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1986 Unimog U1700L (435 series)
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Discussion Starter #1
The truck engineer inspected my vehicle today.
I need to get my speedo recalibrated.
Everyone who changes from the standard tyre to the 395 tyre needs to do this (or has done this) before they can get their certificate for roadworthy.

Question: Does anyone know of a mechanical product for this or if the speedo has some sort of adjustment capability?
 

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Unimog Moderator
250GD Wolf
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There are different gear sets for the speedometer angle box to change the ratio generally for unimogs, since they came with many different options from the factory.

A quick search yeilds some good results:



 

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1986 Unimog U1700L (435 series)
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Discussion Starter #3
Thanks tkv000

Not sure where to turn here in Australia. Lots of people fitting the larger tyres, but I'm still not sure who is doing the speedo adjustments?
 

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Ex ADF 1987 U1700L Crane, 1987 U1700 with winch and a parts truck 1987 U1700L with winch
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On the ex ADF U1700’s, there is a small device on the speedo drive at the transfer case (where the speedo cable connects) this device is a ratio change, you could try moving the cable onto the other output to see if it helps.
I suspect most people change wheels after registration and live with the discrepancy or change the speedo to an electronic version (calibrate via dip switches from memory), this is certainly the most reliable option in the long term.
 

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1986 Unimog U1700L (435 series)
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Discussion Starter #8
Thanks TREBOR110.
The ADF 6x6 recovery vehicle used the 395, I'm wondering if they used the same adapter but the other port? That would be almost too good to hope for. I wonder a lot, and wonder if anyone knows the ratio difference is between the two outputs?
 

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U1000Ag
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The ratio should be on the unit itself - as long as the tag is intact of course. The other port will be 1:1. In my case the used port was less than 1:1. If you are lucky, this may be the same for you and the 1:1 port may be within the legal requirement - time to do some maths !!
 

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U1000Ag
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The ratio should be on the unit itself - as long as the tag is intact of course. The other port will be 1:1. In my case the used port was less than 1:1. If you are lucky, this may be the same for you and the 1:1 port may be within the legal requirement - time to do some maths !!
2611724
 

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Unimog S 404.114
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You have to change two gearwheels in the angular gearbox on the gearbox, or the whole angle gearbox.
how the size of the gears is calculated is described here.
Google translator helps!

then you can choose the right gearwheels or the right angle gear.
another possibility is to install another tacho scale
 

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Unimog S 404.114
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Krietpiels picture shows an intermediate gearbox with a gear ratio of 0.997 to 1, one input two outlets, for path-dependent additional equipment such as salt spreaders.
So it is rusty all over!
 

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1986 Unimog U1700L (435 series)
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Discussion Starter #13 (Edited)
Hello everyone.
Just pulled the ratio box adapter out (part Z4067/0005423409) from Kienzle ARGO. Not sure why but I also see two other part numbers in the list 6680 66-139-0624 and D8046/0005423409. Has a nice lead seal over a screw. Obviously not intended to be fiddled with.
Mine is ratio 0.857 :1 Thus for every turn of the input, the output does 1.167 times.
The origional standard ADF tyre (12.00R20) diameter is 1131mm
New 395 tyre (395/85R20) diameter is 1189mm
The bigger the diameter of the wheel the more the speedo is showing slow (thus more opportunity to accidentally break the speed limit)
Therefore the need is to speed up the speedo shaft.
Therefore a lower ratio number is needed so speedo cable turns 1.227 times every turn of the input (instead of the current 1.167 times).
A ratio of 0.815:1 (unless my minds gone to total putty) is needed. Maybe some one would like to check my logic.
I could try to buy cogs, or a new unit with different ratio.
Not sure if parts available?
Found M22 speedo correctors for US$265 but only for round shaft, not rectangular )-:
Worst still, the engineer wants a certificate of calibration from an independent authorized company.
Difference is only about 5%. Rule seems to say that error can be +/-10% + 4km/hr. Only way to know, is to drive and see if its within the limit. May not need to replace converter?
Also, I read that laden, the wheel diameter reduces by about 50mm.
Testing should be done with vehicle laden.
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PICT1064.JPG This all assumes that the speedo is presently operating within acceptable limits.

