87 Accord Automatic transmission SHAKES terribly while in drive and stopped -- help!

I've worked on this car a lot. 1987 accord, carb, auto trans, with very low miles--50,000. Yes, 50,000 original miles after 20 years.
The remaining problem now is that the car shakes and rattles while at a
stop. When it's in park or neutral, it's not bad. But when it's in gear it sounds like a jackhammer, so I generally have to shift out of gear at every stop light. The shake isn't visible from outside the car, nor is it apparent while looking at the engine, but inside the car it sounds like a jackhammer. Loud, as the dash rattles all over. The dash is not loose, nor has it even been removed as far as I know. While driving or moving over 5mph, there's no abnormal noise. But when stopped it's terrible. Same in reverse or other gears. Otherwise it works great.
It passes smog here in california, which tells me that it's pretty well tuned. When the idle is over around 1100, the jackhammer is much quieter, but the car is tugging and that doesn't feel right. When set at factory recommended idle of 750, it's awful.
My only remaining guess is that it might be the transmission fluid. I changed it over a year ago and it didn't really make any difference. I used dexron 3, or mercon or whatever the manual says, but it's not oem. If anyone is sure that the oem ripoff fluid will fix it, I'm happy to pay the $30 extra or whatever, but otherwise I don't want to waste any more time & money. It's not due for a change. It just seems to me that there's so little wear on the car, that it HAS to be easily fixable. But for all I know, there's something wrong with the trans.
This car belonged to my grandmother, and I don't remember it being noisy at all, but as long as I've had it, it's been fairly loud. Are these cars supposed to be fairly quiet inside the cabin? Is it possible for a non-standard muffler to cause this stuff? Help please!
Thanks. Greg
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On Wed, 03 Jan 2007 01:12:32 -0800, Greg wrote:

Perhaps a faulty motor mount? they have rubber that will wear over time, and could easily present itself at low RPM...
While I don't think your transmission is the problem at all, I would always recommend using the OEM fluid as opposed to the off the shelf stuff.
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Sounds like the rear engine mount. Some Accords have a hydraulic rear engine mount, which can fail in the manner you describe.
Have the mounts inspected.

Replacing the fluid now could be a dicey proposition. You may dislodge crud that may plug the valve body. But if you don't replace it, that will cause damage as well.
Your car takes ordinary Dexron-III.

They are, but over time noise intruses into the inyterior as the sound- proofing ages.

Yes. But you may simply have an exhaust leak somewhere.
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Thanks guys for the responses. Yes, motor mounts. I forgot to mention that. That was one of the first things I suspected. I replaced the torsion mount (name?), and it was somewhat worn, but replacing didn't make much difference. I think my mechanic looked at the other motor mounts, and said they looked ok. They're kind of pricy, and not quick to install I understand, so is there a way to see if they're bad by looking at them? Please tell me how to locate them on the car.
Greg
Tegger wrote:

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The mounts are pretty obvious (you have four), but the one at the rear is hard to see without lying on the engine and peering down the back with a flashlight.
I don't have a manual for your car so I don't know if you have one of those fancy hydraulic rear mounts. If you do, there will be lines coming out of it.
How do you check to see if it's bad? Start engine, warm up until idle drops to the point where it vibrates. Use pry bar on the two upper side mounts to torque engine forward so the rear mount is unloaded. Vibration stops? Answer found.
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and only automatic tranny versions had them) is on the passenger side while the control valve is on the firewall, near the top, almost dead center. It's a small device with a connector on top and two hoses beneath; one goes to the manifold and one goes to the mount.
With the engine in gear and somebody you trust holding the brake, you can probably just squeeze your hand in to help the lever on the valve move. If that smooths the engine out, you can try silicone lubricant on the actuating lever. I hope you have more sucess than I did :-(
Mike
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