Help with Losi DB Pro Drivetrain Issue, I think

[parcou]

@razorrc @SrC @ncnative

Check this out...

Paused doing some job work to go back to the RC bench and clean up a little. I discovered the REAR CVD dogbones are just eaten off at the diff outdrives. Would this be more evidence to add that the diff cup internal gears were locking and forcing the dogbones to spin but more eat them off? Just guessing not really sure.

At the same time, the front dogbones which have full power and were not doing as the rear....still look good, round, and not eaten down at all...

1. I can order two dogbones which finding on back-order at some places.
2. Or, replace the pin. I do not have the tools for that so has to be #1 unless this is something a LHS can do

What are your thoughts on the eaten up rear CVD dogbones?

Rear...

Front

 

[Ruzty1311]

I second that looking at your pics of the sun gears the one on the left looks a bit chewed up. That's enough to cause the binding. As far as your dogbone issue goes, I don't have a good enough answer haha

 

[ncnative]

Me neither......I always put a small dab of Mobil red grease on the dogbones...at least as best as I can get to them. These things are going to wear out eventually based on how hard and how much you run your car.......it's unavoidable.....even with lubrication. The long dogbones and the axle cv assemblies are two items I keep spares on. They will break and wear down and bend. Expensive hobby......just as I told my son over 25 years ago when he had an Associated truck and tried to race it on a regular basis. I told him he might want to get some lawn care jobs around the neighborhood since his allowance and my wallet couldn't fund a racing team.

 

[SrC]

I tried many methods of lubing exposed dog bones/output cups in many of my rigs for many years. Grease attracts dust and dirt and turns to a grindy paste and this actually will accelerate wear in the long run. ( dirty running) Then lube disappears anyway.
I have tried coating the dog bone ends with a Dry Lube that wont attract dirt. With decent results, but just wont last too long. Needs reapplication frequently. But works. Dry Lube works excellent on the front CVD's pins and barrels. A must do for sure. Keeping the cups very clean helps much also. Use a Q tip and solvent to wipe them out occasionally.
This dry lubing while also chamfering the cup ends edges and polishing the pin contact surface areas of the cup helps prevent wear to the pins and cups. Many track guys do this to new cups. Using a file, then fine sand paper to the cups. Tedious but does work. I do this to new cups before installing. But usually either the cups or the pins wear out. One or the other. Just the way it is.
The cups are machined rough and this causes much wear to the pins. And a Dry lube works best if anything, or use nothing at all. IMHO.
MIP had used the replaceable Puck Pins as an option years back for many popular Track rigs.. Since discontinued.

To extend the life of axle dog bones pins, it is a great idea to swap lefts to rights periodically. ( rotate them L. to R.) Also while servicing a used diff, best to rotate used left cups to the right. Wear occurs with the forward rotational loads and it's contact area to the cups. You can double the life of the pins and cups in this way.
Some ideas.

 

[parcou]

I tried many methods of lubing exposed dog bones/output cups in many of my rigs for many years. Grease attracts dust and dirt and turns to a grindy paste and this actually will accelerate wear in the long run. ( dirty running) Then lube disappears anyway.
I have tried coating the dog bone ends with a Dry Lube that wont attract dirt. With decent results, but just wont last too long. Needs reapplication frequently. But works. Dry Lube works excellent on the front CVD's pins and barrels. A must do for sure. Keeping the cups very clean helps much also. Use a Q tip and solvent to wipe them out occasionally.
This dry lubing while also chamfering the cup ends edges and polishing the pin contact surface areas of the cup helps prevent wear to the pins and cups. Many track guys do this to new cups. Using a file, then fine sand paper to the cups. Tedious but does work. I do this to new cups before installing. But usually either the cups or the pins wear out. One or the other. Just the way it is.
The cups are machined rough and this causes much wear to the pins. And a Dry lube works best if anything, or use nothing at all. IMHO.
MIP had used the replaceable Puck Pins as an option years back for many popular Track rigs.. Since discontinued.

To extend the life of axle dog bones pins, it is a great idea to swap lefts to rights periodically. ( rotate them L. to R.) Also while servicing a used diff, best to rotate used left cups to the right. Wear occurs with the forward rotational loads and it's contact area to the cups. You can double the life of the pins and cups in this way.
Some ideas.

Thank you and all the others for the replies...

I am a cheap SOB but I hate doing things twice. I have the sun/spider gears on order waiting for delivery. As far as the dogbones these are very expensive...but I will give the Tekno a try. They "claim" a better design and over time I could pay this with all the extra OEM parts....my hope here is a one-stop shop I plan the have this rig for a long time. Time will tell on these

https://www.teknorc.com/shop/tkr2210x-m6-driveshafts-and-lightened-outdrives-frontrear-scte/

 

[SrC]

Tekno is known for better grade parts. Just don't come cheap. Give it a try. Best option for you.

