Ok so I have a 1971 Chevy Caprice 2 door green that has now upgraded it’s status from back up car to daily driver. So in light of this I decided to replace the u-joints as they have been “popping” for a while now when i moved from reverse to drive. Normally i would do this work myself but I hurt my arm doing something stupid. so I took it to a garage close to where i work to have new u-joints put in. 2 days later I went to check why it was taking so long and they had just got it done a few minus ago i was told. OK good.Then the mechanic proceeded to tell me that the reason it took so long is that the drive shaft in my car was a non-rebuild-able drive shaft and that they had to take a die grinder and a carbide bit and make the new u-joints fit. My jaw hit the floor as i hit the ceiling i have been working on cars for 30 years mostly old cars like my 71. I have never heard of a non-rebuild-able drive shaft in my life. after they calmed me down and explained that they didn’t grind on the holes for the bearing cups but on the inside of the saddle so that they could get the c clips in. I still feel that they must have done something wrong. Got the wrong u-joint or didn’t get them fully pressed in or something! The water under the shade tree that i work on my old cars has not dried up yet from all the rain we are getting so i have jack up the car and look at what was done. i have not drove the car at highway speed yet but at 40 it seems to have a very small vibration but this might be my imagination. so my question is 1. did Chevy make a non-rebuild-able drive shaft in 71? 2. could the old u-joints have lasted 44 years and 115,000 miles because i know they had no grease zerk’s on them?
Back then GM came out with what was called a constant velocity U-joint drive shaft.
These drive shafts had two U-joints at the rear of the drive shaft.
The U-joints in these drive shafts were plastic injected into the yokes of the drive shaft. So if you wanted to replace the U-joints you would take torch and burn out plastic injection that held the U-joints.
Then the replacement U-joints were held in place by cir-clips on the inside of the yokes. And this sometimes required a little grinding to get the cir-clips to seat properly.
These double U-joint systems cannot possibly provide a constant linear torque output.
This kind of chintzy penny-pinching has gotten GM in trouble before. It’s the reason the rear axle slid out o my '72 Vega. And it’s the reason I turned away from GM cars until '93… and that one was the wife’s choice. I’ll spare everyone rest of the list of chintzy penny-pined parts that broke on my Vega.
Wait a minute… this is a ‘71, isn’t it? Yup, those were bad days in the GM engineering departments. Those were the days of “value engineers”, whose sole function was to cut the cost of every part and assembly to the bone. Usin’ 12ga on the fenders? Use 14ga.
I had a 72 Impala with the poured plastic retainer. I just pressed the old ones out with a large vise and a couple of sockets. A few pieces of plastic were easy to pick out and the new u-joints with the internal snap rings were easy to install.
Make sure your back end isn’t riding low or the joints won’t last as long as they should. The joints get no benefit from the grease unless the needle bearings get to move back and forth.
No knowledge of 71 Chevy’s, but one time I was replacing a u-joint on my early 70’s Ford truck and the parts place gave me the wrong part. It was too big of a diameter, and wouldn’t fit in the hole in the drive shaft. This happened when I was taking an auto repair class, and I found out later the instructor got pretty steamed and phoned up the parts place, saying he didn’t appreciate them giving his students the wrong part. Learning auto repair is tough enough without dealing with the wrong parts I guess is what he thought.
When I went back in to get the right part, the parts place was very nice and apologized profusely. The correct part as you might expect was the exact right size, I pounded it in using a socket, never had any problem at all with the c-clip. The c-clip fit perfectly in the recess.
We have tons of GM trucks in our fleet, and even some of the models from the 90s and 2000s use those plastic retainers. I think it was called “nylon injected”
If it was a bad idea, they didn’t get the hint
@db4690 … have you figured out a way to install replacement u-joints in your fleet vehicles having this “plastic retainer feature” or do you just replace the entire driveshaft ass’y if a u-joint fails? It does indeed seem like a questionable design idea.
@GeorgeSanJose As a matter of fact, I haven’t had to replace one of those yet
In any case, the service manuals show you how to cut the plastic. Once that is gone, a more conventional u-joint . . . with the retainer on the inside, however, can be installed
Guys, I was doing some reading . . .
I’ll quote a few things from a book now
“A few manufacturers swage (upset or deform) the yokes to lock the bearing cups in place, and these joints normally cannot be rebuilt in the field.”
Here’s a picture
“Driveshafts with bearing cups located by swaging can be disassembled and remachined by some driveshaft specialty shops to accept standard u-joints using snap rings.”
“Driveshafts using plastic intrusion . . . the manufacturer has the ability to align then input and output yokes slightly offcenter to compensate for any yoke runout. Injecting the plastic locks them in this position, and the the driveshaft will run vibration free. This is also true with driveshafts using swaged bearing cups. A vibration can occur if a u-joint is replaced on these driveshafts because the two yokes will now be aligned by the new u-joint.”
Sounds like OP’s driveshaft may now have to be rebalanced. I’m sure one of those shops that makes custom driveshafts for those offroad guys should be able to handle it.
Did the driveshaft have a double cardan joint that the shop couldn’t handle or was the plastic keeper used on GM joints the problem. If a shop is overwhelmed with either of those problems another shop needs to be found.