Center drive line keeps popping out.

[swahlquist]

Sorry if this is a dumb question. I am really new to the nitro scene and to the 4x4 stuff. Just bought a Losi LST2 that has the FOC on it. After buying it I ran two tanks threw it and then noticed it was running funny. After looking at it I noticed the center drive line that goes to the front wheels popped out. So I was going to try to fix it but It looks like it is too short. Any suggestions?

 

[Greywolf74]

The drive shafts are actually a little short in the sense that they just barely sit in the outdrive cups but I've never had one pop out and I've bashed the hell out of mine. I would check and make sure your transmission and your diff are seated where they are supposed to be.

 

[NHB_RC]

Agree ^

Is it popping out of the diff or tranny? Check your outs and make sure they don't have a bunch of slop..

 

[swahlquist]

okay thanks for the input. it is popping out of the tranny. I torn into it a little deeper and I think I am going to have a lot of work a head of me. There was all kinds of surprises. Striped out screws broken screws and other broken parts. No wonder I got the truck so cheap ($100)

 

[2revo1maxx]

Welcome to the rc life.

 

[MudSlinger33]

Stripped screws may allow the tranny to move slightly, causing the shaft to pop out.

Sent from my XT907 using Tapatalk 2

 

[2revo1maxx]

Chassis broke?

 

[olds97_lss]

If the chassis rails are cracked, it will allow enough flex to do that, or if the diff holder yoke is broke, it will also allow enough movement to pop out.

I broke many chassis rails on my aftershock... ended up making a skid plate that tied the front/center together, then I never broke another set again. The thing was a tank after a few "upgrades".

You can find alloy diff holders on ebay, but LST parts are getting harder to find. Search for LST11A08, they aren't a great brand (hot racing), but it's what I had and they held up just fine.

 

[swahlquist]

thanks for all the help. So after taking some stuff apart this is what I have replaced to make this truck work the way it was supposed to.

Chassis Plates, Top & Bottom x 2
Chassis Side Rails
4-40 x 1/2" FH Screws (6) x 7
Front and Rear Bumpers & Braces
Tranny Outdrive Cup Set
Radio Box & Hardware
Front/Rear Shock Tower w/Pin Mounts
Motor Plate & Chassis Brace
Right & Left Bulkheads & Differential Retainer
Front and Rear Suspension Arms
4-40x3/8” Flat-Head Screws (10) x 2
4-40x7/8” Cap-Head Screws (10)
5-40x1.25" Caphead Screws (4)
5-40 Lock & Hex Nuts (4ea)
3.6x10mm Washers (6)
Inside Gear Cover

All of it was either striped out, bent, cracked, or broken and just rattling around. Almost like a new truck.

 

[aqeel200]

just sharing.

flexing of the chassis during bad landing can cause the center drive line to pop out of the tranny outcups. It is even worse if something is not fixed properly or something else cracked, like upper brace, diff retainer has free play, side rail got cracked etc..You only have this problem for the front center shaft, right?

this is what i do:

1. you have to find the right shim (i believe 0.3mm or a few 0.3mm to make it thicker should be fine) it fits in nicely both inner diameter and outer diameter of the shim - so that the entire shim sits flat into the pinion shaft of the diff and the diff itself.

2. Once you are able to do that, your center front shaft will be positioned more longer and the pin of the shaft goes deeper into the tranny (by 0.3mm)

This will reduce(practically never) possibility of the front center driveline to pop out.

Note:
a. I use a spare alloy spacers that is much thicker than 0.3mm. This alloy spacer is the alloy spacer in the diff(pinion) - the one between the 2 bearing.

I grind this a bit. I also grind the pinion (flat portion) to be slightly deeper and outer( direction is nearer to the edge of the pinion shaft - away from the pinion gears).

b. Just be mindful, if u use a thicker shim(spacer/washer), you may not be able to have a good grip when fitting the center drive shaft..because it is too much to the edge of the pinion. That is the whole reason why i grind the flat spot in the pinion shaft to be a bit deeper and outer so that the grub screw can hold it hard.

just to share with the DIY i did to resolve this permanently.

Also - just make sure that there is no freeplay in the diff retainer(both on the diff itself and the chassis) and it snugs in firm during installation. Any freeplay will move the center drive shaft to the point that it is nearing to a 'popping out' situation.

enjoy your truck..i do.