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Manual operation of the automatic transmission on Scania TGB30/40


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Sounds like the throttle pedal switch. If it does not disconnect you cannot engage gear, a locking function in the gear selector prevents it.

 

You can find the culprit behind the front grill on the right side (viewed from the front). It's connected to a roller arrangement via a wire from the throttle pedal.

Try drenching it inWD-40, often does the trick.

 

If you search the forum you'll find many more details. It's not the first time this has happened ;)

 

Also worth checking that the throttle pedal is simply not just obstructed.

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As a side note to what bsvensson writes above, has anyone fiddled with the rocker switches under the cover in front of the gear select switch? There is one marked "Drivhjulsfrånkoppling" that will disengage the transmission from the drive shafts. This is used for running the winsch only without turning the drive wheels.

 

Also, if the switch bsvensson mentions is faulty, the transfer box will not shift to V or T, as it thinks the throttle is not at idle...

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Very useful hints, thanks bsvensso and Wingflyer.

 

I will try the throttle pedal switch first.

I just read it in the description that there is some kind of switch but sadly it is in swedish and I cannot speak swedish.

 

What is this switch used for at all on this truck?

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Very useful hints, thanks bsvensso and Wingflyer.

 

I will try the throttle pedal switch first.

I just read it in the description that there is some kind of switch but sadly it is in swedish and I cannot speak swedish.

 

What is this switch used for at all on this truck?

 

The switch does several things.

 

With the throttle at idle, it lowers the fluid pressure in the torque converter and thus the torque from the engine to the gearbox, allowing the truck to remain stationary at idle, even with gear selected and no brakes applied. It also prevents shifting the transfer box V/T if the throttle is not at idle.

 

There are a few other interlocks and conditions in the transmission controller electronics associated with this switch, but the above functions are what is crucial to driving the truck.

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Sounds like the throttle pedal switch. If it does not disconnect you cannot engage gear, a locking function in the gear selector prevents it.

 

You can find the culprit behind the front grill on the right side (viewed from the front). It's connected to a roller arrangement via a wire from the throttle pedal.

Try drenching it inWD-40, often does the trick.

 

If you search the forum you'll find many more details. It's not the first time this has happened ;)

 

Also worth checking that the throttle pedal is simply not just obstructed.

Can you provide the link to the english forum threads.

 

Because I could find only swedish regarding this truck.

 

Thanks a lot.

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I gonna check it in the afternoon.

 

If this switch is alright, can that be that the transfer case switch is stuck between V and T?

 

I assume the truck will not move than as well right?

 

No the switch can not make the gear get stuck in between. The transfer case switch is not connected to the transfer case solenoids directly. The switch tells the controller box to change gear, the box then checks if the throttle is at idle and if so, sends a two second pulse to the appropriate solenoid at the gearbox to push the air piston that engages the gear selected.

 

If you have airpressure, with the engine stopped, ingnition on and the driver door open, you can easily hear the gear change when you shift V to T, or T to V.

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Listen to Wingflyer, he knows ;)

 

I had this happen to me a few times when shifting between V-T so if your friend did try out the terrain gear then it may well have happened to him. Basically the switch need a proper clean. WD-40 or similar seems to help.

 

I'm not sure we have many English forum threads but you'll find the odd discussion. Otherwise Google translate may help ;)

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Hmm, thinking about it a bit more, I didn't loose drive in these instances, rather just got stuck in T. Which is annoying enough when trying to go somewhere which is not off-road.

 

So maybe WF's comment about the torque converter makes more sense then?

Anyway, you still want this switch to work properly so worth checking, and a common fault.

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Thank you for all of you guys.

 

I went to the place in the afternoon and checked the accelerator pedal switch which was working good.

I did some WD40 on it just to be sure.

I jump in and the truck wont move.

 

And I tried the the pull switch once more which releases the air from the hanbrakes but before I have read it in the manual (thanks to this forum) that I have to hold it until it releases the pressure.

I held it for like 1,5 secs and voila the truck moves.

 

I told the customer this before but I did not know he was not pulling it for enough time.

The valve might go slow.

But I knew in the back of my brain that this was not a huge problem.

And it was not.

 

Anyway good forum and very helpful members.

Many thanks who helped me once more.

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