Loud, rapid knocking coming from rear

Help! I really need some input, this is my first taco and I've only owned it for a couple of weeks. I have a base 2WD,auto. And there's loud, rapid knocking/clunking metal on metal noise coming from the rear underneath the bed. i

The knocking becomes faster as I increase in speed, but it seems to quiet down at higher speeds. It ONLY happens when I'm cruising or on decel, doesn't seem to occur during I'm accel. It's worst at 5-30mph, seems like it goes away at 40+mph. Also, while m in neutral it doesn't knock at all.

Today after a 35min drive I peeked under and noticed the diff was extremely hot, too hot to touch... Is that normal? My next plan is to inspect the driveshaft, but I wanted to know if you guys have some suggestions of what it might be?

 

sounds like the drive shaft....could be the carrier bearing being shot, or the slip yoke worn out.

 

yeah that sounds alot like drive shaft issues to me

 

breakindrifts,

Have you been under it to look for "Shiny" surfaces,metal on metal leaves true signs.....I too had an eractic noise out back.....one of the 4 caps on the "uni" seeped .......bear to replace..machine shop pressed it out but from there on out.....noise and vibration free...

I would plan on changing all fluids in areas that got that hot,price of oils and grease = CHEAP PM plus if you use a screen or mesh cloth to drain through.....the results can be eye opening.and save $$$$ later on...

Snoope back quiet

 

Is the rear diff leaking?

 

Having a differential being way too hot to touch is not normal. The heat is from insufficient lubrication on the hypoid gears or something like a carrier bearing has gone south inside and you've got metal on metal contact, therefore boku frictional heat. You need to crack open your pumpkin and find out what's gone awry inside. I'm guessing you're going to find alot of metal inside and gear lube that depending on how long you continue to drive it, may smell God awful from coking due to the heat. I would not drive it again till you do investigate what's goin on inside. Whether the gears are stripping out or the bearings are looking to seize, you'll end up stranded once it fails.

 

Just wondering what you've found BD, My "new to me" taco base model had a dry differential as the result of a wheel cylinder seal leaking. I felt the vibration on the ride home and pulled the plug only to find everything dry and as you noted, hot. Took just over a quart of lucas 75/90 to fill her up and i've not had any trouble since but i was just curious what your trouble turned out to be and how tough the fix is/was. J

 

Well finally had some time to inspect the truck and update:

The noise is definitely coming from the diff. I changed the fluid and the old fluid seemed alright. There was some sparkle, but I didn't notice anything significant in the fluid.

Up close the noise sounds almost like a chattering, which leads me to believe it might be the pinion & ring gears; but I'm not sure.

I peeked in the fill hole and couldn't see much, the spider gears do have some markings from where they mesh, but again nothing seemed out of the ordinary.

Any ideas of what could have gone wrong in the diff? It's really frustrating it's just a damn open diff.

How much work is involved in removing the diff to inspect it?

I really appreciate everyones help. Thanks

 

Sounds like a ujoint from description.

 

Thanks for the suggestion, but I already pulled the driveshaft and confirmed the chatter/knocking is something in the differential.

 

Did your truck come with limited slip? Is it an ex cab or SWB? Checked carrier bearing?
The only other thing I can think is a broken ring or pinion tooth.

 

Its a base model standard cab/bed 2WD open diff. Yeah I guess it the ring or pinion gears may be damaged. Though I have no idea how that happened, the truck seems to be in perfect condition. My truck has the 7.5" diff right? Sorry noob question.