Clanking noise in drivetrain (1970 4X4 c10 4spd).

[Boxxman]

I'm new to this site. Came here completely baffled by my 1970 4X4 C10. There is a significant noise coming from what sounds like right beneath the cab. It happens when torque is let off, or applied to the drive train (shifting gears/letting off the gas). I've had buddies watch the driveshaft where it enters the transfer case and the CLANK noise is perfectly in sync with the application/removal of torque. That said, I've had three shops look at it. The first changed the gears in the rear differential/U joints, rebuilt the clutch (4 speed BTW). The second shop swore they found the noise in the front lockouts in the hubs and replaced those. I just picked the truck up this morning from a transmission shop (the first two weren't just tranny shops); who said all was tight in the tranny AND the transfer case (205PT) didn't know what else it could be. I've got about $2500 invested in all of the above and the noise hasn't abated at all. It drives great and shifts great BUT Sounds like crap in the on/off torque situations. At this point I'm out of options, each of the three places that worked on it are reputable, but still couldn't fix it. Of all the c10's out there, I'm hoping someone with a fix will recognize my description. Please help!

[kwmech]

Can you post up a link to a video or something?

[CUSTOM/10]

To me it sounds like the coupling between the transmission & transfer case is worn & the output shaft is also worn on the tranny. On the standard trucks the splined output shaft & coupling only have about 2" of contact length and they get worn and have slop kind of like a worn out u-joint.

Gary

[cleszkie]

Originally Posted by CUSTOM/10

To me it sounds like the coupling between the transmission & transfer case is worn & the output shaft is also worn on the tranny. On the standard trucks the splined output shaft & coupling only have about 2" of contact length and they get worn and have slop kind of like a worn out u-joint.

Gary

X2. This is what I was thinking as well. Its a 10-spline female coupler that can get worn out quicker with hard use, or with many years of regular use. New couplers are relatively inexpensive and easy to find. However, you will have to pull the NP205 off the back of the SM645 4-speed to access your current coupler. You will also want to pull the SM465/NP205 adapter off the back of the tranny to inspect the tranny output shaft. If your output shaft splines are worn out, you will probably have to have a new output shaft installed to get rid of the slop.

[CountofMonteCarlo84]

This is kind of simple, but it seems like you have exhausted several potential solutions. Perhaps it is as simple as your exhaust flexing under load. I have had exhaust that has been on vehicles for years suddenly become noisy from more flex, hitting the floorboard, or other changes that impact it.

[jjzepplin]

Mine had that clunk and as stated above the rear output of the trans was badly worn and the coupler was dang near broken.

[Boxxman]

Thanks for the responses guys. I'm not a gear head so I took my computer to the shop that started the process so they could see your posts. Turns out that all splines and shafts to and from the transfer case have been replaced. They're a 4X4 shop and said this was their first thought as well. They just told me the only thing that still has some play in it is the carrier (pin is sloppy). They didn't change it as it was in the rear and the noise was coming from the front (or so we all think). Possible that a loose carrier can cause this type of event/noise?

[Spullar]

How about a possible broken mount or bolt?

[Boxxman]

Also checked and re-checked. Several of the shops first suspected either a motor or tranny mount issue. Both have been ruled out.

[jeffahart]

Start with the easy thing first. Unhook all linkage from the transfer shift lever to the transfer, see if clanking stops.

When I first got this particular truck, I took it to a radiator shop to get it flushed. My son and I were talking about an annoying clacking noise. Talked maybe trans or transfer. The man from a neighboring trans shop stuck his nose in, without being asked. He said the trans and transfer needed rebuild. I said thanks. When I came to get the truck later, after radiator was done, the man came over again, and he said he took a look, and the trans and transfer needed to be rebuilt for sure. So, couple days later I'm riding in my truck with my son. He driving, me in the passenger with the window open. There was that dang noise at speed again. I grabbed the antenna and the noise stopped. I grabbed the styrofoam 76 ball from the end of the antenna. It was catching wind and clacking against the drip rail. looked over at my son and said "Just fixed the tranny and transfer".

Bottom line, noises are tricky. You don't really know where its coming from. We both could have swore that noise was coming from under the floor board. Chase it by buttoning everything down first. Then toss the bucks at it.

My two cents... probably worth the price paid!

[Boxxman]

Changed the carrier and at the same time put posi-traction in. The carrier replacement eliminated most of the noise. The pin holding the spider gears was "sloppy", the new carrier tightened it up and help significantly. Thank you again for your suggestions.