Got a drivetrain noise for you guys to listen to.
 

So I posted a couple weeks ago in the "what did you do today" thread about shock loading the system and I thought I damaged the differential. Let me just say to everyone, if you cut an oak tree and have to pull it... Cut it into smaller pieces.

Anyway, my own dumb mistake. Happens. Well, it's not the differential as far as I can tell. I tore it apart, replaced the pinion, replaced the carrier bearings, set it back up, and reinstalled it. Unless the problem was on the ring gear, which I don't believe it was because I inspected it as well as the spider gears, then the noise isn't coming from the diff. I guess it could be the pinion bearings, too, since nobody had any in stock, but I don't see shock loading damaging the bearings too badly.

Now I inspected the CVs when I rebuilt the diff. I weeble bobbled them around and they didn't feel gritty or crunchy nor did they make any noise. There was a little bit of in to out play in the length, but there was no play rotationally. Both of them felt the same. I'd prefer it to be one or both CVs because I have extras. There's also no change in the sound when turning either direction vs going straight.

I only hear the sound under 30mph and only on deceleration. You can't feel anything at any speed. I have a video so you all can hear the noise for yourselves. It seems like it's more than once per tire rotation. I thought it sounded 3-4 times, but could be twice.

If any of you have ideas I'd appreciate them.

Oh, it's not the front driveshaft by the way. I pulled it and the noise was still there.

Thanks, guys!

Nevermind, I just caught the end of your message.

Duh

Alex, it's very difficult to hear on the vid but I can just hear tat, tat, tat on deceleration. But it's difficult to analyse, but here goes, it sounds like a pinion on the ring gear running too deep that or a pinion bearing on it's way out. It's worth checking all of your diff flanges for backlash and noise but also check the LT230 flanges whilst you are looking under the truck. There should only be 5-max 10 mm rotational backlash on any of the flanges and no play side to side or front to rear thrust. Sorry can't be of more help.

Yeah, that that tat tat is pretty much it. It's a little more audible in the truck, but the radio and air have to be off to hear it. Not super loud.

I'm really hoping it's not the transfer case, and I don't think it is. It happened immediately after I shocked the system yanking that tree to get it moving. Backlash on the diff is fine as I set it myself when I rebuilt it.

Could shock loading the system trash the pinion bearings? I'd be happy as a lark if it was just pinion bearings, but they felt fine on the bench, obviously without any load of course

I'll check the backlash on the transfer case next warm day I get. Maybe swap the CVs at the same time. Might be a few weeks yet, still.

Well that's a flashback, just went through this last summer on a DII I picked up and it was the same sound/presentation. It turned out to be a bad pinion bearing. I tried using a torque wrench on the pinion flange bolt before I replaced the bearing to see if the sound decrease. The torque was out of spec and the sound decreased some with the proper setting. Of course this confirmed the bad bearing and once replaced, torqued properly....back to Happy Town.

I hope this is the solution to your problem!

Two votes on pinion bearing, that makes me feel good. That's a really easy fix if that turns out to be the case.

It's worth replacing the bearing and seal. And as you know it's a very easy process.
Just get a quality bearing like a Timken or SKF, and definitely get a CORTECO pinion seal (FTC5258G) > https://www.lucky8llc.com/products/p...-pr2-corteco-4

X1 .......... and don't forget to torque up the the nuts correctly and replace any felt washers with new ones. Genuine Timken or SKF and Corteco are the original equipment and are the best, don't compromise on these.

Felt washers? I didn't see any felt washers when I had it apart. Where are they used?

I really appreciate it gentlemen

Based on my experience I'm still leaning toward the pinion bearing.

I found this video with a noise similar to yours, only this is far more pronounced. The solution is just as easy a fix as the pinion bearing and with the drive shaft removed there will be access.

Have a listen/look >