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Unimog 404 TDI AHU swap

13807 Views 105 Replies 9 Participants Last post by  joeblack5
Howdy folks, Happy 2021.

Have been thinking about diesel conversion for a while and think I have read most threads and posts on this and other forums.
We are attempting a camper with our second 404 and would like the fuel efficiency of the diesel. For that reason the TDI above the OM617.
In this camper the 404 cab will be hard connected to the camper shell.. all on pivoting frame...and the front seats of the 404 will have swivel so that the cab becomes part of the living space.
For that reason I do not want to reduce the cab area or modify the engine dog house unless it is going to be smaller.
The cab will be raised about 2" to make space for 12.5-R20 tires

Looking at the available picture and taking some measurement it seems that if I pull the TDI engine to the front of the mog and remove the alternator and oil filter then it all could fit with out interference.
The front of the 404 engine bay is wider ( 22") with space for the original distributor. This would help with space for diesel pump. With alternator removed less then 20". Worst case would be to use the pump duse engines BEW and so on.

The 5 speed transverse manual transmission of the TDI can be split and the engine / bell housing section can be used as spacer / adapter.
This would have several advantages:
-TDI flywheel / clutch assembly can be maintained, power upgrades are available
-Clutch cylinder is already attached to bell housing.
-Starter is attached to bell housing. along the transmission
-readily available.
- the lighter weight TDI engine slid to the front gives max pressure on the front axle.

Another adapter / spacer has to be manufactured to adapt from the TDI bellhousing / half transmission to the bell housing of the 404.
M180 engine length 31" with pulleys... without fan.
TDI ALH 18"
TDI 5spd bellhousing / half transmission 5"
TDI ALH with transmission 32"

Problems:

Depending on that exact space the original TDI starter will not interfere with the 404 bell housing. unknown

The TDI ALH 5 speed has no pilot bearing and the input shaft no stub for a pilot bearing.

The TDI ALH longitudinal transmission has a pilot bearing so a shaft swap with bearing might need to happen.

The TDI transmission shaft has to be extended and adapted to the 404 input shaft , probably nicest with the spline of the clutch.. It looks like the 404 shaft's spline id long so for best alignment maybe two clutch centers could be welded together

The differential housing has to be cuttof from the TDI transmission.
ideas.

ideas??
The TDI with 5 speed is about as long as the M180.
Potentially the cover 5th gear steel cover of the 5 speed can be removed, the transmission gutted and an adapter flange from the back of the transmisisson can mate to the 404 bell housing.
The splined old 5th gear can be welded to the clutch spline of the 404.
Bearing would have to be replaced with enclosed ones or if pilot bearing/ new shaft is used then both tdi transmission bearings can be removed.

In the pics of the TDI / 5 spd.. the starter motor is removed.

Anybody has tried / see this approach?

Johan by

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Discussion Starter · #61 · (Edited)
Some more machining of the extension of the transmission shaft. It fits perfect. . More bolts in my adapter contraption.
Hung the tdi motor.. smooth ..
Mounted the cab without raising it. Just to confirm clearances. Fits nice. The tires are 40" ..if I do not need to raise the cab for tire clearance then I will leave it like this.
Need to cutout the aluminum adapter plate a little more to easily mount the starter motor with the cab on.
Now more time can be spend on the clutch... cable or hydraulic. At the clutch pedal the attachment moves 27.5 MM... The first lever is 155 MM the one inside the bellhousing 85 MM.
So at the clutch plate the movement is about 15MM. sounds reasonable, will see what the TDT clutch requires
Also now more in the picture are the remote oil filter....front engine mount/ alternator mount.
Johan
 

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Discussion Starter · #62 ·
Since we were so happy with it all fitting we decided to press on.
The water pump inlet is pointing the wrong direction.. our oldest daughter is wrenching on it. Seems it can be modified .

We made some oak " motor mounts"
Then Tanya crafted the cardboard pieces that tie it all together.

With the original M180 the engine hangs in swing arm. I do not see it critical where the swingarm is located along the cross member.

With the tdi a little under and angle and the moor mounting options favouring the passenger side we decided that the pivot pendulum has to move direction passenger side as well. A similar horse shoe brace that is used in front of the M180 is made no under the oil pan and the pendulum is behind the crossmember. All will be bolted so that the oil pan can be dropped easily. Also to benefit the removal of the thermostat housing / water inlet that now is hidden behind the driver side motor mount.
If anyone see a problem please comment.

The original tdi motor mounts and some additional will be used. The alternator will be integrated on the passenger side.
 

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Discussion Starter · #63 ·
So please comment on my proposed action above. The motor mount pendulum/ swing arm has moved 4" down and 4" to the passenger side. The pendulum itself has changed from about 2" ctc to about 4"ctc. Original it was on top of the crossmember now it will be 2" to the rear. So it will allow some torque on the crossmember as well. I do not see a problem with this being a lighter engine but of course others have a better perspective.

