What is this part?

[NHRA225]

That appears to be a fracture in the U- Joint - If it in Fact is - you need to have it repaired As soon as possible !

[Rkesselus]

Originally Posted by Skeggo

Appreciate the concern but I am confused. The techs at Freightliner did not show concern. They did grease it and inspect it, even test drove it. Should I take it to another shop for a second opinion? I have no problem getting it repaired if needed, and assumed it would need it. But service techs thought otherwise.

I would trust the Freightliner guys and ignore all the sidewalk experts Richard.

[guardrail53]

Originally Posted by VoiceNinja

I just did my 30,000 mile Freightliner service list and can tell you exactly what that part is for and why I'd ask for clarification from the Freightliner Service Center.

The cap is plastic and covers the end of the splined drive shaft. There's also a small hole in the center of the cap that comes into play during the service procedure.

During the driveshaft service, you connect a grease gun to the Zerk grease fitting on the outside of the shaft and pump a LOT of grease into the driveshaft interface. Eventually, grease will start to come out of the hole in the center of that cap, at which point you cover it with your finger and keep pumping until grease appears at the far end of the splined shaft interface. It takes a lot of pressure and a surprising amount of grease.

With the crack in the cap, I'm curious how they were able to properly service the splined shaft. It seems like the grease would have poured out of the crack and wouldn't have developed the pressure needed to migrate all the way down the splines and exit at the far end of the splined interface, which is required to properly lubricate the drive shaft.

I'd also be concerned that the crack would let the grease that's intended for the splines exit the assembly post-haste under normal driving conditions.

I'm not saying that they're pulling one over on you - I'm just a backyard personal mechanic, not a pro - but given the step by step published procedures that Freightliner gave me for my service intervals, that cracked cap seems like a potential problem to me.

There's also a separate Zerk fitting for both of the U-joints on the drive shaft. Grease should be applied until it comes out of the seals at all 4 of the bearing interfaces. In your photos, those interfaces look very dry.

I'd love to see a set of photos of the same area, post-servicing, if you could get them for us.

Great answer!

Originally Posted by NHRA225

That appears to be a fracture in the U- Joint - If it in Fact is - you need to have it repaired As soon as possible !

You need to look at the pic's again! 1st pic clearly show's that this plastic cap is not even close to the u-joint!
If it was the u-joint, your right, but after he had the MH checked out and given the OK from Freightliner, ?

Rail!

[Unplanned Tourist]

Have to say, too many amatures chiming in here. That is a plastic cap to hold to grease in and around the drive line splines. It would be a good idea to replace it, but as long as you grease the splines often, it will go a long way. Keep it greased often enough that it slides easily. Probably around every 2-3000 miles.Once it's replaced, you can go back to your regular maintanence routine.
In the 40 years I spent in the HD truck repair buisness, I replaced many of those caps.
Good Luck.

[Dtwallace]

Originally Posted by Unplanned

Have to say, too many amatures chiming in here. That is a plastic cap to hold to grease in and around the drive line splines. It would be a good idea to replace it, but as long as you grease the splines often, it will go a long way. Keep it greased often enough that it slides easily. Probably around every 2-3000 miles.Once it's replaced, you can go back to your regular maintanence routine.
In the 40 years I spent in the HD truck repair buisness, I replaced many of those caps.
Good Luck.

I agree with Unplanned's statement, This is what I've also experienced through out the years, I'm just not as fast to tell someone else to run their equipment this way.

We don't know how long you've had this issue, but keeping it lubed will also keep you rolling, without worry.

DTW

[twinboat]

You guys are looking and seeing a broken cap.

I'm looking a little further and wondering why it broke. There has to be a reason.

What caused it, is far more important then the fix.

[CJ7365]

Originally Posted by twinboat

You guys are looking and seeing a broken cap.

I'm looking a little further and wondering why it broke. There has to be a reason.

What caused it, is far more important then the fix.

here is a picture of what it is, I know Twinboat you have worked on trucks for x amount of years, but how would a u joint cap get inside the slip yoke?


Ok maybe I misunderstood, it is a cap, and agree with you about wondering why it popped out, to much collapsed


Wondering why freightliner did not replace it.

[Unplanned Tourist]

Originally Posted by twinboat

You guys are looking and seeing a broken cap.

I'm looking a little further and wondering why it broke. There has to be a reason.

What caused it, is far more important then the fix.

Just a guess, but I suspect the rig was moved with the suspension dropped down. The u-joint can handle the excessive running angle, but the yoke moved in far enough to hit the grease cap and break it. A common failure. The grease cup in the pic is for excessive slip joint travel, normal with such a short drive line. Usually they are shorter (not protruding as much) in a longer drive line. JMHO.

[dennis45]

Originally Posted by Unplanned

Just a guess, but I suspect the rig was moved with the suspension dropped down. The u-joint can handle the excessive running angle, but the yoke moved in far enough to hit the grease cap and break it. A common failure. The grease cup in the pic is for excessive slip joint travel, normal with such a short drive line. Usually they are shorter (not protruding as much) in a longer drive line. JMHO.

I think you win the prize.

[Unplanned Tourist]

Originally Posted by dennis45

I think you win the prize.

I am not a genius, but 40 years of fixing tucks taught me a couple of things.

[Dtwallace]

Originally Posted by Unplanned

I am not a genius, but 40 years of fixing tucks taught me a couple of things.

[Skeggo]

Thanks for all the comments about this. Wanted to follow up to close out the topic. Sorry for not replying sooner.

I did take the rig back to the Freightliner shop and showed them the pictures of the part in question. They noted it was the cap and agreed it should be fixed. They dropped the shaft, repaired it, and replaced it the same day. All fixed now.

[JohnRR]

Thank you for the update they are important for those who may do a search of the subject in the future.

[glenn allen]

Originally Posted by VoiceNinja

I just did my 30,000 mile Freightliner service list and can tell you exactly what that part is for and why I'd ask for clarification from the Freightliner Service Center.

The cap is plastic and covers the end of the splined drive shaft. There's also a small hole in the center of the cap that comes into play during the service procedure.

During the driveshaft service, you connect a grease gun to the Zerk grease fitting on the outside of the shaft and pump a LOT of grease into the driveshaft interface. Eventually, grease will start to come out of the hole in the center of that cap, at which point you cover it with your finger and keep pumping until grease appears at the far end of the splined shaft interface. It takes a lot of pressure and a surprising amount of grease.

With the crack in the cap, I'm curious how they were able to properly service the splined shaft. It seems like the grease would have poured out of the crack and wouldn't have developed the pressure needed to migrate all the way down the splines and exit at the far end of the splined interface, which is required to properly lubricate the drive shaft.

I'd also be concerned that the crack would let the grease that's intended for the splines exit the assembly post-haste under normal driving conditions.

I'm not saying that they're pulling one over on you - I'm just a backyard personal mechanic, not a pro - but given the step by step published procedures that Freightliner gave me for my service intervals, that cracked cap seems like a potential problem to me.

There's also a separate Zerk fitting for both of the U-joints on the drive shaft. Grease should be applied until it comes out of the seals at all 4 of the bearing interfaces. In your photos, those interfaces look very dry.

I'd love to see a set of photos of the same area, post-servicing, if you could get them for us.

Top notch description on how to properly grease the spline on the drive line. There might also be a screw on cap on the spline end of the yoke. It should be snug enough to let old grease out under pressure but not let the new grease be slung out under use. Same as the hole in the cap.