Sheetmetal scraping sound from rear of Kirkham

[TimG427]

I’ve got an interesting noise issue on my bronze Kirkham. After about one mile of driving I hear a strange sound like something bouncing or rubbing against sheet metal. This immediately turns into a screeching noise and goes away after about two seconds. It will reoccur about every five minutes. At first, I thought is was something loose in the clutch or flywheel getting bounced around in the scatter shield like a stone or piece of metal. There is an open area in the scatter shield and nothing is in there and all the bolts are in place for the clutch. The clutch works perfectly with no shifting issues, so I’ve ruled that out. I raised the rear end and removed the wheels. There is no evidence of tires or wheels rubbing on anything at all and there is plenty of clearance everywhere. It doesn’t appear this is in the differential as I’ve had bad differentials before and it’s not a tinny type noise like this is. Also, I don’t feel any vibration or grinding of gears, the car runs fine. If I shift to neutral while the noise occurs, the sound continues for the same two second or so period. Its always the same noise with no variation due to speed or RPM.

I thought it may be the fuel pump as this is mounted adjacent to the differential on a Kirkham. When the sound starts, I’ve turned off the fuel pump and the sound will continue as usual. Maybe the fuel tank shifting? It seems to be mounted soundly in place. The sound seems to be coming from the rear of the car and I haven’t been able to reproduce it while the car is stationary, but I’ll try to let the car idol for a while to see if that creates the sound. My last thought is that the headers/sidepipes may be expanding internally and making the metal to metal noise, they are some big honker pipes and mufflers made out of stainless steel. It really sounds like something rubbing against sheetmetal. Any thoughts from fellow Kirkham/Cobra owners would be appreciated. I’m driving the Cobra regularly as right now it doesn’t seem to interfere with performance. With another week of wet weather predicted here in Austin, I may not be able to get the car out for a spin.

[LMH]

Brake issue?
Larry

[TimG427]

I thought it may be the emergency brake, they have pads that squeeze the rotor and are separate from the regular brakes. I may explore that. Thank you.

[t walgamuth]

Sounds like something rubbing the driveshaft....or half shaft if IRS.

[TimG427]

Here is what the rear looks like, I'll put it on my lift again and check driveshaft and half shafts.

[Racer_X]

Do you have an inspection camera and/or a Go Pro?

Check inside the bell housing with the inspection camera and try mounting a go pro at various points of the car while going for a short drive to try and narrow down the source of the noise.

HTH

[t walgamuth]

It there is something rubbing half shaft or DS there would be shiny rings on them where it is rubbing.

Beautiful suspension parts!

[TimG427]

The bell housing appears fine and the internals are fine. I don't have a go pro, but may need one.

[SSSammy]

1) Look around at the sheet metal in the front and rear wheel wells and see if any panels, outer/inner fenders might be rubbing a tire. It might only happen if suspension is set too low, on bumps or on turns. My billboards used to rub in front.

2) Inspect the clearance between the driveshaft and the safety hoop and the tunnel sheet metal. Make sure it is all tight.

3) Check clearance between the raised "Wilwood" logo on the brake rotors and the wheel spokes. I have had those rub in the past.

Sam

[Gaz64]

Originally Posted by TimG427

Here is what the rear looks like, I'll put it on my lift again and check driveshaft and half shafts.

I see a brake hose rubbing on the top control arm, the braiding is fraying, and a rub mark on the control arm is evident.

Gary

[1795]

Good eyes Gary! Whether that was it or not, it definitely needs to be addressed.

[spdbrake]

This emer brake thread may help.
Parking brake fouling wheel

Quote from Tom K.
Yes the tolerances are very tight. Unfortunately the tolerances on the rims are not so tight. This is further compounded by our customers wanting the biggest rotors they can get. The original rear rotor diameter is 11.2 and we are now using an 12.2 inch rotor. This helps in braking performance; but makes the brake package very tight.

If the e-brake caliper is left on and driven in reverse, the rotor torques the e-brake caliper out far enough that it can then catch on the rim. This in turn tweaks the caliper out enough so it will drag on the rim.

You will need to loosen the caliper just a little bit and tweak the caliper back. Of course you will then need to retighten your caliper. You will also need to dress up the caliper arms.
__________________

[Gaz64]

Originally Posted by 1795

Good eyes Gary! Whether that was it or not, it definitely needs to be addressed.

Yes, I don't think that is his noise, but needs to be looked at.

[ERA 626]

I agree I think it is e-brake related, when the sound happens GENTLY engaige the e brake and see if the sound changes...

[olddog]

U-joint bearings can have a very high pitch that sounds like something much smaller.

Also a bad shock can make some strange sounds.

Good Luck

[TimG427]

I'll keep looking. I've pulled the wheels and there is no visible scraping evidence on the inside of the rims. I'll address the brake line, also. Thank you. I need to clear my lift and get it up there again. The driveshaft goes from the transmission to the fixed differential, so I wouldn't think there would be much movement. I'll inspect it.

I think the emergency brake needs further inspecting

[olddog]

The drive shaft from transmission to differential should have 3-5 deg angle on the joints. If there is no angle, the rollers in the cups will never move (turn). This usually isn't a big deal with a live axle, as the axle is always moving up and down (changing the angle). On an IRS the angle is pretty much the angle. If the needles stay in one spot they wear flat spots.

I never tried removing a drive shaft from a Kirkham, so I do not know the difficulty factor. It's not all that hard to pull the caps and check the needles, once it is out. Do make sure you have a very clean spot that will not let the little buggers get lost. It is a bit harder to get then all back in place. Do one cup at a time and don't mix needles.

I'm not saying there is a big hurry to check these. Maybe save it to last. A bad U-joint will make a lot of noise when closer to a failure.

[TimG427]

Guys, good news. It appears the source is the emergency brake interfering with the rotor (not the wheel). I believe the emergency brake caliper spring that keeps the halves separated is scraping the rotor. The spring is loose and can easily make contact with the rotor. I drove the car this afternoon with the emergency brake on the first notch and no sound at all. Of course, I don't like the idea of the emergency brake partially set, but it was barely set and the car could still roll fairly freely.
I'll explore more as it appears this is the source of the issue. Thanks to all the suggestions, your guidance helped me solve the issue. Thanks to ERA 626 in beautiful Danville, CA.

One other issue noted was the brake hose close to the top of the control arm. The picture was taken with full extension of the rear tire. With the tire on and the car on the ground, the hose clears the control arm by a big margin. There is no fraying of the hose.

Thank you again guys. I'm very relieved this issue appears to be close to being cured.
It was a fun 10 mile test ride.

[ERA 626]

Originally Posted by TimG427

Guys, good news. It appears the source is the emergency brake interfering with the rotor (not the wheel). I believe the emergency brake caliper spring that keeps the halves separated is scraping the rotor. The spring is loose and can easily make contact with the rotor. I drove the car this afternoon with the emergency brake on the first notch and no sound at all. Of course, I don't like the idea of the emergency brake partially set, but it was barely set and the car could still roll fairly freely.
I'll explore more as it appears this is the source of the issue. Thanks to all the suggestions, your guidance helped me solve the issue. Thanks to ERA 626 in beautiful Danville, CA.

One other issue noted was the brake hose close to the top of the control arm. The picture was taken with full extension of the rear tire. With the tire on and the car on the ground, the hose clears the control arm by a big margin. There is no fraying of the hose.

Thank you again guys. I'm very relieved this issue appears to be close to being cured.
It was a fun 10 mile test ride.

your welcome!!! glad I was able to help...