Just did the maiden on my ET48 2.0 and have a few driveline issues need help to resolve

[RCmaniac88]

let Me start by saying I have done little more then basic visual inspection at this point to figure out the issue and I may be missing something simple. I don’t usually into an issues on builds that I am not able to at least diagnose cause of fairly quickly, but the cause of this problem isn’t jumping out at me. I have a lot of builds under my belt, this year I built several Arrma hybrid full parts builds, I’m finishing up a 12s losi 5ive T build and this isn’t my first Tekno kit, I built a mt410 / ET48.3 hybrid earlier this year. so While I certainly may have missed something simple or made a dumb mistake, it would not from a lack of experience.

Problem: I get a clicking sound on hard braking. The clicking sound is like when you put a playing card on your bike wheels as a kid so it would hit the wheels spokes. I also started losing drive to the rear wheels. I took a quick look in the field and noticed the universal driveshaft coupling‘s grub screw loosened. I tightened the grub screw and figured the issue was resolved, but once I started driving again the sound on braking was still there. I thought it may have been something binding because I hadn’t adjusted my suspension yet, so I did a basic adjustment of droop and shock springs, but the sound is still there, I also tried removing the body to rule out anything rubbing but still had the issue. I applied throttle with the wheels off the ground and then hit the brakes to see if I could still hear the sound, I think it is still there, but hard to tell because the wheels stop too quick. rolling the rig on a workbench, it has perfect mesh sound and feel, nothing seams unusual Unless it’s driving.
I have to check more thoroughly but any inside or recommendations would be much appreciated. I’m guessing that the issue is something in the drivetrain that is loose or out of alignment enough to slip under load. the other possibility I thought of is it’s related to the front suspension compression during braking that causes binding of something.

The build details
i used mostly stock parts with the exception of m2c Aluminum rear brace, steering top plate and a few other generic aluminum pieces like a center brace and rear brace bracket. I also added front and rear t bone style Kydex bumpers. For electronics I went with a castle 1515 monster 6s combo and steering is handled by a Power HD brushless s50 servo. I also went with a little stiffer diff fluids then stock, I went 10k above stock for front and rear diff oil and 200k in the center.

tonight I am probably going to get deeper into things. I’ll pull off the front and rear clips and check mesh on ring and pinion, etc. I love these Tekno’s but they are tight on space inside and it can be fidley getting a proper look at everything

 

[Lynny]

let Me start by saying I have done little more then basic visual inspection at this point to figure out the issue and I may be missing something simple. I don’t usually into an issues on builds that I am not able to at least diagnose cause of fairly quickly, but the cause of this problem isn’t jumping out at me. I have a lot of builds under my belt, this year I built several Arrma hybrid full parts builds, I’m finishing up a 12s losi 5ive T build and this isn’t my first Tekno kit, I built a mt410 / ET48.3 hybrid earlier this year. so While I certainly may have missed something simple or made a dumb mistake, it would not from a lack of experience.

Problem: I get a clicking sound on hard braking. The clicking sound is like when you put a playing card on your bike wheels as a kid so it would hit the wheels spokes. I also started losing drive to the rear wheels. I took a quick look in the field and noticed the universal driveshaft coupling‘s grub screw loosened. I tightened the grub screw and figured the issue was resolved, but once I started driving again the sound on braking was still there. I thought it may have been something binding because I hadn’t adjusted my suspension yet, so I did a basic adjustment of droop and shock springs, but the sound is still there, I also tried removing the body to rule out anything rubbing but still had the issue. I applied throttle with the wheels off the ground and then hit the brakes to see if I could still hear the sound, I think it is still there, but hard to tell because the wheels stop too quick. rolling the rig on a workbench, it has perfect mesh sound and feel, nothing seams unusual Unless it’s driving.
I have to check more thoroughly but any inside or recommendations would be much appreciated. I’m guessing that the issue is something in the drivetrain that is loose or out of alignment enough to slip under load. the other possibility I thought of is it’s related to the front suspension compression during braking that causes binding of something.

