99 tacoma prerunner 2.7 sb auto/ driveline problems

I just bought a 99 tacoma prerunner 2.7 shortbed automatic . The last owner ran over a stump and hit the rear end, so they replace the rear end , one leaf spring , shocks , muffler ect . He had a drive shaft built for it but had the wrong flange installed on it . So ( for some odd reason ) he thought it would be a good idea to drill holes in the tail shaft flange on the transmission. So now it has extra holes in it , and the truck has an awful driveline vibration especially around 80 it feels like the rearend is coming out from under it . What id like some help with is what exactly is the flange on the back of the tail shaft called I can’t find the part to save my life . Also does anyone have any experience changing this part and how hard is it . Thanks for any help you guys can give .

 

Is this guy my cousins husband? Lol, his name Rob? Oh mannn, so you need to find a flange that fits the “custom” shaft or are you going back to original? That flange is a female spline held on w/ a big nut. I can’t find a drawing for it, you might want to check with a tranny shop as it actually is a tranny part. Good luck!