driveshaft------shafted?

[Former member Yoder213]

New here after some months of watching from the sidelines
I got a 1970 C20 FOUR WHEEL DRIVE (that's what the badges say, doesn't sound like anything I've seen posted about yet)
He's got the 292, bored .40 or .60 over
4 on the floor, 4.56 with factory Detroit locker and impossible to find drums.

I'm the third owner, PO had it since '73, added power steering, switched to HEI, and added a couple gas tanks. I love the truck and plan on caring for it like he had, but...

I've developed a strange, or what I think is strange, sound and behavior in my driveshaft.

when parked, (cant remember if it was in gear or not) I can rotate freely my driveshaft what seems to be a normal distance counter clockwise (looking at the pumpkin out through the back of the truck). then it tightens up, makes a loud "tink" that sounds like it comes from the shaft, then it frees up and rotates another distance equal to the first.

Where should I start looking to figure this out? I can hear the noise happening when driving and at times where I think the shaft would be allowed to "play" but I wasn't raised around a mechanic and try to absorb everything I can from the older mechanics and ones who sound logical, like these forums hahahaha

thank you all, I plan on becoming familiar with this site as I restore my truck.

[cleszkie]

Do you have a CV joint in your rear diveshaft? If so, That is the first place I'd look for that noise. The CV joint probably needs to be rebuilt. The CV joint will be located at the transfercase end of the driveshaft.

BTW, The badge (or entire fender) on your truck sounds like it was monkied with some time ago. A 3/4 ton 4x4 would have K20 badges.

[Former member Yoder213]

Thank you, I'll get under and find out about the CV joint tonight.
and about the badge, your probably right clesckie. The PO is pretty trustworthy, but maybe a little boastful. He said it was an earlier model before they made that distinction, but I haven't found anything to back him up yet.

[Former member Yoder213]

actually just found a picture of a 1970 C10 with the same four wheel drive badge, so maybe

[Ol Blue K20]

The only places you will see the K is on the VIN and spid. The fender emblems will say C, there was no K emblems except on Blazers K5

[TBONE1964]

I have had the same problem on a 1/2 4x4 and my front shaft had a CV near the transfer case. I rebuilt mine myself and solved the problem. You need a little patients to do one and it usually takes 4 1/2 hands and a vise, but it is doable.

Also I concur with Dale about the K/20 badging, no such thing except on the spid.

[SS Tim]

Originally Posted by cleszkie

Do you have a CV joint in your rear diveshaft? If so, That is the first place I'd look for that noise. The CV joint probably needs to be rebuilt. The CV joint will be located at the transfercase end of the driveshaft.

BTW, The badge (or entire fender) on your truck sounds like it was monkied with some time ago. A 3/4 ton 4x4 would have K20 badges.

Movement with a metalic sound like a u-joint going away. There should be no movement between the bearng cups and the center trunion of a u-joint. If the joints test good look at the splines on the driveshaft, again there should be little relative movement.

On the fender badges, Chevrolet did not use "K" badges on the 4x4 trucks until '73 with the lone exception of 69-72 Blazers.
In you case the truck sounds like a base C-20 (3/4 ton) truck. A four wheel drive emblem will be under the front marker lamp and if the 292 is factory there should also be a 292 engine badge directly below the series C20 emblem.

A quick check of the VIN number will indicate if it is a factory 4x4. Again in your case the VIN on the door post plate and the glove box door SPID should start off KS240. Might want to review the decoders in my signature if you still have a question there.

[Ol Blue K20]

Originally Posted by SS Tim

Movement with a metalic sound like a u-joint going away. There should be no movement between the bearng cups and the center trunion of a u-joint. If the joints test good look at the splines on the driveshaft, again there should be little relative movement.

On the fender badges, Chevrolet did not use "K" badges on the 4x4 trucks until '73 with the lone exception of 69-72 Blazers.
In you case the truck sounds like a base or Custom C-20 (3/4 ton) truck. A four wheel drive emblem will be under the front marker lamp and if the 292 is factory there should also be a 292 engine badge directly below the series C20 emblem.

A quick check of the VIN number will indicate if it is a factory 4x4. Again in your case the VIN on the door post plate and the glove box door SPID should start off KS240. Might want to review the decoders in my signature if you still have a question there.

Not to hijack the thread but this made me think about something. Did the 2 wheel drive Blazers have a C5 badge or the K5 only? I would test the u joints first for the noise by the way.

