Ultima Diff Slipping - What Is Wrong

[Snaab9-2]

I adjusted the screw in the diff the other day. When i drove the car today, it off and on would slip so bad the car wouldn't move. I tightened it all the way and the car drove ok for a free min but then it started slipping again. I kept fooling with it and sometimes even when the set screw was as tight as it could go, it would slip.

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually fail?

[alcyon]

I adjusted the screw in the diff the other day. When i drove the car today, it off and on would slip so bad the car wouldn't move. I tightened it all the way and the car drove ok for a free min but then it started slipping again. I kept fooling with it and sometimes even when the set screw was as tight as it could go, it would slip.

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually fail?

Check the diff rings. Are the grooves that the balls run in too deep ? Measure your diff balls too. If they are 0.1mm less than 3mm they must be replaced. Lastly your thrust bearings must have 8 balls ..and you must also have the black springy washers pressing on the outside of the thrust bearing.

[Snaab9-2]

I adjusted the screw in the diff the other day. When i drove the car today, it off and on would slip so bad the car wouldn't move. I tightened it all the way and the car drove ok for a free min but then it started slipping again. I kept fooling with it and sometimes even when the set screw was as tight as it could go, it would slip.

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually fail?

Check the diff rings. Are the grooves that the balls run in too deep ? Measure your diff balls too. If they are 0.1mm less than 3mm they must be replaced. Lastly your thrust bearings must have 8 balls ..and you must also have the black springy washers pressing on the outside of the thrust bearing.

I noticed it is missing a spring for the dogbones on one side. Is this what pushes into the thrust bearing? I am so clueless... so much to learn. Thanks

[alcyon]

I adjusted the screw in the diff the other day. When i drove the car today, it off and on would slip so bad the car wouldn't move. I tightened it all the way and the car drove ok for a free min but then it started slipping again. I kept fooling with it and sometimes even when the set screw was as tight as it could go, it would slip.

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually fail?

Check the diff rings. Are the grooves that the balls run in too deep ? Measure your diff balls too. If they are 0.1mm less than 3mm they must be replaced. Lastly your thrust bearings must have 8 balls ..and you must also have the black springy washers pressing on the outside of the thrust bearing.

I noticed it is missing a spring for the dogbones on one side. Is this what pushes into the thrust bearing? I am so clueless... so much to learn. Thanks

Give me an hour i will post pics. There isnt supposed to be a spring to push the dogbones.
are you using the 80s type ball diff or the mid 90s wbd5 which uses seperate diff rings..and has a spring on the nut side


try this
http://www.rc10talk.com/viewtopic.php?f=30&t=12804

[integra22t]

the diff rings could be slipping as well .. back in the day we use to have to super glue the diff ring to keep them from slipping

you can bench test it by putting 2 allen keys throu the diff outdrives and see if you can turn the diff gear with your thum.. you shouldnt beable to

[Snaab9-2]

Thanks for the info guys. When i get some time I will have to drive into it deeper.

I am not sure what kind of diff it has. It has some aftermarket parts on it and it is a pro XL. I really don't know what I am looking at but will learn.

It does have a spring on one of the dogbones and the other dogbone is sloppy so whatever the setup is, it seems to need the springs.

[tamiyadan]

.

[CHKTM]

the springs help center the dogbones so they don't fall out, you can also swap the springs for Orings.

you can change over to universals and use some spacer O rings in the diff.


The diff will need to be serviced.
a couple things could be going on, but assuming no damage or major wear you could be looking at an issue with the adjustment bolt.
there are conical washers that wear out and go flat making the diff loosen up. the washers act as a spring that gives the adjusment bolt tension and holds a diff setting.

the bolt itself should be crimped on the threads slightly and have a slight bend at the end. over time the bolt can loose this bend or somebody takes the bend out thinking it was damaged, and the crimp on the threads wears away making the bolt un tighten too easy.

the crimps hold the bolt in the threads tighter and the bend acts as an additional barrier to keep the bolt from loosing it adds extra tension.
you can compensate for a worn bolt, or flat conical washers with lock tight. you can also in some cases install a grub screw from the opposite side of the diff to lock the adjustment bolt in position.


either way you will need to open the gear box take the diff out and service it. the bolt is loosing for a reason, if you keep tightening it and it slips you will melt the gear or cause damage to the ball bearings or diff plates.

a ball diff is a high maintenance item especially if using a brushless motor, in that case you may want to switch to a gear diff.


so take it out, take it apart, clean it up, and inspect to find the cause, you can find replacement conical washers and additionally you can mare the bolt threads slightly and put a slight bend in the last 5mm of the bolt with a pair of pliers that will help lock the diff setting in place and not allow the bolt to loosen.

