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C280 2009, Unimog 406 1978.
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Discussion Starter #1 (Edited)
I’m searching for some help on fixing a leak of my recently bought Unimog with Torque Converter.
I really could use so me help because it might be a severe problem or an easy one to solv, its just that people over here doesn’t have knowledge of the system and I really wouldn’t want to bring down the transmission without being sure that I really need to do it.

I'm attaching a powerpoint presentation with the detail of where the oil is coming, I think there's a threaded plug missing in the torque convertor case, but that’s not all. I’m not quite sure if the oil should be there, let me explain myself...
The guy from transmissions showed me a automatic transmission. It as a case and then inside the case, theres a shell that contains the blades, stator etc, inside that shell (or lets call it inside case) is where the oil is, he says that between that shell and the transmission case (this case is the one you can see from outside the vehicle) there shouldn’t be oil, oil should only be inside the shell.
So he thinks that it’s the same with this torque converter. We think that the turbine is what you see thru the hole of the missing plug, and that oil should be inside that turbine (that has a shell), and that by a failed retainer oil is coming out of that shell, and then filling the torque converter outside case and since there's no plug, oil is coming out.

Is that correct?? Or oil is supposed to be there??
Please take a look at the presentation and let me know you comments, because there's 2 possible solutions: 1.- build the plug and we are done. Or the other one is bring down the transmission, blab la bla search for the leak, change retainer etc etc, bring up the converter a gain, which I don’t want to do, because I’m afraid it won’t fit perfectly as it is now. Plus the very high cost of repairing this leak.

I hope you guys could give me a hint on this, sorry to bother but im far away in Mexico with no help
Regards
 

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2015 Rubicon Unlimited (Let the shame be upon me!)
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4Sale: 230G, U1200 Ag, 1017A, lots of MB cars, Volvo c303, 416 raildoka, LR D110 TDi
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First off, I couldn't open the document, so I am just going to give an overview of what I think you are describing.

There should not be oil in the housing around the torque converter (often referred to as the bell housing). The plug in that area is to be installed in situations where deep water fording is necessary, and is usually left out so that leaks can be seen. If there is oil comming out of this plug, you have a problem. There are only two things that can cause a fluid leak in that area, one is the torque converter seal to the torque converter housing, and the other is the drain plug that is actually in the converter itself (or I believe what you are referring to as the "shell"). I can't remember if all of the torque converters had this plug, but I don't think it is accessable without disassembly anyway, so it looks like you will probably be taking things apart.

In order to get at the parts you need to work on, you would be much better off tilting the cab and removing the engine with the torque converter and clutch assembly attached than removing the transmission. Just about anyone with some lifting equipment can take out an old diesel engine and reinstall it, but taking out the trans can be a real nightmare for someone who has never done it before, and is not necessary to get to the seal in question. If you plan on doing it yourself or haveing someone who does not know mogs work on it, I suggest that you get a shop manual to help you better understand what needs to be done to get to the torque converter.

If you need further assistance, let me know.

Cheers,
Ben
 

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1970 406 Unimog with 9'2" Boss V-Plow....... 1974 404 Unimog Rock Crawler
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I had no problems opening pandilucciano's Power Point presentation, so here's the photos.
Sorry I can't offer any advice regarding this torque converter problem...
 

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C280 2009, Unimog 406 1978.
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Discussion Starter #6
Thanks Mega-Mog for posting pictures.

Merz-Ben: Well I think that with the pictures you will confirm your theory. Bad news for me, but at least now I'm sure i need to bring down the converter and engine. Now I need to make sure I find a good workshop to do this, since its heavy equipment and so.
thanks for your time and support, I'll post some news once i start with the repair.

Regards!
 

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'76 406.145 Doka tug
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The drain plug in my torque convertor came loose a few years ago. It leaked pretty good and I can confirm that it can't be reached without removing the engine. I removed the engine with the torque convertor housing attached. If you decide you need to press the turbine/ flywheel shaft out of the housing make sure to order a spare 'piston ring' or two because the little interlocking fingers break so easily.
 

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C280 2009, Unimog 406 1978.
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Discussion Starter #8
The drain plug in my torque convertor came loose a few years ago. It leaked pretty good and I can confirm that it can't be reached without removing the engine. I removed the engine with the torque convertor housing attached. If you decide you need to press the turbine/ flywheel shaft out of the housing make sure to order a spare 'piston ring' or two because the little interlocking fingers break so easily.
Thakns Crash, do you have more details on taking out the converter and shaft?
do you need to completely extract the engine? or just move it a few inches apart?

Got more details on taking out the shaft?
Do you remember or have part number for the piston ring?? or a photo maybe? or diameter??

THank you!
 

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421 DOKA/406DOKA/406 full agrar/2450 DoKa
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hello Pandilucciano and all the guys,

I own a 406 airport tug fully restaured with this kind of torque converter
I have replaced all the seals between the converter and the flywheel,it's not very hard to do..... when the engine is out of the truck !
I you need some info of pictures of the workshop manuel,i will be glad to help you and the community.
Regards
Renaud
 

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C280 2009, Unimog 406 1978.
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Discussion Starter #10
hello Pandilucciano and all the guys,

I own a 406 airport tug fully restaured with this kind of torque converter
I have replaced all the seals between the converter and the flywheel,it's not very hard to do..... when the engine is out of the truck !
I you need some info of pictures of the workshop manuel,i will be glad to help you and the community.
Regards
Renaud
Thanks Renaud, I have the grey workshop manuals, but if you have any additional pictures or information I'll be glad to get them.
[email protected]

Thank you.
 

