'81 U-joint bolts - size of heads

[John Chesher]

My '81 appears to have the factory bolts holding the U-joint straps to the front drive shaft/tranny yoke. They are the ones with the small 12-point heads. Can anyone confirm the size of the heads? They are larger than a 6mm and smaller than a 7mm, so I am guessing 1/4" SAE, but I don't have SAE 12-point sockets that small. Can anyone confirm the size of those bolt heads before I head out to the tool store?
Thanks!

[Joe L.]

Re: '81 U-joint bolts - size of heads

John------

I can't tell you what size socket you need, but it's going to be a very small SAE size. The bolts used for the 1981 with auto trans are 1/4-20 X 5/8". A standard hex head bolt of this size uses a 7/16" socket. So, you'll be talking about 3/8" or 5/16" 12 point socket. You'll probably have to use a 1/4" drive ratchet and socket.

The 1981 with 4 speed uses different bolts. They are 5/16-24 X 3/4". Once again, the size for 12 point heads will be quite small---perhaps 3/8".

It might be time to buy yourself a 1/4" drive ratchet and 12 point socket set. They aren't too expensive. I certainly wouldn't be without one in my tool inventory. In fact, my set came in handy just today.

[John H.]

Re: '81 U-joint bolts - size of heads

The SAE fastener standard for 12-point bolts calls for a 5/16" 12-point head on a 1/4" bolt and a 3/8" 12-point head on a 5/16" bolt.

[Harmon C.]

Re: '81 U-joint bolts - size of heads

That socket set will come in handy if you need to adjust your T-Tops also.

Lyle