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Manual operation of the automatic transmission on Scania TGB30/40

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Since I have been asked abuot this a few times and understand that it may be difficult for non-Swedish speaking people to follow the discussions in our forum I thought I would try a simple summation of the matter.

The automatic transmission for Scania TGB30 / 40 is relatively easy to operate manually (with electric voltage). The easiest way is to locate the electrical connection piece to the right in the fuse panel located at the dashboard (see picture).


This connectionpiece contains all the cables required for control of the gearbox(cables number 18, 18A, 503, 521, 522, 523 and cable number 526).
Connect power to the cables for the gearbox according to the schedule at the top right of this wiring diagram.
You can obtain the connectionpiece from ELFA (https://www.elfa.se/elfa3~se_sv/StartPage.do?ignorecookie=true) part no.44-221-04 https://www.elfa.se/elfa3~se_sv/elfa/init.do?sq=44-221-04&cat=0 and the contaktpins part no.44-221-13 (https://www.elfa.se/elfa3~se_sv/elfa/init.do?sq=44-221-13&cat=0)

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  • 1 month later...

bandar, replying to your PM question about why the gerbox does not change to higher than H3.


First thing,

check that the brake light is not always on,

check that the trailer brake lever under the left part of the steering wheel is fully up/forward.

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  • 1 month later...

The rear switch that is marked V and T should be in position V (road)! Also check that the indication light for frontweeldrive (framhjulsdrift) is turned of.

With the engine turned off you should be able to hear the sound of the magnetic valve when changeing from V to T and back. The controlbox just sends a momentary puls on lead 527 to engage V and 528 to engage T.

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  • 2 weeks later...

i have checked all of the above but still same problem the gear changing upto three with 60 km . it canot move more . do you think the problem from the auto transmision controll unit which undernith the  gear swithch ( aluminum box ) ?

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If you know a little about electrical circuits, etc., you may try with a manual switch between +24V and wire number 524 in the connector block in the picture above.


When driving the truck in 60 kmh, flipp the switch so you get 24V on 524. The gearbox should then change to 4'th gear (M3). If it does, your problem is in the control unit. If not, the fault is in the gearbox or the electrical harness...

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thank you all.  what do you mean by flipp the switch and which switch ?


This is why I asked if you are familiar whit electric schematics and circuits. You can insatall an extra switch as described, and thus manually test the gearbox fouth gear...

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  • 7 months later...

Hello all.


We have a problem, we bought such military truck from the army and the truck was working flawlessly until now.

We have sold the truck, and today morning the customer has driven the truck to another place and left it there.


In the afternoon the guys from that place wanted to move the truck but it is not moving when switched to D.

The terrain and street switch is on V.


Before when you put it into drive you could feel that the truck started to move a bit, now nothing happens.

Please help.


Could this be an electrical problem.


We have checked automatic transmission oil, while the engine was running and the level is good.


I tried to lift the back axels, because I thought that the truck is stuck between street and off road gears, but it is not.

Need your help.


I doubt that the gearbox went bad on an empty truck, because it was working in the morning, and in the afternoon it does not do anything.


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