I've been chasing this issue for a few weeks now and I can figure out what it is. Will attach video..

The sound is for sure coming from the passenger side front end. It only makes the noise in reverse or if I turn very sharp to the right. Sounds a lot worse in the video than in person lol.

Replaced:
outer tie-rods
Cv axels

Thought for sure it was cv but the noise is still here. Just took those video 10 mins ago.

Edit: should also add I just recently got the truck running, before then it had sat in a shop for 15 years

 

Does it change with the front hubs locked/unlocked? If they are auto-locking hubs, you should be able to unbolt them and move slowly backwards for a short distance. That would help narrow it down to the front or rear, or the hubs themselves. Jack it up and spin the tires to see where it is coming from. If it only does it under load, then check the U-joints in the drive lines and make sure the bearings in the differentials are ok.

 

Thanks for reply. Yes it still makes noise if I lock hubs in. Only does it in gear. Don't have enough jacks to pick whole truck up and roll tires in gear. But jacking up front end and rolling doesn't make noise. If I coast in reverse (not in gear) makes no noise. How do I check differential bearings? Also I checked drivelines they seem to be okay. They have no play and make no noise spinning them from under truck

 

Have you checked the motor mounts are not dry rotted ??

As well as the transmission mount

When in reverse the torque is in the direction opposite of normal

So something is moving when your shifting into reverse.

 

Interesting suggestion wyoming9!! Will look into that after work this evening.

Although when I put engine in and did 5spd swap I did inspect all 3 mounts. They all looked pretty darn good for their age. Will definitely take a second look now that they've got some weight on them.

 

If you have not already done so, try jacking up the rear and spinning the tires. It might just be sounding like it is coming from the front. If the hubs are unlocked, then anything drivetrain related would have to be in the rear unless it is the wheel bearings or something in the brakes.

By the frequency of the sound, I would lean towards drivetrain rather than wheels, brakes, or CV axles. I just got done replacing U-joints in an '86. They were squeaking only under load, but felt tight when the driveshaft was on the truck. When I took it off, I found one of the U-joints was dry and almost seized. If the U-joints are greasable, make sure they are greased along with the slip-yoke.

Your problem could also be the ring and pinion. Maybe you can check it from the filler plug to see if there are any chipped teeth?

 

Thanks the_supernerd

I think you're right, definitely drivetrain related and I also now believe it's ujoint or ring and pinion..

Had a buddy stand outside and try to pinpoint the sound. He was pretty positive it sounded like it was coming from middle to rear of the truck. He thought it was probably a ujoint..

Got off work too late to take a look at her but tomorrow in going to grease them up since they do have the grease nipples. If that doesn't help I'll check out rear end.

Had both drivelines out when I did 5spd swap and they both looked great! But who knows, wouldn't be the first time I was wrong lol

 

I should add it's definitely not brake related. Just did brakes all the way around it and wheel cylinders as well a week ago. Noise existed before and obviously still does.

 

Could also be rust in the differential when moving in reverse.

 

my truck is making the same noise i have an 85 sr5 efi manual on 37"s. my transmission runs great no complaints about it.. but when in reverse there is a loud knock that it makes thats consistent every time in reverse (same as in shagool22's video). its been going on for a few years and theres no loss of power, ive still wheeled with it, pulled plenty of out, all in reverse with no loss of power what so ever! I know its coming from the trans by getting it on jack stands and running it in reverse, getting under and listening to it. it ill do it in 2 or 4wd hubs locked or unlocked
ive considered it might be the transfer case but it will make the knock in everything (2hi 4hi and 4lo)

 

Hmm very strange. My transmission is great as well. Previous owner claims its a recent rebuild and it no doubt feels like one. Everything about my trans is nice and smooth, no play or slack at all. Very happy with it.

But yup everything you explained I can contest too. No loss of power or anything in reverse. I just pulled a buddy up a clay bank in reverse the other day without any issues at all.

All my ujoint a feel stout!! I don't want to replace them if they don't need it. Just greased them up tonight and my reverse knock is still there lol. Very interesting.

Mike1818 please let me know if you ever figure more out! I have a second transfer case I might throw in some day to eliminate it from the question. What transmission do you have? I've got w56 top shift.

 

shagool22,
I will let you know as soon as I know which might be a while, im an ignorant SOB when it comes to trannys..
the knock has been going on for a few years and all the yota guru's i talk to have no idea....this is why im on the internet looking now!!

my trans is the same as yours w56 top shift...

 

Wyoming9 im pretty sure its not rust in the diffs because i put 5.29s in after the noise started..

 

Yeah I'm not too worried about it. I'm sure you can vouch for me when I say that it sounds wayy worse in the video than it does in person lol.

I may put it on jack stands and double check to confirm its coming from tranny or trans.

 

If you want to check the transmission, remove the shifter boot in the cab, then you or a passenger should be able to get to it with a mechanic's stethoscope while driving. I bought my stethoscope at Harbor Freight a few years back for only a few dollars. A large screwdriver or piece of metal pressed against your ear work well, also.