Alright guys, pretty sure I've got an idea of what it is... just running it by you all before I get to it.

Noise started up a couple days ago, accelerating and decelerating, dont hear much at highway speed other than the counter shaft whine that it's always had. At first I thought it was the transmission going so I changed the fluid and it was dirty but not horrible. Had a little play in ujoints so changed them. And still have the noise. Drove with the door open and listened and pretty sure it's the rearend. Pulled rear shaft and drove it in 4hi with front end pulling, no noise at all. So my guess is I should open the diff and check gear lash. It is coming up on 300k so would not be surprised if it's going out.
What do you guys think.

 

My first thought would be U joints if there is no noise operating in front wheel drive only. Since you already replaced them that likely isn't the problem. However, does your truck have the 2 piece driveshaft with the support bearing?

 

Nope. Standard cab short bed 4x4 shortest driveshaft a truck can have lol. Well other than a bronco.
Hoping to be able to pull the cover tomorrow before work. Just hard to get to things when you work 70 hours a week

 

My bet is pinion bearings.

 

See I thought that too, but when I had the driveshaft out I tried to wiggle the pinion but it had no lateral play. There is quite a bit of rotational slop though.

 

Quick update, was able to get under the truck today. Popped the diff cover off and the fluid was almost green. I know when I cavitates it will have air bubbles that can the change color, but this was olive green. And yes found some flecks of metal so I'd think the diag of the pinion bearing going is probably correct. Local yard has a rear end with 125k on it for 125 bucks so I'll probably go that route as I dont really have the time to setup a new bearing set and what not. And since it's my dd I've had to drive it, so who knows if the housing is still good or if the race is spinning in it.

 

Well, picked up the rear end for the truck today. Ring and pinion look good, spider gears look good. So it will be an oil change and diff cover swap before it goes in. Then put my new shoes and drums on it.. then I have to pull the companion flange off the shaft and bolt it to the yoke. The 89 diff doesnt have the companion flange on it so I decided to just use the hardware on it instead of pulling the yoke and swapping parts. Unless someone knows better that I should change it over.

 

Well, I'll finish this off, changed out the rearend. And the noise is gone, haven't highway driven it yet though Around town shes very quiet.
So if you end up with a noise and you are able to drive it in 4wd without the front shaft I recommend trying it to narrow down the places the noise is coming from.

 

Glad to hear the replacement is quiet for you. Do you plan to scrap the old one or will you dig into it further?

Do you mean to say if you can run in 4x4 with the front driveshaft, and rear removed, that'd be useful for diagnosis? I suspect so just clarifying.

 

As for digging into it further I'm going to pull the pinion side of the companion flange off of the pinion( the rear I bought has the old style yoke as it's from a 89 or 90 truck). The rest of it is going to my buddy that let me use his driveway to do the swap. The daughter had people over today so I didnt want to be at the house. He may rear into it before scraping it. He was thinking about keeping the gear set as long as the pinion is good. I looked at them a week or 2 ago and the teeth were fine so i think the front pinion bearing was going.
As for the driving in 4wd yes i meant with the rear shaft out. I did that for a few blocks and there was zero noise as the bearing was not having a load applied to it.

I also scored a rear sway bar and hardware, new rear brake lines, a 2 year old rear tank and class 3 hitch and alternator during the swap. My buddy is scrapping his 95 150 (same year as mine)and it was on the trailer it the driveway next to me. He kept putting stuff in my bed saying here have this and dont you need this. Lol