97 Cobra Weird rattle/metallic Shuddering noise between 2k-3k RPM IN GEAR

[97blackShnake]

Hello everybody, this is my first post and I'm hoping problems with SN95's still get attention even though I haven't seen many recent posts or threads about my particular problem, let alone proposed solutions to said problems.

Anyways, I'm experience some sort of metallic rattle/shuddering sound heard only under load and usually right around 3k RPM. I've ruled out a few things such as rod knock and exhaust leak. I checked all exhaust bolts from header to catback and all are tight. I also made sure there was clearance between the headers and k-member, steering shaft, trans mount, etc. I can rev the car all day long in neutral no matter the RPM and not hear the noise.

With all of this being mentioned, I am leaning towards a transmission problem. I got under the car and took the inspection cover off of the trans and realized there was a little bit of play on the clutch fork, but I have read that it is normal. I had just replaced the flywheel, clutch, and throwout bearing about 1000 miles ago when I put LT headers on the car. The shift fork seemed to be in good condition and so was the pivot stud. I also deleted the EGR when I put the headers in the car as well as the SMOG pump, but could this be of any importance? The sound doesn't sound a whole lot like detonation but more of a metallic slapping that gets really loud around 3k RPM in all gears. I even put a spacer in between the inspection plate and the bellhousing to rule that out as well.

I am really lost on the cause of this.

 

[xblitzkriegx]

Cobsidering the clutch, flywheel, and TOB were replaced the same time as the headers, I'd start at looking to see if the headers are contacting due to a bad motor mount. Then, I'd look in to the clutch job, bolts might have backed out.

Those are all things that have been recently changed in the car so chances are that the issue is in there somewhere.

 

[97blackShnake]

Thanks for the response.

I should mention that I did change the motor mounts at the same time as well because the old ones were cracked. I used OEM replacements. The passenger side header looks really close the the k-member and motor mount and it could be rubbing. I will entertain the idea of the clutch job being botched in some way. I did use thread locker on the flywheel and pressure plate bolts, though. Everything was also torqued to spec. Nothing was off about the install which is why I feel so helpless about a solution to this noise. I have straight pipes after the O/R H, could that matter in some way?

 

[97blackShnake]

HUGE UPDATE:

I wanted to see if it had anything to do with the trans and the car being under load so I put the 2 front wheels on ramps and the rear on jackstands and took it through the gears, and no noise! I think I can confidently say that the trans and motor are out of the question. However, I noticed that my right tire will not spin when in first gear unless I give it gas, but the left one spins? I also cannot turn the wheel manually when the car is in neutral. I notice that the left wheel has some play if I try and pull it away from the diff and move it towards the diff (in and out play). Could this have something to do with the noise that I was hearing when the car was moving on the ground? I guess I should also mention that when I was doing the headers and clutch job I decided to throw some lowering springs on there as well, but did not change out the shocks or struts.

 

[jgt58]

New front hubs are in your future....

HUGE UPDATE:

I wanted to see if it had anything to do with the trans and the car being under load so I put the 2 front wheels on ramps and the rear on jackstands and took it through the gears, and no noise! I think I can confidently say that the trans and motor are out of the question. However, I noticed that my right tire will not spin when in first gear unless I give it gas, but the left one spins? I also cannot turn the wheel manually when the car is in neutral. I notice that the left wheel has some play if I try and pull it away from the diff and move it towards the diff (in and out play). Could this have something to do with the noise that I was hearing when the car was moving on the ground? I guess I should also mention that when I was doing the headers and clutch job I decided to throw some lowering springs on there as well, but did not change out the shocks or struts.

