Grinding sound post gear install

[Jeff Elliott]

Hi Folks -

I have installed two re-geared diffs and have completed my first few test drives. The gears were professionally done by ECGS. I have a grinding sound that occurs as I transition on and off the throttle and is louder at higher speeds.

I suspect a drive shaft install issue as, like an idiot, I didn't mark the shafts when I pulled them. I pulled the entire rear shaft and only the yoke of the front shaft. When I reinstalled them, I put the rear back together out of phase and had the front one tooth off. I drove it about 10 miles with about 4 of that at highway speeds and clearly heard the grinding at throttle transition. This am, I pulled the rear and reinstalled in phase and corrected the alignment of the front. I have just completed another test drive and the issue persists. I'm stumped in terms of what to look into next. I know the transfer case bearing can go bad but I didn't have any of these issues pre-gear install and can't believe having the rear out of phase and front one tooth off for so few miles would have caused it to go bad.

Here's a video where you can, if you listen closely and watch the tach, hear the sounds.



Also, here are some pics of the shafts after correction:

 

[bryson]

I'll bet that the lower gears (meaning faster driveshaft spinning) are just amplifying a joint/angle issue that was already there. I'd start by checking u-joints, and then check pinion and driveshaft angles and correct (if necessary) with caster plates/bushings (front) or adjustable control arms (rear). I see you have radius arm drop brackets up front already, but there could be additional adjustment needed to get it right on the money.

Could also be dry/under-lubed spindle bushings in your front axle?

I would not mess with driveshaft phasing - leave the slip yokes exactly as you found them (they shouldn't necessarily have been disassembled anyways). I know the manuals all tell you to mark pinion>driveshaft and t-case>driveshaft flange alignments, but I am not convinced that it makes a difference - if all components are in good condition and properly installed, it does not matter.

 

[jfz80]

All i hear is mud terrains Possibly your rattle at transistion but its not clear.

Stock form has the rear shaft in phase and front 90* out of phase. You could try putting it back to OE specs but since you are lifted all bets are off. Some report better performance as you have it now.

 

[Jeff Elliott]

Thanks guys - Listen closely at seconds 35-36, 40-41 and 49 - 50. That fast grinding is what I'm hearing. Truck has 89K on the clock so it would surprise me if it's tcase bearings.

@bryson - you might be onto something... I don't recall putting grease on the bushings that the birfs ride in... could that be it? Wouldn't the moly have seeped into that cavity if the knuckle housing is 2/3 full of grease?

 

[Etxmike]

What size lift? Im going through the same exact thing right now after gears. Everythings led me to rear pinion angle since i went part time. Im waiting on rear arms and am hoping that and new u joints will solve all me noise. Mines definitely coming from the tail shaft of the t case area. My t case was 100% gone through so the tcase output should be good to go

 

[bryson]

...

@bryson - you might be onto something... I don't recall putting grease on the bushings that the birfs ride in... could that be it? Wouldn't the moly have seeped into that cavity if the knuckle housing is 2/3 full of grease?

Yes, dry spindle bushings can certainly make goofy noises. And if you didn't add the grease during assembly, it's not likely to make it there on it's own. The surface of the bushing that faces the bell of the birf seals pretty well against the birf. Not to mention that the spinning of the shaft would be likely to force the grease outward, not inward. If interested, SLEE makes a cap that screws on to the spindle and allows you to grease the area around the shaft without much disassembly. Others have made their own greasing tools out of PVC and similar. Or you can obviously disassemble and add grease that way.

IMO, you need to add grease to the spindle bushings even if they are not the source of your noise. It won't take long at all to nuke the brass bushings when they're run dry.

I'd also still look hard at your driveshaft angles.

 

[baldilocks]

From what I could see in the pics, your rear most ujoint has almost no angle where as the upper end does. Higher driveline rpms could be bringing this issue to the surface.

I’d call whoever installed the gears and ask what brand gears they installed and if they are cut such that they would produce more noise than factory gears.

The sound video sounded exactly the same from start to finish to my ear and it did sound like mud tires.

 

[Tools R Us]

... Wouldn't the moly have seeped into that cavity if the knuckle housing is 2/3 full of grease?

The bushing will self grease.

 

[nukegoat]

You're talking about the higher pitch grinding that sounds like it's in the t case and evident between coast and drive (I.e. float)? Not your tire whirring?

 

[LINUS]

I swear I’m seeing a ton of caster correction up front, but no DC shaft.

