning on driving the car till your dead, its worth the extra $125.

I just finished this swap (I'm still dealing with lingering hydraulic issues) and I took the flex disk from my car off (I marked it and the crank first) and took it to a machine shop along with the flywheel from my donor car and had them resurface the flywheel and balance it to match the auto flex disk. I only paid $75 for the whole service so it is well worth it. FWIW both of mine were neutral balanced.

Are you putting the 4 speed behind a 616 or 617?

There is at least one voice in this thread who does not seem to know, that for the engines in question, the auto trans flywheel/ring gear, and the torque convertor flexplate, are two distinct pieces. The flexplate is not involved in the balance process.

All of his cars listed are 240D`s, so as I read it, he is putting a 240 FW off a 240 onto a 240 that has a auto trans. So we don`t have to throw the 300 FW into the discussion here.

Putting a 240 FW (OM616) on a OM617 engine is another thing, and there have been some vibrations at certain RPM`s mentioned.

I did the swap on the 85 300D, and originally used a 240 FW, had it matched balanced to the auto FW. It was off by a few grams, and the guy had to drill a few holes to get her balanced.
I did have a vibe issue if I dropped below 3K rpm`s, and around 50 mph. I have the 2:88 Diff. Dropping into 3rd it would smooth out, and could run it up to maybe 55mph.

I since found a FW off a OM617 engine. had it matched balanced, but so far have not driven it.

I have not read of any short lived engines with this swap...so far, but we don`t know if these members still have their cars or are still around.


Charlie

Then exactly what is it we match balance to? Yes the Torque Convertor plate (Triangle piece) is a separate piece that is bolted to the Crank with the FW Bolts. So are you saying it would be used along with the Auto FW (Ring Gear) Plate? Or the Convertor should be in with the balance.

yes I have read the Posts that if MB wanted a manual behind a Turbo engine they would have done it, and there must be a reason they did not.

Charlie

charmalu:

Only the Auto FW/Ring Gear are involved in the balancing process; not the triangular flexplate or torque convertor.

I have always called the ring gear the flex plate/flex disk/auto flywheel. The small triangle doesn't have enough mass to balance.

That was my understanding also. That is the way I have done it, and read how others have done it too.

I may have misread what you typed.

We need to keep this thread on track as to what NC-Diesel is asking.


The MB FSM mentions that the crank and FW are balanced as an assembly.
Using a FW from one engine, and attaching to another engine after the new FW is matched balanced exactly as the original, can get them close, as close can get them.
Throw in the human factor, and things can get off some what. Ie, telling the machinist you want it matched balanced to the auto FW or even swapping in another 240 FW from one eng onto another 240 engine. The machinist may be thinking to just balance the FW and call it good. How you to know?

Charlie

Charlie

I made witness marks before removing ring gear. Removed ring gear, lined witness mark of 240d flywheel up with a orange paint dot on the crank. My 617 swap is vibration free unless I go below 46 mph in 4th gear and lug it.

My swap ('83 Getrag 4spd. behind a '85 OM617) but have yet to fire it up. Nothing was marked on either engine so my assumption is that all were neutral balanced.

Having worked for over 30 years in dynamometer testing I have a fall back. The finished product can be taken to an industrial balance specialist and they can balance the assembly in place. We did it frequently. They'll hook up several accelerometers that read in all planes and determine any imbalance, then add or subtract weight as needed to resolve any issues found. From there on you can mark any pieces you might have to remove (say, to renew the clutch) and maintain balance for the life of the car. Most cities of any size will have a balance specialist and most don't charge a ton of money for this. Our guy came to us but you can work out those details with the vendor.

Dan

Sounds about right, what rpm and what Diff you using? 3:07?

My 80 240D 4-spd manual, anything below 40mph, and the engine is starting to lug down, so then run it in 3rd gear.
Iam using a 3:58 Diff instead of the 3:69 all 240`s use. so maybe a 3:69 anything below 35 or so, shift to 3rd.

Charlie