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Discussion Starter #1 (Edited)
Just wanted to create a post dedicated to the famous clunk that many FJ Cruisers are experiencing.
I know that has been discussed before, but it seems there no information on identifying the actual problem with the drive shaft (aka drive line). This is what I will try to provide here.
Simptom: FJ comes to an abrupt stop and the operator feels a kick in the back (aka thump).
Toyota has come forward with TSB 0045-12 which says to replace part #37110-35a00 , with an updated part number 37110-35b00.
Some owners have suggested that lubricating the driveshaft with moly based grease, or Ford Motorcraft PTFE lubricant (xg-8) will resolve the issue (Some have suggested to not to over-lubricate, other said that over lubricating works better). Some owners have reported that it did fix their issues (until the next greasing interval).
I have tried a few different ways to resolve my thump because I didn’t feel like spending close to 500$ on a new drive shaft. I tried:
1. Under lubricate and over lubricate – no result.
2. Use thinner lubricant (which had better results, but didn’t resolve the problem completely).
3. Use the above Ford Motorcraft grease – no result
4. Disassembling the drive shaft, cleaning it out and refilling it – no result.
I have finally purchased a replacement 3711-35b00 and have found that both drive shafts are identical; the only difference is how the sliding yoke moves.
On the bad drive shaft, the yoke has only .5-1” of free movement due to vacuum/pressure that builds up inside the York (pressure inside the yoke can be positive and negative).
On the good drive shaft, the yoke has about 3-5” of movement until I feel very little vacuum -this yoke will work much better.
So, the only difference is that the new shaft has an air vent somewhere that allows for air to move freely (I was not able to find it on the outside of the drive shaft, so maybe it is internal, or installed under a cap located under one of the spiders).

Here is a link to a patented drive shaft venting system https://google.com/patents/US6722991
This patent is not the same vent as the one on the new drive shaft, but the supporting information goes in to more detail and maybe of interest to some people.

If you are considering fixing an existing drive shaft, I think the existing driveshaft could be modified to allow for better operation.
I think that the following would work:
1. Make sure to mark the drive shaft on each side so that you would put it back on the same splines as it was.
2. Drill small, 1mm holes (breather holes)., opposite side to each other, at the deepest part of the splines, of the male (long part of the drive shaft) portion of the yoke. Do not drill the short, hardened steel female portion of the driveshaft
3. Use a rubber boot 3-4” long, same diameter as the drive shaft (clamped on both sides) to cover the holes from debris and from leaking grease.
 

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Great info. I had my "propeller shaft" switched out with the modified one and the clunk went away...you have to be careful not to over grease the slip yoke to avoid hydrolocking it, or so I am told.
 

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A quote from somebody who appears to understand the reason why you don't grease the heck out of the slip yoke: "when you over fill it, the grease takes up the space inside the driveshaft where the yoke is supposed to slide into. Air compresses, grease doesn't (easily), so it is now acting more like a solid driveshaft." If the slip yoke is no longer able to flex, it doesn't take a rocket scientist to come to the conclusion that you are going to end up stressing the driveline and possibly cause premature failure of some components. IMHO.
 

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Guys, the design is what it is.... so clunk will always come back... I use amsoil moly nlg2... it does a oil change interval easy... tried other brands and clunk came back after a gas refill interval!!! So the right grease is critical... otherwise take a chill pill and enjoy the FJ!!


Sent from my iPhone using Tapatalk Pro
 

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Hello all, hello omega53513,
thank you very much for your interesting post.
I am posting to ask you for a favor: Could comment the drawing I posted, in particular the position of possible venting holes? Was it this you ment? I am french, my english is not advanced enough to get the very details of your suggestion. .
Many thanks in advance.
Simon
 

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Discussion Starter #8
Thanks to all who responded. Similar design is used in most other SUVs and Trucks. All of them are vented.
If your clunk comes back then just check the free movement of the inner yoke, as previously mentioned it should slide in and out freely.
If it has very little movement then try to find out what is preventing the movement:
Is it air lock (bad vent), hydro lock (too much lubricant or lubricant is too thick) or rust.
Also, as previously mentioned, adding too much lubricant will fill the empty space of the yoke and prevent movement. This will negatively effect all driveshaft facing bearings.
Here is the edited diagram from above. Unfortunately i don't know exactly where factory vents are supposed to the marked locations make the most sense.
 

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I had a company called Drive Lines rebuild my drive shaft and add the hole. After 6 months the bump came back, not as bad. I went to J&S Gear Co and they told me to buy a new re-engineered drive shaft from Wholesale Import Parts which is just down the street. It has a vent hole in the top of the slip yoke and cost me $281.60 with free shipping. Everything is greaseable and replaceable. One year warranty. I'm sure it will wear out too but they had some words of advice - use moly grease and lube it every oil change. https://www.wholesaleimportparts.com/Toyota_FJ_Cruiser_Driveshaft_2010.php
 
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