The Stovebolt Site Forums The Shop Area Driveline Rear end yoke/flange?

I have a 1955 1st Series 1/2 pickup, 3speed, 3.9 rear end
It is my understanding that the this was the first year without the tube drive shaft for a 1/2 ton. Please correct me if that isn't correct.

I am looking for the correct part name and part number and locating the rear yoke(?) Flange(?) whatever it's called that goes into the rear differential where the U joint is bolted to, has splines and bolts to the pinon and the seal runs around to seal the differential in the front
I am having a rear leak from that area and have replaced the seal a year or so ago but is still leaking. If I am going to replace the seal again and remove that flange/yoke, I might as well replace it with a NOS or correct new one.

In looking through my parts books, I am confused because of the short model run of the 1st series and the change from the tube type. Should I consider the Yokes/flanges for a 2nd series and newer?

Thanks for any information everyone can provide.

That part is called a companion flange. I'm not sure if is reproduced. The corporate Eaton
rear differential was used from 55 first series through 62. It's unlikely there would be any
difference in that component. If it is worn where the seal rides, a speedy sleeve should
solve the problem.
Fred

Nothing in the parts books references a companion flange? What's a speedy sleeve and where can I get one

The "rear yoke"- - - -"companion flange" etc. is the part where the rear universal joint attaches to the center section of the rear end. Is that part missing? Why do you need to replace it, if it's still there? It's held on by a single, VERY TIGHT nut and flat washer. New yokes are probably not available, since that rear end was discontinued sometime in the late 1950s or early 1960s. A "speedy sleeve" is a thin repair sleeve that is pressed over the seal surface of a yoke to cover a groove worn into it. You would need to measure the diameter of the seal surface and consult a bearing supply company catalog such as Timken, SKB, Bower, etc. to get the right size. Repeated leak problems there are usually caused by one or both of the pinion bearings deteriorating, that allows the pinion shaft to wobble and cause the seal to fail.
Jerry

How so I check to see if my pinion bearings are ok?

If I get a speedy sleeve, wont I need a different pinion seal with a larger circumference then a stock one?

Take the rear end apart and inspect the bearings, and the cones they run in. Be sure to check the tooth contact pattern of the gears BEFORE you disassemble anything, as getting the contact pattern wrong on reassembly will create a permanent gear whine. Use Prussian blue or white lead to check the tooth pattern, and take pictures of the results. A speedy sleeve only increases the diameter by a few thousandths- - - - -which the garter spring on the seal will expand to compensate for. Most garter spring seals will handle diameter differences of +/- .010" or so. Find an old geezer who is familiar with setting up hypoid gears to mentor you- - - - -we're getting about as scarce as honest politicians!
Jerry

Thanks for sharing your knowledge AND Windom

FWIW - The Master Parts Books list the pinion gear u-joint flange as Parts Group 5.545, Flange w/deflector. Earliest open drive '55.1 part number listed was GM# 3708838, which was replaced by GM# 3714791 in '57. The latest number that I could find that fits the '55.1 thru '62 1/2 ton truck pinion shaft is GM# 3741822.

That part number also fits all '55-'62 passenger cars and '55-'59 Corvettes. If you really need to replace it, there are a few used and NOS pieces on ebay, mostly listed as Corvette parts to seek higher prices.

Alternatively, there are many after market companies that offer replacements for the flange, for far less $$$ than the Corvette priced pieces. Just do a web search using "GM# 3741822" and you'll have lots of possibilities to go through.

That's great information Gdads51, it appears that I should be able to purchase a new one.

Here is another question that popped into my head. In the past you marked the flange along with drive shaft to insure they are installed in the same location as removed, I am assuming for balance's sake. Now with the flange removed what's the proper way to reinstall the drive shaft on the new flange?

Thanks again everyone!

My off-the-cuff answer is to reinstall the new flange in the same orientation as the original, if known. The splining and flange u-joint cup spots should match up with your original flange, but never hurts to check and confirm before install.

If original alignment not known, then we need to look for info on the proper "phasing" of the driveshaft flanges/yokes, which IIRC is listed in the Shop Manual. I'd have to go look to confirm where specifically. You could most likely use the 1955 Models (Second Series) Shop manual as that's going to have the same info applicable to your '55 First Series open driveline.

If you're replacing the pinion yoke or flange, it won't really matter which way you put the driveshaft u-joint on it. Phasing is taken care of by the position of the yokes on the driveshaft itself and those don't change unless there's a slip joint involved. That yoke would need to go back on the splined shaft the way it was originally installed. Many times there's a single wide spline, making it dummy-proof.

The driveshaft along with the truck is still together and drivable so I know the current position of the yoke. I was hoping there was a single wide spline, as Klhansen has suggested. I am in the process of ordering a new yoke and seal so it will be a while before I get to it.

I can't thank everyone enough for all the help and suggestions. I can only speak for myself, but I am sure that this forum has kept many, many trucks on the road and keeps my enjoyment of my truck as high as it is.

I will update my work as it advances.

For reference, below is a screenshot of a for sale NOS GM# 3741822 flange. No single wide spline for indexing evident. Would be just too easy - lol! (eye rolling emoji goes here)

If the yoke goes on the pinion shaft, there wouldn't be a need for a wide spline. That's only used on a splined end of the driveshaft to line up the yokes on both ends to keep the shaft in phase. It doesn't matter where on the pinion shaft that yoke installs, as the pinion itself is concentric.

Check this site for a demonstration of driveshaft phasing.

Wow, you learn something every day! That Video was very informative.

Kevin that's an excellent resource! One that I think might benefit our "Big Bolter's" most of all with their multi-piece driveshafts.