[gtobully]

Is this rear end the code for a '66 or '67 Goat?

Thx, rob in nor-cal

[fyrffytr1]

That would be the casting number and I couldn't find it on line. Maybe someone else will be able to help with it.
There should be a two letter code on the passenger axle tube that would help with the ID.
I can tell you that if it is a w_ code it is an open rear and a y_ designates a limited slip. The second letter in either one is the ratio code.

[428goat]

Maybe 71 or 72 pontiac

['ol Pinion head]

Though not an original rear for a '66 or '67, a 9799100 center hsg rear will have tapered bearing axle bearings which is a huge improvement over the old sealed axle bearings. 9799100 was the center housing casting number for a gray iron '70-72 Pontiac 8.2 10 bolt rear. Expect a factory stamped axle tube code for a 2.56, 2.78, 3.08, or 3.23 gearset. '70-72 3.55 4 pinion STT rear would use the nodular center housing, not the 9799100.

[gtobully]

Had rear on jack stands, car in neutral, and did the ol turn one of the rear wheels test to see how much the driveshaft rotates to get the ratio. Mine went 3.5 turns, so I was thinking 3.55, but based on the above maybe it's 3.23.

['ol Pinion head]

Originally Posted by gtobully

Had rear on jack stands, car in neutral, and did the ol turn one of the rear wheels test to see how much the driveshaft rotates to get the ratio. Mine went 3.5 turns, so I was thinking 3.55, but based on the above maybe it's 3.23.

Most likely it's a 3.55, just original dealer did not order as a Safe-T-Track. The 9799100 hag would be correct for that.

[fyrffytr1]

If you can find the two letter code on the passenger side axle tube it would be WF for a 3.23 and WH for a 355.

[gtobully]

The PHS docs say the car came with a 3.55 and Safe-T-Trac.

[jd66]

A little more info for you, my original rear on my sept 65 built 66 GTO has a casting # of 9783893 and a cast date of July 8 65, and ZE stamped on the housing which means 3.08 posi with metallic brakes, hope this helps. jd grim 66 gto