Sierra U-joints 18-6406

[300sflyer]

This U joint comes with 3 different sets of retaining clips. How does one know which set to use? Also, there is a note in the box saying to make sure the sharp edge of the clip is positioned away from the bearing cap. Maybe its my eyes, but both edges look the same to me. Thanks!

 

[harringtondav]

Use the snap rings that best match those you removed. I've always had the snap rings angled ends that form a point at the outside diameter. There is no inside or outside that I've noticed.

 

[300sflyer]

These snap rings go on the end of the bearing caps.

 

[achris]

They are 'internal' circlips. They go in the end of the yoke to stop the bearing cap 'flying out' as it were.

Like this....

As those clips are made by stamping them, there will be one sharp edge and one 'rounded' edge. Run your finger over the edges. The 'sharp' edge MUST face away from the cap. If you put it the round edge away, that is the face that takes the load, and the clip can ride on the rounded edge, and that will promote it slipping out... Not the best idea.


Most Mercruiser joints (but not all) use 'external' C clips, and are set up like this...

Chris....

 

[300sflyer]

Thanks for the info Chris. I still don't know which of the 3 sets of clips to use. Its a 2007 Alpha Gen 2 if that makes any difference, and the existing clips are black in colour. Thanks.

 

[achris]

All of the Alpha Gen IIs that I know of use the external clips. Are you sure it's using internal clips?

 

[300sflyer]

[No message]

 

[harringtondav]

Per Chris' comment above see if your yoke bores have internal grooves, or if your old U joints have the grooves in the end caps. 1998 and later Alphas have two possible drive shaft assemblies. If your old U joints have the grooves in the caps you need 18-2097. If your yokes have the grooves in the yoke bores you have the correct U joints.

I suspect the difference between the 18-6406 retaining clips is their thickness to accommodate different applications. Use a micrometer or caliper to measure the thickness of your old clips, and use new clips that are the same thickness. Install them per Chris' post #4

 

[300sflyer]

Does anyone else see a difference in the two edges? I sure don't.... The bearing caps seem really tight in the yoke too. Very difficult to press in!

 

[300sflyer]

I figured out the clips. Its more obvious when looking at the lobes where the holes are.

So I have one u-joint installed, joining the splined shaft and the center yoke. I used the thinnest clips in the kit [gold coloured ones] and the movement is way too tight. The caps are butted up tightly against the clips on both sides. Not sure what to do now...

 

[300sflyer]

Any thoughts guys? I can't use them like this, and the thought of buying OEM from Merc at more than twice the price is ridiculous.

 

[harringtondav]

It's not unusual for installed Unis to be stiff. This is a result of the cross being slightly off center from the pressing. Smack the yoke ends with a dead blow hammer. It will loosen up. As long as the clips are fully seated install the drive shaft. It will loosen up w/in the first few revs.

 

[300sflyer]

I have already smacked them in both directions, and they are still quite tight. I am afraid to just go with them as they are, as the heat build up will be real factor once the drive shaft is spinning.

 

[harringtondav]

Remove a clip and press the cap against the opposite clip. This will move the few thousands of clearance away from the clip groove. Reinstall the clip and smack the other yoke toward the reinstalled clip. Repeat on each cap. If this doesn't help, reinstall your original clips and try again, As long as they seat tightly they'll be OK.

The stiffness is from a cross end being in tight contact with the inside end of the cap. These are hardened, finished surfaces that function as thrust bearing surfaces in operation. In operation the U joint self centers. If you install the assembly as is, it will most likely loosen up on its own. If you're concerned, run it on muffs for a few minutes, pull the drive and check for stiffness. My bet is it will be loose.

 

[300sflyer]

Thanks for the suggestions. I had already removed the clips and tried to adjust things. It did not help. The original clips are thicker than the ones I chose to use from the kit, so they will only make it worse. I'm wondering if the u-joints are just a bit too big...

I will probably do as you suggest, put it back together and run it on muffs for a few minutes. I am in process of doing the bellows as well, and the plastic drive oil line connection that goes through the gimbal housing just broke on me... Something else to fix now too... LOL!

 

[300sflyer]

So I removed the clips, gave the ujoints a tap with the hammer in both directions, and they loosened up. Course now the clips won't fit back in...

Has anyone used Moog 344AG u-joints before? They are the same size, and unlike the Sierra or the Quicksilver ones, these ones have zirk fittings in the centre.

https://www.moog-suspension-parts.com/moog-344ag

 

[nola mike]

Those look like internal clips as well, did you figure out what you have? I've used the Moog 315g on my A1/G1 drive without issue. Just installed a couple of them, getting ready to reinstall the drive...

 

[300sflyer]

The Moog 344AG uses external clips.

 

[harringtondav]

So I removed the clips, gave the ujoints a tap with the hammer in both directions, and they loosened up. Course now the clips won't fit back in...

Has anyone used Moog 344AG u-joints before? They are the same size, and unlike the Sierra or the Quicksilver ones, these ones have zirk fittings in the centre.

https://www.moog-suspension-parts.com/moog-344ag

Buy the Moog's. But pull the caps and put your caliper or micrometer on the cross needle bearing journals. I'm betting they're considerably smaller diameter than the Sierra. I've researched many automotive Unis as a cheap alternative to marine U joints. All have come up short with this measurement. Smaller journal diameters mean much less needle bearing area. And this is where Unis fail.

Earlier you said you'd try running the drive with the 'tight' Sierra's to see if they would loosen up. Did you try this? Newer Merc/Sierra Unis are 'pernalube'. Meaning they supposedly have better seals and no grease zerks. I pump extra grease into the caps before installing until one cap lifts when the others are seated. Permalube joints have room for more grease than the mfg. shot in. As I said before, the ends of the caps and journals are bearing surfaces. That's why you'll see the cross cuts in the ends of the journals. These are to allow the grease to lube the thrust faces.

 

[300sflyer]

I ended up taking a few thou off of the thickness of the clips, and all is good now. Thanks guys!

I do wish the Sierra and Quicksilver ones had zerk fittings though! Seems to be trend now not to install them, and not just in boat parts, but vehicles too... :facepalm: