Weird rattle like sound from 6MT under load

I have been hearing a weird rattle like sound when I am under load from what I think is from the transmission, or when I am almost lugging the engine in a higher gear, and even at times when I am starting on a hill in first.

I am trying to get a sibling to help me see if I can get some audio of it...

But, does this sound like something to be worried about?

What might it me?

What can I check or research to understand what this might be?

Thank you for any help.

 

If it is a metallic/clatter/rattle sound from the engine it may be pre-ignition (aka: spark knock, octane knock, detonation, pinging). This is common with manual transmission vehicles when you are in too high a gear for the road speed - rpms are too low, lugging the engine.

Does the sound immediately go away if you shift down or if you gain a bit of speed taking off in first gear on a hill?
Did this just start? It may be just a low quality tank of gas. Try some name brand premium, Chevron, Shell, Mobil, Exon, etc..

Should you be worried: Pre-ignition is bad for your engine. If you hear it briefly under the above driving conditions probably not, if it is sustained while driving (cruising for example) yes.

I see you list a tune in your profile, I am a stock guy and know very little about tunes, do you have a "premium gas" tune? One of the tune guys here could help you more there.

 

Sounds like engine knock or ping.
Are you running 87 piss fuel? Or premium?

 

Just filled up 87 at Sunoco and it does seem to run much better than…. hmm… some places

 

been asking this for years now. It went away for me for after I changed my clutch and ToB and am always worried it’ll come back. Tacomaworld didn’t know what is was and neither did the dealership. I was always worried to shift at high RPM when it was rattling. I still have the annoying chirp… drive-throughs are noisy for me.

 

Nothing in the trans will rattle, but the clutch and/or throwout bearing may.

 

Yes, it goes away when I gain speed or shift to a lower gear.
I do not hear it under regular sustained driving
I do have the KDmax regular gas tune (at least I was told I do when I flashed it) and the sound seems to be new with this as I can not recall hearing this sound before.
How can I tell if I am getting detonation/pre-ignition?
I run regular 85 gas

 

I am running regular 85 gas with KDmax regular tune. Perhaps this is the issue
@PapaRee

 

How can I tell if this is the issue?

 

If you are sure it is 85 octane this could be your problem, most "regular grade" fuel is 87 octane.

Section 9.1 of your owners manual under the Fuel Information heading states "select octane rating 87 or higher".

Try filling up with name brand (Mobil, Exon, Shell, Sunoco, etc) premium grade fuel, 89+ octane.

BTW: Octane rating is a measure of the fuels ability to resist pre-ignition, it has nothing to do with "power" in the fuel.

 

I will try a few ranks of 87 and see if I can duplicate the issues.

 

Possibly a catalytic converter heat shield. Mine would make this terrible rattling under only certain RPM and load conditions.

 

I would start high with 89-90 and work my way down. If the noise goes away then try the 87 and see if it comes back.

My stock tune truck running 87 will only knock if I am doing something wrong -- too high a gear for the load. However you have a tune, this may change that behavior.

In "the old days" when vehicles weren't so sophisticated we tinkered with this quite a bit and one might have found that their particular car ran better with Mobil than it did with Shell for example.

 

I will try a few ranks of 87 and see if I can duplicate the issues.

 

Do the tunes do anything with the ignition timing, or is it all in the fuel maps?
85 might be barely enough octane on a stock engine, but if the KDMax tune advances the timing at all, 85 isn't going to cut it.
Not even sure where they sell this low of an octane.

87 as a minimum, also if you're under load, you should have the engine speed up (like 3-4k)

 

85 octane? I've seen it listed in small engine manuals and such but never noticed it anywhere. Not from Florida to Maine. I'm not being snobby or anything, this just seems like a great time to ask.

I bet 87 will at least alleviate part of what you're hearing. It's not a Ford 8N tractor, you do have some compression, might as well make use of it. Look at your timing, I bet it's waaaay retarded.

 

This is a good question...

 

I remember seeing it at a station recently, but I can't recall where. Might have been somewhere when I was driving from TX to CA... maybe in AZ or NM somewhere?

 

You're lugging the engine under load and it's making noise but it gets quiet when RPMs increase.

 

Thank you, for your thoughtful and enlightening comment that adds value to the question...../smh
It's people like you that ruin forums....

Had you read MY post and the question I had you would know my initial concern was with the transmission under load and hearing a noise I do not recall hearing before.... Then others offered the idea about the engine.....

Please, if you not not have value to add, stay out of the conversation, thank you.