Lately I have noticed that when I come to a complete stop (stop sign/light/etc) I go to give it throttle and I feel a slight slip/thud from the drive train. I want to say this could possible be the transmission mount that is worn. Could this be the problem? I remember this same thing happening when I owned a LT1 Camaro back in my teens. Replaced it with a poly mount and it shifted smooth with no thud. Truck has 89k miles.

 

It's possible. It's even more likely that the slip joint in the driveshaft is dry and binding. Ford sells a special grease just for slip joints I recommend getting some.

 

Thanks for the info. I will look into that.

 

X2 on Marks reply, (wiping my chin)

But if you haven't dropped the shaft to do anything to it, that thud labors your ujoints.

I would drop the shaft and replace all joints as well as service the slip. It's very cheap and one of the most popular complaints about drivetrain issues.

If you don't want to drop the dime, just do a heavy inspection and if they are serviceable, grease em up. If they are not, just take the time to renew.

Whip back thru thread cats here and you'll find more often than not that joints are the root cause of anyone's complaints.

I never thought I had problems because they felt tight and did what they were told, but I couldn't shake a vibe. Went all in and you can't quite cut a diamond, but the feel is real.

Denny

 

Ford XG-8 is what you're looking for to grease the slipjoint.

 

Thanks for the info. Few more questions for when I tackle this...

How much do I need?
Do I need to clean out the old stuff first?
If so how/what do I use to remove the old grease?
How much do I add inside the joint?

 

1. You don't need much. One tube will last you awhile (probably years).
2. I would recommend it.
3. I use a rag and a screwdriver (see explanation below).
4. Some.

I will preface this with saying that there a several version of the driveshaft depending on your wheelbase so this may not be exactly how you accomplish it. I have a CCSB (156" WB IIRC).

1. CHOCK YOUR TIRES. Once you disconnect the driveshaft the parking brake is the only thing keeping your truck from moving if you don't.

2. Mark your driveshaft with some tire chalk or similar. The slip yoke is keyed to only fit one way and if you don't raise the truck the driveshaft won't turn and if you don't lift the truck off the ground you can only put everything back together the way you took it apart. That being said you never know what could happen and it's always nice to have the lines to make sure everything is going back together correctly.

3. Cut the strap at the forward end of the slip joint boot (see picture). Mine has two zip ties there. I don't have the tool to clamp on a new strap each time so I improvised with a couple of zip ties plus they're easy to snip when I need to go back in there. I've been doing that for at least 8 years and haven't had a problem.

4. Unbolt the 4 u-joint strap bolts (8mm) at the forward end of the shaft section you are removing (see picture).

5. Push in on the axle to compress the slip joint then drop the shaft down. You should be able to pull the short yoke section off with no problem (there might be a little suction from the grease if there's any left).

6. There should be a blue coating on the slip joint pieces (if not your joint is worn). Clean any residual grease off with a rag (including between the splines). For the female section I use a rag and a screwdriver to carefully get down in there to clean it out. There is a pocket at the end of the female section that can fill up with grease. As the slip joint is exercised grease is pushed out of the splines and into that cavity.

7. Apply some Ford XG-8 grease to the splines. I make sure that there's grease in every spline then make sure a thin coat coveres everything (on both the male and female ends). Any extra grease is going to be pushed into the cavity. This doesn't take much grease to do. I guess the best way to describe it is be liberal but not excessive.

8. Re-insert the yoke section into the shaft . The shaft is keyed (there's one section that is solid making it a "double" spline) so it only goes back together one way.

9. Compress the shaft enough to get the u-joint back into the cradle (compressing too much will evacuate some of the grease into the cavity).

10. Re-install the u-joint straps but don't overtighten! The torque spec for the 8mm bolt holding the u-joint strap is 26 ft-lbs. That's a lot of torque for a small head. Personally I use a 6 point socket to prevent rounding out the bolt head.

11. Install a new metal strap or zip ties to hold the boot to the yoke shaft (keeps debris out of the joint).

12. Unchock the tires and enjoy clunk-free driving!



Again, this is just how I do it, YMMV. I cannot stress safety enough and chocking the tires. Personally I would not place my life in the hands of nothing but a parking brake. It doesn't take much to render your parking brake ineffective without you realizing it. Once you drop the shaft there's almost nothing between you and a moving truck while you're under there. It's also not easy to just "jump out" either.

Hopefully this helps.

 

Great post with pictures Brian42. Should help a lot of people who search.

 

"I cannot stress safety enough and chocking the tires."

Ask me why I ALWAYS use heavy duty jack stands anytime I go under a vehicle. Fortunately a Volvo 122 S is not TOO heavy.