Thread: Mercedes gearbox settings

  1. #21
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    Nov 2012
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    Quote Originally Posted by ianc View Post
    Sitec,
    I'm only going on the decals over the switches but the one on the very left looks like the centre diff lock to me
    Aggreed, far left is center diff lock not 4wd.
    The fact that we can lock the center diff in high and low indicates to me the truck is full time 4wd. As I say I would love to hear from someone who KNOWS.
    1993 Mercedes-Benz 917 AF

  2. #22
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    Dec 2013
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    Williamstown, South Australia
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    I had it spinning on the block in clay... back axle only, and then engaged 4x4 to get out... Might have to test this out. Looking at the size of the box, there's not enough room for a center diff.. Will lift the front up with the 6 tonne forklift tomorrow and see what happens when I put it in gear.
    Where there's smoke there's poke...
    The more the smoke, the more the poke!

    1995 Mercedes 1222 4x4.
    1995 Range Rover 3.9 EFI.

  3. #23
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    Dec 2009
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    Wicklow, Ireland
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    A centre diff lock would almost certainly be fitted.

  4. #24
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    Feb 2010
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    Essex UK
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    Joe 917 .

    Canals 1164 KNOWS.. He has the same vehicle as yours, 917AF , but his is 2wd and selectable 4wd.

    I would suspect yours is the same.

    Neil

  5. #25
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    In a limited slip full time 4wd setup (without modern traction control, etc) power will be sent to the tires with the least traction (power takes the path of least resistance), the limited slip mechanism will try to overcome and stop that, but if the rear tires were on slippery clay but the front had great traction, the open center (a limited slip is still technically, an open diff) the power might have all gone to the rear (especially if something is worn out in the Limited slip, or it's a torque multiplying setup, remember in a torque multiplying setup, 0 x anything is still 0, so if the torque multiplier is setup to multiply torque to one side of the diff 3 times, but the traction is 0, 0 x 3=0), when you engaged 4wd, that might have actually been locking the center diff, and thus power was distributed evenly front/rear. Modern vehicles with full time 4wd and open or limited slip centers can get away without a locking center by using traction control and braking the wheels with no traction, sending the power to the wheels with grip. Limited slip is designed to do exactly that, "limit" the slip, by using spools, cones, cam and prawl, clutches, or torque sensing (such as) torsen setup, but in my experience that doesn't always work in the real world. Sometimes, you still gotta lock that diff. (My daily driver is full time 4wd, open center with locking function for what it's worth)

    You could PM me or post up your VIN, and perhaps we could get to the bottom of the mystery. Maybe. I usually stick to Unimogs but I'd give a go at a 917 decode for fun.

    knob.jpg

    Here's the drive portion from a 917AF for instance, you can see the shift dog (item 122) that engages front drive (ie, locks the center diff, I think). This might not be the case for your 917, this is just a random one I brought up in the EPC to see what's inside it's transfer case (again, might not be the same as yours)

    you can see the sun gear (152) and planetary carrier (131) as well Annulus (155) for the rear drive. Someone smarter than me will have to comment on whether or not that's full time or part time 4wd. To me that looks like full time 4wd with a locking center diff to engage the front for offroad conditions. But again, someone smarter than me will have to say for sure.

    frontdrive.jpg

    Either way, IF your VIN brings up the data card in the EPC (again, I've never run a Ma Benz truck but I'd give it a shot) it should tell you for sure, as example:

    transfercase.jpg

    Only reason to have a limited slip center is if it's full time 4wd. In this example.
    Last edited by mogwildRW1; 08-09-2016 at 10:06 PM.
    -Trev
    1977 Unimog U84 "bagger"
    250GD "Wolf"

  6. #26
    Join Date
    Aug 2012
    Location
    Norway
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    171
    My 815da has permanent 4x4, low range and locking of center and rear diff. No front diff lock. The center differensial has a planetary setup distributing 28% of the power to the front and 72% to the rear. Without locking the center, the truck will easily spin om the rear only, especially with no or little weight on the bed.
    Jostein
    Norway

    MB Vario 815 DA
    MB GLC 350e

  7. #27
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    Oct 2010
    Location
    Canada
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    Joe917,

    My apologies, sometime back you did send me your VIN, did I send you your data card? In any event, the transfer case originally fitted to your truck is the 750.517transfercase.jpg

    Which we can see is indeed fitted (I've removed your VIN from the screencap for privacy reasons) with a limited slip center

    I see two valves listed for transfercase control:

    One is ONROAD/OFFROAD SPEED, that's likely the Hi/Low transfer case

    and the other is LONGITUDINAL DIFFERENTIAL LOCK (for engaging the center locker I'd imagine).

    Does that help any?
    Attached Images Attached Images
    -Trev
    1977 Unimog U84 "bagger"
    250GD "Wolf"

  8. #28
    Join Date
    Oct 2010
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    Canada
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    Quote Originally Posted by Toby2 View Post
    Hi,

    I don't know for certain, I have no paperwork with the truck so figuring it out as I go along. I thought it was permanent 4x4 and certainly other 1124 AF 4x4s seem to be permanent. Looks like in all these scenarios the 0 should be neutral so the fact I still have drive when I'm on that setting is confusing.

    Cheers Tobias
    PM me your VIN number and we'll take a looksie
    -Trev
    1977 Unimog U84 "bagger"
    250GD "Wolf"

  9. #29
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    Nov 2012
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    Ontario Canada
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    Toby2, apologies for hijacking your thread. Just to confirm, the knob in question switches between high, neutral and low in the transfer case. It is very easy to tell if it is working. you will hear a clunk from under the truck when it is switched (only do this when stationary, clutch depressed). There will be no power to the wheels in neutral and max speed of 60km/hr in low(depending on tires and gearing).
    As it is obviously not working there are a number of possibilities, crimped or broken air lines(probable), bad selector valve(doubtful), seized actuator at the transfer case(probable), ceased transfer case internal(?)

    Neil, when you get a light on the dash is it 4wd or the center diff symbol? (my truck has no 4wd light, only lights that correspond to the 3 diff locks and pto).

    Every 2wd/4wd I have driven has a 4wd light that comes on and a selection of 2wd, 4wd high, neutral, 4wd low. (four choices not 3).

    I recognize Mercedes makes many variants of these trucks.

    MogwildRW1, thanks for the 4wd open diff explanation. Writing 4wd in pen beside the center diff lock does not make it a 4wd switch.
    All your info confirms these are full time 4wd trucks with open center diffs.
    You did not send a data card, if you get the time it would be appreciated,

    Joe.
    Last edited by Joe917; 08-14-2016 at 03:46 AM.
    1993 Mercedes-Benz 917 AF

  10. #30
    Join Date
    Oct 2010
    Location
    Canada
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    PM me your email address, I'll send the data card (it's PDF)

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