4wd front drive shaft - need help

[CCCC]

1972 K5 Blazer, 350, 4 speed, NP205 TC. Started hearing a steady "bump" sound at slow speeds when in 4wd with hubs engaged. Seems like it is the front drive shaft because, although the two universals are tight, there is play at the joint in the driveshaft and it gives a slight clunk when I move the shaft up/down at the joint - the two parts are not mated firmly.
Never before noticed that the shaft is two-piece and, of course, never seen inside the joint. The shop manual does not show or describe the drive shaft. So, before I start taking things apart, need some wisdom from you experienced guys.

Is that joint splined, and how is the connection made tight and without play? Is there a bearing in there, or? Does anybody have a pic of the inside setup or a parts blow-up showing what is going on inside there?

All help will be appreciated. Thanks for reading.

[csb#356]

Its a cv joint and its two u joints and then a "thing" in the middle of them, Can't really remember what its called, Its been a while since I've taken one apart. But I believe the "thing" is the part that commonly wears out. Should be able to have a driveline shop rebuild it for not very much. I'm sure somebody will correct me if I'm wrong or give you the correct terminoligy.

[Stocker]

Originally Posted by csb#356

Its a cv joint and its two u joints and then a "thing" in the middle of them, Can't really remember what its called,

Double cardan joint?

[csb#356]

The picture that Stocker posted is what I was talkin about but I forgot about the slip yoke. Oops

[Blazer1970]

Yes, it is a spline and yours is worn out. You need to take the shaft to driveline shop and have a new slip joint welded in. It is very common for that slip joint to wear out over time. Should be $150 - $200 at the most.

[CCCC]

Great. csb#356, Blazer1970 and Stocker - thanks for the info. I am in good shape and will remove and fix - except that the closest drive line shop is over 200 miles from home. Maybe I can find a good on on the Forum.

It seems simple enough once encountered, and have to look at the other 72 Blazer to see what shape it is in.

Actually, this part would seem to be a really weak spot in these Blazers because, although this truck has over 100k miles, not very many of them are actually in 4wd and the remainder of the stuff from TC and forward is strong and tight. Now that I think about it, I have to wonder why GM did that spline joint - seems like the earlier 4wd had a solid shaft. Anybody?

Thanks again.

[Mkcustums]

It has to be splined for the shaft to get longer and shorter when the suspension cycles.

[CCCC]

Anyone know any sources on this forum (or elsewhere online if necessary) to reasonably purchase a good used, or new/rebuilt splined front drive shaft for 72 Blazer?

[Mkcustums]

I'm not super familiar with the pre '73 stuff, what are the differences with the front driveline at the year/body change? Copied from Craigslist~~ "73 4x4 blaxer front and rear drive shaft for sale" - (albuquerque )

[CCCC]

Thanks Mkcustums - I am following up on that ad. Does anyone here know off the top of your head if the stock drive shafts on a 73 Blazer are identical to the 72? Thanks for any info.

[csb#356]

If the one out of the 73 is from a 205 t case then it will work. 203 and 205 transfercases have different length driveshafts. You also just have to make sure that your driveshaft and the one your getting have the same yokes. Some 70s trucks have square yokes on the transfercase. And its also hard to be sure that this other shaft doesn't have the same issue as yours because I have seen a lot with that problem.

[Mkcustums]

Yeah, it's kind of a gamble really. Like he said, it might be as bad, possibly even worse.

[DavTay]

I just had my front drive shaft completely rebuilt.
I think it was around $350 for everything.

Slip Yoke, CV Joint and U-joints.

Once removed you should be able to feel/see what is wore out.
If the center ball of the CV Joint is good and the Yoke is good you should be able to replace the U-joints yourself.

[CCCC]

With the shaft still on the truck, both universal joints seem very tight - no play at all in the joint connections at either end, so maybe will just need to clean and re-pack them with grease while apart.

