it is quite possible your cat has broken up internally and the pieces are rattling against the outer walls

What part of the exhaust did you replace?

Is there any chance it could be the heat shield on the catalytic converter?

Probably you would have noticed but sometimes things are hiding in plain sight.


--
'80 DL 2 door, '89 DL Wagon

How many miles, please?

And the transmission fluid is a bright, pink color, clear? How long since your replaced or performed the transmission fluid flush. That AW-70 specifies the GM Dexron III. While GM no longer support the spec, you can find quality Dexron III fluid. Some will flush with dino Dexron III, then go to a synthetic like Mobile 1 Dexron III or some such.

This board is rife with such information. Please try the search feature and use Google to target www.brickboard.com/RWD/

The transmission fluid does not smell strongly of phenolic like burning PC or circuit board, hot brake on a large over the road tracker trailer after it descends a steep grade, and the like.

While your fluid may be clean, if the filter screen, accessible by dropping the transmission oil sump pan, and checking for chunks of friction disk. In spite of the screen, these chunk may be small enough to futz with the overdrive solenoid valve body. When dropping the pan on these AW series, please employ great care when separating the transmission dip stick tube from the pan.

Same care required should you need to remove the transmission lines to the transmission fluid cooling portion of your radiator.

Though not sounding like a failing U-Joint, have to twist tested all three U-joints. And you know of the bright buzzing, hissing, whining sound of a failing drive shaft center support bearing? Best heard at about 25-45 MPH, with passenger windows down, with a high curb paralleling your track. The curb does nicely to reflect the sound back into the passenger compartment.

If coming from your non lockup AW-70, see issues with a clogged screen filter in the 700-900-90 FAQ:

https://www.brickboard.com/FAQ/700-900/TransmissionAuto.htm

And see:

https://www.brickboard.com/RWD/index.htm?id=718253&show_all=1

http://forums.turbobricks.com/showthread.php?t=288068

http://www.nuceng.ca/bill/volvo/database/tranny.htm

https://www.brickboard.com/RWD/index.htm?id=718253&show_all=1

http://www.volvo-forums.com/t19734-aw-70-transmission-servicing.htm

If a failing transmission, you can find replacement such as upgrade to the AW-71. These transmision are found on other cars, like Toyota, I guess.

Again, how many miles. With care, these transmissions can last for quite some time.

Though most people that purchase RWD Volvo autos neglect the crap out of them, believing these RWD Volvos are nearly invulnerable, and that just ain't true.

RWD Volvos are nearly invulnerable, with care, and love, and you drive them. A RWD Volvo dies if left to sit, unless you mean to properly store it.

Though other brickboard members here are vastly more qualified to answer your question than I with respect to the AW-xx series.

I'll fix, 'em ...

Questions?

Hope that helps.

Manual M47 II Transmission Boyeeeeeeeeeeeeeeeeeeeeeeeeeeeee on my RWD Volvo.
--
The Volvo 164: The Mightiest of All Volvo Automobiles in Perpetuity

I believe you can go to www.advanceautoparts.com and get the standard Dacco reman torque converter. The best part being that you can use their online coupon codes and get up to 20% off typically.

I have a similar problem: a metallic hissing when the transmission is torqued by the throttle. Let off the throttle and the car coasts silently. I have contemplated swapping the torque converter, but the last time I separated the transmission, it was so much fun I vowed not to do so again unless I was going to be certain of fixing the problem. I am not 100% sure the pump isn't the problem, nor am I sure the clutch packs haven't suffered any overheating or wear from slipping due to the torque converter issue.

Please let us know how it turns out.