I'm getting ready to do an engine swap in my '82 300TD. I want to put an M104 3.2 engine in it, most likely from a w124 e320 or 300e 3.2. The engine could also come from an S320 I suppose.

I'm not familiar with tranny numbers, bolt patterns, etc for these cars. I have a few questions:

1. Will the original transmission in my w123 mate with an M104 engine?

2. Will the M104's transmission mate to my driveshaft? I could make an adapter easily but I'd rather save the time.

3. Are there any 5-speed automatic transmissions that I could use?

4. Are there any trannies with a locking clutch that I could use?

Thanks in advance!

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

#1 No.

#2 Doubtful but changing the yoke on the trans isn't difficult.

#3 Yes and dont.

#4 Later electronic trans can lock, but is a whole other can of worms.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

What's wrong with the 5-speeds?

I probably wouldn't bother with the hassle of using a later tranny and messing with Megashift at least until the swap is done and working. Maybe a few years down the line.

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

5th gear

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Could you elaborate? Do you just not like having a 5th gear? Or are there problems with it?

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

5th gear is essentially an "over drive" unit and it is the weakest gear in the system. What usually happens is when you install a 5 speed in a car not designed for it the tranny experiences premature failure.

You might get away with using a 5 speed since your W123 diesel model will have a lower (higher numerically) differential.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

As written in my sig, I have a 2.47 diff in my car, in preparation for the gasser engine. Yes, it is a dog (with the diesel, anyway)! However, I only did it to make gears 1-4 act more like 2-5 and get lower revs on the freeway and a quieter ride. So if I could fit a 5-speed I'd probably go back to something shorter like the stock 3.07.

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

According to this:
W124-320E-2-Getriebe/en

The diff ratio on the e320 (with 5-speed auto) is 3.69 and the 5th gear ratio is 0.75, so I could grab a 3.69 diff from a 240D. But since I like a final gear that is on the taller side (lower cruising rpms), I might go back to my stock 3.07.

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

The 104 is a poor choice of engine to lug at lower RPMS. The 4-valve cylinder head is designed for high RPMs. The advanced cam timing at low RPM is a crutch to mask poor flow in the port at lower engine speeds. Continually operating one well below its designed RPM range in a heavy vehicle and expecting it to be efficient is likely to be a disappointing endeavor.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

But revving it higher can't be more efficient. Besides, I'm only talking about 20% lower ratio, so maybe about 500rpm lower. It wouldn't be "chugging" at 65mph, would it?

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

The speed of the car is only a piece of the puzzle, its the speed of the engine and where you are in the power curve that determines fuel efficiency. the m104 engine is most efficient (power to fuel used ratio) between 2.5 and 3.75k rpms.

The 3.2 L (3199 cc) version produced 220 hp (161 kW) at 5500 rpm and 310 N·m (229 ft·lbf) at 3750 rpm

According to "How stuff works" the best place to shift gears for fuel economy is the max torque rpm. That means that in the m104 you're nearly at 4k before you shift for max economy. On my 606 however I should be shifting at 2200 rpm. Such is the difference between gas and diesel I guess.

My hypermiling has always been just upshift as fast as you can and don't push down on the accelerator if you can help it. I'm wondering if I'm missing out on free power by upshifting too early and hanging out in lug territory too long.

__________________

77' 300D, "Cartman" SOLD @ 150K (didn't know what I had)
83' 300SD, "The Superdon" 325k+ @ 28mpg
95 E320 wagon, "Millennium Falcon" 231k+ @ 24 Mpg
95 E300D, "Sherley" 308k @ 33.69 Mpg, currently anticipating a head
99 Suzuki Intruder "Trudy" @ 45 mpg

Maximum torque occurs where the engine is most efficient at converting fuel into work. In the 104's case it occurs at a relatively high RPM. You can operate it at lower RPMS with less fuel but a smaller percentage of that fuel will be converted into work.

The 104's 4 valve arrangement is great for high RPM flow but it falls short at low RPMS for a couple of reasons. With the relatively large area of valve opening the velocity of the air fuel mixture entering the cylinder is quite slow at lower RPM. This allows fuel to drop out and puddle in the port. Additionally the 4 valve setup introduces no swirl of the mixture entering into the cylinder. It relies totally on tumble. Swirling the mixture in the cylinder makes for a more homogenous and complete burn which equals power and efficiency. Unfortunately for the 104 a low velocity tumble doesn't move the mixture around very much at all. Hence power and efficiency are poor in low RPM compared to a traditional small port 2 valve design. To make up for the low output MB introduced variable intake and cam timing. These two tricks basicly allow the engine to ingest a larger fuel / air charge at lower RPM to make up for the poor output. So the low RPM output is up to acceptable levels but it takes more fuel to do it.

I'm not saying the 104 is a bad motor, its not. I just think its not the best choice in a build with high rear ratios and efficiency targets. If the goal was a sporty car that would spend a lot of time in lower gears and higher RPM it would be hard to beat. From what I understand about your build's goals you'd be better served by an engine designed with a lower RPM operating range.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

First off, thanks for the great (and clear) info. I never knew that about the m104.

I agree that an engine is most efficient in converting fuel into work at the torque peak. But I think the engine is more efficient in converting fuel into distance at a lower injection rate (or lower rpm) - to a point. Without analyzing the dynamics of combustion and knowing everything about the engine, I like to put the freeway cruising rpm a few hundred above where it would chug or shudder with open throttle.

I haven't even driven an e320 yet, so I will before choosing my diff.

The goal of my swap.... good question! I guess the main goal is to convert it to a gasser. I'm sorry, I know people on this forum love the diesels, but I don't. I love them for their reliability and simplicity but they're too slow for the big cities, and I've had it. So in a nutshell:
1. convert to gasser
2. easy to swap in
3. can pass minivans and priuses at any speed
4. some efficiency would be nice, maybe 20+ mpg

#2 precludes V8s in my opinion. I don't want to cut the tunnel open for a big american transmission. And I don't want to convert to rack & pinion if I don't have to.

__________________
'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

Admiral:

You have, I trust, considered the M110 which was used in W123s originally.
Direct bolt-in, mates to your transmission, carbs or injection, plentiful.

Also consider US 60 degree V-6s from both GM and Ford; narrow enough to fit in W123, short enough to bring the trans forward to have minimal floor interference problems.