Drive line not smooth. Possible diff wobble? Please help.

[Benlee1012]

Hey guys,

I'm almost finished with my ET48 2.0 build. I watched a build series on YouTube. There's mention of the whole driveline being super smooth. I wouldn't think anything of it if this was a cheap kit with large tolerances.

The issue is when I try to spin the driveline by hand (either spinning the spur gear or wheel hexes, I can feel a slight loosening and then tightening. I appears to come and go every 2-3 turns of the spur gear. It's only slight but you can definitely feel it.

The only thing I can think of is that the front and/or rear diff ring gears are wobbling, so it's mesh with the diff pinion is getting closer and then further away if you know what I mean. Everything felt fine as I was building the diffs and shimming them to the diff housings. Front diff took one shim and rear diff couldn't take any shims.

Anyone experience this issue before?

Thank you for your help.

 

[sandblaster]

Have seen this. I figure there is a high spot on a ring gear. Give it run time and check again. Probably will be gone. One can get rid of it by taking out shims. I prefer to set the gears so no play and let the high spot wear down.

 

[Benlee1012]

Have seen this. I figure there is a high spot on a ring gear. Give it run time and check again. Probably will be gone. One can get rid of it by taking out shims. I prefer to set the gears so no play and let the high spot wear down.

Thank you so much! As long as it's a minor tolerance issue which will sort itself out after being broken in, I'm happy. I wouldn't want any wobbles in the driveline going 100km/h+!!

I actually started pulling the diff apart and found that it's the diff gearbox cover. I can't tighten the bottom screws all the way down. The front end is now completely free but with the rear end, I can only get it perfectly smooth if I back out the bottom screws so much that the head sticks out half a millimetre, so I just made a compromise and tightened just enough for screwhead to be completely countersunk.

Will check again after driving softly for one battery pack, doing some figure 8's to break the diffs in.

 

[sandblaster]

Sounds like you have the wrong length screws in. Double check the manual for the correct length screws in the correct spot.

 

[Benlee1012]

Sounds like you have the wrong length screws in. Double check the manual for the correct length screws in the correct spot.

Thanks mate, I didn't think of that before but now looking at the manual, It's not possible for incorrect length screws for this particular section of the build because TKR1349 are the longest flathead screws in not only bag J but the entire kit. Unless they supplied screws which are too long! Should be M4 X 20mm according to the manual. Just a slight tolerance issue I reckon.

 

[sandblaster]

Thank you so much! As long as it's a minor tolerance issue which will sort itself out after being broken in, I'm happy. I wouldn't want any wobbles in the driveline going 100km/h+!!

I actually started pulling the diff apart and found that it's the diff gearbox cover. I can't tighten the bottom screws all the way down. The front end is now completely free but with the rear end, I can only get it perfectly smooth if I back out the bottom screws so much that the head sticks out half a millimetre, so I just made a compromise and tightened just enough for screwhead to be completely countersunk.

Will check again after driving softly for one battery pack, doing some figure 8's to break the diffs in.

Thanks mate, I didn't think of that before but now looking at the manual, It's not possible for incorrect length screws for this particular section of the build because TKR1349 are the longest flathead screws in not only bag J but the entire kit. Unless they supplied screws which are too long! Should be M4 X 20mm according to the manual. Just a slight tolerance issue I reckon.

Make sure the long ones are in the correct spot. Seems two long and two shorter in front and back.

 

[Benlee1012]

Yep, I'll check tonight. Hopefully all ok because the shorter ones at the back are an absolute pain to screw in. They were super tight! Forgot to use some Chapstick/grease. Almost stripped out one screw

Make sure the long ones are in the correct spot. Seems two long and two shorter in front and back.

 

[Matthew_Armeni]

Most likely the diff cover is slightly touching the ring gear at some point in its rotation. The M4x20 screw is causing the cover to expand slightly. We have very tight tolerances inside the gearbox. I would tighten the cover down correctly and run it. Any touching will wear away in the first battery pack. If you want, you could also take an xacto and shave that area just a bit. Either way, it will be fine, but definitely tighten down the cover all the way. If the cover is too loose it could allow the ring/pinion mesh to skip under heavy braking or throttle.

 

[Benlee1012]

Most likely the diff cover is slightly touching the ring gear at some point in its rotation. The M4x20 screw is causing the cover to expand slightly. We have very tight tolerances inside the gearbox. I would tighten the cover down correctly and run it. Any touching will wear away in the first battery pack. If you want, you could also take an xacto and shave that area just a bit. Either way, it will be fine, but definitely tighten down the cover all the way. If the cover is too loose it could allow the ring/pinion mesh to skip under heavy braking or throttle.

Thank you so much for your reply Matthew. I guess it's better to have some rubbing which will correct itself than to have improper gear mesh! I'll go ahead and tighten those screws down all the way.