Alignment of driveshaft yokes & mystery vibrations

[Black Rhino 13]

Things seem better after the brake job and all new fluids. Just got one tire today from Treadwright, too. Looks good and balanced fine. After the new tires get done + alignment, and then a tune up, I'll have the guy look at the drive shaft. Maybe it can be balanced like that.

 

[bsmith123]

"Between 70 and 75 it gets really bad."

"If you've ever been in a C-130 airplane you can imagine this. In the plane, the engines send a rhythmic vibration through the fuselage. It's like that in the LC at 70 and above."


You are surpassing the "do not exceed speed for this airframe"

 

[Black Rhino 13]

Ha ha! Yeah, the old Herc is a slow and low bird for sure, though the new J-models have much more powerful engines.

Sorry I missed this back in Sept. - I'm a newbie and didn't realize I wouldn't get an email if there were replies.

I spent a few minutes in the back of a C-130 between the southern U.S. and north Africa once. Well, that was the "direct flight" via Bahamas, Azores, and Sicily. The way home was via Germany, Iceland, and Nova Scotia. Great in-flight movies and restroom facilities.

 

[Slickdog]

Hi

I am unfamiliar with the term 'Zerk' Can anyone explain it please?

 

[Black Rhino 13]

A Zerk Fitting or Grease Fitting is a little metal nipple sort of thing that you attach a grease gun to in order to squeeze grease into the object the Zerk is connected to. Often you find Zerks at the end of driveshafts, u-joints, frame lubrication points, etc...

I once bought aftermarket leaf spring shackles for my 85 4Runner which had zerk fittings to lube the bushings.

You can google Zerk Fitting or grease fitting and pretty much get the same answer.

 

[DaneDK]

Great stuff this thread... After I liftet my LC there was noise and vibrations. Removed front DS to rule out this as the problem. Still noise and vibration. Looked at rear DS and noticed that the yokes were misaligned. So a quick job and yokes are now aligned and all vibrations are gone. Previosly I replaced u-joints on both shafts and nowhere in the FSM is it mentioned that yokes need be aligned. Just to mark up positions when removing and assemble according to markings (as earlier mentioned). So reading this thread was a big help... thanks.

One question: It my be overkill, but should the front and rear shafts be aligned together in any way? Should all 4 yokes be aligned?

 

[handcannon]

One question: It my be overkill, but should the front and rear shafts be aligned together in any way? Should all 4 yokes be aligned?

No direct experience with this, but I don't think it will be possible to align the front and rear shafts and keep them aligned. Unless you have front drive plates instead of hubs, the front system will be "off" when you are in two wheel drive. The front shaft will not be turning. Also,the shafts will turn at different speeds since the wheels turn at different rates when the vehicle is turning a corner.

Don

 

[lostmarbles]

There is nothing to be gained from trying to align the yokes between two separate drive shafts.

 

[74FJ40newbie]

Just a sequel here.

As mentioned earlier in this thread, in my ignorance I had COMPLETELY misaligned the yokes on my front driveshaft when I had removed it for painting many moons ago. Vibrations should normally have been expected from this error but I think my sagged suspension and consequent "lack of significant drive-line angles" meant I noticed nothing untoward.

So a few days ago I unbolted the foremost flange on my front driveshaft and slipped the driveshaft apart at the splined joint (leaving the short end dangling from the "transfer case front-drive output flange").

It was then a simple matter to reconnect the splined joint with the yokes aligned properly (confirmed with taut string again) and with all the grease nipples on roughly the SAME side.

So anybody who thinks aligning the yokes perfectly is difficult - Think again. (I heard someone in another thread say they thought it was a specialist job or required special tools.)

I would have taken photos but the front crossmember gets in the way. (Lack of access to that end is why I chose to unbolt only the FRONT driveshaft flanged-joint.)

As usual - I reused the original flange bolts but simply applied fresh blue loctite to the threads. (I think money and time is wasted by always fitting fresh new bolts - These are the same ones that left the factory 29 years ago!)

[/QUOTE
Just found this thread and read through the whole thing, then immediately ran out to check my recently purchased 74 FJ40 to find both of mine out of alignment. Thank for the heads up. Is this something someone new to working on FJs do, or do I need to have someone do it? You made it seem really easy. Any chance you could share how to do it here?

 

[Warloc]

You should also check the angles of the rear drive line in particular. If you have to much variation, more than a couple degrees out of plane it will create a vibration also.