The build details
i used mostly stock parts with the exception of m2c Aluminum rear brace, steering top plate and a few other generic aluminum pieces like a center brace and rear brace bracket. I also added front and rear t bone style Kydex bumpers. For electronics I went with a castle 1515 monster 6s combo and steering is handled by a Power HD brushless s50 servo. I also went with a little stiffer diff fluids then stock, I went 10k above stock for front and rear diff oil and 200k in the center.

tonight I am probably going to get deeper into things. I’ll pull off the front and rear clips and check mesh on ring and pinion, etc. I love these Tekno’s but they are tight on space inside and it can be fidley getting a proper look at everything

I would pull the cover off of the rear bulkhead and make sure the pinion is pushed all the way forward and not able to move back and forth because the rear driveshaft came loose. Also check that the grub is properly seated on the flat of the pinion gear and isn’t slipping.

 

[Nicochau]

The clicking on brakes very much sounds like front diff gears skipping. Which on the other hand sounds very surprising given how mesh is usually right out of the box on those trucks.

 

[RCmaniac88]

I would pull the cover off of the rear bulkhead and make sure the pinion is pushed all the way forward and not able to move back and forth because the rear driveshaft came loose. Also check that the grub is properly seated on the flat of the pinion gear and isn’t slipping.

I was thinking that the output may no longer be properly seated against the bearing and need to be adjusted, I haven't gotten back on it to check yet, but ilove start by going through the mesh

The clicking on brakes very much sounds like front diff gears skipping. Which on the other hand sounds very surprising given how mesh is usually right out of the box on those trucks.

Im sure both the front and rear diffs where properly seated and had a tight mesh when I assembled the housings. If memory serves me correctly, the fit was so good in fact that no shims where needed. That may not be the case with the pinion / cup anymore however. I tightened up the grub and indexed it to the flat spot, what I didn’t get a chance to verify is that it is seated tight;y against the diff housing bearing

 

[Nicochau]

I was thinking that the output may no longer be properly seated against the bearing and need to be adjusted, I haven't gotten back on it to check yet, but ilove start by going through the mesh

Im sure both the front and rear diffs where properly seated and had a tight mesh when I assembled the housings. If memory serves me correctly, the fit was so good in fact that no shims where needed. That may not be the case with the pinion / cup anymore however. I tightened up the grub and indexed it to the flat spot, what I didn’t get a chance to verify is that it is seated tight;y against the diff housing bearing

Agreed, fit is usually to the point in the gear box.

What is acceptable though is to have rubbing in certain areas of the driveline that very quickly disappears after a pack or two and some wear.

I remember reading this from a comment made by Matthew at Tekno.

 

[RCmaniac88]

I looked over the driveshafts for Amy rubbing today and didn’t see any wear, though the rigs only been run maybe a total of a pack for testing so it might not have run enough to show wear from rubbing.
I checked over the front and rear differential pinions. There’s play in both the front drive shaft cup / pinion and rear pinion ‘ universal joint. they both had a few mm Of play. I removed both assemblies and the bottom differentia; covers to see if the play effected the mesh enough to cause issues. It looked like mesh between the pinion and gear remained engaged well enough regardless of the play but to be sure I tested with the drive cup set screw engaged as far back on pinion shft to reduce play and then with it set somewhere in between, it did not make a difference. the sound on breaking and overall issue didn’t improve.
everything is moving freely in the drive train that I can see. Really frustrating

 

[nub]

Throwing this out there based on your description of the sound. Have you checked the back side of the wheels to see if there are any witness marks on the ribs/bracing?

 

[RCmaniac88]

Interesting, I haven't removed the Backflip LP's to inspect. I will check to see if theres something rubbing there. I'm not hopeful, but if its not this I am going to remove the bulkhead diff housings and look over the inside of the cases etc. I have removed the front and rear clips and had a limited look based on removing the bottom cover, but it is a limited view from the bottom. Maybe something has caused binding in the bulkhead cover.
final item that may be causing some issue is that I have aftermarket index from and rear bumpers, I believe I used slightly longer screws to compensate for the added depth the bumpers added. If I over over compensated and have a few screws slightly longer then needed im wondering if it could be deforming a bulkhead?