New tyre
2612016
2612026
PICT1062.JPG PICT1064.JPG PICT1065.JPG
 

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Ex ADF 1987 U1700L Crane, 1987 U1700 with winch and a parts truck 1987 U1700L with winch
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Krietpiels picture shows an intermediate gearbox with a gear ratio of 0.997 to 1, one input two outlets, for path-dependent additional equipment such as salt spreaders.
So it is rusty all over!
MagMog, would this be the case for all these adaptors (one in two out)? It does make sense to be driving equipment that is distance dependent.

Thanks, Rob
 

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1986 Unimog U1700L (435 series)
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Discussion Starter #15 (Edited)
I have been looking on line for digital speedos. Found brand new Unimog speedos for US$125, sensible price but no good as in mph. Found a km/hr replacement kit for about 700 pounds from England.
I have been advised by a local company that they can change the cogs for about A$240, but big hassel, to take the vehicle in to them and lose a days pay. No sensible easy solution option so far.
I'm now following up a lead by a post from Lian_Unimog who mentioned that he got the gears from SGESCO in Australia (Kienzle rep)..
 

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1988 U1300L RW1 Working gears Mogauspuf Dual Tanks Other Goodies 91 F250 HD 4x4
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I have been looking on line for digital speedos. Found brand new Unimog speedos for US$125, sensible price but no good as in mph. Found a km/hr replacement kit for about 700 pounds from England.
Jason, have you dug into Michael's solution? I think he probably took the shortest route around the barn.

Here is a key portion, cut and paste:

After much research and comparing, I ordered a programmable electronic VDO dual unit speedometer. It has a zero-able trip odometer and is compatible with several sending unit types. I ended up ordering it from Amazon. I got the VDO 437152. It was only about $130, but it is really quite nice. The speedometer will accept an input signal from any source at 500 to 399,999 pulses per mile (or km). It runs on 12-32 VDC....

I decided on a generic Hall Effect sending unit. I ordered the sending unit from Fastforward (Quesnel BC). It's a simple little sender and is totally sealed and waterproof. It was only $59.95....

After looking at a few sending unit installation options (on non-mogs, a lot of people put them on a driveshaft or brake disks..), I decided to make an adapter and put the Hall sensor directly on the old speedometer calibration box on the transfer case.....

Calibration was super easy. All we did was start a calibration mode, I started driving, my wife called out one mile from her GPS (from the passenger seat), and I then stopped the calibration mode.
Link to the full thread:

I did a bit of my own research, and there are a number of variations in the VDO product, both in max speed and in mph vs. kph, or combos.

Edit: I am curious how you have a 5% difference with 395's. I had Conti 365's put on and have about 7% difference over the stock 12.5 / 335 tire size.

One other thought: road speed will depend on the tire circumference, and NOT on the "diameter", which is NOT to be confused with the the height to centerline (which varies with inflation pressure and loaded weight, neither of which affects the revolutions per mile/ km of a given tire). If you get really precise, tire wear changes (reduces) the circumference, therefore affects speedo calibration, but I am certainly not going there myself.
 

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1986 Unimog U1700L (435 series)
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Discussion Starter #17 (Edited)
No matter what I do, I have to get a certificate from a reputable company.
For mechanical option, there is the risk of calculating the wrong cogs.
A dash adapter plate for a small speedo is too much work.
Atkinson Vos have the direct electronic replacement kit but its too expensive for me..
VDO have a very nice 140mm drop in electronic speedo. 24v 125kph part 437025002 Can buy in on ebay with 340.824 plug kit (no sensor) for about A$500.
Spoke to the VDO rep company here (Airco 02 9560 2755), and they can do the kit with cable loom and sensor to suit and provide details on how to calibrate it if needed, or they can do the calibration with certificate. Awaiting price but it will definitely be under $1000.
Anyone know what pulse output I should be considering for the Hall effect sensor (2, 4, 6, 8, 10, 16 pulses per revolution)?
 

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U1000Ag
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Your money at the end of the day - but if I was you, I would stick with the MB recipe. If you are allready involving a certifying automotive engineer - he can do the calcs for you and sign off on it as part of the wider certification process. See extract from blue data book that gives all common tyre sizes as well as the part numbers for the various angle drives.
 

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Unimog Moderator
250GD Wolf
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I agree with krietpiel, I bought a brand new one some time ago for my U1700AG (437.100), and it was $350CAD, that's under 400 upside down money I think, and it's done.
 

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1986 Unimog U1700L (435 series)
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Discussion Starter #20
Does anyone know if the inner cable shaft is meant to be able to be removed? I tried pulling it out from the bottom, but it would not come out, I don't want to force it. Need to lubricate it.
 
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