My '85 MGM, "Maisa"

[DerekTheGreat]

I've gotten into the audio hobby. Turns out I listen to music far more than I drive or even feel like driving my old stuff.

[gadget73]

Not sure if this helps, but a loose pinion has noise on decel, too tight is noise on acceleration.

this, and crush collars are far more likely to make it loose. Had this on the Continental, inadvertently fixed it when I replaced the pinion seal because I wound it back up to spec as per the service manual instructions. Rear in that thing is perfectly quiet with so far as I know just north of 200k miles on it.

[Arquemann]

Took her for a proper test drive, really checked out how the whine comes and goes.
Whine is present from ~70 to a bit under 80 km/h. But it is actually present on heavier throttle, and disappears off throttle.
Can't really make heads or tails if the rear whines in other situations, the trans makes some noise.

So whine on acceleration/on throttle would indicate more of gear mesh issue than bearings, right?
Atleast the pinion bearing shouldn't be too tight, since no one's touched the pinion nut in ages, or probably ever.

So either something started making glitter in the rear end and is currently wiping out the gearing and bearings. I'd have thought that in that case the bearings would start whining faster than the gears.
or
this is just a stupid coincidence.


Also in my everlasting hunt for eliminating rattles, I managed to break the passenger front door lock/unlock indicator nub. The rod didn't want to come off and decided to break the bottom of the piece. Managed to save the piece and the locking clip, so hopefully my superduper strong epoxy will keep it together. Stupid old plastic.
Pissed me off but I atleast found the rattle on the pass. front door panel.

[Tiggie]

So whine on acceleration/on throttle would indicate more of gear mesh issue than bearings, right?
Atleast the pinion bearing shouldn't be too tight, since no one's touched the pinion nut in ages, or probably ever.

My bad bearing experience was been more of a growl that is continuous and increases in pitch with speed. Never had a pinion bearing issue but it could be that headed south. Not sure what I'd do in your case. Maybe slip a magnet in there and put that 75w-140 in to see if that helps and then if not, the magnet will at least let you know something is going bad quickly.

[Arquemann]

My bad bearing experience was been more of a growl that is continuous and increases in pitch with speed. Never had a pinion bearing issue but it could be that headed south. Not sure what I'd do in your case. Maybe slip a magnet in there and put that 75w-140 in to see if that helps and then if not, the magnet will at least let you know something is going bad quickly.

Can't really put a magnet in there without popping the cover. Or does someone have a trick up their sleeve for that?
If something's making glitter in there, could I see it just dropping the oil? It's had 2 oil changes within 100 miles, so the fluid ought to be pretty clear.

Changing the oil (for the third time) for 75W-140 and looking for glitter wouldn't be too bad and maybe I'd see if there's glitter in there. Dumb thing is the availability of 75W-140... I can get 9.99€ bottles of 80W-90 in whatever flavor pretty much anywhere, but 140 is hard to find. One chain sells a no name brand for 15€ per liter and one store sells Red Line 140 for 28€ per liter! Dummy expensive!

[87GrandMarq]

Do you have a pic of that little clip that holds the lock rods on the slider? I lost mine years ago in the 87 and would like to get replacements.

[DerekTheGreat]

The trick is to just get one large, very powerful magnet and slap it on the cover somewhere along the bottom, adjacent to the ring gear.

[Arquemann]

Do you have a pic of that little clip that holds the lock rods on the slider? I lost mine years ago in the 87 and would like to get replacements.

Just a tiny D shaped spring clip. Bet you could "borrow" a bobby pin off a gf/wife/sister/mother and bend and shorten it a bit.

[87GrandMarq]

Just a tiny D shaped spring clip. Bet you could "borrow" a bobby pin off a gf/wife/sister/mother and bend and shorten it a bit.

Perfect thank you. These tiny things are unobtainium and I couldn’t find any pics of them.

[Arquemann]

Popped a couple of thumb-sized neodymium magnets on the diff cover.
While the rear was on jackstands, I put it in gear while running, I can't hear anything else than the drums. Wheelbearings didn't feel any looser than before (with the new bearings).

Reassembled the pass front door arm rest and trim after hopefully fixing a couple possible rattles.
I noticed that the second from front screw for the "wood" trim bottoms out and breaks/bends the arm rest piece. I've got 4 identical screws. The other middle screw has a clearance hole made for it. I just put in a shorter screw for that one.
Are these supposed to have different length screws or is it some sort of oversight?

[sly]

There should be a short screw in that location and the long screws got into the door itself through the panel.

[gadget73]

yeah the hardware mix and match on these things is sort of obnoxious.

[Arquemann]

I had enough of guessing what was going on in my diff, so I popped off the cover again!
No chunks, no shavings, no smoking gun and only a little bit of glitter.

Thoughts:
- Everything is shiny! When I opened the diff first time around, everything was black. A whole lot of oil washing has happened, and all that crap has to go somewhere, aka into the oil.
- This time I tilted the axle and the fluid from the axle tubes was still quite black, I guess the diff fluid doesn't circulate too well.
- Gear mesh pattern looks fine, surfaces are smooth, initially it looked like the drive side was touching barely at the crown of the teeth, but it's actually in the middle just fine.
- Magnets gathered some crap, which looks way worse in the pics than in person. There's no depth to that in person, also way blacker. Doesn't even feel gritty between fingertips.
- A bit of glitter settled into the pan, again looks worse in pics, also the pan was dirty, those larger bits were there before, most likely.

What I'm gonna do is get a new gasket on monday, sploot in some 75W-140 (probably 85W-140 due to availability) and get on with my life.

Pics:

[jaywish]

You can just use RTV, I use black. I always let it have a final dry overnight and never had a drop of seepage. Do you have instructions on this procedure?

[Arquemann]

You can just use RTV, I use black. I always let it have a final dry overnight and never had a drop of seepage. Do you have instructions on this procedure?

I thought of using just RTV, but I find it kind of hit n miss on too much / too little RTV. Maybe I'm just picky, or maybe I was just lazy today and needed an excuse to quit early. I'm driving close by the US parts store tomorrow anyways, so I'll spend the 10€ and feel a bit better about the rear end. I put a light smear of RTV on the gasket anyways. I dunno who I'm fooling...