The Stovebolt Site Forums The Shop Area Engine Shop Grindiing on decelleration

'53 Chev 3/4-ton recently restored. I've got a loud grinding noise on decelleration from higher speed (around 30-40). This occurs with or without the clutch pedal depressed and not at lower speeds. I would describe it as more of a grinding noise than a "chatter". Any ideas? It has been sitting for the most part since the restoration was completed. I'm trying to remember if I put grease on the pilot bearing when I installed the tranny. Could that cause it? Any ideas would be appreciated.
Rick

Hi Rick
I am no expert but I think it is more serious that the pilot bearing. Was the rear end and transmission gone over too? I would think that if is noise occurs in any gear, then it would be the rear end.
Good luck
Ter

Rick,

I doubt you would ever hear anything from the pilot bearing area...it's too small and rigid to do anything but maybe issue a little squeal.

Remember that the clutch disconnects the transmission from the engine and slipping the transmission into neutral, for the most part disconnects the drive train from the input shaft. Could this grinding noise be a u-joint or center bearing that is reacting when it is powered from the back forward.

Stuart

Do you have a carrier bearing? I have a similar noise and vibration that I suspect is either the rearing or the bushing.

Could be Stuart. If you recall a few months ago I was posting about the vibration I was feeling at low speeds. I ended up disconnecting the driveline and putting the front and intermediate u-joint in phase. That pretty much fixed the vibration. Since then it has been sitting. I didn't notice the grinding when I first drove it following the prolonged sitting period. I drove it for about a mile before noticing the grinding and it is a little intermittent. I'll check out the intermediate bearing. I'm stymied. The rear end was not rebuilt and it was fine before I did the restoration. The u-joints are new. Tranny and rear end fluid levels are both fine as well. I've noticed if I drive it at slow speed (3rd gear and lower), there is no grinding. I'll check out what you mentioned. Thanks.

Yes, Mike, mine has a carrier bearing. By the way, I didn't mention it, but I replaced the pillow around the carrier bearing as well. The vibration is gone, but replaced with grinding. I'll try to figure out if that is the culprit. I haven't greased the truck since the rebuild, but the u-joints were packed with grease when I bought them, so I don't think that's the issue. The saga goes on.
Rick

Rick,

This might sound real hokey, but with someone else driving, laying your ear on the gearshift lever is just like listening through a stethoscope. If the grinding is coming from the transmission itself, you might hear it in living color just by 'listening to the stick'.

Stuart

Okay guys, here's what I found. I double-checked the tranny and rear end fluid levels. Both are full, but when I pulled the rear end plug to check the level, I discovered nasty dirty chocolate-colored gear fluid and it is gritty to the touch. When I was doing the restoration, I had disconnected the driveline and covered the u-joint connection with a cloth (if I remember right). My truck was also missing the vent plug on the rear axle at that time. I sand-blasted the frame and I suspect I got a bunch of sand inside the axle by way of the vent plug hole. Would gritty fluid be sufficient to cause the grinding sound I'm describing? I suspect it could be. Regardless, I now need to fix this problem. Never having take a rear end apart or pulled the axles, I'm not sure what I'm getting into. I didn't pull the rear end cover, but I did drain the fluid before sand-blasting and I can't remember how I removed the fluid to do it. I also replaced the pinion seal when I had it all apart. I'm now wondering if I had the old seal off when I sandblasted. So, how do I go about cleaning this mess up? Suggestions? I haven't checked the shop manual yet. Does it sound likely I will need to pull the axles and dismantle everything to correct this problem? Thanks for the responses by the way. This is a 3/4 ton with the 8-hole rear lugs.

Blasting sand and rear end lube makes a great grinding compound! You'll need to do a full teardown on the rear end, and wash and inspect everything. That would need to include cleaning up the axle bearings, and installing new seals everywhere. Even a little sand, like 2 or 3 tablespoons full will cause major damage in a hurry.
Jerry

Rick,

While I agree with Jerry's comments, I don't think your rear end would have gone to heck that fast, and I don't think you would hear it grinding clear up in the cab.