Excellent advice, if the diff has been slipping I'd replace the balls and plates for best results, however if you can source a gear diff as suggested this would be the ideal way to go since you have no experience with ball diffs. Building and setting a ball diff can be a bit tricky if you aren't familiar with the process. The correct lubes need to be used in the correct places and with setting and adjusting experience helps. A gear diff is build and throw in and your all good to go.

[alcyon]

I thought only the old yokomo diffs use bent bolts. Of all my kyosho diffs none use bent bolts. If you run on a high traction track a gear diff will work great and almost maintenance free. If you are running on low traction ball diffs works better.

[CHKTM]

From memory my Kyosho Ultima Pro used a bent diff bolt. I think I replaced it thinking there was something wrong. As suggested loctite worked fine with a straight bolt also. One reason a diff can slip is contamination from other lubes in the gearbox if over lubricated. When assembling a ball diff the rings and balls and also the gear must be clean and free from any oily substance. I clean mine with motor spray or similar and then allow to dry before using the correct silicone diff grease. This grease must be used on the main balls and plates to prevent slippage. Any other grease used will cause major problems with slippage. The thrust balls can be lubed with a normal black grease or similar.
I know the thoughts are ball diffs work better on slippery stuff but I've found the Scorpion gear diff works quite well on slippery stuff, you can see the outside wheel maintaining traction while the inside one drives.

[Snaab9-2]

I adjusted the screw in the diff the other day. When i drove the car today, it off and on would slip so bad the car wouldn't move. I tightened it all the way and the car drove ok for a free min but then it started slipping again. I kept fooling with it and sometimes even when the set screw was as tight as it could go, it would slip.

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually failThanks

Give me an hour i will post pics. There isnt supposed to be a spring to push the dogbones.
are you using the 80s type ball diff or the mid 90s wbd5 which uses seperate diff rings..and has a spring on the nut side


try this
http://www.rc10talk.com/viewtopic.php?f=30&t=12804

It has the spring on the right side and a white plastic ring and an oring on the left. I guess I need to figure out how to take the diff apart next.... oh joy.

[alcyon]

I don't really know what I am doing but obviously something is wrong or not adjusted properly. AM I missing something? Can something in the diff actually failThanks[/quote]
Give me an hour i will post pics. There isnt supposed to be a spring to push the dogbones.
are you using the 80s type ball diff or the mid 90s wbd5 which uses seperate diff rings..and has a spring on the nut side


try this
http://www.rc10talk.com/viewtopic.php?f=30&t=12804[/quote][/quote]


It has the spring on the right side and a white plastic ring and an oring on the left. I guess I need to figure out how to take the diff apart next.... oh joy.[/quote]

I have never seen that version,hmm..i thought the ball diff parts for the optima mid and lazer and ultima used the same parts..oh well.

[GoMachV]

Just in case it helps....

[Snaab9-2]

Well, I got the gearbox out and cleaned everything up.... there was lots of dirt and grit around it.... but now i am a little lost. The diff seems to grab tight and takes a decent amount of effort to spin the rear hubs different directions. The set screw seems to be the issue. Even when screwed in all the way it doesn't seem to hold and things spin freely seperate from the rest of the gears. There looks like there is a hole that the set screw screws into when aligned properly but the hole seems slightly off from the set screw would seat and like it doesn't fit in quite right? It isn't holding things tight and the shaft is spinning freely. This one doesn't seem to have a bend to it? I am really not sure what is wrong.... the set screw doesn't look like it would bend? Is this the normal Ultima Pro gearbox?








Also, I can't seem to figure out who to put this spur gear back together with the bearing, oring, metal and plastic washer..... any tips? It kind of fell apart while i was cleaning everything. Also, do the bearings or gears need any lube?

also, anyone ever seen this motor? I can't find any info on it.

[alcyon]

. Its difficult to tell from angle of pics. Also looks like your gears are stripped.