Mercedes Truck (original version)

[Herb]

Hi,

I won a Mercedes Zetros Trial Truck in a completion and as such, it is my first Technic build.

Everything was groovy until I powered up the engines for the first time.

On the first attempt, I only had 3 wheels driving in 4 wheel drive mode whilst the differential worked fine. 

I then rebuilt the rear suspension unit (assuming a mistake was made) and now have perfect 4 wheel drive but the diff isn’t working as it should (one back wheel moves fine, but one totally unmoving)

In both cases, it is the rear left wheel (looking from the back) which is the problem.

I am as certain as I can be that the rear suspension unit is 100% correct so am looking for other solutions. Could it be the orange diff cog further to the front?

All suggestions welcome.

Thank you.

H.

[1gor]

well first suggestion is to see some pictures...

 

[2GodBDGlory]

1 hour ago, 1gor said:

well first suggestion is to see some pictures...

Which can be added via an external hosting website, like Bricksafe.

[M_longer]

You have put 5 small gears inside each differential?

[Maaboo the Witch]

2 hours ago, 2GodBDGlory said:

Which can be added via an external hosting website, like Bricksafe.

Or Flickr.

[XTN]

30 minutes ago, Maaboo35 said:

Or Flickr.

Or imgur.

[Herb]

52 minutes ago, M_longer said:

You have put 5 small gears inside each differential?

Yes. Definite.

I’ll grab some pics.

[Herb]

https://imgur.com/z17BlPm

https://imgur.com/2vLPDOH

https://imgur.com/KNVCn0I

https://imgur.com/NrACF1s

Any good for ya? 

[Zerobricks]

Did you put all the bevel gears in the rear differential? That would explain the lock only locking 3 out of 4 wheels.

[Herb]

48 minutes ago, Zerobricks said:

Did you put all the bevel gears in the rear differential? That would explain the lock only locking 3 out of 4 wheels.

Yes. As said, I'm 100% convinced that the rear suspension/differential is spot on after a complete rebuild. However, two separate builds have thrown up 2 different problems...ugh. 

[gyenesvi]

27 minutes ago, Herb said:

Yes. As said, I'm 100% convinced that the rear suspension/differential is spot on after a complete rebuild. However, two separate builds have thrown up 2 different problems...ugh. 

I don't quite get what the two different problems are. In the first case, you say that 3 wheels were moving out of 4, so you rebuilt the rear axle. In the second case, you said that one back wheel was not moving. It sounds like the same problem to me. And how do you have perfect 4 wheel drive if one back wheel is not moving? It's sounds kind of a contradiction.

What I would do is I'd trace the path of moving parts when the motor spins. How far the spinning is transferred? Does it go to the front / rear axle properly? Inside an axle, is the housing of the differential is spinning properly? Finally, are the wheels spinning? If the differential housing is spinning and the wheels are not spinning, then something is either wrong in the differential itself, or one wheel is jammed and the diff is routing the power to the other wheel. Can you spin all wheels by hand? Isn't one harder to spin than the others? To check the differential itself, if you take it out from the axle, and spin one end (one thin axle coming out of it), the other end should be spinning in the opposite direction (that's normal), and the movement should be smooth / easy. How is that?

[Herb]

1 hour ago, gyenesvi said:

I don't quite get what the two different problems are. In the first case, you say that 3 wheels were moving out of 4, so you rebuilt the rear axle. In the second case, you said that one back wheel was not moving. It sounds like the same problem to me. And how do you have perfect 4 wheel drive if one back wheel is not moving? It's sounds kind of a contradiction.

What I would do is I'd trace the path of moving parts when the motor spins. How far the spinning is transferred? Does it go to the front / rear axle properly? Inside an axle, is the housing of the differential is spinning properly? Finally, are the wheels spinning? If the differential housing is spinning and the wheels are not spinning, then something is either wrong in the differential itself, or one wheel is jammed and the diff is routing the power to the other wheel. Can you spin all wheels by hand? Isn't one harder to spin than the others? To check the differential itself, if you take it out from the axle, and spin one end (one thin axle coming out of it), the other end should be spinning in the opposite direction (that's normal), and the movement should be smooth / easy. How is that?

I didn’t think I explained it well!

In the first build, I only had 3 out of 4 wheels working in normal 4-wheel drive mode. The diff worked like a dream, though.

In the second (extremely careful) build, I have perfect 4-wheel drive. However, one wheel (the same one that didn’t move in build 1) does not work in diff mode.

Thank you for your suggestion, though.

I’ll give it a go.

[Nazgarot]

Still sounds like a sun gear in your diff is missing. This model is always 4WD, but has lockable diffs. I guess that is what you refer to with "diff mode", while locked being 4WD?

With the diffs locked it would work anyway, but with open diffs no power would be transferred to that wheel. A simple way to  test this is to set the difflock off and test that the opposite wheel on each axle counter spin when you rotate the other wheel. You should also be able to feel if the wheel is connected to the driveline or not.

The diff should have 5 internal gears, but it is easy to forget the last one... If this is not the case short video of the problem would be very helpful for us to help you further. Just upload a short clip of the problem with some explanations to Youtube and give us a link.

_ED_

[MikeTwo9398]

When I got my 2nd truck it had the same problem (was completely build).
I think it is not the differential. It is the orange selector that should go into the differential.  I think that in your case when diflock is selected the orange selecter locks the bleu gear instead of the differential. And because the blue gear is standing still it locks the axle of that wheel (left back). 

Remove the back axle again. 

On the left side is a lever added in step 163 of the building instructions. Make sure that one of the nobs of the orange selector is on the same side of the lever as shown in step 163.

The lever can only move 90 degr. If you move the lever the differential should be locked and not the blue gear. Move the lever and see what is being locked the differential or the blue gear.

You can fix it by removing the level and put it in the correct position.

[JoKo]

On 1/24/2023 at 6:17 PM, Herb said:

I didn’t think I explained it well!

In the first build, I only had 3 out of 4 wheels working in normal 4-wheel drive mode. The diff worked like a dream, though.

In the second (extremely careful) build, I have perfect 4-wheel drive. However, one wheel (the same one that didn’t move in build 1) does not work in diff mode.

Thank you for your suggestion, though.

I’ll give it a go.

 

I don't get it: What does a not working wheel means? turning freely? blocked? If the diff worked like a dream why did you rebuilt it?

And if you have perfect 4-wheel drive now you should keep it like this.

Honestly I'm pretty sure there is no mistake in this set instructions, This looks like human error to me!

 

[gyenesvi]

I believe @MikeTwo9398's explanation is a quite probable one! @Herb might have just not aligned the orientation of the orange selector with the locking lever but rotated the selector 180 degrees, which is an easy miss for someone not used to that mechanism.

Edited January 26, 2023 by gyenesvi

[williamyzfr1]

6 hours ago, JoKo said:

Honestly I'm pretty sure there is no mistake in this set instructions,

Having recently built this model I did not find any issues with the instructions.

[Herb]

3 hours ago, gyenesvi said:

I believe @MikeTwo9398's explanation is a quite probable one! @Herb might have just not aligned the orientation of the orange selector with the locking lever but rotated the selector 180 degrees, which is an easy miss for someone not used to that mechanism.

This is my hope. I’ll crack on and feedback. Thanks all.

21 minutes ago, williamyzfr1 said:

Having recently built this model I did not find any issues with the instructions.

Oh. 100%. It’s my error somewhere not the instructions.

[williamyzfr1]

Hope you sort it out its a great model, although not fast by any stretch of the imagination.