Well I rescued a g body 8-1/2 rear. The fellow I bought it from said it came from a Grand Prix. I'm not so sure. On the axle tube is stamped 6 TR G 332. It is a posi, with 3.73 gears in it . The ring gear has 3988518 11 41 11 83 stamped on it. It has 9-1/2 X 2 inch brakes and I think metric studs. I say I think because some clever person welded in 7 metric bolts in place of some of the studs. They are the correct thread (12 X 1.5), but they have to go. So while I'm redrilling the axles for 7/16 X 20 studs I figured I would ask here. What do you think I have as far as where it came from?
8-1/2 identification
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Easiest way to be sure is to compare the rear to the pics in this thread.
viewtopic.php?f=14&t=18896
viewtopic.php?f=14&t=18896
Actually, I was hoping one of the hard core code/ part number guys would be able to figure out what the origin was. I know what it is, just wanna know where it came from. One of the joys of a "swap car" (of which I have created several) is having the "ancestry" if you will of the different stuff you swap in. Limits your grief when you go to the parts store and there are no books to be had, just people who ask you the same litany of questions as they scroll though computer menus. I miss having a good, local, parts house operated by old guys who know their stuff.
Are you sure it is 6 TR and not 6 TF or maybe an 8 TR? Reason I ask, I have the books (actually computer system) to look up the axle codes, in 84 6 TR mean a 7.5 3.73 posi, can't find any 8.5 for a G body with 6TR in any year. However your ring gear part# does coincide with an 8.5 3.73. On another note the books are not always right. (oh and any GM dealer can do this, not all know how) 
The easiest way to tell an 8.5 rear from a 7.5 is to look at the bottom lip of it. If one side of the little triangle "fangs" are attached to the pumpkin and theyre hanging down its a 7.5. If two sides are attached and it looks like the triangle is attached on 2 sides its an 8.5.
Theyre pretty easy to tell when you actually get under the car. Thats always my give away for pictures, despite the fact that I try and confirm with others too.
Theyre pretty easy to tell when you actually get under the car. Thats always my give away for pictures, despite the fact that I try and confirm with others too.
I'm reasonably sure about the 6TR. I'm going to wire brush it and double check. I understand the G says it was made in / at Detroit and based on the Julian code, early in a model year. After that, I'm without answers. There were no Gbody Pontiac offerings that came with a 8-1/2 that I can find, unless maybe it was some special order. If they even did such a thing then.Oldsmoletick said:Are you sure it is 6 TR and not 6 TF or maybe an 8 TR? Reason I ask, I have the books (actually computer system) to look up the axle codes, in 84 6 TR mean a 7.5 3.73 posi, can't find any 8.5 for a G body with 6TR in any year. However your ring gear part# does coincide with an 8.5 3.73. On another note the books are not always right. (oh and any GM dealer can do this, not all know how)
Thanks for all the answers so far, I'm sure the answer is out there.
This topic got me to go out and check my 1984 H/O rear end. The code stamped on the axle tube ( these are the only numbers and letters stamped on the axle tube! ) is: 6 TF G 209. 6=(?) TF= conventional rear G= Chevrolet gear and axle 209= calendar days it was produced. No indication of which shift it was built on.
I have the 200R4 trans from the same vehicle.
Doug
I have the 200R4 trans from the same vehicle.
Doug
Ah ha! I'm reading the julian date wrong then. I also found the "sun" in the center casting plus "K116(or 8 )". The sun was pointing straight up,which would indicate mid day. And after wire brushing, it is still 6 TR G 332. So perhaps based on the post above, it is an Oldsmobile axle after all. I love a good mystery.
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