Return of the Rear Axle Clackity Sound

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Sat Jul 24, 2021 5:03 am

That's a good one, 1263.
Wonder what the sound would be like as a comparison if you took a small ball peen hammer and pecked on the differential housing ???
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Re: Return of the Rear Axle Clackity Sound

Post by GPW1263 » Sat Jul 24, 2021 7:17 am

Well, now that I actually hear it I'm beginning to think that the hollow quality of it (think, coconuts) may well be outboard, as mentioned by a previous member....like maybe something going on inside a drum.

I would jack that thing up very securely, put it in gear, get under there, put an old screwdriver to my ear and poke around until I figured out EXACTLY where that sound was coming from. For anyone else I would only advocate doing that on a honest-to-God LIFT.

Do as I say, not as I do.

BUT

Everyone seems to agree that, whatever the sound is, it's in the rear end so... why not pull the drums off and do a brake inspection? That seems a sensible course of action. If nothing can be found, well, that rear end HAS to come off and out. Simple as that.

I would also love to hear what that sound might be like while NOT under a load (i.e. running it with the rear drive shaft removed and motivating with just front drive engaged.)

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Re: Return of the Rear Axle Clackity Sound

Post by dinof » Sat Jul 24, 2021 9:08 am

2 rear ends making the same exact noise? How does one explain that?
Time for him to play the lottery!
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Re: Return of the Rear Axle Clackity Sound