[TBONE1964]

http://arrc.ebscohost.com/ebsco_stat...t_Velocity.htm

Figure 6 on the link shows the cardan constant velocity set up, which is what you should have. I will tell you from experience that it is very difficult to diagnose a bad u joint on this set up because of the way it is set up. The centering ball and seat under spring tension and is also known to fail and will cause the problems you describe.

[Former member Yoder213]

Thanks everyone. sounds like a job for someone with the right tools, time, and location.
K is in the VIN. Right on the money there.

For being my first post I'm incredibly impressed with the responses.
glad I quit stalking and joined.

[Ol Blue K20]

Originally Posted by Yoder213

Thanks everyone. sounds like a job for someone with the right tools, time, and location.
K is in the VIN. Right on the money there.

For being my first post I'm incredibly impressed with the responses.
glad I quit stalking and joined.

Well I'm glad you quit "stalking" too, that word creeps me out.. Welcome from the middle of the state...

[SS Tim]

Originally Posted by Ol Blue K20

Not to hijack the thread but this made me think about something. Did the 2 wheel drive Blazers have a C5 badge or the K5 only? I would test the u joints first for the noise by the way.

Would need to look into it but IIRC all 69-72 Blazers were badged K/5 Blazer. Funny part is GM still considered them CK10s.

[Ol Blue K20]

Originally Posted by SS Tim

Would need to look into it but IIRC all 69-72 Blazers were badged K/5 Blazer. Funny part is GM still considered them CK10s.

apparently they were considered they're own animal. I've never paid any attention to it....I've only had 4x4 Blazers

[Keith Seymore]

Originally Posted by SS Tim

Would need to look into it but IIRC all 69-72 Blazers were badged K/5 Blazer. Funny part is GM still considered them CK10s.

Because...."Marketing".

Marketing can ask for whatever they want on the side of the truck but it doesn't change the engineering content of the vehicle itself (or the engineering release).

A good example of this was the later change from C10, C20 etc to "C1500", "C2500" etc.

Nothing changed on the truck itself but it sounds "bigger".

K

[BrianG]

Originally Posted by Keith Seymore

Because...."Marketing".

Marketing can ask for whatever they want on the side of the truck but it doesn't change the engineering content of the vehicle itself (or the engineering release).

A good example of this was the later change from C10, C20 etc to "C1500", "C2500" etc.

Nothing changed on the truck itself but it sounds "bigger".

K

I've been wondering this a while myself. I have 69 "C-10" 4x4. I always figured someone put 2wd fenders on it before me. .... so what did a 69 K-10 have on the fenders if it were a stock model. custom model, super model, etc.

Thanks,

[SS Tim]

Brian, This is getting way off track but to answer your question the emblems were as follows for a 69 K10.

Fender series emblem: base is C/10, Custom is Custom/10, Custom Sport Truck is CST/10.
If the truck has the Custom Camper option it superceeds all others with a CustomCamper/10 emblem.
Below the series emblem if the truck has an optional engine there will be a badge, 292 or 350.
Under the front marker there will be a four wheel drive emblem.

[BrianG]

Originally Posted by SS Tim

Brian, This is getting way off track but to answer your question the emblems were as follows for a 69 K10.

Fender series emblem: base is C/10, Custom is Custom/10, Custom Sport Truck is CST/10.
If the truck has the Custom Camper option it superceeds all others with a CustomCamper/10 emblem.
Below the series emblem if the truck has an optional engine there will be a badge, 292 or 350.
Under the front marker there will be a four wheel drive emblem.

Thanks, I know it was off topic from the original thread, but others had brought it up so I just had to ask. Thanks for the reply. Seems rather strange that they would put C/10 emblems on a K/10 truck, but I suppose it could have been a cost thing.

[brad_man_72]

Best to take a double cardin style joint to the pros, even when done properly you can change the ballance enough to cause the shaft to fail.
Also if the pin isn't within specs your shaft will need a new weld yoke welded on and reballanced.
If the shaft changes angle easily without snapping over center the center kit is worn out. Also if theirs any play in the joint something is wrong.
Besides checking for those 2 things theirs not much anybody that doesn't work in a driveshaft shop can do. Don't take it any place that doesn't specialize in drveshaft work, I know they seem smple but there's quite a bit of specialized knowledge and tools requred to do the job correctly.
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