Thank you,
Johan
 

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Discussion Starter · #65 ·
I agree. Although first I thought that because of the construction of this TDI engine that I would have to move it over . Here some pics of the first attempt..
Unfortunately I do not have the original M180 front motor. Wonder if I can jam that in there.
 

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I agree. Although first I thought that because of the construction of this TDI engine that I would have to move it over . Here some pics of the first attempt..
Unfortunately I do not have the original M180 front motor. Wonder if I can jam that in there.
It your motor is not centered, you can create your mount to be cantilevered. If you need dimensions or pictures of the original, I can help.
 

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Discussion Starter · #69 ·
More work on the front motor and alternator mount. The water pump pulley is a separate v belt that would require an additional tensioner. To keep the design clean and save space we decided to replace it and incorporate it in the serpentine belt loop.
To get more friction with the crankshaft pulley an idler was added. The alternator is pivoting around the top bolt.
 

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Discussion Starter · #70 ·
It goes slooooowwww. To many other things that time can be spent on to.

The passenger side motor mount in all it's glory. The driver's side fits as well.

The serpentine is 41" 6 rib... Looks a 40" would be a better fit.

Next stop will be the remote oil filter.
Motor vehicle Automotive tire Automotive lighting Rim Automotive wheel system
Bumper Gas Wood Automotive exterior Auto part
 

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Discussion Starter · #72 ·
Interesting images.

I have to look up if that is the original radiator of that unimog. First I thought that it had an intercooler on the side but after looking at the turbo setup that appears to be the air filter.

It is nice that they were able to maintain the steering pump. In my setup I position as much to front as I could ,like with the m180 but as a result the crossmember is in the way of belts going downwards.

That is an intriguing front motor mount. Looks like they used a threaded rod along the crossmember, but not sure why.

One day I hope that mine will be that finished looking.
 

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Discussion Starter · #73 ·
A little bit of work.. the original m180 has extra braces to the bell housing.. I would think in pull arrangement.. they are strips, so push would buckle. Mercedes must have a reason so I will follow.
I will pull all the way from the bell housing to the front motor mount. This just to show the principle.. actual rods will be M12 thread. I will reinforce the front motor mount so it will able to handle the additional forces.
 

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Discussion Starter · #74 ·
Oh no, I forgot to make pics.

Front motor cradle reinforced and tested.
Shorter serpentine Installed. Looks much better.
Took motor out to measure the transmission input shaft one more time..made drawing of shaft coupler.

Started looking at exhaust routing but figured it would be better with the cab on.

Looked at location of throttle pedal ...this is drive by wire.

Some fine tuning of starter motor mounting.

Sorry about the pics.

Johan
 

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Discussion Starter · #75 ·
Second try,
Time goes fast and other projects needed attention as well.. here is our 1820 log house.. the path to it is not so wet right now so the gd240 was perfect.

On the 404....the material for the transmission shaft extension / coupling is in the lathe and also the remote oil filter is making progress.

Johan
 

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Discussion Starter · #76 ·
Another small issue resolved.. the original coolant intake pointed backward... Besides being in the wrong direction it also interfered with the new motor mount. Originally I tried to remake the original one and rotate it 90 degree but this one from a VW gasser 1.8T does exactly what I want. This one is plastic but an aftermarket aluminum one is available.
 

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Discussion Starter · #77 ·
One month idle time...filled with higher priority projects..but now back on the ball.

Today finished the extension shaft..The VW shaft has a bore that fits over the clutch pilot stub of the 404 shaft.. then a sleeve that is gones to fit precise around the splines of the 404 keeps the two pieces in one line.

The spline from the old clutch disk is bolted to the sleeve.

Next step is make an adapter for the end bearing on the VW shaft.
 

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Discussion Starter · #78 ·
Some more parts..the VW tranny tdi combo does not use a pilot bearing.. the original bearing in the tranny was a tapered one with an od of 45 mm and ID of 22 mm.. the closest deep groove I was able to by was a 44*22*12.
So I had to machine a spacer with a wall thickness of 0.5 mm.. our oldest did the rough in work at the lathe.. this being an 50 yr old 3/4HP south bend ....not much roughing in...but it worked.
Getting closer to final assembly I decided to do some paint work..

All tolerances worked out well.. the tranny shaft can slide 1/16" axially..
 

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Discussion Starter · #79 ·
The last two pics from this boring transmission stuff .
To prevent the pilot bearing spacer disk from backing out I drilled the m7*1 and tapped them to thru holes.. nice enough my HB cheap tapset had a M7x1 tap...amazing..
Three screws with washers keep it where it belongs.

The next picture is taken thru the inspection hole in top of the 404 belhousing..
Another thanks to Choprboy for the clutch spline he shipped to me.

In the mean time I cleaned the tdi's manifold and intake from carbon/ oil crap. Took a peak at the cam shaft ..looked ok..and made a plate to block the exhaust EGR.
 

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