Strange Noise Under Load

[Ericks2002]

A couple weeks ago my 1975 2002 4 speed developed a weird noise. When I’m under load around 2-3k rpm there’s a rattling that starts coming from the front of the car. The noise continues to redline I’m fairly sure but it’s hard to tell because the exhaust is loud. It happens in all gears. I don’t have to be at full throttle either, even maintaining speed in 4the gear the noise can still be heard. When at low load it’s very inconsistent but sounds like a box of rocks rattling around. 
 

Sitting with the car in neutral not moving and revving it up the noise is gone. I’m pretty sure something is wrong with the transmission. If anyone could maybe pinpoint what part of the transmission it is that would be great. Guessing some kinda bearing because it happens mainly under load. 

The car also makes a scraping noise once it’s warmed up and at idle. It sounds related to the other noise. It doesn’t go away if I put the clutch in either. 

I appreciate the help

 

[tech71]

First thing I would do is check out/make sure the driveshaft to trans bolts are all tight.

Next, check your exhaust system for looseness/rubbing anywhere.

Edited November 3, 2022 by tech71

[stephers]

Sure that it is not " pinging "    too much advance?

 

Thanks, Rick

[Ericks2002]

The engine runs fine. Pulls as it always did and idles good.

[Son of Marty]

I'm with Rick, check the timing and mixture then the exhaust and d/s bolts. 

Edited November 3, 2022 by Son of Marty

[Ericks2002]

Okay I will check timing and mixture when I get off work. 

[John76]

Also check the shift tower bolts. If these come loose, things can droop and start hitting the driveshaft parts.

Do you still have the guibo heat shield in place? Check for tightness and cracks. Ditto for the heat shield above the steering arm bushing on the passenger side..

On the '75s, there is a bracket on the exhaust that is bolted to the intake manifold/downpipe connection.

The duct to the fresh air thermostat box connects to this. Check this bracket for cracks, especially the smaller bolt-hole ear.

[Hans]

3 hours ago, Ericks2002 said:

The engine runs fine. Pulls as it always did and idles good.

Doesnt mean the ignition has too much advance. Start with points.

[Ericks2002]

The car has electronic ignition 

[Hans]

1 hour ago, Ericks2002 said:

The car has electronic ignition 

ok, just timing

[Ericks2002]

I checked the timing and it was good. I had a friend come over to check it out and he said it sounds like an exhaust leak but at the same time it doesn’t. Checked the exhaust gasket at the headers and below the car and no leaks. We also checked the driveshaft and it’s good.

 

I was able to get the noise to be constant while driving in 2nd gear at 3500 rpm. I might try and record it this weekend because I can replicate it now. 

[dlacey]

bad engine mount? fan hitting something under load?

[Ericks2002]

Engine and transmission mounts were replaced. I’ve had issues with the fan in the past so it is pretty chewed up. I’ll maybe try and remove it and drive this weekend.

[aldo.navarro]

I can't help, but I have a very similar noise as what you describe.

For me it kicks in at 3000rpm.

My mechanic says engine needs to be rebuilt.

But I'm convinced something else is the culprit.

 

[John76]

26 minutes ago, aldo.navarro.13 said:

My mechanic says engine needs to be rebuilt.

You mean his wallet needs to be rebuilt?