Here's the actual problem:
The driveshaft has separated.
They are two pieces of sheetmetal, bonded together with rtv.
The RTV lets go.
Ive had two fail. One was loose, and rattled; the other spun inside itself.
I thought I blew the tranny, lol.
High speed interstate driving killed mine; the new car I bought got a new one the first week.
Search my posts from ~2005; I had several threads on "Vibration problem"
BTW, If the tailshaft bolts are loose, the tailshaft bushing and seal are wasted as well.
It also put a funny pattern in the bearings in the rear wheels, as well as took out the diff gears. (vibration was bad before it failed)
It killed the tranny, being perpetually low on fluid, (0-1 qt low will kill it, eventually)
While replacing the tranny, I found the bad driveshaft; it sounded like a baby rattle when shook.
It was loose from end to end, 2 separate pieces.
The spec sheet from sccoa says it's "collapsable" WETF that means.
Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.
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