Post by warbirdphotog » Sat Jul 24, 2021 5:38 pm

Wolfman wrote:
Fri Jul 23, 2021 6:22 am
Drive shaft length. I brought this up way back. There is a difference in CJ and GPW drive shaft lengths. CJ or GPW springs installed ?? I am wondering about the bolt location of the spring center bolt on the each type axle ?? Like CJ springs with a GPW axle and GPW driveshaft so the drive shaft is not centered correctly ??? Like when the CJ axle was on a CJ spring ??? Screws up the drive shaft length needed ???
It's the original GPW driveshafts (both marked) and original GPW springs (bolts/riveted brackets marked on all 4 springs). The springs are the correct angled edge style as well and the correct earlier style with the 9 leafs (for the rear). No reason to think that anything, other than the rear axle (only talking about the rear here) was CJ. It literally looks like the farmer, sometime in the Jeep's post-war life, removed the original GPW axles only. He got a set of CJ axles (early style) with CJ leaf plates, CJ U-Bolts, and the CJ steering (drilled holes and mounted it to the front cross member) with a CJ drag link. Everything else remained original GPW. So, I removed all those things, got the GPW axles, NOS GPW drag link, U-bolts from Ron (F marked), and repro leaf plates.
Wolfman wrote:
Fri Jul 23, 2021 6:22 am
Still a little fuzzy on the pinion bearings & races. You say they were new. ??? Is this new bearings and races installed in the first axle and moved to the second axle or new bearings and races installed on the first axle and a second set of new bearings and races installed on the second axle ??
If the same bearings & races in both, the noise moved with the bearings & races ???
Negative, brand new bearings/races for each axle. So nothing was shared between the ring/pinion/carrier between axles. Those are totally different TIMKEN bearings/races on all of that. It's the same bearings/races for the drums, but they were brand new. I think the only bearing not Timken is the pinion ones, those I got JMP bearings/races each time.
Wolfman wrote:
Fri Jul 23, 2021 6:22 am
As for the load on the pinion bearings, I am not sure you understand what I am saying.
As you saw in my video I posted, one theory was that the angle of the axle dip was causing extreme movement of the pinion to the point it was causing abnormal striking or clattering with the ring/bearing. But keeping the axle near level would mean the pinion is now moving with a lot less force, which (in theory) should change the sound even slightly since there's less torque on deceleration. But the video showed that the sound did not change at all, which I think proves that this theory was not the cause here. However, if there is something wrong with the pinion bearing (the inner one), the problem would be that it's a different pinion, different bearing, different race, different axle. So that's where I wouldn't think the bearing would be the case here?
Wolfman wrote:
Fri Jul 23, 2021 6:22 am
Still of the opinion, if we get this figured out, it is going to be something simple like what I have just suggested. Not something, "Catastrophic". Mike
That's my hope! :-D I still am hesitant to have the thought that we'll ever truly figure this out, but as someone said, if we do finally figure out the issue it'll feel all that much better.
W. Winget wrote:
Fri Jul 23, 2021 7:23 pm
Seem to hear it klacking as it's going up in speed, then really klacking fast as it backs off.
Now I don't see this as center gear/shaft issues, more thought along the line of a wheel lug head (stud) impacting a brake piece inside the drum perhaps?
I've heavily inspected all those items (and they've been painted with Red Oxide, so any striking I would have been able to ID). After the first axle had the problem and I went to work on the second axle, I had to reuse the drums from the first axle. I made sure to REALLY check them out for any marks, scratches etc. After the second axle had the issue, I had the drums re-honed just in case that was the issue. I again checked for anything striking on the brake plates or drums and found nothing. Furthermore, pointing the GoPro at the wheels and the sound is not nearly as loud as pointed at the differential housing.
W. Winget wrote:
Fri Jul 23, 2021 7:23 pm
you have likely covered a video of the rear axle up in the air spinning, but I cannot recall, that would really let you hone in on it better, tires could be removed, put in gear and driven in static with walk around to maybe narrow the knock better.
That's the problem. On Jacks, the sound is 100% gone. If the wheels are not under load, the sound is not present. I've tried this with the wheels on driving in all gears, quiet as can be. Makes things even more PIA as you say!
dinof wrote:
Fri Jul 23, 2021 7:36 pm
One last thing from me......from the area of the front yoke flange to parking brake drum. Are the bolts tight? Maybe you say yes, but the 4 bolts, make sure there is not any shoulder on the bolts that appear to be tight, but it's merely running out of thread. Worth a look.
Yes, not only are they tight, but I welded the bolts to the drum. As you know, it's a pain in the butt to keep those bolts in place as you're trying to get the nut on. So, since I have a repro drum (from Ron), I went ahead and welded the bolts. It makes things so much easier! BUT, the sound appeared first before I did this. I welded them when replacing the first rear axle with the second one. It's also a brand new flange (again, sound appeared before I replaced the flange).
GPW1263 wrote:
Fri Jul 23, 2021 7:38 pm
I'm beginning to understand your annoyance with that sound.
Maybe you should look around carefully.....and if you see THIS guy.... :lol:
That's pretty funny! Ha ha. Could also be one of these guys in the rear axle!
Image
GPW1263 wrote:
Sat Jul 24, 2021 7:17 am
I would jack that thing up very securely, put it in gear, get under there, put an old screwdriver to my ear and poke around until I figured out EXACTLY where that sound was coming from. For anyone else I would only advocate doing that on a honest-to-God LIFT.
That's the biggest problem. When not under a load (on jacks) the sound is 100% gone. I've tested this twice now. No matter what gear you put it in, no clackity what-so-ever. Frustrating to say the least! The only time you can really diagnose it is when you're driving!
GPW1263 wrote:
Sat Jul 24, 2021 7:17 am
Everyone seems to agree that, whatever the sound is, it's in the rear end so... why not pull the drums off and do a brake inspection? That seems a sensible course of action. If nothing can be found, well, that rear end HAS to come off and out. Simple as that.
Drums have been off. Remember, this is the second GPW wartime axle that's had this same sound. I've re-honed the drums, readjusted the brakes several times, checked for any strike marks or paint being rubbed away. I can't find anything on the brake plates or drums. I also took my out-of-spec GPW drums and put them on just to test, sound was still there. Two different set of drums completely with a different set of bearings/races on each.
GPW1263 wrote:
Sat Jul 24, 2021 7:17 am
I would also love to hear what that sound might be like while NOT under a load (i.e. running it with the rear drive shaft removed and motivating with just front drive engaged.)
If the driveshaft is removed, the sound goes away 100%. Again because the rear axle isn't under torque load from the driveshaft. So I can drive it in 4-wheel drive without the rear drive shaft and have no sound. As mentioned, I have swapped the rear driveshaft out with another wartime one, and the sound was still there. So it's not driveshaft-related.
Last edited by warbirdphotog on Sat Jul 24, 2021 5:43 pm, edited 1 time in total.
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Re: Return of the Rear Axle Clackity Sound

Post by warbirdphotog » Sat Jul 24, 2021 5:41 pm

A few people are mentioning things that have already been tested/ruled out. I thank you ALL for your questions, observations, suggestions, etc no matter what, but I wanted to point out this post I made that goes through everything I've tried so far up until about a month ago: viewtopic.php?f=4&t=323316&start=105#p1887104
Britt
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Re: Return of the Rear Axle Clackity Sound

Post by GPW1263 » Sat Jul 24, 2021 7:50 pm

I don't want you to take this the wrong way but you seem to be justifying things in a way that is an impediment to the logic that is going to help you get to the root of the problem.