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Discussion Starter #11
The drain plug in my torque convertor came loose a few years ago. It leaked pretty good and I can confirm that it can't be reached without removing the engine. I removed the engine with the torque convertor housing attached. If you decide you need to press the turbine/ flywheel shaft out of the housing make sure to order a spare 'piston ring' or two because the little interlocking fingers break so easily.
Crash, we've look in to the parts to find out which is the "piston ring" you mentioned, but couldnt find anything with that name, I'm attaching 2 pictures of the exploted view of the converter, see if you can tell me which is the so called piston ring.! Thanks!!
 

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the piston ring may be referred to as a o-ring in your picture but it is #17 in the attached picture. It is cast iron, maybe 2" diameter and the very very tiny cast iron fingers on the ends interlock as per the rough sketch in the attached picture. Being recessed in the groove on the turbine/ flywheel shaft it is very difficult to remove and install. You would only need to remove it if you plan on pressing the shaft out of the torque convertor housing to service it's sealed support bearing.

If I remember right the fluid that the seal in the turbine shaft support bearing seals is only fluid that seeps past the piston ring to lube the bearing.

Due to marks all around my torque convertor and on the drain plug itself I determined that a rock had gotten into the housing and bounced around until it hit and loosened the drain plug. I installed screen over any places rocks could have gotten in.
 

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Discussion Starter #13
the piston ring may be referred to as a o-ring in your picture but it is #17 in the attached picture. It is cast iron, maybe 2" diameter and the very very tiny cast iron fingers on the ends interlock as per the rough sketch in the attached picture. Being recessed in the groove on the turbine/ flywheel shaft it is very difficult to remove and install. You would only need to remove it if you plan on pressing the shaft out of the torque convertor housing to service it's sealed support bearing.

If I remember right the fluid that the seal in the turbine shaft support bearing seals is only fluid that seeps past the piston ring to lube the bearing.

Due to marks all around my torque convertor and on the drain plug itself I determined that a rock had gotten into the housing and bounced around until it hit and loosened the drain plug. I installed screen over any places rocks could have gotten in.
Crash, sorry for very late response, I really appreciate your help. Right now I have my mogs cabine tilted and tomorrow we will start with the engine removal (see pics) Do you mind helping me once i have the torque converter down?? nobody here seems to know it, and i dont want to screw it! if you can write me to my email ( [email protected] ) maybe i can get in contact with you. Thank you Very Much!
 

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Discussion Starter #14
Hi to everyone, in order to create a file and record my problem to help others, here I paste some pictures of the repair I'm doing, you will see as well the little cap of the "shell" some people has mentioned.
Regards.
 

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I looked through my stuff and do not have any useful pictures.

The seal does not seal to the bushing. The seal should seal to the torque converter itself. If you look back at the cross-sectional picture I posted earlier it shows the bushing #4 - friction bearing, is installed behind the seal. It should be a press-fit into #5 - bearing flange. The bushing should fit fairly easily onto the torque converter.

I would suspect that the bushing for whatever reason came loose in the bearing flange and spun damaging the seal lip.

I would recommend for re-assembly to remove the torque converter housing from the transmission so you can turn it horizontally to re-install the torque converter. Otherwise it may not be possible to get the turbine which is inside the torque converter back onto the turbine shaft splines if you try to do it in a vertical position where it will tend to drop downwards and out of alignment. It is much easier and less likely to do damage getting to clutch disc back onto the transmission input shaft splines while hanging the engine from a hoist. Also this gives you the opportunity to clean and grease the throwout bearing shaft and support.
 

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Discussion Starter #17 (Edited)
Thanks crash, so, Any way I should be replacing both? the bushing and the black seal?? the ones im attaching here right?
Or I'm I missing something??

I didnt get you very well, metallic bushing should go inside the rubber seal?? or it should go inside the groove that the rubber seal has (where the red arrow is pointing)??


Thanks for reply.
 

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Yes, I think you need both, the seal as it is leaking, and the bushing because it came loose. The bushing is difficult to press into the bearing flange without damaging it. If it's cheap - get two. I had a cylinder that just fit inside the bushing with a lip on it made so there was no chance of bending the bushing or having it go crooked when pressing it in. Hopefully there is no wear to the bearing flange where the bushing presses in that would make the new bushing fit too loosely. If so you might consider green Loctite bearing and sleeve retainer 640 or having the part spray-welded and machined back to the proper size.

There are not many other possible sources of leaks; the seal you have shown, the torque converter drain plug and the o-rings clamped under the bearing flange and stator support tube. I can't imagine the clamped-down o-rings leaking on their own but I would replace them as I bet you will need too disturb them by taking the bearing flange off to press in the new bushing. If the sealed support bearing leaked it would leak to the clutch side but it isn't even pressurized.
 

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Discussion Starter #19
@Chrashmaster

Apparently this should be the position of the bushing right??
1st Picture: Rubber seal where you can see the inner lip that I think it acts as a stop for the bushing right?
2nd Picture: The way I think bushing seats on rubber seal.
3rd Picture: Same as before but from back.

Is this correct??

Other question whichone faces the engine?? the rubber or the bushing side??

Thank You Very Much!
 

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The bushing should not touch the seal. The bushing is just a support for the end of the torque converter like a pilot bearing in a flywheel for a transmission input shaft. The bushing is pressed into it's bore first until it is flush with the edge where the bore increases diameter to the size of the seal. The bushing should not be loose enough to move at all. Then the seal is pressed in which rides on the sealing surface of the torque converter. The hollow side of the seal will face away from the engine.

If the bushing is loose it will spin around and rub on the seal wearing the seal out quite quickly.

In this picture the part shown as the torque converter is not yet in, it would normally be all the way to the right inside both the seal and the bushing.
 

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