What kind of car did my 8.75 come out of?

[WH23G3G]

Is there anyway to break it down to what vehicle my 8.75 rear end came out of? I know it's a 3.91 limited slip with the small pinion stem diameter. I remember researching the casting number on the side one time. But is there a way to find out what model it came from? Would it tell you what size driveshaft yokes should be used? It's going to a 727 and a 400 big block both non-original to my 73 Charger. It was originally a 318 car no idea what rear end it should have in it. Probably an 8.25. So I don't know if the previous owner swapped the rear end out and didn't get the driveshaft or reused the old 318 driveshaft. It vibrates like crazy at 65+ mph. When I took it a few years ago to have it balanced the first shop said it was junk and that it didn't go into the transmission far enough. The next shop said it was ok. So I don't know who was right but obviously something isn't right. I was told by two different mechanics that drove it that the driveshaft needs to be replaced or balanced.

[birdsandbees]

I removed all doubt on mine yesterday... Thought we'd pulled mine out of a '68charger... it was a 66!

[crj1968]

Well you could measure the distance center to center of spring perches and narrow it down a bit....by body style/year.

But since it is in a 73 I'm not sure there will be a right size OEM drive shaft out there. Could be your drive shaft is too short like first guy told you.

How much of the yoke can you see sticking out of the trans tailshaft?

[crj1968]

here is a link for drum to drum measurements- I know theres a perch to perch one out there somewhere too

http://www.bigblockmopar.nl/tech/mopar-rearaxle-dimensions/


der......it's all there if you scroll down.   

[RallyeMike]

It's a pretty sure bet no 73 Charger came with 3.91 small yoke, but what it came out of won't fix the problem.

Start with the easy stuff - 1) driveshaft length and balance, 2) tire balance, 3) then checking pinion angle. If you post your yoke to yoke measurement here, someone can verify. A driveshaft shop can check your tube and rebalance for not a lot of dough.

[John_Kunkel]

Wrong pinion angle is a guaranteed vibration, especially with the driveshaft speed associated with 3.91 gears.

[hemihead]

Make sure your U Joints are good and Trans Mount also .