kinda a long read so thanks in advance to anyone who responds!!! its much appreciated!!! first 5 paragraphs are an overview of everything that broke in the past for the point skip to last two...

So I've had quite a bad year for my drive line so far... The basic rundown is 3-4 clutches began slipping about a yr. ago, had a local shop do their performance build on it. dont remember everything but included; 3k stall, beast sunshell, billit servo's, alto clutchbands, transgo shift kit, zmax pack, ect. that lasted 18,000mi.

Then my pump stator or roter broke in half and took out the trans. pump, my flexplate was also cracked @ all three holes out towards the ring gear....
stator, pump and flexplate were replaced, only piece upgraded i believe was the flexplate for an s.f.I. approved piece. that lasted two days...

First w.o.t. run I snapped my output shaft which took out i think the rear shell, rear planet ect. and cracked the trans. case... upgraded to 5 pinion rear planetaries, and hardened output shaft, replaced the rest with stock parts... had some vibes mostly in manuel 3rd gear and more noticable on decel. didnt think too much of it since I have a prothane trans. mount...

two weeks later I blew my 10 bolt @ 3/4 throttle in 1st, snapped every tooth off the pinion gear, ring wasnt much better, torsion lsd was replaced also. upgraded to 3.73 from stock 3.23 ... when I picked it up I had a bad driveline vibration, found my driveshaft was about a 1/8th of a turn twisted and was bubbling @ the twist, replaced with stock used aluminum piece...

about 2 months later brings me up to date have a few dozen wot 1/4 mi. runs since the rear went everything was ok till last friday night was running some evo's out in the country and started to notice the vibes getting worse.

So the next day I'm on the freeway and its vibrating pretty bad! 3rd gear is more of a pulsating vibration especially on decel which really seems to be something internal... 4th is more of a steady viberation... anything over 80 in 3rd or 4th and it feels like its going to come apart on me. then I checked manual 2nd when i got in town and it was realy smooth before but is now vibing pretty bad on accel and decel now...
Was hoping it was just the replacement driveshaft but I pulled it off today and ran the car with it out and was still getting the vibrations pretty bad... didnt want to take it too fast cuz i'm not sure if its bad for it? but I took it up to 80 without the ds in and the whole car was shaking...
When i put it in neutral the output shaft was still spinning and it was still vibrating (is this normal?) So I know I should go with a sponsors race built trans soon and I plan on it but in the meantime anyone have a guess to my problem? could it be my flexplate, converter or something internal in the trans? has anyone else experienced the kind of pulsating vibration i'm experiencing the worst in 3rd???

 

It is possible the rear failing damaged the transmission, Its also possible that the rear case bushing in the trans is damaged or missing. Just some ideas

 

ok went to the shop today and took a drive with the owner, he seemed more intrestead that its vibrating when in neutral and the rpm's are raised, he seems to think its a converter issue. The brand he used was d&b out of sacramento I believe and its a 3k stall, he said something about he remembered it being a wierd fit So idk...

 

so does this rear case bushing keep the output shaft perfectly centered even with the d.s. removed? I ask cuz when I ran it in gear and looked at it while spinning the output shaft did seem to be somewhat wobbly... But with the d.s. in its a pretty snug fit to the rear seal, wouldnt that keep it stabilized

 

Yes it would ,

 

did you ever figure this problem out?