Thanks for the info DavTay. Never have had this assembly apart, so have never noticed a "CV Joint". The front of the drive shaft connects directly to the front diff, so when you mention "CV Joint" do you mean the joint at the front of the transfer case where the back end of the drive shaft U joint connects? If that is a CV Joint, is it ordinarily a bad wear spot?

I am checking out the shaft that is for sale - hoping that it fits properly and is not worn at the splined joint.

Thanks for all info.

[DavTay]

Originally Posted by CCCC

With the shaft still on the truck, both universal joints seem very tight - no play at all in the joint connections at either end, so maybe will just need to clean and re-pack them with grease while apart.

Thanks for the info DavTay. Never have had this assembly apart, so have never noticed a "CV Joint". The front of the drive shaft connects directly to the front diff, so when you mention "CV Joint" do you mean the joint at the front of the transfer case where the back end of the drive shaft U joint connects? If that is a CV Joint, is it ordinarily a bad wear spot?

I am checking out the shaft that is for sale - hoping that it fits properly and is not worn at the splined joint.

Thanks for all info.

Pictures help. The drive shaft is composed of a front universal joint, slipe yoke and the rear of the shaft is attached to the transfer case with a CV joint. The CV joint is like the picture Stocker posted.

I think the rear CV joint would be an area of wear because it very difficult to grease. It has three grease fittings, one for each u-joint and one for the middle ball. My new ones have the flush grease fittings.

Sounds like the middle ball is wore. This would allow you to push up on the shaft and feel movement if the u-joints feel good.

Removing it will really tell you what is wore.

When i removed mine the u-joints seemed decent but the middle ball in the CV joint had a whole lot of slope.
Removing the drive shaft is relatively easy. The hardest part is removing the long bolts at the t-case. You can only turn the bolts a very little at a time.

I found laying on back, propping up my head on a soccer ball and using a short wrench I was able to remove them. Find the position which works and then just rotate the shaft to loosen each bolt. I found it easier to remove the bolts when they were located on the top.

If you do a search you will find other posts on front drive shaft removal.

[CCCC]

Thanks for the notes guys. I am getting ready to remove the shaft today or tomorrow. The splined joint DEFINITELY is worn and has noticebale play. I now understand about the location of the CV joint/ball and will take a good look. I have kept this truck very well lubricated and am hoping that there is no big wear at the CV ball. Right now there is NO play or movement at that universal and CV joint no matter how i position the shaft. Hoping for just a splined joint repair, but am also looking for a good/tight shaft and CV joint to buy here from someone. Know anyone?

Here are a couple of pics of the situation.
#1 Splined joint. #2 Front joint #3 Rear CV to transfer case

[Mkcustums]

Easiest thing would be if you could snap a couple pics of what you have. (if you can)

[Mkcustums]

CCCC Here is a page that might answer some questions and get you a little more familiar with what you are dealing with. I hope it helps!

http://www.pirate4x4.com/tech/billavista/PR-shaft/

[CCCC]

Thanks Mkcustums - excellent site with nice illustrations and gives the correct terminology. I hope I don't have to use those terms too often in the future, but there are four old 4wd Chevs here..

Having taken the double cardan apart I understand how it works and what is needed. Now I have to decide between pre-lubed/sealed or periodic lubed joints and where to get the best quality stuff for a price. After reading everything, I want to get Spicer parts, and this site may be the place.

Thanks again.

[boundstaffpress]

I bought a whole front shaft off of ebay from this guy. http://myworld.ebay.com/cjtatton
I have been very happy with it. I think I payed $250. It came with 7-9 inches of slip spline.

[brad_man_72]

this style double cardan will have alot of snap when moving across center (watch your fingers) since you need to have a driveline shop weld in a new slip stub and supply a new slip yoke it would insanity to do the double cardan yourself. Be sure they ballance your like new shaft.

I'm pretty sure theirs no way to get a standard grease gun on a zerk fitting in the DC joint. Get spicer life ujoints and then all you have to worry about is greasing the center kit of the DC joint and the slip.

building driveshafts is my job. A professional knows what to look for and how to fix it and how to make the repairs last a long time.