I'm having some serious vibration issues that I think I have narrowed down to the DOJs but I'm not convinced they are bad. I get crazy vibrations under load, but only once the car is warmed up and i've driven about 5 miles.

 

I removed the spare tire and grabbed the passenger side DOJ and if I shake it up and down there is a lot of movement, but it seems to be at the base of the joint where it goes into the transmission. There is no play in the joint itself, no torn boots and it does not click when turning. Is there a bearing or something in the transmission that I can replace or is this a sign of a bad axle?

Is there a bearing or something in the transmission that I can replace or is this a sign of a bad axle?

Is this about the Gen 1 wagon in your avatar? There are bearings in the trans. that could be replaced, but I would disconnect the DOJs from the trans. and check for play in the splined stubs on the trans before doing anything else.

 

What kind of transmission does it have in it?

 

If the bearings in question are bad, unless you have a show-piece stocker wagon, I would consider a D/R 5MT trans swap rather than R&R on an old 4 speed. Assuming it's a 4WD model.

If we assume your joint is ok, check that the output shaft seal plate has not loosened somehow. This threads into the trans and also holds the output bearing in position. It has a locktab to hold the plate in position. If your bearing is loose you can adjust this plate to tighten things up, but careful not to overtighten. Assuming it was adjusted properly to begin with, things are probably getting worn. Might buy some time.

Yes its the 78 4WD wagon in the picture. Sorry, forgot to include that. It does have a 4 speed in it currently and I was hoping not to have to replace it!

 

I'll check the seal plates tomorrow. I'm assuming the axle shaft needs to be removed for that? I supposed I should also just pull the axle and take a looksee in there to figure out what the heck is going on.

I finally had a chance to take the DOJ out and didn't find any play in the transmission output shaft or seal covers. I did go ahead and clean the DOJ and repack it with grease. The vibrations are a bit better, nothing violent but i think I'm back to the level of vibration I'm used to in this car.

 

The HTKYSA manual mentions if the bearings in the DOJ fall out easily or the casing is severely worn it should be replaced. I wasn't sure how to quantify that though. I could pop the bearings out by applying a bit of pressure to them and there were some wear marks but nothing severe enough that I could catch my fingernail on it (my general gauge for if something is worn or not). Should the bearings not be removable, and how much wear is too much?

 

I also came up with a pretty clever way to separate the DOJ without needing help to pull the wheel outward: hook one end of a bungee cord on a wheel spoke, wrap it around your leg below the calf and hook the other end to another wheel spoke. Now you can lean in to pull the DOJ apart and just use your foot to leverage the wheel out so it can be slipped around the tranny output spline.

Check your motor mounts, transmission mounts, and u-joints. The vibration you feel may be caused by something other than the DOJ. The trans. mounts on the older models are puny. Whenever they go out in my '81 I feel it in the DOJs.

When the vibrations first got really bad, I did find a broken tranny mount and replaced both of them. After replacement it was fine for about 5 miles of driving then the vibration came back, so I'm not sure if the broken mount was cause or effect. However the violent vibrations are gone after repacking the DOJ.

 

Whats the best way to check the motor mounts? I've grabbed the motor by the valve covers and tried to lift up and don't get much movement (I'm assuming I could probably lift this motor out by hand if it was completely unbolted). I don't want to just replace them on a hunch because they run about $50 a piece.

U joints are definitely worth looking at. Remove your driveshaft and check both ends. Both were trashed on my '78. By that I mean corroded and binding up.

Wondered what you found. My truck is now on the road and I get a weird low freq harmonic from the transaxle under load above about 60mph. Slower than wheel rotation, like maybe one vibe to every 4-6 tire rotations or so. Everything's been apart and either replaced or inspected and greased, except have not split the transaxle case. Anybody want to take a shot?

Narrowed it down to the rear LSD. Low freq harmonic above 60 mph, only in FWD, disappears in 4WD. Just pulled it out to check gear lash- it isn't binding but feels pretty tight.

Reshimmed the LSD: loosened the backlash and bearing preload slightly. Test drive today. Only noise is the snow tires and my kids farting.

I did change the u-joints in my driveshaft. I've also previously changed the u-joints in the rear pass. axle. I guess all my driveline stuff is wearing out after 34 years.

 

I still think I need to clean and grease the CV joints in the front. Plus the front right wheel bearing is making some noise. Eventually.

 

I haven't done any comparison of w/ and w/out 4WD, but I usually try not to go too fast in 4WD anyway. I do still have harmonic vibrations over 60, but I'm hoping cleaning and greasing the CVJ will help that.