Spinning the driveshafts at a faster speed makes for new harmonics, or you have dry UJ’s - I’d grease them each including a pump in the DS splines, doing each one & taking it out to see if you need a new UJ.

Otherwise, that caster correction weld looks fresh despite the dirty steel on that rear arm pivot so if you did that with the 3rd members out for re-gear - you may just need a DC shaft up front.

I just heard the tires IMO.

 

[Jeff Elliott]

Thanks so much for all the replies!

You're talking about the higher pitch grinding that sounds like it's in the t case and evident between coast and drive (I.e. float)? Not your tire whirring?

Exactly - that's the sound and it only occurs in that moment between throttle on and off - if I feather the throttle just right, I can make it sustain.

I swear I’m seeing a ton of caster correction up front, but no DC shaft.

Correct, no DC shaft

Spinning the driveshafts at a faster speed makes for new harmonics, or you have dry UJ’s - I’d grease them each including a pump in the DS splines, doing each one & taking it out to see if you need a new UJ.

I will give this a try... I need to read up on how to determine if you need new UJ. I agree that the shafts going faster will exacerbate issues - however, if those issues were there before they would have revealed themselves at higher speeds than I'm currently hearing them at.? For example, I have now about 20% taller gears (I believe that math is right) - Currently I can hear the grinding at around town speeds (45mph). Thus, if this problem was there before, wouldn't I have been able to hear it at 20% faster or in this case 54mph?

Otherwise, that caster correction weld looks fresh despite the dirty steel on that rear arm pivot so if you did that with the 3rd members out for re-gear - you may just need a DC shaft up front.

I didn't add the caster correction or lift - those have been on the rig since I bought it.

 

[Jeff Elliott]

Yes, dry spindle bushings can certainly make goofy noises. And if you didn't add the grease during assembly, it's not likely to make it there on it's own.

The bushing will self grease.

I don't mind busting the knuckles apart and greasing them if that's a likely culprit - that said, if they can self grease would that happen in a mile or 1000? I've also thought about pulling the front drive shaft and taking the same drive to at least determine if its a front axle or rear axle issue.

Thoughts?

 

[nukegoat]

OK, if it's that, then I don't know exactly what it is but mine has done it for a long time. I believe the noise is backlash in the transfer case caused by some harmonics somewhere.

 

[Jeff Elliott]

Thanks - I'm going to give pulling the front shaft a try to start isolating some variables... Are there any issue with running without the front shaft?

 

[890man]

You must lock the CDL first.

 

[ajordan1975]

Mine does the same. I haven't figured it out yet, but i thing the driveshafts need to extended due to the lift. I'm pretty sure it's from my front. I have a 2wd conversion and gear reduction to install first, and if the 2wd conversion dosen't make it go away i'm going to get new driveshafts made for it.

 

[Lexonroids]

Just a heads up on what happened to me. Super weird but the bolts holding the new ring gear on the plate. Overtime started backing out. They were hitting the pumpkin face on the inside and a couple completely backed out. Before I finally discovered what this was it was the most unusual of sounds. Only happened on acceleration and would then go away on deceleration. When I finally opened the diff I had bolts in the bottom of the pan. Like I said weird. Make sure your bolts are loctited torqued correctly.

 

[Jeff Elliott]

You must lock the CDL first.

Thanks for this! Since I don't have one installed yet, I'll cross this off my trouble shooting list.

Just a heads up on what happened to me. Super weird but the bolts holding the new ring gear on the plate. Overtime started backing out.

Good to know - I verified that the bolts had locktite on them when I installed the 3rd member and it's only got ~10 miles on it - I'm going to assume for now that the bolts haven't backed out.

 

[LandLocked93]

Just my 2 cents...your issue occurred to me immediately following a transmission rebuild. My build out is mild compared to most here (<4" lift on 30" 265's atm). I am working it down with the help of many here, but I'm getting more results from fiddling with drive shaft phases and drive train bush refreshing than anything else.
Try driving without the front shaft...if you can. I bet your noise will be reduced.

 

[Jeff Elliott]

Well folks, I put another 4 hours into her this am and it's still problematic. Things I"ve isolated:

1) Spindle bushings - I pulled the spindles off and lubed 'em - so that's not an issue. I can confirm that they were self-lubricating
2) Grease in u-joints and slips - greased 'em all - no bueno

So, guess I need to order a CDL switch and remove the front shaft - where would a fella get one of those?

Many thanks!