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U-Joint conundrums

unik5

unik5

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Littleton, Colorado
Hey all I have been having some confusion in the past 48 hours. I've got an '87 Jimmy with a 12 bolt rear end:rolleyes: . Basically I need to replace both rear u-joints:whistle:. I know that the 12bolt uses the 1310 size u-joint. My confusion is the size of the driveshaft. Napa part #348 fit the drive shaft side. So Im wondering if the driveshaft might be bigger? Or if I was supposed to use the spicer? u-joint and hopefully didn't mess up my driveshaft. I did research but im at the point that I am confusing myself:doah:which is why im posting. I bought napa 348 for the slip yoke side thinking it would work too but the caps are too small slip yoke side... Here is a picture of the cap that came from the slip yoke (np208)
IMG_0665.jpg

Any help would be greatly appreciated :bow:

IMG_0665.jpg
 
You will need a conversion u-joint since the 87 never came with a 12 bolt and it uses a different u-joint than the 10 bolt axle and the blazer.
 
4X4HIGH said:
You will need a conversion u-joint since the 87 never came with a 12 bolt and it uses a different u-joint than the 10 bolt axle and the blazer.
Click to expand...

Yup, and that's exactly what is under my '90 Blazer. Should need PN # 5-3022X which converts a S44 to 1310.
 
Thanks for the links tRusty thats alot of info to look at. The thing confusing me is that the 1350 side of the Napa 348 ujoint fit into the driveshaft. I thought it was supposed to be the s44 size but then the napa 348 was in there when I bought the truck. I see the cap dia. for the s44 is 1.125 and the dia. for the 1350 is 1.188. would this be enough for them to be "interchangeable" in a way

edit* the slip yoke caps had the inside locking clips i guess you would call it. WOuld that make it the spicer? and 1310 is definitely not the size for the slip yoke or the driveshaft
 
unik5 said:
Thanks for the links tRusty thats alot of info to look at. The thing confusing me is that the 1350 side of the Napa 348 ujoint fit into the driveshaft. I thought it was supposed to be the s44 size but then the napa 348 was in there when I bought the truck. I see the cap dia. for the s44 is 1.125 and the dia. for the 1350 is 1.188. would this be enough for them to be "interchangeable" in a way

edit* the slip yoke caps had the inside locking clips i guess you would call it. WOuld that make it the spicer? and 1310 is definitely not the size for the slip yoke or the driveshaft
Click to expand...

No way shape or form will a 1.188" diameter cap fit into a smaller hole of 1.125"

Spicer is merely a brand name not anything to do with the sizing of the u-joint. You just need to measure the diameter of the caps that came out of the driveshaft and know if they are internal or external clips and if external then also the distance between the clips, then measure the diameter of the cap that was in the pinion Yoke and also the width between the "ears" of the Yoke and we can help you get the correct u-joint.
 
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Yup, this is where a set of calipers come in really handy.

I feel your pain, having BTDT with my '90. The funny part for me is I ASSUMED my '90 had a 10 bolt. It was only much later that I even looked at the cover and saw 12 bolts. Apparently someone fragged the original 10 bolt and this 12 bolt was handy and had the same (poor) gearing... :rolleyes:

The Dana site is a good resource, and the page I linked for you is only one of about a dozen or so. :haha:

What I did was jot down the Spicer number and take it to my local auto parts place. They don't carry Spicer, but were easily able to cross reference the number and get me the equivalent U-joint in another brand.

I see the cap dia. for the s44 is 1.125 and the dia. for the 1350 is 1.188. would this be enough for them to be "interchangeable" in a way
Click to expand...

It might go together, but it'd fail in short order. Cup size and yoke size is pretty crucial.
 
Okay i measured thecaps via micrometer.
The slipe yoke caps with inside clips measured 1.1254. Ear to ear is approx 3.575
The driveshaft side with outside clips measured 1.1885. Ear to ear is 3.625
Hopefully these help a bit. S44 to 1350 perhaps?

**Fixed!!** The napa 447 did the trick. Thanks for all the help:thumb:
 
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