While it certainly needs to be addressed, I wonder if thats the noise you are hearing. Wouldn't it howl more under load if it was in the tank?

Stuart

I'm not sure, Stuart. I do know the fluid in the rear end is really dirty and gritty as well. I was reading the shop manual and it talks about a 12-bolt rear end for a 3/4 ton. Mine has 10 bolts, but guess that is immaterial to the issue at hand. I read about how to pull the axles and am wondering if I pull the rear cover plate and the axles if that will give me sufficient access to clean everything up. I'm not sure if everything will fall apart inside once the cover plate is pulled or not, having never done this before. I wonder if pumping some cleaning solvent through the axle shaft after pulling the axles will flush everything back to the differential and then drain out with the rear cover plate off? And then hit the axle shafts with air from my compressor. I don't want to use any type of solvent that will damage seals etc. I am guessing that there is no seal at the end of the axle shaft where it goes into the differential since I believe the axles get their lubrication from the differential itself. I was checking Patrick's catalog looking at higher speed rear ends and I don't see one offered for the 3/4 ton. I was kind of thinking about putting in a higher speed rear end after going through all of the trouble of tearing things apart, but doesn't look like there is one for a 3/4. Again, this grinding noise wasn't happening when I first drove it. Back when I had the vibration problem, the grinding wasn't happening. So although I have driven it no more than maybe 3-4 miles total since I fixed the vibration, I suppose that could have been long enough to circulate the gear lube and pick up all of the sand. I don't think the grinding is coming from the transmission either. The sound I'm hearing is very similar to grinding of gears when you miss a gear, but it isn;t happening during shifting but more like during decelleration from a speed of about 30-40. Doesn't do it at low speed. Nor does it do it during acceleration. I had thought about trying to drive through it to see if putting a few miles on it would fix the problem, but now that I've seen the condition of the gear lube, I need to fix that first.

These noises are tough. Ride in the bed and see if you hear which area it is from, front or back, left or right. Hang your head out of each window. Be sure it's not wheel bearings in back or front. Check those both for high heat when done driving.(feel inside and outside of the wheel) If you start to go crazy, get someone to pull you in a quiet area with a long rope so you don't hear the tow vehicle. This is done with the driveshaft(s) removed. At least you will forever eliminate all that then start eliminating other parts. BUT if you have sandblasted near a rear end, it's curtains!! To all others: DO NOT sandblast rear ends, transmissions and such unless you are going to rebuild and don't buy one from some guy who just sandblasted one of these items to get it clean for paint. This warning is in all restoration books I have read.

You might want to try disconnecting the speedometer cable at the transmission and see if the noise changes. It may be the little gear set for the speedometer, stranger things have happened.

Also, check for water in the transmission. I have found water in mine even with no apparent source, just from sitting and condensation. It doesn't seem to have caused much damage but I've gotten into the habit of checking it after the truck has set for more than a month. That was when I kept it outside, though. My garage I keep it in now is pretty well temperature controlled.

I would flush and clean the rear end a couple times before a tear down. It might be needed but try just cleaning first to see if you caught it before it was damaged.

Rick

I had the exact symtoms that you describe. To me, it sounds like your pinion bearing is going bad. To confirm or deny this, remove the differential cover entirely, and see if the you have any chew marks on the carrier. That is what I bet the noise is. If your carrier looks like this, then that is what the issue is.

I dropped by a mechanic friend's house and we took the truck for a spin. The noise is not coming from the rear end, but more from the area of trhe tranny. However, we drove through the problem and it stopped making the noise. Not doing it at all now. The truck has been sitting for 5+ years during restoration. It has a new clutch and clutch housing as well. The tranny wasn't torn down, but some gaskets were replaced as it was leaking. At any rate, I am going to flush the rear end and get rid of the sand before driving it anymore. The grinding noise seems to have stopped.