Odd deceleration grind/noise

[Azonic84]

Ok, My 80 has been making a noise upon throttle lift that only happens while the engine is losing rpm.

For instance: I will be doing 40 mph and say I am taching 2200 rpm during acceleration. When I lift off the throttle I hear a grinding-esque noise that stops once the transmission is done lowering rpms. So once the Rpms fall to 1200 or so there is no more noise.

No noise with overdrive off that I can tell.

No noise on acceleration from any speed or stop.

No noise in 2nd only or L in acceleration or deceleration, only in D.

Its not very loud. I have to have the windows up and radio/air con fan off to hear it.

I just know its happening in the back of my head so its annoying haha

I have narrowed it down to either the tranny or VC or center diff. I checked the fluid in the tranny and its clean and doesnt smell burnt.

I havent had a chance to drop the pan yet and obviously its the 1st thing that needs done. I was just hoping someone would have some input.

Thanks in advance!

 

[SSSUPRA]

Honestly that sounds like the same noise my truck makes which is coming from the rear driveshaft u-joints.

 

[landtoy80]

Prob not your problem..
Look near the ends of the front sway bar and find the clamp that holds a wire. Mine is loose and makes noise. Black tape stops the noise. Also look at the mount at the end of sway bar. If the mount is broken, it will make a noise too. Took me a long time to find that the sway end mount was broken as it looks fine at rest.
Heat shield on cat make noise too.

 

[scrowley]

Mine makes that noise and I am sure it is due to needing a double cardan drive shaft for the front due to the lift kit. I see in your sig you have 2.5" lift. Not sure if that is enough to do this but mine is only 3" J's. If you feel like this could be it just take the front driveshaft out, lock CDL (if you have 7 pin mod) and go for a drive...see if the noise is gone.

 

[Azonic84]

what strikes me as odd if it is a driveshaft/u-joint oriented noise is that it stops once the rpms settle at 1200 or whatever it is during coasting at 40 mph.

i will check these things.

 

[SSSUPRA]

It's not necessarily stopping at a certain rpm, it's stops when the trucks weight is no longer being transferred to the front affecting the attitude or pitch of the truck, hence the reason I believe mine is the rear shaft. (results may vary).

 

[Azonic84]

Valid point. I will check u joint play tonight.

 

[Jpkllr]

Mine is making the same noise. It started right after they dropped the tranny and did my main and crank seal. Trying to figure out what it is

 

[SSSUPRA]

I've found that my noise is directly related to rear height and will get louder as my tank gets empty. Also installing and removing 30mm rear spacers, when they're in the noise is there all the time and when they're out it's only there under heavy breaking unless I'm almost out of fuel at which point it becomes a common thing again.

 

[Funner]

Well based on this new information it definitely sounds like its caused by drive line angles. the added weight of the fuel is allowing it to squat enough to relieve some stress, deceleration or braking is pulling the front down and rear is lightened/lifting just enough to cause the increased angle and thus the noise. You will want to check those u-joints, maybe they just need some additional grease. Also, just to be safe check the caliper bolts to make sure they're tight.

 

[Land Shark]

Would not hurt to check your knuckles and make sure you have sufficient grease in there. I had been putting off a front axle rebuild. Had the same noise you have. Come to find out my grease in my knuckles were very low.

 

[SSSUPRA]

As far as mine goes the knuckles were rebuilt within the last few months but I've had the noise for over a year.

 

[Azonic84]

Front u joints felt good. Need to check the back ones. Pretty sure the grease in the birfs is good as I pumped a good bit in them a few months ago. I will double check those. Brake caliper bolts are tight, I checked those before I moved to grand junction 2 weeks ago.

I am low on fuel. I am going to fill up and see if the added weight makes a difference.

Will report back.

 

[thirdmatt01]

Rear slip yoke. Well that was my issue, same symptoms

 

[Azonic84]

Thanks for all the suggestions on where to check guys! I will look into all these.

 

[Azonic84]

Well I replaced the u-joints with OEM Toyota ones. Expensive bastards! The noise persists. With the front driveshaft off the noise was completely gone. Maybe it’s the slip joint? I need to get some grease I can put into the slip joint and see if that helps. I did notice a very minute amount of play in the slip joint. Doesn’t seem like enough to cause any grinding noises though.

Anymore input would be great. I am thinking of dropping the rear shaft and doing a test drive.

Or I am just being neurotic...

 

[scrowley]

Its not the slip joint. I replaces my u joints also and the noise is still there. You need a double cardon front driveshaft to take care of the noise. I have left mine on and its fine. The slightly excessive angle on the front driveshaft is the problem.

Well I replaced the u-joints with OEM Toyota ones. Expensive bastards! The noise persists. With the front driveshaft off the noise was completely gone. Maybe it’s the slip joint? I need to get some grease I can put into the slip joint and see if that helps. I did notice a very minute amount of play in the slip joint. Doesn’t seem like enough to cause any grinding noises though.

Anymore input would be great. I am thinking of dropping the rear shaft and doing a test drive.

Or I am just being neurotic...

 

[Azonic84]

was your noise a grinding noise? this is a definite grind, not really vibrating anything either. just noise.

i am going to repack the wheel bearings in the next week and refill the birfs, been about 6 months since i have done that. hopefully i can whittle down this noise.

its also kind of intermittent, it has different intensities. sometimes very pronouced and others times it fades in and out. i just hope something isnt eating away at itself

 

[scrowley]

Well I replaced the u-joints with OEM Toyota ones. Expensive bastards! The noise persists. With the front driveshaft off the noise was completely gone.

I did the same thing....take the driveshaft off and the noise was gone. Mine is a grinding noise to. Not crazy loud but there when I let off gas when I am floating the pedal.

 

[Azonic84]

Welp, thats identical to my situation. Have you just gotten used to it?