As another member pointed out, you are claiming that with TWO separate axles both are making that noise? You would never get odds on that in Las Vegas because it's purty near impossible.... UNLESS the same fella did the exact same work on both rear ends and/or ended up using the wrong parts on both rear ends or some other similar set of circumstances....but it's still a real stretch in logic when you think about it.

NOW I'm thinking that this issue is more likely something else altogether. It's a BIG knock and that means whatever it is, is BIG. That is not a small needle bearing ratcheting noise like in a universal joint. It's a knock. Eliminate the load on the rear end and it suddenly stops...on BOTH rear ends?!! Then it's not the rear ends. Nope.

More likely you're going to find your culprit up in the output shaft bearing in your trans which is the point at which both rear ends intersect in any way (discounting the drive shaft of course).

Driving it until it breaks really doesn't make a lot of sense to me. BUT, taking it out for a good long drive does... Then, pulling the fluids out and seeing what that tells you. That's a pretty big knock and I'd be looking really hard at any of the larger bearings. They're what's carrying the load.

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Re: Return of the Rear Axle Clackity Sound

Post by 1944gp » Sat Jul 24, 2021 10:16 pm

Can you get access to a dyno to load it up but may get a look/hear under neath when not moving?

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Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Sun Jul 25, 2021 5:54 am

Still not sure you understand the point I was making.
I am not talking about the pinion gear and shaft actually moving fore & aft in the case.
I am talking about bearing load on the pinion bearings & races from the tapered/spiraled pinion gear forcing the ring gear to rotate under load, forcing the pinion bearing into the race. Jeep on the ground accelerating or decelerating, with the driveshaft installed.
With the driveshaft out, this bearing pressure does not happen. The pinion & shaft is free wheeling.
This was also working on the theory that one of the bearing rollers was defective and you moved the bad bearing in question to the second axle assembly.
I now know this did not happen.
Still thinking.
Mike Wolford
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EAA ( 49 yrs)
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Re: Return of the Rear Axle Clackity Sound

Post by W. Winget » Sun Jul 25, 2021 7:35 am

ok, pull the rear drive shaft, drive around on the front axle, then the driveshaft and all 'transmission of noises up it' would be eliminated. :wink:
V/R W Winget

Still sounds like it's not in time with the driveshaft speed, rather the brake system impacting an errant length lug, but it's been dismissed
Brake shoe slightly wider than spec hitting the drum inspection hole as it rotates :?: WAW
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Re: Return of the Rear Axle Clackity Sound

