U-Joint cap size (1.063 vs 1.078 vs 1.125) ?!

[MoPar~Man]

I don't know if this is a year-thing, or Dodge/Chrysler/Plymouth thing, or Canada vs US thing, but when looking at rockauto for ujoints for my '67 Canadian Monaco that came with poly 318, RA is listing ujoints with cap diameters of 1.063, 1.078, and 1.125 inches.

A year+ ago when acquiring parts, I bought a 1.063 and 1.125 joints, not knowing which one I actually needed. The manual doesn't spec the cap diameter.

Fast forward to today. After wrestling with the drive shaft, I have the front joint out, and yes, it's 1.078.

Is there any knowledge base out there that knows which C-bodies have which siize U-joint caps?

And regardless what the size is, is it the same for front and back?

 

[1970FuryConv]

I don't know if this is a year-thing, or Dodge/Chrysler/Plymouth thing, or Canada vs US thing, but when looking at rockauto for ujoints for my '67 Canadian Monaco that came with poly 318, RA is listing ujoints with cap diameters of 1.063, 1.078, and 1.125 inches.

A year+ ago when acquiring parts, I bought a 1.063 and 1.125 joints, not knowing which one I actually needed. The manual doesn't spec the cap diameter.

Fast forward to today. After wrestling with the drive shaft, I have the front joint out, and yes, it's 1.078.

Is there any knowledge base out there that knows which C-bodies have which siize U-joint caps?

And regardless what the size is, is it the same for front and back?

For my 1970 Fury I had a big block/727 driveshaft and 318/904 driveshaft
Both rear u-joints were 3 3/8" wide with 3 1/4" wide pinion yoke. I used NAPA 246 u-joint, 1.078 caps
Front u-joints were 3" W for 904, 3 1/8" W for 727. I think NAPA P# is 315, but I did not replace front u-joint

 

[Big_John]

AFAIK, the smaller 1.062" diameter U-joint is used on a 7 1/4" and 8 1/4 rear. That (7 1/4) would only be used in an A body. I think that is a 1310 u-joint

The 1.078" is the 7260 u-joint and 1.125" is the 7290 u-joint. Generally speaking, the larger u-joint is in big block cars, but I always say to check first. These you will see in 8 3/4" rears and Dana rears (B/E body)

7260 and 7290 are easily identifiable by the width of the u-joint. 7260 is 2 1/8" inside dimension and 7290 is 2 5/8" inside dimension.

 

[MoPar~Man]

So you guys are saying that not only do I have to look for the right cap diameter (1.078) but I also have to measure the width?

Is the 1.078 a common or uncommon size for a c-body? Or a slab C-body? (yes I have 8 3/4 rear, 2.95 gears, 727 transmission, 318 poly (now LA 318).

 

[Big_John]

So you guys are saying that not only do I have to look for the right cap diameter (1.078) but I also have to measure the width?

Is the 1.078 a common or uncommon size for a c-body? Or a slab C-body? (yes I have 8 3/4 rear, 2.95 gears, 727 transmission, 318 poly (now LA 318).

Not really. You don't need to measure the cap diameter. The only u-joint you are going to encounter in a car like yours is the 7260 or the 7290. That's a quick check with a ruler. AFAIK, those are the only two u-joints with the 8 3/4" in a car.

Chances are, with the 318, you are going to see the smaller 7260 u-joint, but I always advise to double check... While it's generally excepted that the 7290 is a big block application, things could have been changed in the 57 years since the car was built. A rear end change for example or maybe the car just came through with the wrong u-joints. Who knows? The hardest thing will be getting under the car to measure... and the difference is enough that a lot of guys can "eyeball" it. Nothing but a ruler or tape measure needed.

I've also seen guys use that 7260-7290 conversion U-joint when doing a rear swap, so to me it's time well spent figuring out exactly what you have before opening your wallet for new parts.

The 1.078" end cap diameter is the 7260 and 1.125" is the 7290. Those are the two end cap diameters you will find in a car with an 8 3/4 rear ... but you won't find a 7260 with a 1.125 diameter end cap and vice-versa and they don't interchange, so no need to check end cap diameter if you check the u-joint width.

Also... Just to be clear... That 1.062" end cap isn't going to show up on an 8 3/4" rear.

 

[MoPar~Man]

Also... Just to be clear... That 1.062" end cap isn't going to show up on an 8 3/4" rear.

Well, RA is showing 1.063 end caps for '67 Monaco's, even with 383 engine. My first instinct was to see how well the new bearings fit in the hole, and that's how I figured out I have the wrong parts. I wasn't measuring any of the other lengths or widths - didn't know I had to. RA's parts have INFO pages that show dimensions like "Axis 1" and "Axis 2" but without a diagram I have no clue what's being measured.

 

[MoPar~Man]

The Moog 315G specs at RockAuto shows it as 1.078 bearing cap, OE series Detroit 7260. I called a few local retailers and asked for price/availability by that P/N. I also gave them the application (1967 Dodge Monaco) to get the big picture list of what their computers are showing.

Fun-fact: If I give them 1967 Dodge Monaco, they ask for engine size, the only options (on their screen) being 383 and 440. If I give them 1967 Dodge Polara, the 318 then comes up as an engine option.

I'll be getting a couple of the Moog 315G's. $30 CAD ($22 USD) each plus tax.

BTW, the manual says to press on one bearing to pop the opposite side cap out. I tried that in a vice, I was concerned I was bending the yoke arms I was putting so much force on the vice (with 3 ft pipe extension). Caps did not budge. I went to u-tube and found an Uncle Tony video where he pounds them out on a concrete floor with a hammer, banging away at the cross to force the caps out. I ended up doing that, and it worked.

 

[1970FuryConv]

The Moog 315G specs at RockAuto shows it as 1.078 bearing cap, OE series Detroit 7260. I called a few local retailers and asked for price/availability by that P/N. I also gave them the application (1967 Dodge Monaco) to get the big picture list of what their computers are showing.

Fun-fact: If I give them 1967 Dodge Monaco, they ask for engine size, the only options (on their screen) being 383 and 440. If I give them 1967 Dodge Polara, the 318 then comes up as an engine option.

I'll be getting a couple of the Moog 315G's. $30 CAD ($22 USD) each plus tax.

BTW, the manual says to press on one bearing to pop the opposite side cap out. I tried that in a vice, I was concerned I was bending the yoke arms I was putting so much force on the vice (with 3 ft pipe extension). Caps did not budge. I went to u-tube and found an Uncle Tony video where he pounds them out on a concrete floor with a hammer, banging away at the cross to force the caps out. I ended up doing that, and it worked.

I have always used the vise, a nut, and a socket to press out the caps. Never had a problem
I used Napa 246 7260 style u-joint. Interested to heart if 315G works for the rear u-joint.

 

[Big_John]

I have always used the vise, a nut, and a socket to press out the caps. Never had a problem
I used Napa 246 7260 style u-joint. Interested to heart if 315G works for the rear u-joint.
View attachment 676253

I've always done it that way, either in a vise or a press.