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87 - 419 SEE,90 - 1300L
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Thanks for the quick reply. This is for my 1300L. I have the tech manuals for the 1300L but unfortunately the 3/65 gearbox was reportedly only installed late in production of the 1300L on the ambulances so the service manual only covers the 3/45 not the 3/65. The 3/45 speedometer drive shaft does look like it can be changed from the outside. If anyone has a hint where I can find a 3/65 technical manual I would appreciate the lead.

I hope that once I open up the speedo gearbox I can pull out whatever shrapnel is keeping it from turning.

With my spare tire out of the way I have pretty good access.
 

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87 - 419 SEE,90 - 1300L
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Looks like its a 718811 UG 4/65. (this came from a print out of my VIN from the Teilkatalog EPC on the web)

My VIN is WDB4351151W163155.

My EPC skills are definitely entry level so a part number would be appreciated. (I get lost in the EPC finding the actual transmission parts breakdown) I am guessing the P/N is A4252641206 ?
 

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250GD Wolf
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Looks like its a 718811 UG 4/65. (this came from a print out of my VIN from the Teilkatalog EPC on the web)

My VIN is WDB4351151W163155.

My EPC skills are definitely entry level so a part number would be appreciated. (I get lost in the EPC finding the actual transmission parts breakdown) I am guessing the P/N is A4252641206 ?
That's indeed it:
 

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Well the speedometer adaptor is also "toast". It is set up with 1 to 1 ratio output and a .857 to 1 ratio which is the one used on mine. The .857 output shaft looks like it lost a bushing at one point and the intermediate gear also has bad bushings. The input shaft works but the tabs that accept the speedometer shaft from the transmission were bent. I got them straightened out and by stripping the intermediate gear, I can get 1 to 1. Looking at it I may be able to hook up the speedometer shaft directly to the fitting on the transmission and skip what is left of the gearbox. I will pull the shaft tomorrow evening from the transmission and see if its repairable.
 

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U1000Ag
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Your correction gearbox must have lost its lubrication or it has done serious miles :eek
Pics show mine before/after rebuild. Gears wear a bit worn, but still serviceable.
I changed the ratio on mine by re-arranging the gears with a new offset - this converted my mph speedo into kph. I was lucky the gears had the correct teeth for obtaing the correct ratio - otherwise it would have meant a new box. IainUnimog bought a new box for his vehicle from a VDO agent - was not as expensive as MB :smile
 

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'76 1300L,HE351CW,H15P Winches,Konis,Hydraulics,All Gears,10mm Plungers,Aftercooler,Lots of Littles
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the speedometer shaft directly to the fitting on the transmission
Thats what I did on that end. A speedo recalibration is much cheaper than a new box. If you care. For direct drive (aka 4th high, 6th, or 8th) in my truck:

1500rpm = 35mph*
2000rpm = 45mph*
2500rpm = Normal full speed, use when speed limit = 55+
2800rpm = 67mph

*These are not accurate.

But the speed'o is in KM/H, so you should be able to get out of any ticket anyway.

Cop is more likely to want a ride.

C.
 

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Well I removed the speedo drive shaft from the transmission, it just slipped out. The tang that engages the speedo gearbox was definitely sheared off. Rather than order a new one I fired up the MIG welder and laid down some bead where the tang used to be and used a fixed belt sander to rough in a new tang. Its not a precision fit so it didn't need to be perfect. I did screw the cable directly to the transmission minus the gearbox. Driving around the neighborhood the tachograph does work but its sticky. I expect with a bit of driving it will start working smoother. Now that I have the old cable ends I might be able to rig up an adaptor for the 419 speedometer I bought. It has the same thread as the gearbox connections while the tachograph uses a half turn connector.

The gearbox appears to have had water coming in the output shaft attached to the cable and that rusted the shaft of the input gear. The bore is oblong. the actual gears are in reasonable shape. I could rebuild it, if I had access to a bridgeport and a tool room lathe. I would need to sleeve the rusted shaft, install a new bushing in the oblong bore and redo the pivot points for the intermediate gear. I expect I will research a VDO dealer and keep an eye out for gearboxes. I will probably go up a tire size at some point so the ratio will be off no matter what.
 

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Your correction gearbox must have lost its lubrication or it has done serious miles :eek
Apologies. I've had a few Unimogs.

The SBU (437.100) is the one that piled up inside, couldn't even turn it, it did have some "goop" inside.

