Kraton Did something to rear differential - Back wheels do not turn

[cordell12]

Well I knew better, I knew driving the Kraton around the house would be a bad choice. But I talked myself into it, I was just gonna go up and down the road lol. After a few back and forths I got bored, tried to jump the driveway and couldnt stop quick enough. The Kraton ran into a guide wire for a power pole, hit in the middle and spun around the wire. The top messed up, up no worries there. Put the Kraton back on the pavement and knew something was wrong right away. The rear wheels do not spin. The driveshaft is in place and spins, so something busted in the differential. I see differentials on eBay for $30, anyone ever tore one apart to fix whatever piece was broke, or will the whole differential be the better option to buy?

 

[chevys10zr2003]

Well I knew better, I knew driving the Kraton around the house would be a bad choice. But I talked myself into it, I was just gonna go up and down the road lol. After a few back and forths I got bored, tried to jump the driveway and couldnt stop quick enough. The Kraton ran into a guide wire for a power pole, hit in the middle and spun around the wire. The top messed up, up no worries there. Put the Kraton back on the pavement and knew something was wrong right away. The rear wheels do not spin. The driveshaft is in place and spins, so something busted in the differential. I see differentials on eBay for $30, anyone ever tore one apart to fix whatever piece was broke, or will the whole differential be the better option to buy?

You could always buy the new completed differential for $30, put that in to get you running and then take apart the broken one and fix that one and keep as a backup. But taking apart the differential and replacing the broken pieces isn't bad to do at all.

 

[Canadiantech]

I always rebuild diffs, so i can shim and fix the weak link that caused that failure,
can you spin one wheel at a time or are both locked?

 

[hotshot24mi]

Could be several things, a rebuild kit that includes the planetary gears which are inside the diff is pretty cheap and it' not hard to install.

 

[Jerry-rigged]

And it might not be the diff?

1st - do you still have all three rear dogbones? One for each tire, and one from the center diff to the rear diff? That was my first though, threw a dog bone. Rare, but done that before. Usually something else hidden is broken that let the dogbone run free.

If you still have all of them, hold the front wheels off the ground, body off. apply throttle, and watch the rear driveline. Visually walk it down. 2- Is the rear driveshaft spinning? - If yes, 3- are BOTH the dog bone cups NOT spinning? If yes, check the grub screw on the diff input cup. Tight? on the shaft flat? If diff input cup is good, and the rear bones are not spinning, then it may be the diff... If one rear dogbone is spinning, then check the wheel hex. Did you round the hex in the wheel? did you shear the hex pin?

With all that said, buying the $30 diff from ebay is a good idea, if only to have the spare parts.

 

[cordell12]

Figured it out! The cotter pin on the piece that holds the driveshaft had somehow loosened up, or the impact knocked it off the flat part.

Thanks for the tips

 

[cordell12]

I don't know what or why it's happening, but today this cotter pin has slipped. The drive shaft spins, but it does not turn the differential. Is this by design that the cotter pin comes loose, or do I need locktite? It's almost as if the pinion (correct name?) sticking out of the differential is not ling enough to allow the cotter pin to keep a good hold. Haven't had time too look, but I believe the front differential has the same trouble as well. Any thoughts?

 

[Jerry-rigged]

By "cotter pin" I am guessing you mean the set screw? There is a "Flat" on the diff input shaft. If the set screw is not on that flat, it will quickly spin no matter what you do. And also, yes, use locktite once you find the flat. And Yes, same story on the front diff.

Cotter pin -


Set screw:

 

[cordell12]

By "cotter pin" I am guessing you mean the set screw? There is a "Flat" on the diff input shaft. If the set screw is not on that flat, it will quickly spin no matter what you do. And also, yes, use locktite once you find the flat. And Yes, same story on the front diff.

Cotter pin -
View attachment 15759

Set screw:
View attachment 15760

Yes, it is a set screw, my bad on miss terminology. I did have it on the flat spot, the thing is the input shaft from the differential just doesn't stick out very far. I will buy some loctite and lock them in place and report back. Thanks.

 

[Jerry-rigged]

The set screw on my front diff was coming loose every 10-15 minutes for a while. I think it took 2 or 3 coatings of Locktite before it finally stopped coming loose. I started to carry a set of cheap "L" allen wrenches whenever I would go bash it, because I knew it would come loose as some point.

 

[cordell12]

The set screw on my front diff was coming loose every 10-15 minutes for a while. I think it took 2 or 3 coatings of Locktite before it finally stopped coming loose. I started to carry a set of cheap "L" allen wrenches whenever I would go bash it, because I knew it would come loose as some point.

Good idea with the tool set!

 

[cordell12]

So my set screw either came loose again, or the input gear shaft has rounded some. I had the same thing happen again today, my motor pinion also has come loose as well. Kraton took a pretty good flip/crash this afternoon

Below is just a stock pic, not of mine, but the shaft on mine is a shorter shaft like the pic here. The front one has a longer shaft though. Is there a reason the rear is shorter, and if I need too could I just file the rounded part flat again?

 

[nulli]

Same part front/rear.

 

[cordell12]

Same part front/rear.

Why would the shaft on the front diff be much longer than the shaft on the rear diff then? I have to push the coupler all the way against the diff in order to get a bite on it with the set screw. I've LockTite the set screw again, will see how long it holds this time. Seem like every other run it comes loose *sigh*

 

[Jerry-rigged]

My guess is there is something very wrong inside your gearbox. Or you snapped off half the exposed shaft. The way the pinion rides on the ring gear, the ring gear is pushing the pinion forward, so it should not be able to slide back into the gearbox without something being out of alignment.

The more I think about it, I am suspecting the shaft broke. Never heard of that happening, but there is a first time for everything, I guess...

I'd buy the whole assimbley, so I would have spares of the other diff parts too.
https://www.ebay.com/itm/Arrma-Krat...ft-Outdrive-/381668164361?hash=item58dd320309

 

[Jjaroch]

This same thing kept happening to me after I replaced my gear box (the thing you showed in your picture), it turned out I forgot to put the internal bearing back in. Once I realized this and put it back in, I never had an issue again. This most likely isn’t the case because of it being new but thought I would throw it out there.