Fireteam Rattling sound

[ribka]

Hey guys,

Recently i hit a lamppost at about 25mph. Full stop. Broke the front arm and suspension and funny enough, bent the frame sideways a little bit. That's kinda hard to explain, but if you look top down on to the fireteam, it looks as if the front diff-block is a little off center. I'll post a pic of it tomorrow.

So i took everything apart and repaired what needed to be repaired. Assembled everything, checked it all and ran it. Then i noticed a hard rattling sound when i pull up fast, like some diffs are missing some other gear. Checked the pinion on the motor to the center diff and that seems to be fine.

So i can't figure it out. When i pull up slowly to a high speed i don't hear it. But then when i hit the brakes, i hear it again.

The front and rear diffs are fine, i can't find the problem.

Can someone help?

 

[nino]

Check all 6 of your dogbones.
When you say the diffs are fine, did you open them up? I've had internal gears or pins break.

 

[ribka]

Check all 6 of your dogbones.
When you say the diffs are fine, did you open them up? I've had internal gears or pins break.

Yeah, i opened them up and they seemed fine. Maybe i should look at it again. The dogbones have wear on them but i think they are ok. Will check them them too just to be sure. Can worn dogbones make a rattling sound?

 

[SrC]

If you twisted the chassis well. The Center diff/mount may be tweaked as well? Coulld even be a blown out Ball Bearing. Remove all the wheels and look at everthing closely again.
>>>Don't overlook the Fr and Rr Diff "shims". Done correctly!
Also Check both Bulkheads for cracks from that big crash. Again look very closely. Not always apparent.
Sounds like the main gear/ input gear chattering? F or R. One of them.
I bet this.
If the bulkheads are not cracked or split, re-shim again.
I shim mine on the snug side. Just not jammed completely.

 

[ribka]

If you twisted the chassis well. The Center diff/mount may be tweaked as well? Coulld even be a blown out Ball Bearing. Remove all the wheels and look at everthing closely again.
>>>Don't overlook the Fr and Rr Diff "shims". Done correctly!
Also Check both Bulkheads for cracks from that big crash. Again look very closely. Not always apparent.
Sounds like the main gear/ input gear chattering? F or R. One of them.
I bet this.
If the bulkheads are not cracked or split, re-shim again.
I shim mine on the snug side. Just not jammed completely.

Thanks for that great info! Gonna check all of what you mentioned. Never even thought about the shims! I noticed a crack in one of the bulkheads, but really really tiny. Don't think that would be the big problem, but i'll keep it in mind if i can't find the issue. Thanks!

 

[RC Steve]

If it sounds like a muffled chainsaw when you brake hard but fine when you accelerate then it's your front gear box. Your diff isn't seated properly or the case is flexing due to damage. Or a lot of other things. The front gear box is where I would start.

 

[ribka]

If it sounds like a muffled chainsaw when you brake hard but fine when you accelerate then it's your front gear box. Your diff isn't seated properly or the case is flexing due to damage. Or a lot of other things. The front gear box is where I would start.

This is exactly what it sounds like. The damage is in front of the car. I'll check that first. Thanks for help!

 

[SrC]

Thanks for that great info! Gonna check all of what you mentioned. Never even thought about the shims! I noticed a crack in one of the bulkheads, but really really tiny. Don't think that would be the big problem, but i'll keep it in mind if i can't find the issue. Thanks!

The slightest crack in a Bulkhead, and it needs to be replaced. They are cheap enough to replace. Been there. Under hard loads, the bulkhead will twist and the main gear mesh is affected because of this. Replace that cracked Bulkhead absolutely. You had a bad crash. been there.
Wasting your time trying to reuse it. Just because it looks like a "small" Crack. The Bulkheads are a structural part of the chassis aside from housing the high loads/gears of the Drivetrain. Front end hard impacts will always get the best of the Fr bulkhead. Same at the rear. Use a good front bumper. Like the EXB Basher bumper. Or RPM's. If you don't have any bumper. Front and rear.

 

[ribka]

So here's the deal. I took it apart when at first i didn't look good and figured this couldn't be the problem. BIG MISTAKE.

The front gearbox was broken, that is not a small crack as you can see.

Ordered the parts which are pretty cheap (€15 for a set).

Thanks for all your help!