Kraton Noisy front bulkhead/diff Help

[332_RC]

The front diff on my K6 is very noisy. Removed the center diff & driveshafts. Removed the diff completely out, no cover, just the pinion. Smooth & no noise & bearings seem good no play. Put the diff back in with no cover & spin the front & it's very noisy. Like the mesh is wrong. No shim on outside of diff bearing against the bulkhead. New rebuilt composite diff, properly shimmed to manual spec. I bought this K6 used & found it took a hit on the left front after a teardown. The hinge pin was warped so I replaced all of them. The A arms are new RPM that came on it suggests it was wrecked & arms replaced & sold as is. The bulkhead must be warped causing the noise. The diff is not tight in the bulkhead & I've spun it w/o the front driveshafts & it's still there. Warped bulkhead from a crash?? Thoughts??

 

[slick2500]

The front diff on my K6 is very noisy. Removed the center diff & driveshafts. Removed the diff completely out, no cover, just the pinion. Smooth & no noise & bearings seem good no play. Put the diff back in with no cover & spin the front & it's very noisy. Like the mesh is wrong. No shim on outside of diff bearing against the bulkhead. New rebuilt composite diff, properly shimmed to manual spec. I bought this K6 used & found it took a hit on the left front after a teardown. The hinge pin was warped so I replaced all of them. The A arms are new RPM that came on it suggests it was wrecked & arms replaced & sold as is. The bulkhead must be warped causing the noise. The diff is not tight in the bulkhead & I've spun it w/o the front driveshafts & it's still there. Warped bulkhead from a crash?? Thoughts??

Well this most certainly could cause noise. In what way is it not tight in the bulkhead? Can you move it side to side? Also the manual shim specs are for reference only, you need to add or remove shims as needed.

I would recommend watching a few videos of diff shimming to help you understand what needs to be done.

 

[332_RC]

Well this most certainly could cause noise. In what way is it not tight in the bulkhead? Can you move it side to side? Also the manual shim specs are for reference only, you need to add or remove shims as needed.

I would recommend watching a few videos of diff shimming to help you understand what needs to be done.

It will move side to side without a shim against the bearing. I've tried the shim on either side & without. Still noisy with any combination.

 

[RCbuzz]

Check the bulkhead for cracks. Sometimes very hard to see and usually the culprit. The cases are inexpensive as well.

 

[332_RC]

Additional info. On that left side, the front & rear hinge pin block holes for the lower A arm were damaged i suspect from a hard hit. I replaced both when I replaced the pin. Makes me think maybe the bulkhead itself is damaged.

 

[slick2500]

It will move side to side without a shim against the bearing. I've tried the shim on either side & without. Still noisy with any combination.

Can you describe the noise or possibly take a video of the noise, upload it to Youtube then link the video here?

Additional info. On that left side, the front & rear hinge pin block holes for the lower A arm were damaged i suspect from a hard hit. I replaced both when I replaced the pin. Makes me think maybe the bulkhead itself is damaged.

If it was hit hard enough to damage the holes it is likely the gearbox is cracked, they tend to do that. I've broken my fair share of gearboxes.

 

[332_RC]

Spins freely. No shim against diff inside bulkhead case.

I even tried a different differential I have. Same issue.

 

[RCbuzz]

Spins freely. No shim against diff inside bulkhead case.

I even tried a different differential I have. Same issue.

Original Input Gear? New ring gear?

 

[slick2500]

It's hitting the case somewhere.

 

[332_RC]

Original Input Gear? New ring gear?

Yes. Tried it two ways. New ring gear & the original. Same noise.

 

[RCbuzz]

I would get a closer look at that input gear, can you get a close up pic?

 

[dgitalchaos]

These use spiral gears and are directional. It’s possible someone moved the diffs to the opposite side. As looking towards the open diff case, the ring gear should be to the left. Make sure both front and rear are on the left. You might have to change motor running direction as well.

 

[332_RC]

I would get a closer look at that input gear, can you get a close up pic?

It looks fine. All teeth look good.

These use spiral gears and are directional. It’s possible someone moved the diffs to the opposite side. As looking towards the open diff case, the ring gear should be to the left. Make sure both front and rear are on the left. You might have to change motor running direction as well.

View attachment 343415

It's on the left.

 

[razorrc]

IME if you crash hard enough to bend a hinge pin you probably broke a bulkhead.

 

[SrC]

Check the bulkhead for cracks. Sometimes very hard to see and usually the culprit. The cases are inexpensive as well.

+1
I would also make absolutely sure the Chassis' Fr. kickup hasn't been tweaked or bent even the very slightest. Even with a new Bulkhead, once buttoned up at top and bottom to chassis will distort the Bulkhead making Shimming and backlash a nightmare. The issue you have there pops up from time to time. It's a thing. It can be like chasing a ghost.
Need patience.
Try setting the mesh with the whole Bulkhead removed and verify backlash with the cover bolted back on. Off of the chassis. Then mount the whole bulkhead to the chassis. And verify it again.

 

[332_RC]

+1
I would also make absolutely sure the Chassis' Fr. kickup hasn't been tweaked or bent even the very slightest. Even with a new Bulkhead, once buttoned up at top and bottom to chassis will distort the Bulkhead making Shimming and backlash a nightmare. The issue you have there pops up from time to time. It's a thing. It can be like chasing a ghost.
Need patience.
Try setting the mesh with the whole Bulkhead removed and verify backlash with the cover bolted back on. Off of the chassis. Then mount the whole bulkhead to the chassis. And verify it again.

That makes sense. I had the entire front system off couple days ago to replace the bellcrank bearings with TRBRC ones. I just removed the front bumper, the bulkhead mount screws & hinge pin mount screws & chassis brace one & pulled it all up as one unit arms shocks & all. The noise was still there & I had a tricky time lining the screws all back up just right back down on the chassis. Had to move them all in close to snug, got them all started & nearly flush, then tightened them. Tighten one here & one there & another one was slightly off a small fraction & wouldn't start. The front shock tower was bent slightly too on the left side & I didn't notice that until a few days after I got it, a month ago. Luckily I had a spare from my Notorious & swapped it out back then. I bet the bulkhead is warped & the chassis has a draw to it. All in all the thing is like new & barely used. I think the previous owner wrecked the crap out of it, & punted it. It's a V3. I have a spare bulkhead & can set up the diff on the bench but if the chassis is warped I guess I can try to determine where & how to straighten it before I get a V5 chassis. Ugh. I didn't pay much for the thing. But it's adding up.

 

[Dan B.]

Keep us posted, I’m interested to see what the culprit is. I’d also be leaning toward a cracked bulkhead, but who knows.

 

[332_RC]

Keep us posted, I’m interested to see what the culprit is. I’d also be leaning toward a cracked bulkhead, but who knows.

Took it all back apart. Chassis is not bent & bulkhead was not bad.

 

[Dan B.]

Took it all back apart. Chassis is not bent & bulkhead was not bad.

If that’s the case it must be a shimming issue, right?

 

[PrerunninF150]

Is it greased at all? The part that gets me is that it spins freely, if it was hitting something i think that you would feel it when you spin it. Are all the bearings good? If all else fails bulkheads are pretty cheap and you can get a combo bulkhead and diff off Jennysrc for like 50 bucks.