Kraton Lost rear drive but nothing is damaged🤷‍♂️

[Notorious J]

I've been blasting around with the KEXB running paddle tires this winter, and having a good time of it. This weekend, things went wacky. On Saturday, a freshly built center dif seized up. Everything inside was virtually locked up and the inside of the case basicaly welded itself to the gears. It still ran like it was a spool, but with giant paddle tires, kept thermalling out. Fixed that on Saturday night and got out again on Sunday. This time, after about 15 minutes of good bashing and no jumping, the dreaded click in the rear dif started. Eventually it lost all drive to the rear wheels. While going through the motions of repairing/replacing the rear dif, I realized that no teeth on the spur were chipped and the gears inside were all fine. Cleaned and filled the dif with 60k and ran it on the bench. Buttery smooth. Haven't tried it under load yet, but if it goes well, then I have no idea what's going on. Anyone else ever have something similar happen? It's a HR aluminum gearbox and there was no sign of damage or cracks to it. Rear input gear is fine too. Is it possible that the center dif is blown but somehow managed to keep spinning the front tires? Again, on the bench everything seems fine.

 

[gotnitro]

Is it possible that the center dif is blown but somehow managed to keep spinning the front tires? Again, on the bench everything seems fine.

Very. If the rear output sun gear is damaged in the CD and it somehow locked up the front with gear salad you could be only getting power to the wheels with the least amount of traction, the front.

 

[jondilly1974]

I've been blasting around with the KEXB running paddle tires this winter, and having a good time of it. This weekend, things went wacky. On Saturday, a freshly built center dif seized up. Everything inside was virtually locked up and the inside of the case basicaly welded itself to the gears. It still ran like it was a spool, but with giant paddle tires, kept thermalling out. Fixed that on Saturday night and got out again on Sunday. This time, after about 15 minutes of good bashing and no jumping, the dreaded click in the rear dif started. Eventually it lost all drive to the rear wheels. While going through the motions of repairing/replacing the rear dif, I realized that no teeth on the spur were chipped and the gears inside were all fine. Cleaned and filled the dif with 60k and ran it on the bench. Buttery smooth. Haven't tried it under load yet, but if it goes well, then I have no idea what's going on. Anyone else ever have something similar happen? It's a HR aluminum gearbox and there was no sign of damage or cracks to it. Rear input gear is fine too. Is it possible that the center dif is blown but somehow managed to keep spinning the front tires? Again, on the bench everything seems fine.

My guess would be a loose input cup on the rear diff input pinion. Just a guess. Sounds like you’ve covered everything else.

 

[Yas]

What @jondilly1974 said I've had this before. The input cup's grub screw tip was flat and worn out after it had been slipping on the flat point on the pinion shaft. Hopefully an easy fix for you

 

[Notorious J]

Very. If the rear output sun gear is damaged in the CD and it somehow locked up the front with gear salad you could be only getting power to the wheels with the least amount of traction, the front.

I'll know for sure once I put it on the ground to run, but I can see how something like that might happen. Just enough metal fragments to keep one side turning. That would really suck though since I had rebuilt it the day before.

My guess would be a loose input cup on the rear diff input pinion. Just a guess. Sounds like you’ve covered everything else.

What @jondilly1974 said I've had this before. The input cup's grub screw tip was flat and worn out after it had been slipping on the flat point on the pinion shaft. Hopefully an easy fix for you

That was the first think I checked and with the new D thingy cover, even if the set screw came loose, it would still turn the pinion. That said, it was on well as I check it after every run since it's so easy to get to. My guess is an issue with the center dif like @gotnitro said. Just enough left to keep one set of axles turning, likely the one with the least resistance.

 

[#ARRMArcfanboy4life]

Did you check the pins which connect the diff cups to the gears?

 

[K-BASH]

Impressive, ya tore up a exb diffBIG paddles + snow is torture on a drivetrain.

 

[Notorious J]

Did you check the pins which connect the diff cups to the gears?

Difs were completely disassembled and reassembled. Nothing broken or missing.

Impressive, ya tore up a exb diffBIG paddles + snow is torture on a drivetrain.

Ran it so many times this year without issues. This weekend is the first and it hit twice.

 

[Yas]

That was the first think I checked and with the new D thingy cover, even if the set screw came loose, it would still turn the pinion. That said, it was on well as I check it after every run since it's so easy to get to. My guess is an issue with the center dif like @gotnitro said. Just enough left to keep one set of axles turning, likely the one with the least resistance.

Ah fair... if the clicking is definitely coming from the rear, just make sure the thread lock isn't tricking you in to thinking the grub screw is tight I always take mine off and drive out all the cured thread lock

if it's not this and you had lost drive altogether, then a drive pin somewhere may have broken, but as it's clicking and you've already checked the rear one, I'd agree and say it's more likely to be the center diff internal gears