Speedo correction

Hello easydeluxe,

Your Speedo reading can be adjusted by fitting the correction gears, or replacing the Speedo gearbox.  This is fitted to the rear end of the transferbox, to which the Speedo cable is attached to (I am fairly sure of that, or around that area, of which I am certain of).

Your local Mercedes Benz dealer should be able to calculate the correction gearing required and order the right part for you.

When going to your dealer, take the chassis number, preferably the data card of your vehicle with you, if you do not have the data card, take the gearbox and transfer box numbers also.  If, that is a problem, you should be able to ask the parts department to rise another data card for the vehicle and work from the information from that.  You may need information on your replaced and replacing tyres.
A late thought, you may get your local tachograph specialist to do the work or give you further advice or suggestions.
Good luck,

Hello easydeluxe,

Unfortunately I don't have your vehicle's VIN. I presume it matches WDB 461 336 17 1XXXXX (where X any digit 0-9).
Your vehicle should most likely be fitted with tranfer case 750.602 (VG080 - selectable 4 wheel drive) bearing a mechanical speedometer drive with characteristic curve No.7 (ratio I=0,471, MB Part Number A460 280 09 29).
A speed signal sender unit A005 542 94 17 attached to the mechanical drive should provide the necessary pulses to the electronic speedometer.
Presuming you vehicle was originally fitted with 31 inch tires, moving up to 33 inch tires requires the use of a lower ratio speedometer drive in order to keep the speed reading correct. The new required ratio should be (0,471 X 31 / 33) = 0,442.
The closest available ratio is 0,448 (characteristic curve No. 3, MB Part Number A460 280 05 29, currently available from MB as a spare part, German List Price Euro 171.27 + VAT).
I could provide you with more accurate information if you provide me with your vehicle's exact VIN number and tire configuration.

Best Regards

Michael

Hello again easydeluxe,

There might be another possibility to adjust the speedometer, but you will have to check with your local MB dealer.
The instrument cluster might be able to be coded with a different variant coding ('K-factors' coding) which will compensate for the difference in tire diameter. The vehicle will have to be connected to a STAR-Diagnosis unit to find out if this is possible.
Even though such coding is 99% possible to exist, there might not be possible to change it, unless you install a new instrument cluster (which is quite expensive). Such codings are performed during the initial starting up (installation) of the instrument cluster and from there on interlocking takes place and you can no longer modify them.
Have in mind though that there is also the possibility that the instrument cluster might not be 'diagnosable' at all (no diagnosis possible with either STAR-Diagnosis or HHT - Hand Held Tester, the predecessor of STAR-Diangosis).

Regards

Michael