I just completed (well, still waiting for a shift boot actually) a manual conversion on my wagon. Things are ducky. I love it.

But... everyone else here has said they had no change in final drive rpms. I am reading 3000 rpm at 75; with the slush drive it was 3500 at 70. The needles used to be parallel on the highway. Now 60 mph looks in 2000-2500 rpms.

New speedo cable (old 240 style, my trans is from a 79) same rearend, same instrument cluster.

California car, not that I think that means anything.

Any ideas???

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

If you were really at 3500 at 70 mph with the auto tranny, something was wrong. At 3500, you should have been in the 80-85 mph range with an '85 (2.88 ratio). 3000 rpm at 75 sounds just about right with no slipping.

I agree what craig said. I think maybe your torque converter was slipping.

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1983 123.133 California
- GreaseCar Veg System

Torque converter = a few hundred RPM slip between the engine and the tranny.
Clutch = 1:1 RPM transfer from the engine to the tranny.

The auto trans was failing, and I suspected slippage. Moving off a stop would produce major groaning if I leaned into it. Hence the swap.

What is interesting is that I was getting a consistent 24 mpg with that auto, which led me to believe that it wasn't slipping that much on the highway, since that did not seem particularly low mileage.

I know some folks have claimed upwards of 30mpg. I never believed them. Maybe I'll change my opinion.

I'll post some results my next fill-up. Thanks for the replies

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

I predict 26 or 7 based on your previous experience.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

First of all, the speedo drive gearing inside the transmission is different between the manual and the automatic so, the original automatic speedo will indicate a higher speed when it is connected to a manual transmission.

I don't recall anyone ever stating that the speedo indicated correctly after a conversion (Go here and see posts #119 & 122). My conversion to manual (tranmission only, no change in speedo and the car has 3.07 gears) resulted in an approximate 7-10% error at the speedo ie: an indicated 75mph is actually 68-70mph. Likewise the odometer indicates high.

I assume that your car has a 2.88 rearend so, I suspect that you had/have a couple of things going on:

1) Your speedo was already reading a bit fast. A car with a 2.88 rearend will turn 2750-2850 RPM at 65 MPH. At 70 it will turn a shade over 3000 RPM. For reference, a stock 300D with a 3.07 rearend, an automatic and standard tires running at 3450 RPM would get you 75 MPH as seen below (speed confirmed by GPS in this situation):

2) Your automatic was slipping pretty badly. Per above, 3500 RPM at 70 MPH is higher than the normal revs for either a 2.88 or 3.07.

What's the solution? Well, I'm not sure. I believe that there are three different internal gearings available in the 123 speedo so, one thing might be to use a speedo out of a manual-equipped 123. But, there will still be an error since the manuals have 3.60someting gears and you have 2.88s or 3.07s.

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Never a dull moment at Berry Hill Farm.

The 85 300D and 300SD came with the 2.88 gearing. 84 on down to 81-82, IIRC came with 3.07. I believe the non turbo 617 had different gearing than the 3.07.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

I have an 85 300 SD with a 2.88 rear end. With an automatic 70-75 mph is 3000 rpm (note it moves around a bit depending on the torque converter's mood at the moment). I would love a manual transmission. I dream about a CVT though.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

http://ecomodder.com/forum/fe-graphs/sig692a.png

Guess the consensus is my old auto was slipping more than a bit. Glad I got rid of it! I probably would not have done this were it working well, more because of the time and energy expended than anything else. Spent about $800 (donor parts, driveshaft shortening, new clutch master cylinder, rubber pedal pads, clutch plate, speedo cable, flexdisks, used crossmember), so savings over rebuilding the auto made the hours worth it.

I generally like the responsivness of the stick. I couldn't go left out of my driveway with the engine cold, it's a steep hill after a blind corner, and I could only do about 15mph until I got to the top. Now I can pull right up.

