Driveshaft bump when stopping (slip yoke)

[sundance21]

I thought I would share my experience when dealing with the bump from behind on stopping from the slip yoke.

Like most, I started with greasing. That didn't work.

I replaced all the U-Joints, that didn't work but I will say the GMB U-Joints from rock auto worked very very well. They fit good and they are very smooth.

I also cleaned the yoke completely multiple times. That worked for a short amount of time.

Then I realized what is going on. Here is my opinion. Once you get some much grease in the yoke, it creates an issue where the splines are filled completely with grease to the point that it creates a bubble/vacuum lock on the yoke. Then once the yoke extends out so far, it will not collapse easily because of the air/grease in yoke. It doesn't take much grease to cause this issue at all. This is what causes the bump. The yoke extends and then tries to collapses as the suspension flexes when stopping. The air just can't escape easily.

What I did was take the grease fitting out. Collapse the yoke. Put the grease fitting back in. Then I could use a pry bar to extend yoke to bolt it down. This creates a vacuum on the yoke that easily collapse as the suspension flexes. No more bump. Hope this makes sense. Just thought I would share.

 

[blkexp98]

Humm interesting find. Wonder how long it will take to lose the vacuum you were talking about? Has anyone seen the differences of the Lexus shafts that supposedly fixed the issue?

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[dahveeed]

There’s a service bulletin on this. If you have the extra money for this, there’s an updated drive shaft available to resolve this issue.


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[sundance21]

Humm interesting find. Wonder how long it will take to lose the vacuum you were talking about? Has anyone seen the differences of the Lexus shafts that supposedly fixed the issue?

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I believe it will be fine. The only concern is if you take a big bump or over extending the suspension and it breaks the vacuum. So far, that hasn't happened. I had rear end off the ground when I did it.

 

[sundance21]

There’s a service bulletin on this. If you have the extra money for this, there’s an updated drive shaft available to resolve this issue.


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Rock auto has a rear SKP brand driveshift with new U joints and flanges for $180. It is different design than the OEM. That is probably what I'll do if this doesn't work for very long.

 

[venomj]

First time I greased my 08 to solve this problem, I put in so much grease, like more than 10 pumps. It didn't make things worse. It actually solved the bump issue for a long while.
Funny thing was a few weeks later when I did something else under the car, I found the grease spilled everywhere around the shaft. I guess my car can discharge extra grease by itself ...

 

[sundance21]

First time I greased my 08 to solve this problem, I put in so much grease, like more than 10 pumps. It didn't make things worse. It actually solved the bump issue for a long while.
Funny thing was a few weeks later when I did something else under the car, I found the grease spilled everywhere around the shaft. I guess my car can discharge extra grease by itself ...

It probably got past the seal. To me, the mechanism should be vented.

 

[Hunter61]

I grease that slip joint until I see the yoke start to extend.
Then, remove the grease fitting & drive up & down the driveway a couple times to squeeze out the excess grease. Replace grease fitting and done.
While doing this, tie a couple rags around the shaft where the hole for the grease fitting goes to avoid leaving blobs of grease all over the driveway.

 

[Keros]

I raised the truck to max height on the RAS system, back in ~2012 when I got the truck, pumped the driveshaft full of grease until it extended, then lowered the truck to minimum height to push the grease into the splines.

Then I undid the grease nipple, all the pressurized grease came flying out. Be sure not to lose the grease nipple in the chaos.

Get on the back of the truck and bounce it up and down a bunch.

Put grease nipple back on, while still at minimum height. Then it was fine for 9 years until I wore out the joint... replaced the assembly last month.

If the truck doesn't have RAS, then any method discussed above is great too.

Thanks for bringing this up, hopefully others enjoy driveshaft-clunk-free driving

 

[Pilotmatt]

My 03 did that.

I forget but there are 5? Zirc fittings to grease. The first time I did it the truck was 7 years old and took 7-10 pumps per fitting. It helped a lot, but still had it a bit. There are posts here on all the zirc locations.