 

[ncnative]

Good tip about "rotating" the dog bones. I've installed two of the lightened outdrives on the center diff. I haven't run the buggy enough to see any wear issues yet but if they are harder, I'm sure the pins may wear quicker. The Teckno CV's will require some polishing to reduce the shaft diameter for proper fit in the Losi drivetrain. I've watched several videos about them. They do look to be heavier duty

 

[parcou]

Good tip about "rotating" the dog bones. I've installed two of the lightened outdrives on the center diff. I haven't run the buggy enough to see any wear issues yet but if they are harder, I'm sure the pins may wear quicker. The Teckno CV's will require some polishing to reduce the shaft diameter for proper fit in the Losi drivetrain. I've watched several videos about them. They do look to be heavier duty

Thx for the post.....if you have a link to that video please share I am waiting on my Tekno CVs....but they do come with the outdrive I need to replace in the diff (swap the old) so they are paired with the CV they come with.

 

[razorrc]

What are your thoughts on the eaten up rear CVD dogbones?

I wrote like 2 years ago that Losi uses the crappiest metals on these cars.

 

[Surchaufeur]

I tried many methods of lubing exposed dog bones/output cups in many of my rigs for many years. Grease attracts dust and dirt and turns to a grindy paste and this actually will accelerate wear in the long run. ( dirty running) Then lube disappears anyway.
I have tried coating the dog bone ends with a Dry Lube that wont attract dirt. With decent results, but just wont last too long. Needs reapplication frequently. But works. Dry Lube works excellent on the front CVD's pins and barrels. A must do for sure. Keeping the cups very clean helps much also. Use a Q tip and solvent to wipe them out occasionally.
This dry lubing while also chamfering the cup ends edges and polishing the pin contact surface areas of the cup helps prevent wear to the pins and cups. Many track guys do this to new cups. Using a file, then fine sand paper to the cups. Tedious but does work. I do this to new cups before installing. But usually either the cups or the pins wear out. One or the other. Just the way it is.
The cups are machined rough and this causes much wear to the pins. And a Dry lube works best if anything, or use nothing at all. IMHO.
MIP had used the replaceable Puck Pins as an option years back for many popular Track rigs.. Since discontinued.

To extend the life of axle dog bones pins, it is a great idea to swap lefts to rights periodically. ( rotate them L. to R.) Also while servicing a used diff, best to rotate used left cups to the right. Wear occurs with the forward rotational loads and it's contact area to the cups. You can double the life of the pins and cups in this way.
Some ideas.

I once did that by accident swaped the outdrives when by mistake when i serviced a rear diff. Result twice more play because the stock outdrives or arrma gets chewed up. Imo m2c outdrives is the best for longevety of both parts
Im sure not getting a losi db pro. That drive-cup with 2 holes for no reason Weaken the whole thing even more. And that metal looks like alluminium. Steel shouldnt break like that. If that rc is consistently failing get rid of it buy something else. Unless you find the permanent fix

 

[ncnative]

Thx for the post.....if you have a link to that video please share I am waiting on my Tekno CVs....but they do come with the outdrive I need to replace in the diff (swap the old) so they are paired with the CV they come with.

I don't have a link....sorry....but it was a you tube deal that was set up with the Losi Lasernut. Google both of those and it should eventually appear. I'm not tech saavy enough to do a link anyways

 

[parcou]

I got the Tekno CV drives in and the out cups that come with the set.... Man this was not cheap...but I am gambling that over time the dogbones hold up and the out drives compared to what I but in spare parts would win out over time...

The end of the dog bones are nice and beefy. Tekno also list they are just a little longer and the back/forth slop is greatly reduced nice snugish fit but enough room to move....nothing like the OEM in their back/forth movement

Bigger cup and dogbone

Replaced outdrive which were the Losi HD. Cannot use the Losi ones with these dogbones head is too big

Heads compared to Losi OEM and the Tekno

 

[razorrc]

If the dogbone pins are worn, you can just change them out. Once you get the tool, it's pretty much free to change out the dogbone pins.

 

[parcou]

Thx for all the post guys....

Learned a lot with the Losi DB Pro over the past weeks here...

#1
I did replace the sun gears in the earlier post and the entire diff works better and sounds as it should...defective parts. Learned the hard way even if new out the box if something does not sound right, check it out first... I heard a slight noise in the rear on a low level but I just took it as OK since I never owned an RC of this type

#2
Stock bearings although the shield is not the best. I found many that were seizing only after 6-8 packs and no crazy bashing just loose dirt. Even those in the diff housing for the input gear to the driveshaft were catching. A pack of DSM took care of that

#3
Tekno drive shafts and outdrives although costly feel to be so far a good upgrade over the OEM shafts and Losi HD outdrives. The outdrive and dogbone are larger, fit good and very small back/forth movement

Again...thx for all the help

 

[parcou]

@Riko

Sorry that was Tekno, mine here
https://www.arrmaforum.com/threads/help-with-losi-db-pro-drivetrain-issue-i-think.39022/post-541320

And this one post on how the driveshaft WILL wear but it also will eat into the outdrive cups as well
https://www.arrmaforum.com/threads/...ead-by-alex-m-and-slick2500.14799/post-526805