u joints

[Dats Right]

The vehicle is a 69 521 1300 Ive been getting a good squeak when my u joints are under load. so i am looking to replace them, i read datsun mikes thread on changing them, which was informative but am wondering if there is any other parts i should check or switch out when dropping the drive shatft, was going to get the ac delco ujoints from rock auto, do i need to get into differential bearings and such or will changing the univeral joints solve the problem, appreciate any thoughts on the matter. thanks. datsright

[datzenmike]

Do the U joints and then see. Squeaks under load is likely the U joint. If taking it out, might as well do both. The best kind are the ones the the grease fitting so you can grease them regularly.

[Figbuck]

I have been on a long trip driving through the most insane California back roads. My truck started to make noises. I couldn't figure out for the life of me what was going on. The were squeaks, clunking, banging and other weird stuff. I kept getting under there to see if any thing was falling off!  It kept getting worse and I was in the middle of nowhere at night. 

 

I made it to where I was headed, but five miles out, things started vibrating really badly, like running on rain grooves on the freeway. I thought the transmission was about to fall out.  I jacked it up in my friend's garage, got under there to find out what was going on. I had tried coasting down hills in neutral... engine on and off, slow and fast... it just got louder and stranger. I found a muffler bracket was banging and squeaking. Took care of that but now I could hear the hollow bell like clank of something hitting the propeller shaft as it rotated. I thought something got kicked up from the road and was stuck like a playing card hitting bicycle spokes.

 

So on '73 620 there are two shafts, three U-joints, and the infamous carrier bearing. I could drop the rear shaft out easily with 8 bolts, but all we had was my travel tools. No way to press that shit at all. I called a local Datsun specialty shop to see if I could bring the shaft in. They were swamped but turned me on to a machine shop around the corner. 

 

The guy was very familiar with Datsun/Nissan because he does a lot of work for the Datsun shop. A NAPA store was up the street so I ordered two U-Joints in the morning on the phone and picked them up @ noon. I thought about taking the front shaft out to do the U-joint and replace the carrier bearing while I was there... but I just didn't have a burning desire to crawl under my truck... and I had to get going again on my trip.

 

Unlike the OEM part the new U-joints had grease fittings and cost $19 ea. I don't ever remember changing my U-joints so it's pretty mind blowing that they lasted 42 yeast of constant abuse with me towing insane trailer loads and  never being greased. I think it would be pretty hard to break one of these things even with the bearing races disintegrated. I could imagine it happening. I could imagine it happening while going 80mph down Interstate 280... wondering... what the fuck is that vibration?? Bang.

 

Gary @ Clark's auto and marine machine shop in Burlingame, charged me $60 and got on it right away. He said it was a bitch and he really earned his money. His shop is so badd-assed, fuck me for not taking pics. Basically, it took $100 and most of two days to R & R the propeller shaft, run for parts and service. 

 

Runs like a top again. 

[datzenmike]

The center bearing almost never goes bad,. What happens is the rubber doughnut or isolator rots away abd the shaft it then not supported and can wobble. Well $100 is about $2 a year!!

[MikeRL411]

Original U Joints had the Zerk grease fitting on the central spider of the U Joint.  Replacement units have the Zerk [if indeed they have them] on the end of one of the four arms.  Hopefully the manufacturer took this into account when they balanced the unit.  In any case, be sure to mark the drive shaft collars so that you can at least rebolt the drive shaft in a condition where it was at one time balanced!  When I rebuilt my engine I did a U Joint replacement as a "why not, you have the drive shaft on the floor" inspiration.  Thank the lord I didn't go the whole "why not it's up on jacks" default otherwise my car would still be on the jacks.

[Dats Right]

Thanks, just got my u joints,and reviewing the process i realize i  cant find instructions on how to remove the driveshaft.  so do i have to drop the drive shaft by removing the 4 bolts on rear of shaft, and if so does the front just pull out, will that drain out all my tranny oil, i recently changed it hoping that wasnt a waste. and  another foggy area for me is removing the old u joints, so the caps should pop out when i crank the yoke with a hammer, is that right., and when i put the new ones in i first pop the caps off then press them from the outside. am i misunderstanding anything,.ok and by the way i did read the u joint how to, which was great but want to make sure i fully get it. thanks for the help.

[datzenmike]

The spline in the 521's transmission is bolted in. The spline and driveshaft both have a flange where they are bolted together. Just unbolt the flange and remove the driveshaft. Nothing will leak from the transmission.

 

The u joint has clips that must first be removed before hitting with a hammer.

[Dats Right]

thank u datzen mike, sorry last question on this but are there two flanges to unbolt one near tranny and one near differential?, thanks much

[datzenmike]

Hold it! This is a one piece driveshaft!!!! So yes the oil will come out the back of the transmission.

 

The '70 and on 521 is as I described so forget that.

 

Probably best to drain the transmission oil and refil with fresh GL4 90W. Sorry about this but the one piece driveshaft just pulls out of the transmission. Just unbolt the single flange at the differential.

[Dats Right]

Thanks got the message just in time, greatly appreciate the follow up, probably would of figured out the hard way. thanks much

[datzenmike]

I did once changing a speedo pinion. The GL4 comes out pretty quick!

[Dats Right]

Holy shit, just switched out the u joints, that was a knuckle busting project indeed, though my neighbors suffered worse with my hammer banging till late night, thanks again datzen mike, dumped the gl4 first. had needle bearings falling out of grease fitting hole at one point, pulled apart and repacked. done, datsright.