Mercedes gearbox settings

#1
Hi,

This is the gearbox control on my automatic Mercedes 1124 AF. As per the picture, I have a the black selector cog that I can turn for the three settings. Initially I had guessed that this was high (2 straight lines), neutral (oval), low(wavy lines) however I can drive equally in all three (so no neutral). The performance in each seems to be the same so doesn't feel like a high / low. I get an air sound when I move the selector between settings so feels like it is moving between them. It has separate controls for the centre and rear diff locks so not thinking its that. Any help appreciated.

Merc gearbox control.jpg

Cheers Tobias
 

UpperCrust

Building and Learning
#3
Toby,

I have the same in my 917. My manual says what you said. high, neutral, low. Myself, I've never played with it.
 

Neil

Observer
#5
Hi Toby
I have the same selector in my 1017a. The two lines are 2 wheel drive. The wavy line is 4 wheel drive and the 0 is no drive which I guess is for when using PTO if you have it. You must only move this when stationary. It takes a few metres for the 4 wheel to kick in and a light on the dash confirms this.
If you have normal drive in all three positions then I would suggest it's not working correctly. I would start with the air valve onder the cabin on the back of the switch.
Neil
 
#6
Hi guys,

thats great thank you. Makes more sense, will have a look why its not going in to neutral. Also haven't seen a light going on for 4x4 so wonder if it is actually engaging.

Cheers Tobias
 
#7
The straight lines are high
oval neutral
wavy low range
The truck us full time 4 wheel drive as far as I know. (I have had the 917AF on the hoist changing a bearing, in high moving the input shaft feeds power to the front and rear)
Sounds like you have a problem if the truck drives the same in all positions. You should have no drive in oval position and low range is very low.
 

Neil

Observer
#8
Hi Joe.
My wavy line also selects 4 wheel drive, and lights up the 4wd lamp on the dash.
I wasn't aware that the 917 was permenant 4wd. This surprises me .

Toby. Is your vehicle 2 or 4wd or permenant 4wd. It would appear that this selector has slightly different functions depending on whether it's permenant 4wd.

In my 4wd it lowers the ratio

Neil
 
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#9
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
 
#10
Toby
Firstly, the 0 setting is definitely " no drive " so if you have drive in this position it's not working . I would s!tart with the pneumatic valve on the underside of the switch.

Secondly if your vehicle is 4wd only ( which would surprise me ) then it narrows you options of MOT stations as you can't use a rolling road so you need to check that they can measure the breaking in a different way.

Joe The AF models were mainly used as fire engines so it really surprised me that yours is 4wd only as this tends to lower the ratio and make them slower. They were fitted with fast axles so that they could get to the fire quickly. It would appear to defeat the object by by trapping them in low ratio.

I am not doubting the fact, it just surprised me . Note to self, never assume.

My vehicle is described in the spec as 4x4 but is in fact both.

Neil
 
#12
Hi Ian
This is what I thought. When mine is in 4wd the reduction is quite considerable so you would want to drive very far on tarmac in it.
On a different note , we are going to the Adventure Overland Show in Stratford in September if you fancy it. It would be good to catch up.

Note for @uppercrust . it is prudent to activate all these selectors on a regular basis . If left for along time the mechanical part can seize and become too stiff for the pneumatic operation. Especially the diff locks

Neil
 
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ianc

Adventurer Wannabe
#13
Hi Ian
This is what I thought. When mine is in 4wd the reduction is quite considerable so you would want to drive very far on tarmac in it.
On a different note , we are going to the Adventure Overland Show in Stratford in September if you fancy it. It would be good to catch up.

Note for @uppercrust . it is prudent to activate all these selectors on a regular basis . If left for along time the mechanical part can seize and become too stiff for the pneumatic operation. Especially the diff locks

Neil
Neil,
I'm not sure yet if we will be able to go to the show. I'll let you know as soon as I can.

I also agree with the sticking pneumatic activators. My centre diff can be a ***** to disengage because I don't use it enough.
 
#14
The small switches are obvious pneumatic locks for the diffs, transfer case and PTO(if equipped)
I am unclear on the large knob. The manual only says it changes the transfer case, high?low, it has nothing about 2wd/4wd.
So does it switch High/Low only or High/Low and at the same time 2wd/4wd. This would limit the vehicle to 4wd in low only.
There are road conditions such as snow packed gravel where you might prefer 4wd high.
Many times you also want low on asphalt(steep hills) and as long as the diffs are not locked it is not an issue.
As for brake testing axles, with the center diff in neutral you can spin either axle independently.

My understanding was full time 4wd with high low transfer case, I would love to hear from someone who KNOWS the actual configuration.
 
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#15
Ian ( canals 1164 ) does, he has the exact same vehicle.

How fast would you go in 4wd. Mine would do about 40mph, can't imagine being to go faster in 4wd

Neil