Strange noise, only under load...

[Jonathan]

Thanks Dave.

I looked back at my notes (I keep a logbook, yea, dork, I know) and the first mention of the noise was 350 miles ago. At that time I thought it might have been related to taking a sharp turn. With that in mind, I thought it might have been the metal portion of the coolant pipe touching the bottom of my metal coolant reservoir. I put a piece of foam padding at the point where they might have touched, but the noise continued. So while I've heard it while turning, it's not as consistent as it is with accelerating.

The gear whine mention under acceleration or deceleration is the closest match to what I am hearing. I cannot get the noise to repeat if not actively pressing the gas pedal. The car can be in motion at any speed, but there's no noise if you aren't pressing the gas pedal (i.e. coasting while not pressing the gas). Further to that, it is much more evident when initially pressing on the gas and also at times when letting off the gas. However, when keeping a reasonably steady push on the gas pedal, the noise will fade away and stop.

So, yes, much more consistent with accelerating and decelerating than anything else. Almost to the point where I can't get it to repeat doing anything else. I'm not sure what a gear whine might sound like exactly compared to my own noise I'm hearing, but your description of under accelerating (and to a lessor extent decelerating) sure does fit.

For the motor and trans mounts, this could also be it as it's related to accelerating. My mounts are not in great shape. The motor mounts are rusty (like other brackets and fittings on my car have been before replacing them) and the rubber is of questionable condition. The trans mounts are less visible to see frequently, but looked more rusty than the motor ones on my car. I will definitely look closer for evidence of the pivoting like you described. I have not "felt" the noise though, not the seat of the pants variety anyway. It might be vibrating enough to feel, but it's not as obvious as the noise, so either I missed it or it's faint or not happening. Possible though still.

I would not think it is an engine miss. The engine seems powerful and okay when giving it gas. I had the shift computer rebuilt years ago and back then it had done the thing where it stayed in 1st gear and rev'ed at high RPM, but nothing like that for years since the upgrade. About the only sluggish feel I get is sometimes when first leaving my house going for a drive and it wants to hesitate slightly before changing into 2nd. That could be me not pressing the gas pedal down as much as I think I am or a cold engine and trans needing some warm-up time to get the fluids flowing (whatever that might mean). Hearing others describe missing engines doesn't sound like something my car is doing. I'd rate that as unlikely for the time being.

If it is a gear whine that isn't improved by adding differential fluid back in, what would have been damaged and what do you eventually need to do to correct it?

[opethmike]

Have you done this test with your motor mounts?

https://www.youtube.com/watch?v=m-kD9t-cnio

[DMC-81]

If it is a gear whine that isn't improved by adding differential fluid back in, what would have been damaged and what do you eventually need to do to correct it?

I'll leave that for Dave to answer, but since I recently had my gearbox apart, here's a picture of the carrier/conical roller bearing ( 103119 ) on a manual box to give a visual of the part in question.

Bearing
image.jpg

Race
image.jpg

[Jonathan]

Have you done this test with your motor mounts?

https://www.youtube.com/watch?v=m-kD9t-cnio

I haven't done this crow bar test yet Mike, no. Not sure why. I think when I saw it initially, it seemed like a good test but them got rebuked by someone I talked with. I don't have the car on a lift very often and wasn't sure I wanted to go at this while lying on the floor with it on jack stands. I did hear someone advise that poor looking rubber isn't necessarily a sure sign or bad mounts. It can be, but the real test is whether they are separating from the metal.

Here are a couple pics of mine. Driver's side anyway. Passenger is a little better. They don't look pretty, that much is obvious.

IMG_5081.jpgIMG_5082.jpg

I checked the rear differential oil level this afternoon. Pulled the fill port and felt no moisture to the touch anywhere on the threads or the short length my finger could get in there.

I then pulled the drain port and emptied what was in there. The fluid still looked pretty good both in colour and in smell. Gear oil doesn't smell very nice when new IMO though. 80W90 in there.

I got almost exactly 1 litre out, perhaps just a hair more. My notes from when I last changed it said I got out 1 litre back then and was able to put in about 1350 ml. The fill amount is probably a best guess as I recall spilling it all over the map trying to tip a bottle up when you're under there. Yea, fun.

I have not refilled it yet as I need to run out and get some more. Here is what it looked like underneath before draining. See the two drips on the low points of the rear differential casing? They are reddish and aren't at all like what accumulated when I drained the rear diff. Not as pink as new ATF, but too red I would think to be straight engine oil. How would ATF get up this far (or back) to give this drip a red colour? Am I forgetting something? I know my ATF cooler hoses are nearby, but I look at those somewhat regularly and they don't look like they are leaking.

IMG_5095.jpg

[Bitsyncmaster]

Get some small hose that fits in the fill hole. Then fill it from above the engine through the hose.

[Jonathan]

Get some small hose that fits in the fill hole. Then fill it from above the engine through the hose.

Good idea. Any trick to keeping the hose in the hole while you're above the engine and can't hold both things at the same time? I don't have a helper at my disposal.

[DMC-81]

That's good news that the differential wasn't starved of gear oil. Whew!

There are 2 SS heat shields above the crossover pipe. While you have the car elevated, it's a good time to check them for any looseness as you do your troubleshooting.

[DMC-81]

Good idea. Any trick to keeping the hose in the hole while you're above the engine and can't hold both things at the same time? I don't have a helper at my disposal.

I bought a gear oil pump at Advance Auto Parts ( you can probably find them at a Canadian equivalent) and it really makes the filling much easier. I made sure it would fit both quart and gallon bottles.
Here's a link:

https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

[Bitsyncmaster]

Good idea. Any trick to keeping the hose in the hole while you're above the engine and can't hold both things at the same time? I don't have a helper at my disposal.

I had not problem just sticking it in a few inches. I'm talking about the hose so no wise cracks.

[DMCMW Dave]

If it is a gear whine that isn't improved by adding differential fluid back in, what would have been damaged and what do you eventually need to do to correct it?

Replace the differential. it is not really practical to replace just the gears. This is not as bad as it sounds since used ones are pretty readily available, this is the only failure. People sometimes replace an entire faulty automatic trans due to clutch or hub failure, but the differential (a completely separate part) is still in fine condition and available for this sort of repair.

The damage is that you've worn the face (case) hardening off the surface of the hypoid gears, so they don't mesh properly any more and now make noise. Damage is done, and other than the noise there really isn't any harm in continuing to drive it like that for a long time.

It really is a gear whine, not a rumble or flutter. Sorry - sounds/feels are hard to put into typed words.