IMG_20170523_190634-1024x768.jpg

The one from the 406.120 (which I'm still looking for a replacement, anyone has, I'd be more than happy to buy) the casing broke at the spot it bolts onto the transmission, hence no lubrication (well, might as well be none), only missing one cog on one gear though, not bad!:

IMG_20170523_190614-1024x768.jpg
IMG_20170523_190555-768x1024.jpg
 

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'78 CASE MB4/94
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So it’s not the hardest thing to get at, but still challenging. I’m trying to not make things worse. Any tips for removing the speedometer gearbox on the transmission. Here is a blurry photo with some arrows and item numbers. Item 2 rotates relative to item 1 - about 90 degrees constrained by the rectangular gear case against the transmission. Is item 2 supposed to rotate relative to item 3???
 

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To answer my own question - yes. Documenting what I found. Item 2 from my photo has right hand thread on one side and left on the other so just loosen normally from the top view and the gearbox comes off easily - mine took a little penetrant and off it came.
I will be rebuilding the mini gearbox next.
 

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Getting back to this project today, looks I also have the twisted off blade on the end of the speedometer shaft. I have a Case 406, so hopefully the shaft also comes out the same way as the U1300 (same transmission?) so I can attempt similar weld repair.
It appears there is an anti tampering screw on the mini gearbox (photo). I’m guessing the screw head is buried inside a square cup washer beneath a puddle of lead. Can anyone confirm that? I might try carefully melting it with a torch. Unfortunately the input to the gearbox slotted shaft is spread open and one tab broken so I’m going to try running without the gearbox for the time being.
 

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I have been attempting to locate a used tacho shaft rather than attempt the weld repair. In discussions with Neil at Merex, there are two versions "old (2 pieces assembly)" and "new (4 pieces assembly)." Mine is the "old" version. They have bunches of transmissions which they searched for a used part - all with the "new" configuration. It appeared that the new one might be interchangeable so Neil shipped me one. It seems like it should...almost. The only discernible difference is the top nut thread. I would need to rethread the transmission from 22mm diameter thread to 24mm thread (didn't get as far as measuring the thread pitch), or machining down the nut from 24mm to 22mm. Machining the nut seems possible, but I don't have tools handy to do a good job at that. I'm looking at the original weld build option to repair my old parts. Coincidentally, I think the "new" style must have been developed to address a component life issue since the shaft diameter is increased.
Shaft on the left is the "new" version, the right is the old one. Any suggestions?
 

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Andrew and I had some discussion about this in PMs, comparing his to mine. Now that I see them side-by-side I see an immediate problem (besides the thread). The old style uses a narrow shaft with 2 bearing surfaces inside a fixed sleeve that is threaded into the transmission housing. The new style uses a larger shaft that rides on 2 bearing surfaces (of different size and location) inside the transmission housing itself, retained by a nut.

Therefore, it would seem to be extremely unlikely that the transmission housing holding the old style shaft would have the properly machined/ground and located bearing surfaces for the newer shaft style. Thinking about it for a bit... I'm guessing the newer style was developed to give better repeatability in shaft location (for the gear interface). A threaded sleeve doesn't radially locate repeatability (within a thou or so) given many thou of thread tolerance.

If you can't find someone locally, you could send it to me to give the welding route a try.

EDIT: Another thought... shaft on the newer style could be turned down to match the old shaft and used inside the old sleeve.
 

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Thanks so much for the insight. Most likely the shaft is heat treated (hardened) at the gear teeth and also the bearing surfaces for wear resistance. It might be necessary to anneal in order to turn down the shaft diameter, then re-harden. The tab may also be in hardened condition, but if a green welded repaired tab breaks again - no big deal. If the shaft breaks inside the transmission - likely a big problem. I'm leaning toward weld build and machine a new tab. I'll see if I can get someone locally to help me out - it may be a little beyond my skill level with the welder.
 

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Update - Good news! Neil was able to find me a used tacho shaft. No welding for me and I get past this hurdle. I also purchased a new speed conversion gearbox for 12.5 sized tires. Cost was not too bad as Mog stuff goes.
So...I didn't pay enough attention to how the speedometer cable snakes through the engine compartment before removing it many months ago. There's alot going on in that area - wires, fuse block, air intake and defroster hose. Does anyone have a picture of the routing of the speedometer cable on a 406/416? Particularly how it goes around the air filter housing. Thanks!
 
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