Replaced rear u-joint M1009.
The GM factory u-joints in the M1009 are 3R and glued into the end yokes and slip yoke.
After inspecting my driveshafts by blocking the wheels and putting the truck in neutral with the parking brake released, I found play in the rear u-joint of the rear driveshaft.
It is actually quite common for rear u-joints to go first since they get the worst of the moisture.
I pulled the driveshaft.
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By moving the front slip yoke, I can tell it still moves freely and there is no play.
The rear u-joint was rough and removal of the caps showed a dried up rusty mess.
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Not to fear; the moment has been prepared for.
I had a brand new Spicer 5-795 3R replacement u-joint in hand.
I'm crazy like that.
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When I worked in a driveline service shop we had big arbor presses and those factory glued 3R ujoints would pop out with a pull of the handle and a loud bang.
Well now I am a mechanic on a mountaintop sans arbor press.
Here is what you do.
Carefully heat JUST THE CAP of the old u-joint with a plumbers torch.
DO NOT heat the yoke or tubing.
Have the cross set in between the jaws of a vice and keep a hammer ready.
You are going to need to be very careful doing this so as not to strike the tubing, just the yoke right below the u-joint.
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When you see the glue just starting to bubble out between the cap and end yoke (notice right hand side of cap in picture),
quickly put the torch down and accurately strike the ear of the cast end yoke just below the u-joint cap...
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Repeat for the other side.
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Yep, that chaps had it.
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Now you debur the inside of the end yoke; just take the minimum out to clean it up for the c-clip.
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ready for a 3R inside clip u-joint.
Now the new caps are going to have to be tapped in with a hammer or alternately pressed in using sockets and a vice but my peewee vice couldn't open wide enough so hammer time!
Carefully place a cap into the end yoke hole and insert the cross and hold it up into the cap with one hand while you tap the cap into place.
Just enough to seat the c-clip.
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Now turn the shaft over and you will need to "float" the cross between the installed cap and the remaining cap so that when you hit the cap you don't drop the needle bearings inside either cap.
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Now tap that baby home and insert the last clip.
The last step is to tap either ear of the end yoke lightly to "center" the u-joint.
When you are done the u-joint will move freely in the end yoke.
Some problems you may have and their solutions;
If one or more u-joint caps spins in the end yoke and has no press you can; Heat the metal around the eye of the end yoke to cherry red and let it cool naturally.
This will shrink the eye slightly and restore the press fit.
It is however, a stop gap measure and almost certainly decreases the durability of the end yoke.. but we did it all the time at the driveline shop for customers on a budget and not a single one of those shafts ever came back broken.
If you are removing the slip yoke from the drive shaft to change the u-joint MARK THE ORIENTATION OF THE YOKE AND SHAFT BEFORE YOU BEGIN!
If the factory balance was still good, there is no reason you cannot replace all the u-joints in a shaft and still have a reasonable balance.
It doesn't always work this way.
If you use sub standard "GMB" or el cheapo brand u-joints you will very likely need to have the whole driveshaft rebalanced.
Well, that's about it.
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I will replace the front u-joint when I rebuild the transfer case next week.
Post Script:
GM used these glued in u-joint caps in the 80's.
BE WARNED, THERE BE DRAGONS!
I know this is a military vehicle specific website, but I must warn you who would work on driveshafts of the danger of GM products elsewhere.
CADILLAC.
There were some Cadillac driveshafts featuring double Cardan headed driveshafts that were UN-MACHINED for replacement 3R u-joints. BMW did it too.
But the long and short is; IF YOU DON'T SEE A FLAT FOR THE C-CLIP OF YOUR REPLACEMENT U-JOINT TO SIT.. it is because it ain't there.
ALL CUCV M1009 and K5 Blazer driveshafts are machined to accept replacement u-joints.
Only some Cadillacs are not.
It is terrifying to see the un-machined.. rough cast surface..
GOD have mercy upon your beautiful 80's Cady driving soul if your driveshaft gives up the ghost in Meeteetsee Wyoming.
Your only option is to find two H-yokes from a Chevy vehicle that are machined to accept c-clip u-joints..
Nearly impossible.
I just don't want some far future Cadillac enthusiast to tear his driveshaft apart and discover this after the fact.
Carry on Happily.
Don't be scared Humans.