12 bolt yokes not the same

[BigRandy]

I got a rearend to replace one with bad gears. I thought it was bearings but turned out the gears were bad.

Bought another 12 bolt that came from an 81 C10 small block but the yoke is narrower by almost a half inch than the one that came with my 74-454 (3.2" and 3.6" between tabs). Is there a special u--joint I need to look for? I've searched Google and found as ton of 12 to 10 bolt threads stating the need to replace u-joints but nothing on 12 bolt to 12 bolt with a different yoke.

A u-joint swap (if available) would be easier than a yoke swap and new crush sleeve, but I'll do whatever is needed to get it on the road again.

Thanks

[kwmech]

What about the diameter of the caps? I'll bet the 3.6 has 1.188 diameter which would be a 1350 joint. Where as the 3.2 is 1.062. If that is the case there is a conversion joint to go from 1310 to 1350

[Mike C]

Big block trucks had different u-joints. I just rebuilt the shaft in my '71 GMC big block 402 with new joints and was surprised to find both 1330 and 1350 joints in the two piece unit, but no 1310 that the previous 12 bolts I've worked with always had.

[BigRandy]

Originally Posted by kwmech

What about the diameter of the caps? I'll bet the 3.6 has 1.188 diameter which would be a 1350 joint. Where as the 3.2 is 1.062. If that is the case there is a conversion joint to go from 1310 to 1350

That's what I expected but it wasn't what I found today.

My old one that is 3.6" wide has a cap diameter of 1.06.

The "new" yoke I need to match is 3.2" wide and also has a 1.06 cap.

TBH I don't actually have a cap for the replacement to measure. I used a digital caliper and measured the inside center of the yoke. It's identical to the old one. Far as I can tell the narrower width on the replacement is the only difference. Thanks

[kwmech]

So you need a 1310/1330 conversion joint spicer number 5-134x

[BigRandy]

Originally Posted by kwmech

So you need a 1310/1330 conversion joint spicer number 5-134x

Great! Much appreciated

[BigRandy]

One last question (maybe), does anyone know if I can swap the yokes around?

I'm on the fence about getting a conversion u-joint that is narrower and could leave me with a weak spot in the driveline. It's just a stock motor but I figure GM must have had a reason for using the wider u-joint with 454's.

The rearend is on the ground so if I need to swap yokes and reset the preload now would be the time for it.

Thanks

[YoungPup1977]

Using a combination / conversion U joint is not weaker. If you had a 400 hp engine maybe be concerned.....but it sounds like you don’t.

You replaced the old diff with a used diff so why would you take the chance on taking the good used diff flange and change it. Not knowing how to make sure you change it correctly. This is why you bought a “good” used diff. Right ?
Posted via Mobile Device

[BigRandy]

Originally Posted by YoungPup1977

You replaced the old diff with a used diff so why would you take the chance on taking the good used diff flange and change it. Not knowing how to make sure you change it correctly. This is why you bought a “good” used diff. Right ?
Posted via Mobile Device

Mostly.

The 373's needs pinion bearings and spider gears. R&P aren't chipped but the teeth have a have a hazy-brushed look. I posted pics asking someone to take a look and tell me if they were worth using but did not get a reply.

I wold have been willing to take a shot at replacing pinion bearings. but not willing to gut it and find out I may also need all bearings plus all new gears. And if I had gone that route wold have still ended up with 373's which I don't want or need for highway use. To go with a higher gear would require a carrier change as well and that's just more than I wanted to tackle on a first time rebuild.

I was hoping to get a straight answer to my pinion swap question but I didn't so I'll look elsewhere.

[kwmech]

Leave the yoke where it is unless you are adept to getting the bearing preload where it is supposed to be with a crush sleeve. Nothing wrong with the strength of a conversion yoke, it's done all the time.

[BigRandy]

Originally Posted by kwmech

Leave the yoke where it is unless you are adept to getting the bearing preload where it is supposed to be with a crush sleeve. Nothing wrong with the strength of a conversion yoke, it's done all the time.

Will get one tomorrow and wrap it up. Thanks!

[BigRandy]

It's a wrap. Everything is in place and working fine and I'm VERY glad to be rid of those 3.73's.

Pretty sure I was overthinking or over complicating this and I really appreciate all the advice and and suggestions.