The Stovebolt Site Forums The Shop Area Engine Shop Yet Another SM420 Question

There is a part called a "Special Washer" which is used along with a bolt to hold the Universal Joit Front Flange to the Main Shaft. Does anyone know what this "Special Washer" is exactly? What I found in it's place when I dis-assembled the tranny was two not-so-special flat washers. Both washers have a 9/16" ID, but the OD's are 1-3/8" and 1-1/2" and they are both concaved from being torqued down. So my question is has anyone seen one of these so called "Special Washers" or have the dimensions so I might track one down. It would not be a good thing to have my U-Joint fail due to a not-so-special washer. Thanks again for putting up with my ramblings.

Jim

According to the parts books, that washer should be 17/32" ID, 1 5/8" OD, and 5/16" thick. Original GM part number 591472. Don't know what makes it special, besides the extra thickness.

Xram53, Thanks for the info. Does anyone know if this part is available anywhere?

Try a part number search at Partsvoice.

cujo8,

IMHO, what makes this washer "special" is its size..nothing else. I am sure you have come to this same conclusion. I looked in my "special" book for this washer. The ID is standard for a 1/2" bolt, but the OD and thickness are much greater than even a extra-thick washer lists.

Short of a friend with a lathe, you're going to have to search. A machine shop could whip one of these babies out in nano-seconds. It might be more than $1.98, but as my dear old MOM used to say, a bird in hand is worth two in the bush!

Stuart

atomarc, Do you think this washer is heat treated?

cujo8,

I don't know! There are extra-thick washers available in stainless AND case hardened steel. None of these are the proper OD. I would guess that if you look at the yoke, you will see a machined area that accepts the big old washer.


I could see no purpose in heat treating the washer. You indicate there were two funky stacked washers on there before...they worked sort of fine. The bolt with some blue loctite on it and the big fatty washer..all would be well.

I would be more than happy to make you a washer, gratis, and mail it to you. You don't mess around when it comes to work, so I would bet you already have found one and the tranny is in the truck.


Stuart

Stuart, Thanks for the offer to make the washer, but I am all ready on it. I got myself a SBC harmonic balancer washer, which has the proper 5/16" thickness and mounted it to my drill with a bolt, washer, and nut and ran the drill while holding it up to my bench grinder until it measured 1-5/8" OD. I then drilled the washer out to 17/32" on my drill press. Part works great!

I tried Xram53's PartsVoice.com link and They did have the part there for $5.00, but I already made the part myself. But this is excellent link to locate parts in the future. Thank xram53!

Anyone know the bolt dimensions that is used to secure this special washer and U-Joint flange to the output shaft of my SM420? The Grade-8 bolt which was there measures 3/4" long and had 1/2" x 20 fine threads. I am thinking that this will be too short now that I am using the proper thickness washer.

Thanks, Jim

If I'm looking up the right bolt in the parts books, the original was 1-3/8" long.

Thanks Curt! What book do you use to look up this info?

Jim

I have various parts manuals on a CD-ROM that is put out by Detroit Iron Information Systems. I also frequently use this online manual on Keith Hardy's TOCMP site.

Curt, Great link.

Jim