Sent from my SM-N950U using the svtperformance.com mobile app

 

[ViciousBlack97]

HUGE UPDATE:

I wanted to see if it had anything to do with the trans and the car being under load so I put the 2 front wheels on ramps and the rear on jackstands and took it through the gears, and no noise! I think I can confidently say that the trans and motor are out of the question. However, I noticed that my right tire will not spin when in first gear unless I give it gas, but the left one spins? I also cannot turn the wheel manually when the car is in neutral. I notice that the left wheel has some play if I try and pull it away from the diff and move it towards the diff (in and out play). Could this have something to do with the noise that I was hearing when the car was moving on the ground? I guess I should also mention that when I was doing the headers and clutch job I decided to throw some lowering springs on there as well, but did not change out the shocks or struts.

If I was you, I would pop the rear differential cover off and check the condition of the spider gears and everything else inside the rear end.

 

[Re1iK]

I just went through "hell" with my rear end so if you can't work on it yourself, make damn sure the person on it knows what they are doing!! First things first, you've taken the words out of my mouth with your post. I'm experiencing the same sound. I hear most in the morning, even more so with cold weather. Less noticeable after it warms up. Thought it was the lifters maybe to the metallic shimmy/rattle...rattles too fast to be lifters if that makes sense. After a month, and 3 complete rear end rebuilds by mechanic, they finally found that the case where the pinion goes is...was egg shaped. Ordered a replacement from Jasper. Jury is still out on whether I'm happen with the rear end from them. One thing I noticed after the rear end was replaced, that metallic rattle tapping sound immediately was gone. I was so ecstatic...let me tell ya lol. But over the course of the next month, it slowly started creeping back and seems to slowly be getting louder. It's possible it's a bad rebuild by Jasper but with a whole next aluminum driveshaft and new rear end, that issue had to be something else. That sound is coming through by shifter too it seems so I'm thinking it's the input bearing on the transmission. Shifter is perfectly silent in neutral but there is a slight noise when clutch is engaged. You mentioned testing it with the wheels off the ground. That test wouldn't work because of no true load on it. Soon I plan to take my car to a friend who has a dyno. Plan is to run it on there, and use a stethoscope to chase down that noise. Like, you I'm betting it's in the transmission. I hear the noise most in 1, 3, and 5th. So it has to be input shaft and or the counter gears for 3 and 5th. Gonna replace the front wheel bearings to make sure all possible road noise is gone too lol. The rear bearings are replaced so might as well do those too! Good luck. Please post back with what you've found.

 

[Cobra Jet]

Check to make sure the e-brake cables at the center junction within the trans tunnel do not have slack....

It was a known issue that the SN95 e-brake assembly was problematic where it would detach or become loose from the trans tunnel. When it did, the center cable assembly would hang low, low enough to come in contact with the drive shaft. It would not make constant contact with the driveshaft, but when it did it would produce a rattle at certain RPM and speed while in motion.

IIRC to fix it, one would have to take apart the center console and remove the factory body rivet that held the e-brake assembly to the tunnel and just secure it the old fashioned way with a decent bolt/washer/nut combo. Bolt goes through the floor, under trans tunnel place washer and nut on end of bolt. Then if applicable, readjust the e-brake and by doing so it should reduce any slack in the cable assembly where the L and R cables come to tie into the cable connection to the e-brake.


Another source of rattle could be the trans spacer plate. Make sure all of the bolts are securing it. If it’s slightly bent and not completely flat, it can rattle at certain harmonics. Use rubberized tape or felt tape to place in between the spacer plate and transmission. That should reduce any possibility of rattles.

Do you have catalytic converters on it? If so, it can also be highly likely that the catalytic honeycomb has deteriorated and a chunk is rattling at certain harmonics within the catalytic converters shell (OR if it made it down into a muffler). If you have cats, pop the mid pipe off, shake the pipe and see if it rattles... if no rattles, use a strong light to shine down into the pipe and see if you can see any breakage or fractures of the cats.

I don’t think it’s your transmission or related parts, especially if those commenters were recently serviced and everting was reinstalled using proper torque specs. A throw out bearing could rattle, but unlikely if it is new.