Rhythmic Klunk

[Nanoose]

No - not the name of a new band.

The snow has melted and I noticed a rhythmic klunking sound as I coasted to a stop on a smooth road. It may have been there for a few days but the snowy roads mad things pretty bouncy so I may have missed it. (I have a 1955 86")

Sounds like it's coming from the right side and if I had to guess I'd suggested it's the rear. Klunk speeds up and slows down with vehicle speed but seems to go away above 5 MPH or so. Makes no difference if it's in high, low 2WD or 4WD but I did notice that it doesn't happen if I've got any gas applied - it's only when coasting or slowing.

Anything leap to mind as to cause? What's the best way to check?

It's raining in biblical proportions at the moment so I'm hoping to get some idea before I head out into the deluge to check.

Thanks!!!

Dave

[stomper]

Bad U Joint? Grab onto the rear drive shaft and try to wiggle it around. My guess is there will be some slop in one of the directions.

[jonnyc]

I had a similar rhythmic clunk. Turned out to be a few missing teeth on my rear diff.

[Terrys]

Maybe brake drum, slightly out-of-round, dragging on leading edge of shoe. Could also be a U-joint heading for retirement.

[Les Parker]

Have you made sure the parking (handbrake) brake is fully released?
Could be the shoes just catching on the drum as you slow down speed up?
Also could be a bad brake spring inside the hub/drum causing the same noise.

2p

[Nanoose]

Thanks so much for your help!

I get the feeling that it's not brake related. I don't feel any drag at all...maybe that doesn't mean anything but if I had to bet I'd guess universal joint.

Do you know if Series I's use the same parts as Series II/III?

Dave

[stomper]

I don't know the answer to that question, but I do know that it is pretty easy to pop the drive shaft off, and run it down to your local parts house (NAPA) and have them figure out which Spicer U-Joint you need. They are all standard sizes on most trucks, so they should have the right one in stock. Make sure your new one has a grease fitting, and you may want to replace the front and rear U-joints to ensure you don't have to take it apart again in the near future.

[Tsmith]

If it's been sitting in the col for a while, it may be a flat spot on the tire. As it warms from normal driving, it should go away. My tire are old and I get the rythmic thump for the first few minutes.

[cedryck]

check the condition of BOTH universals in your rear drive shaft. Pull both rear drums and check condition of shoes, and springs. Are your hub nuts properly tight?

[SafeAirOne]

If it's been sitting in the col for a while, it may be a flat spot on the tire. As it warms from normal driving, it should go away. My tire are old and I get the rythmic thump for the first few minutes.

SIDE NOTE: This is especially true of bias-ply tires (as opposed to steel belted radials).

[disco2hse]

1. Tyre has a flat spot (most likely cause and very likely on cross plies, even after just a day or two sitting).
2. Hub is not round (but more likely to result in a rhythmic scratching/scraping than a klunk)
3. Wheel nuts are loose (seriously, this is more common than you think)
4. Wheel bearings are worn and about to collapse (this too)
5. A worn uni would be felt rather than heard. By the time you hear it, the joint would just about ready to break. Of course one would be checking the uni's on the steering and not the drive shaft
6. A squirrel is stuck to the tyre (most probable cause: whilst previously frozen to it, it is now impressed upon it)

Series I parts are significantly different to II and III.

[Jeff Aronson]

Generally, if the klunk goes away when you accelerate, then it's driveshaft related because you're now applying steady pressure to the u-joints or the splined driveshaft. Releasing that pressure would allow them to "wobble" and vibrate. Take off that driveshaft and shake the u-joints at both ends; you'll be able to feel the wiggle if one or both are wearing out. Check the splines by twisting each end of the shaft in your hands in separate directions; if you can twist the shaft at all, the splines are worn.

Have you greased the splines and the u-joints regularly?

If your vibration was tire related, it would be unlikely to disappear with such a small change in speed.

As Les noted, if your parking brake were not releasing properly, you'll feel that klunk until your road speed prevented the emergency brake shoes from grabbing.

I've experienced each of these situations over the years. When the splines on my rear driveshaft were weakening, I purchased a new shaft from Rovers North that also came with new u-joints. There were different sized yokes used on the Series II-A and Series III models, and that may be the same with your late Series I.

Good luck and let us know what you find,

Jeff

[Nanoose]

Guys,

Thanks so much for your advice! I've been checking things out this morning and there is a bit of play in the u-joints so I'm working on dropping the prop shafts. It's going pretty slow but cursing is still within reasonable tolerances.

My plan is to drop the shafts and just take them into a local shop to have them fit the new u-joints...I'll keep you posted.

Dave

[Nanoose]

Well - I dropped the front and rear prop shafts and they look and feel fine. No play at all. I think I'll check the wheel bearings.

[Nanoose]

The klunk is gone...

Put it all back together and drove 5 miles or so and the sound seems to have disappeared. Odd... I didn't notice anything particularly loose but cleaned things and greased liberally. But I'm not going to look a gift fix in the mouth.

Also, I realized something halfway through the job.

I fought and cursed the bolts on the top of the flanges. They were a real bugger to remove. No room, no visibility, a sincere pain. Once I got it dropped I took a coffee break and as I sat there pondering I realized that if I put it in neutral and released the shaft brake I could rotate the shaft and the bolts would be accessible. Made taking the rear shaft off A LOT easier. Like, duh...