Post by warbirdphotog » Tue Jul 27, 2021 1:25 am

GPW1263 wrote:
Sat Jul 24, 2021 7:50 pm
As another member pointed out, you are claiming that with TWO separate axles both are making that noise? You would never get odds on that in Las Vegas because it's purty near impossible.... UNLESS the same fella did the exact same work on both rear ends and/or ended up using the wrong parts on both rear ends or some other similar set of circumstances....but it's still a real stretch in logic when you think about it.
Don't know what to tell you on that one. I've stated the facts. Same sound, different axles/parts. Everything has been swapped out and tested aside from the rear axle yoke. Different bearings in each axle. Different ring/pinion/carrier/spider gears in both. Tested different axle shafts, drums, drum bearings, wheel location rotation, drive shaft, etc. I'm not trying to 'impede logic', just stating the facts and what we've tested/tried/changed.
GPW1263 wrote:
Sat Jul 24, 2021 7:50 pm
More likely you're going to find your culprit up in the output shaft bearing in your trans which is the point at which both rear ends intersect in any way (discounting the drive shaft of course).
The GoPro videos prove this not to be the case. The sound is ONLY heard when the GoPro is placed around the rear differential. Anywhere else (including the Transmissions/Transfer Case) and you can't hear the sound. AND when the sound started, my T-84 and D-18 had not been restored (my D-18 I don't think has been open since WW2!). I did a complete multi-week thorough restoration on both to factory standards. I replaced ALL the bearings with brand new ones. Thrust washers replaced. Flange replaced. Sound did not change one bit.
GPW1263 wrote:
Sat Jul 24, 2021 7:50 pm
That's a pretty big knock and I'd be looking really hard at any of the larger bearings. They're what's carrying the load.
I would agree, however, I think some of the other members are trying to say that they think the pattern of the sound doesn't line up with most of the bearings. And it's still the mystery of two sets of different bearings, then, having the same sound.
1944gp wrote:
Sat Jul 24, 2021 10:16 pm
Can you get access to a dyno to load it up but may get a look/hear under neath when not moving?
Sadly, no. I looked around for one in the area and came up short.
Wolfman wrote:
Sun Jul 25, 2021 5:54 am
I am talking about bearing load on the pinion bearings & races from the tapered/spiraled pinion gear forcing the ring gear to rotate under load, forcing the pinion bearing into the race. Jeep on the ground accelerating or decelerating, with the driveshaft installed.
Ah, okay. I think we were just talking about two things. There were others who mentioned in past posts that they thought the pinion was actually moving based on the load applied by (possibly) stress from the yoke/driveshaft from the axle tipping movement. So my point was that the test I did with the straps proved that not to be the case.
W. Winget wrote:
Sun Jul 25, 2021 7:35 am
ok, pull the rear drive shaft, drive around on the front axle, then the driveshaft and all 'transmission of noises up it' would be eliminated. :wink:
Ha ha. If only!
W. Winget wrote:
Sun Jul 25, 2021 7:35 am
Still sounds like it's not in time with the driveshaft speed, rather the brake system impacting an errant length lug, but it's been dismissed
Brake shoe slightly wider than spec hitting the drum inspection hole as it rotates :?: WAW
Don't believe so. I don't see any dragging marks on the side of the brake pads in a way that would signal that. And when manually spinning the tires I don't hear any scraping. The pads are from Ron and matched the original F marked GPW pads that I took out to a T.
Britt
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Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Tue Jul 27, 2021 4:03 am

Did you ever mark the inside of one tire and the driveshaft. Mount the Go Pro on the side frame so the marked tire, driveshaft & differential were in view and go for a drive ??
Still wondering about the tempo of the knock in relation to the position of the rotating parts?
Knock happen at the same spot on the tire or shaft every revolution or completely out of synch ??
And I was serious about tapping on the differential housing with a small ball peen hammer while the Go Pro is running. Jeep can be off.
See if the knock sounds similar and coming from the cast differential housing.
Mike Wolford
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EAA ( 49 yrs)
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Re: Return of the Rear Axle Clackity Sound

Post by YLG80 » Tue Jul 27, 2021 6:10 am

Very interesting test. Mike you are really haunted by that problem :D .
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Re: Return of the Rear Axle Clackity Sound

Post by W. Winget » Tue Jul 27, 2021 8:24 am

You quoted:
"W. Winget wrote: ↑Sun Jul 25, 2021 11:35 am
ok, pull the rear drive shaft, drive around on the front axle, then the driveshaft and all 'transmission of noises up it' would be eliminated. :wink:"

You replied: "Ha ha. If only!"

:shock: Errr..Why can you not pull the rear driveshaft out, engage your transfer in 4x4 low or high and drive around? This wasn't a joke, :)

It just steers a little differently, but it totally safe. The transfer output yoke is retained by a nut, so it's not like pulling a shaft out of an M151, or automatic car where the fluid spills out.
What have you got to lose? it isolates the rear axle and eliminates everything forward of it or driveshaft/ spring angle of attack / u-joint /yoke interference suggestions :!:
Hell I'd even pop out the rear axle shafts (5 minutes) in a 2nd run to eliminate the whole pumpkin turning, then if it still did it you would know it's outboard vs inboard.
V/R W. Winget
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Re: Return of the Rear Axle Clackity Sound

Post by YLG80 » Tue Jul 27, 2021 10:30 am

warbirdphotog wrote:
Sat Jul 24, 2021 5:41 pm
A few people are mentioning things that have already been tested/ruled out. I thank you ALL for your questions, observations, suggestions, etc no matter what, but I wanted to point out this post I made that goes through everything I've tried so far up until about a month ago: viewtopic.php?f=4&t=323316&start=105#p1887104
Hello,
Let’s go on the front side.
Do you have an Engine Stay Cable, correctly thightened to prevent the engine to move too much forward?
And have you double checked if your motor mounts are correct and not broken?
Yves
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serial 164794

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Re: Return of the Rear Axle Clackity Sound

Post by dpcd67 » Tue Jul 27, 2021 12:02 pm

It's in your parking brake.
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