I also think it is not for everyone. With a nicely working auto, the MB drives well and comfortably, and the TC dampens driveline shock. There is a tiny bit more gear noise with the stick, and there is less "mush", so whatever play there is in the diff, couplings, flexdisks (mine are both new) gearbox, etc,. you feel when you let up hard on the accelerator. I have driven lots of sticks, and actually converted two other cars (Grand Wagoneer and a Saab 900), so I don't mind adjusting my driving. Not sure the average driver (not folks here generally) wants that much of the "driving experience".

Rleo, is the difference between the 5-sp and the 4-sp noticeable? Obviously you have better top-end rpm. Any difference starting off? Between gears?

I like the gearing of this old 4-sp, 4th is definitely a highway gear, third keeps you moving between 20 and 45 or so. 2d gear you don't have to stay in long, though you can. I may never have to rebuild this tranny, sounds fine but I know nothing about it. I figured maybe I should pick up the first cheap twin that comes along and rebuild it in my spare time.

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

5th makes all the difference in the world; it's precisely what these cars need in the age of 70+ MPH speedlimits.

Gears 1 -> 4 are the same so there's no difference in functionality there. But, 5th is about a 25% overdrive. My tach only works intermittently but at 75 MPH she's turning about 2600-2800 RPM...right in the fat middle of the torque curve. My economy has increased substantially (I never saw much change over the auto when I went to the four-speed) and, with fuel now pushing $3/gallon, it's feasable that I could eventually amortize the cost of that tranny.

Additionally, the sound level in the cabin is really reduced, making long trips much nicer. It was never terribly loud, but the wagon is overall, noiser than the sedan. The fiver makes it nice.

With your manual, do you have any gear/driveline buzz at specific RPMs?

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Never a dull moment at Berry Hill Farm.

RLeo, you make a good case for re-cutting my driveshafts when and if I ever find a 5-speed.

No driveline buzz that I have heard so far. Don't jinx me, I am still listening hard, and I have had exactly a week with this new beast. The first time I took it on the highway, it seemed noisy; subsequent trips make me think I was just paranoid, worried about the thing falling out. It seems very quiet in all the gears except lugging it up a hill you can hear the gears complaining. I have spent a lot of time in 3d and 4th, less in 1 and 2.

I was expecting vibration based on the testimonies here, but if anything it seems quieter than before. I had the driveline professionally cut and balanced, and put in the alternate 240 trans crossmember which fit like a charm, using a new 300 rear mount (much thicker than the 240). New flexdisks, fresh ATF of course.

I also have the 240 flywheel and did nothing to balance. I could not see any matchmarks on anything but the disc attached to the torque converter, so we just put the thing in where the holes matched, meaning any one of twelve possibilities! It idles smoothly, a tad higher obviously, and not a whisper of anything suggesting major imbalance. The long term results will hopefully bear out what others have found about using the smaller flywheel.

By the way, my tech found me a nice wooden (zebrano) shift knob that is not only pleasanter than stock, it is also shorter by 1.5", shortening the throw and the height above the console. Any interest, I'll find out who and where. I think it was $75 or so. Pricey for frills, but it helps convince my family that my 22 year old car is not just a beater! I don't understand them....

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

Do you mind sharing with us the mercedes part# ang getrag part # of your tranny?

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

Methinks N/A engined cars have 3.69:1 ratios.


And, I can state without a doubt, the speedo drive gearing differs between the manual and automatic transmissions. I don't know about all manual transmissions but, the speedo outputs on the old cast iron 4-speed I had and, the Getrag 5-speed that's in the car now are both the same.

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Never a dull moment at Berry Hill Farm.

a few things.

first the na 300ds have 346 gears, the 240 123 has 369 gears.

second, the output on the speedo is off the tail shaft of the tranny so if the torque converter is slipping it does not know anything about it so the speedo has no need of a different gearing.

you should always get better economy with a stick all other things being equal, less slip and it takes less power to twist a manual tranny than an automatic (these old ones anyway).

Glad you are enjoying your manual conversion. I am too.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.