How to install front u-joints with zerks so that zerk is in compression, not tension?

[Coalsmoke]

I am replacing my front u-joints tonight and they have zerks, which brings me to two questions:



1, I read that you should be careful to install the zerks on the compression side because installing them on the tension side would leave the u-joint weak.

Did you make sure that the u-joint was put in with the zerk loaded in compression? If the u-joint was put in with the zerk in tension then you are just asking for trouble with all of the torque these engines put out.

Could someone please explain how I do this and why, thanks.





Also, my new u-joints came with both a zerk and zerk caps for me to choose from. Why would I want to run the caps instead of the zerks? Should I just put in the zerks?



Many thanks guys,

Stephan

 

[ToolManTimTaylor]

I remember that post. I was under the impression that the zerk faces twards the driven component. Then got to thinking that the zerk is in the cast body. Hmmm I wanna know too Oo.

 

[Coalsmoke]

OK, I just spent many brain cells figuring this out from dave fritz's site: He says:

NOTE: For maximum u-joint strength, you want the zerk fitting to be under compression when the driveshaft is turning to drive the vehicle forward. In the case of this driveshaft, this shaft will rotate clockwise as viewed from the end and the driveshaft yoke will be pushing against the zerk section of the cross.

 

[Coalsmoke]

If you think about it, it makes sense. The tire side of things will be resisting the drive force, and the drive shaft part will be inflicting the force. These two operate in opposite directions. So, you put the zerk so that it is inbetween these two forces, aka compression.



Now I just have to figure out whether to use caps or zerks. Probably zerks, but it would be nice to know what the caps are for.

 

[SS]

If the zerk is in the cross at a 45* angle to the cross, then it should be placed such that it is being "compressed" when the drive yoke is turned in the forward direction. Imagine your finger and thumb of each hand holding the u-joint on the end of the caps: now rotate one hand until your fingers and thumbs touch. The zerk should be installed between the fingers that touched (or compressed between them) when you try to rotate the axle or driveshaft to move the truck forward. Does that help visualize it?



If the zerk is in one of the end caps, or exactly in the middle of the cross at 90* to the cross, then it makes no difference. The zerk caps would be used in a situation where there is a clearance issue or fear of grease contamination or so on.

 

[drrhoades]

The u-joint has 4 trunions at 12, 3, 6, and 9 o'clock. If the u-joint is in the axle shaft; then for an example having the inner axle shaft that goes to the diff with the ears of the axle shaft at 12 and 6 o'clock. The outer axle shaft that goes to the wheel will have its ears at 3 and 9 o'clock. If you are moving forward the differential will be turning the inner axle shaft which is the driver. The outer axle shaft will be the driven component. Therefore the 12 and 6 o'clock positions will be driving the 3 and 9 o'clock positions. You would put the zerk inbetween the 9 and 12 o'clock position or the 6 and 3 o'clock position. If the zerk was between the 6 and 9 o'clock position or the 12 and 3 o'clock position then it would be in tension. Hopefully that is clear as mud it helps if you draw a picture or actually have a part to look at.



As far as a zerk in the body of the joint or zerks in the bearing caps. They are both good to use. If you go with the zerk in the body of the cross when you grease it be sure to get new grease out of every bearing cap. If you dont you are either leaving air or old grease in there and that is not good. If you go with the zerk in the bearing caps then you are sure to get new grease to each bearing cap because you are greasing each one.

 

[ToolManTimTaylor]

Then again I allways thought that a SEALED non greasable u-joint was the strongest out of them all or so I learned at the heavy duty chassis shop I worked at years ago. Some of those rigs were NUTS. Wreckers with 80 ton booms and whatnot ... . Talk about BIG parts

 

[drrhoades]

The sealed non-greaseable u-joints are the strongest, but the problem is if they get contaminated then they go bad. With greaseable u-joints you push everything out and put new in everytime you grease them.

 

[Coalsmoke]

And since I don't plan on running 400hp anytime soon, greasable sounds like a good prospect to me.

 

[24Vpirate]

spicer 5-806x add a little greas to them while installing them and they are good for atleast 100k or if you are determined to use zerks they must point towards the center of the shaft

 

[CFAR]

For those of us who don't picture to well.



#ad

 

[Coalsmoke]

nothing beats a great picture. great job CFAR

 

[Speedo]

greaseable vs. sealed

Originally posted by ToolManTimTaylor

Then again I allways thought that a SEALED non greasable u-joint was the strongest out of them all or so I learned at the heavy duty chassis shop I worked at years ago. Some of those rigs were NUTS. Wreckers with 80 ton booms and whatnot ... . Talk about BIG parts

Not a question, the sealed is stronger. How much strength do you need though. I have broken several stock Dana 60 axle shafts and I have never broken a greaseable u-joint. Since I switched from sealed to greaseable I haven't worn out a u-joint and I have gone through a few sealed ones before I switched.



Gus