The correct way to lube U-joints??

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OK...here are the 2 schools of thought:

1) Keep injecting grease until all of the oil grease has been purged from the joint and the new grease starts to ooooze out of the joint.

2) Inject grease without letting any grease ooooze out of the joint.

Which is it???
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I vote for number one, because you want to refresh the grease completely, but only inject grease with a hand pump. I have had garages blow the seals completely if they used the high pressure grease systems. The seals are to protect from road grit, if they are not there, then no protection.
 
They weren't U-joints, but the shop manual for my Grand Am said add grease until a little oozed out. Slow and easy.
 
What is a universal joint?
A universal joint (U-joint) is a coupling normally associated with automotive driveshafts. U-joints transmit rotation from one shaft to another where the two shafts are not perfectly in line and particularly where they can move relative to each other. A U-joint consists of a cross or “spider” which carries needles roller bearings at four extremities. Bearing cups are fitted into yokes, two on the input shaft and two on the output shaft.

Why are U-joints needed?
Many vehicles use one or more driveshafts, especially those with a long wheelbase and/or with tandem rear axles. At each end of a driveshaft, U-joints are needed since the driving axle(s) is forced up and down as the wheels travel over bumps, potholes, and other variations in the road surface. U-joints must be able to deliver the full power and high torque from a powerful engine into a rear axle assembly to drive a fully loaded truck over long distances. Without the flexibility that U-joints provide, driveshafts would soon break from flexing fatigue. Splined slip yokes are also needed to permit smooth “fore and aft” movement of driveshafts whenever the rear axle moves up and down.

Preferred Lubricant for U-joints and Splined Slip
Lubrication of U-joints and splined slip yokes requires a good quality NLGI Grade 2 grease with extreme pressure/antiwear (EP/AW) additives and high temperature capability.

Recommended Lubrication Procedure
One of the most common causes of driveshaft and U-joint failure is the lack of adequate or proper lubrication. The following lubrication procedures are recommended to prevent premature failure of parts. These procedures also ensure that U-joints are flushed of dirt, salt and other contaminants and the bearing cavities are filled with new lubricant. Always follow OEM lubrication schedule recommendations.

U-joints
  • Apply the recommended grease at the grease fitting on the U-joint until the new grease purges from all of the journal cross bearing seals.
  • Do not assume that bearing cavities have been filled with the new lubricant unless flow can be seen around all four bearing seals. If new grease does not purge at all four seals, loosen the bearing cap bolts and regrease until all four cups purge.
  • If new grease still does not purge, replace the U-joint.
  • If a different grease is being used, make sure it is compatible with the old grease and apply extra grease to purge out the old grease.

Splined Slip Yokes
  • Apply grease gun to grease fitting until new grease appears at the pressure relief hole in welch plug at slip yoke end of spline.
  • Cover the pressure relief hole (so that grease can flow easily to the seal) and continue to apply grease until new grease appears at slip yoke seal.
These procedures should help prevent costly downtime and U-joint-related equipment failures.

Copyright © 1998 Chevron U.S.A. Inc. All rights reserved.
 
Purges, ooozzeees! I.E., keep pumpin' very slowly until the old grease shows outside the seal.
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[ May 28, 2003, 03:38 PM: Message edited by: MolaKule ]
 
More and more U-joints are sealed from the factory and they require no lubrication. I used to think that having a grease fitting on the joint was a good thing. However, the original 3 U-joints on my Cressida are now 20 years old and have never been lubed or replaced so it would seem a factory sealed joint can be very reliable over time.
 
The factory sealed u-joints on my 98 GMC failed at 40000 miles. OEM joints are 80 bucks a piece. So I installed Dana Spicer greasable U-joints for 14 bucks a piece, and have had no problem since.
 
quote:

Originally posted by sbc350gearhead:
The factory sealed u-joints on my 98 GMC failed at 40000 miles. OEM joints are 80 bucks a piece. So I installed Dana Spicer greasable U-joints for 14 bucks a piece, and have had no problem since.

How can you tell when they start to go bad?
 
Any easy way to get a grease gun on the u-joint zerks?

Have found it impossible to get to the u-joint grease fitting without dropping the driveshaft and flexing the u-joint to allow getting the grease gun on.
 
Is this the origional factory installed u-joint? If not, the u-joint may have been installed incorrectly. I had this happen once on my Jeep, and had the shop redo it.
 
quote:

Is this the origional factory installed u-joint?

No it is a replacement. Have had several vehicles (GM) this way, does not matter which way they are installed. Just does not seem to be enough clearance around the yokes. The sealed factory lasted 200k so makes me wonder if that is a better way to go.
 
Although many may argue for the factory sealed ujoint, I much prefer the spicer with the zerk installed. Many "sealed" ujoints will run for lots of miles with the needle bearings rusted almost completely away. (My '94 F150 went 60,000 on sealed units but when I changed them, they were rusted almost solid!) I've seen it many, many times. One telltale sign is a squeek or slight grinding noise at speeds below 10 mph or so. The joint may have no play or show any outward sign of deterioration but when taken apart, it's a rusted mess! Alot of drivelines don't run a harsh articulation angle so if the joint is nearly "straight on" most of the time, you may not know when its lost its lube and is corroding away. The "old timers" always told me to grease the "joints" every oil change and keep pumping until you see new grease flowing from each bearing boot or seal. I think that has been very good advice, at least for me. My '95 F250 4WD has been through plowed fields with mud frame deep, snow bumper deep, hundreds of streams and ditches with muddy running water and God only knows what else, and I always grease up good afterwards. Over 100,000 miles later, the spicers are still in service with no problems and I'd wager they have another 100K in them yet.
My $.02
 
Another reason to keep pumping in the grease is to displace any water that has collected in the joint. I lubed up my truck yesterday and the rear most U joint had a few drops od water in it.
 
I vote for #2. If you put an excessive amount of grease through your U-Joints till it comes squirting out in gobs you stand the chance of drawning dirt and debris back into the U-Joints if the U-Joints are not cleaned of any grease lying all over the U-Joints. I got this advise from professional diesel mechanics. Also, you are stressing the seals on the U-Joints by blasting huge amounts of grease past these seals. I grease my dumptruck every six thousand miles following this procedure and I have never had a problem. I also do this with my personal vehicles, no problems at all. Done this for hundreds of thousands of miles.
 
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