MikeTwo9398

Same problem here. Of course Lego also sells the car for enthusiasts (AFOL's) who just put it in a glass box and don't play with it. I think the tires are to blame for keeping the car in bad shape. The profile of the tire is too high, which creates extra friction and because the tires do not rotate evenly when cornering, it starts to wobble. I put the tires (44771 and 44772) of the Ferrari Enzo (8653) on it and the car steered perfectly.

You can find an IO file on my Bricksafe page. Original is the "42129 bag 1+2+3+4+5+6.io" file. The other IO is my speed me up design.

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.

There's a topic about Third Party Tires. You can add them in this topic.

After several attempts, the 42129 was converted to a 2-speed truck and still kept the differential lock. The first attempt was quite successful, however after a while the truck was no longer able to climb, although the speed was lower and the torque was higher. So I had to start again. This is the final result: Gears for the speed and differential lock Rear axle: Some small adjustments of the rear axle. An extra gear at the differential to prevent slipping gears while climbing. Doors: A simple pin to prevent the doors from opening Bonnet: A small adjustment of the engine hood, a simple small black round stud of 1 in 2 places (one was a spare pice in the box). Driving the truck: The Control+ app from Lego of the 42129 can be used as usual. With the differential unlocked the truck has a slightly higher speed than normal and is able to handle simple low obstructions. Driving through grass is also perfectly possible. When switching on the differential lock, the speed is also reduced to the speed as the original 42129 has. Here you can see the truck in action. At Rebrickable you can find the free building instructions. For building this mod I use below extra parts:

Very nice, works smooth and quickly. You managed to load the new cargo quickly.

That looks more solid then what I used. I had suspension on the axle and used the spring as lever to go up and down.

The pivot point for making the wheel go up and down was an axle supported on both sides. For the wheel I used an axle going through 2 beams, but the pivot point there was a black pin.

I once made an attempt to. My cargo were the walls of the Rough terrain crane 42085 set https://www.eurobricks.com/forum/index.php?/forums/topic/170913-moc-truck-with-inner-loader/ It's hard to get the wheels stable without making the trailer to wide.

The same as for the 42140 more pictures can be found here: https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC01_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC02_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC03_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC04_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC05_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC06_NOBG.jpg https://www.brickmerge.de/img/sets/l/LEGO_42139_WEB_SEC07_NOBG.jpg

Looking at the video it is hard to see what is going wrong but first check if the red levers are correct positioned in the red moving driving ring (building steps 31-33 starting at page 75). What also might help is activating some (or all) of the other motors to make the gears rotate, that might shift the driving ring into the correct position. What I did with my 8043 is changing the two 16 gears, used for switching, into a 12 and 20 tooth (placing the 12, step 29 page 72, on the motor axle and the 20 tooth gear in step 35 page 79). This way the motor needs les torque/power moving the shifting levers.

Very nice looking and fast riding Trophy truck. When I looked at the video the back axles seems to bend through (at 2:09) This might cause more damage to the crossaxles. I would strengthen the rear axle so it doesn't sag. I have made a Trophy truck aswell (based on Madoca1977 Baja Trophy Truck) and yes with the buggy motors the axle started to worn out after a while. I geared it down to gain more control of the car and gave it more power to drive over rough terrain.

22: 10 4: 6 23: 4 17: 3 11: 2 25: 1

Looking at the terrain I think the Zetros performs very good. I agree with @Ngoc Nguyen the hood popping open must be frustrating....

@Jim (or anybody else) can you show us a picture of the Zetros next to the Arocs 42043. I would like to see if the scala of booth models fit.