Please don't pick on me because I don't know the right names for the items.

The truck is an 89 CTD 3sp single cab 2wd.

When I give it lots of power, acceleration, there is a loud mid-high pitch grinding noise that it makes. When I hear that I lift off the accelerator and ease back into it. The heavier the load the more careful I have to be with the throttle. It does this even with no trailer at all if I floor it...

It sounds like its coming from underneath the truck, between the cab and the bed. I looked underneath the truck and what I can see in that location is the driveshaft suspended by a bearing (I believe it is) and then a short shaft with a boot covering 1/3 of it. I guess its called a slip yoke? My drive shaft is a total of 3 separate sections.
(After the short shaft it connects via u-joint and goes back to the rear end.)

I'm thinking that maybe the splines are worn or somethign and when too much power is delivered they slip... but are most of the time just hanging on...

I tried to remove the drive shaft but am running into a problem. on the yolk on the front and rear, there are 4 small bolts (Screws) that hold a U shaped cover on... that that holds the u-joint together. It looks like I can remove the 4 screws on the rear, and then maybe pull off the drive shaft from the section that's held on by the bearing. Then I can inspect it... and HOPEFULLY that's all cocked up... so I can replace it and solve the problem.

Problem is that the screws that hold the u-joint together are of some mysterious size. 5/16 is real close... but too loose 1/4 is too small. 8mm is close but too loose & 7mm is too small.. Do they make a 7.5mm? Is this the right size?

I've pulled the rear differential cover off, and it looks good in there from what I can tell... and i pulled the inside axles out of the rear wheels... that shaft that goes inside the axle and ties into the rear differential via the splines. That all looked good.

I value the more experienced persons advice!!! Please help me out here

Thanks, Keith

 

at the first mention of the carrier bearing, that's what i would be checking first. does it feel like the transmission or converter is slipping when you hear that noise or in other words, does it feel like you have a loss of power?

 

Hi, I dont believe that there is a loss of power (drop in speed) when it makes that noise... though its so startling, it probably only lasts about 1/2 second before I pull my foot of the accelerator therefore I probably wouldn't notice it.

Is the carrier bearing the bearing that I was describing where the noise what coming from? I'm certain that I would be able to replace that myself so I hope it is.

I don't believe that its the transmission because I dropped the pan, changed the filter, and there weren't any surprising amounts of metal on the magnet... just some black sludge surrounding it, and the fluid seemed to be as I expected. Not really to dark in color and didn't smell burnt. Everything seems real tight, and the truck is in quite good shape.

 

what you described and where you said it was located sure sounds like the carrier bearing to me. i really don't think it would be a hard task to accomplish yourself. i've never had to change one, but again, it doesn't look hard if i ever had to. usually just 2 bolts from the bottom side and it's apart from the crossmember it's mounted to. you may have to drop your drive shaft to take it completely out having that slip yoke, but i'm not positive on my thinking. i could take a peek at mine when i get home from work. even though it's a manual and a 2 piece driveshaft, the carrier could be installed/removed the same. i'll let you know what i find and if anything stands out.

 

Those bolts on the driveshaft could be 9/32, right between 5/16 & 1/4. On most other vehicles, the rear u-joint bolts are 12 point. 6 point sockets and open end wrenches don't work well on them. Don't know about these trucks, though. Drop that and the 2 bearing bolts and you should be able to get it off to check it. You might be able to check it by raising the rear wheels and putting the tranny in neutral (with the front wheels blocked) and turning the shaft by hand. Just a thought.

 

Thanks, after you mentioned the different points in the wrenches, I went back and checked it out... the bolts were 6 points and I was using a 12 point wrench... I used a 6 point wrench instead and it worked! Fit like a glove... 8mm.

So now I got the entire drive shaft off... cant figure out how I'm supposed to get the bearing off... use a puller? How do I get it back on. I'm reluctant to just try things because I don't want to tear anything up... and a puller would tear it up if its not supposed to be used i imagine.

 

In a completely different line of thought... sometimes it's hard to tell where the noise is coming from. When I first got my truck (new to diesels at the time) it made a very simular noise to what you describe, a squeally grindy sort of noise only under high power situations and the noise would quit as soon as I backed off the throttle. Turned out the bearings in the turbo were worn just enough that under high boost the impeller (cold side) would get into the housing and make that noise. It's easy to pull the intake hose, reach into the turbo (ENGINE OFF!!!!!) and grab the nut on the impeller, pull it towards the front of the truck and turn the impeller. If you feel rubbing it's likely the same issue I had. Pull the clamp band on the compressor housing and take the housing off and see if the pin wheel is hitting the scroll. You can do this with the turbo on the truck and it doesn't take too long.

 

^ Good point. ^