Return of the Rear Axle Clackity Sound

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
Post Reply
User avatar
YLG80
G-Lieutenant General
G-Lieutenant General
Posts: 4095
Joined: Fri Aug 05, 2011 9:45 am
Location: near Namur, Belgium
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by YLG80 » Tue May 18, 2021 11:52 pm

I would still suspect the rear axle ring gear bolts straps locking plates (WO-A-792) to be the cause of that low frequency knocking sound.

rear_axle_ring_locking-plate-WO-A-792.jpg
rear_axle_ring_locking-plate-WO-A-792.jpg (6.11 KiB) Viewed 1143 times

I would ask the mechanic who has rebuilt the rear axle if he has used the 4 locking straps or loctite ?

rear-axle-knocking-sound.jpg

If yes, one or more locking plate bridges could be touching the rear axle housing while the differential load changes.
This would be in accordance with the "clackity sound" low frequency.
It's easy to visually inspect by only draining the oil and removing the rear axle cover.

I would read that topic where Etienne (Boyso) had published a photo of what Mike named a "meteorite" :D
viewtopic.php?p=1865207#p1865207

I would add that the rear axle housing is likely a very good drum to amplify the sound.
Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
serial 164794


User avatar
JAB
G-General
G-General
Posts: 9588
Joined: Fri Dec 13, 2002 5:25 pm
Location: under the jeep in North Prairie, WI

Re: Return of the Rear Axle Clackity Sound

Post by JAB » Wed May 19, 2021 6:11 am

But......if the differential was set up properly, with the proper backlash, preload, runout, etc. then that cannot happen. Whether on drive, coast, or coast under load, that dimension (the carrier, and straps that go around with it) and its relationship to the housing, cannot change. The straps would rub all the time or not at all....unless something else is loose or incorrect.

I've worked on issues that are "coast under load" related and they are nearly always the result of a pinion issue (loose yoke nut, worn bearings, or some other reason for the pinion to be allowed to move). On a rear axle, when coasting under a load, the pinion is being overdriven and if, for any reason, can move, the ring gear will push it and cause noise. If the problem is indeed in the rear differential, it will most likely be directly related to the pinion. If the straps are rubbing, the there's got to be a problem with one, or both, of the carrier bearings (improper preload). A cracked case could cause this but then there'd be a leak, and this is the 2nd rear end with the same problem, so something clearly isn't right here.
Last edited by JAB on Wed May 19, 2021 6:31 am, edited 1 time in total.
-Jeff

GR8GPN2U!!!

Image

Image

jnissen
G-Sergeant Major
G-Sergeant Major
Posts: 150
Joined: Sun Dec 16, 2018 9:43 pm
Location:
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by jnissen » Wed May 19, 2021 6:27 am

Same guy setup both? Not pointing fingers but I’m waiting to see what the slack is in the pinion. A dial indicator and a breaker bar to help move it fore and aft will be very telling.


Sent from my iPhone using Tapatalk
Jim Nissen
1955 M38A1
Patent Plate MD74784
Engine Plate MD85578
BS Hood Number 20974784

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6880
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Wed May 19, 2021 6:38 am

May be getting close, Jeff & Jim.
The pinion teeth spiral, not straight.
When going forward under load, this would force the pinion to try and move one direction and in reverse or during deceleration in gear, this would try to move the pinion in the opposite direction. Fore and aft. Closer or farther away from the differential carrier.
There is not much room between the rear face of the pinion and carrier.
Pinion depth on set up too far back ???
What appeared to be a very, very slight fore/aft movement of the pinion yoke in the Go Pro video during acceleration and deceleration ???
Be hard to see the rear face of the pinion in the differential but by now, after all the clanking, you would think there would be evidence of contact on the carrier or maybe the spider gear cross shaft a little too long. Sticking out of the diff. carrier ???
Parts that were moved from one differential to another differential ???
Still think it is time to pull the rear diff. cover.
Wonder if you would get a clank if the jeep was backed up a step grade aggressively, in two wheel drive ???
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6880
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Wed May 19, 2021 6:58 am

Now that I think about it, I have seen spider gear cross shafts that have had the ends of the shaft dressed smooth with the carrier surface.
Never gave it much thought.
If contact was made, that would give a knock once or maybe twice for each carrier revolution.
About where we are.
???
The good part, if this is the problem, the shaft could be dressed down in the differential, with the cover off.
Just have to be careful about the grinding dust.
After all this, wouldn't this be something.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

User avatar
warbirdphotog
G-Sergeant Major
G-Sergeant Major
Posts: 176
Joined: Wed Oct 03, 2018 10:54 pm
Location: Southern California
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by warbirdphotog » Wed May 19, 2021 12:32 pm

YLG80 wrote:
Tue May 18, 2021 11:52 pm
I would still suspect the rear axle ring gear bolts straps locking plates (WO-A-792) to be the cause of that low frequency knocking sound.
I would ask the mechanic who has rebuilt the rear axle if he has used the 4 locking straps or loctite ?
I'm not sure how the straps can be making that sound with two different carriers, two different sets of bolts/locking straps, and two different housings. But, just to check, I went back and looked at the carrier from the first axle, the straps/bolt heads have no marks on them I can see that would indicate striking something.

I'm the one rebuilding the axles, I just used the jeep expert/master mechanic's help with setting the ring and pinion. I did indeed use loctite AND the locking straps. I have the lock strap tabs flipped up (and no, it's not a broken tab bouncing around).
YLG80 wrote:
Tue May 18, 2021 11:52 pm
If yes, one or more locking plate bridges could be touching the rear axle housing while the differential load changes.
This would be in accordance with the "clackity sound" low frequency.
It's easy to visually inspect by only draining the oil and removing the rear axle cover.
Since this happened on two different axle housings and two different ring/pinion/carriers, I think the odds would be very slim it's both. BUT, to check I also looked at the first axle's housing. No markings on the housing that would indicate that something is striking from that rear side of the carrier on the housing.
JAB wrote:
Wed May 19, 2021 6:11 am
But......if the differential was set up properly, with the proper backlash, preload, runout, etc. then that cannot happen. Whether on drive, coast, or coast under load, that dimension (the carrier, and straps that go around with it) and its relationship to the housing, cannot change. The straps would rub all the time or not at all....unless something else is loose or incorrect.
That's my thought, and the fact that we used dial indicators, checked the backlash/runout, etc etc. We went by the book and were meticulous on this second axle as we wanted to get it perfect. Not that we didn't do that the first time with the first axle (we did do the dial indicator, grease tests, etc... but this second time we did it multiple times along the way to make sure we were correct).
JAB wrote:
Wed May 19, 2021 6:11 am
I've worked on issues that are "coast under load" related and they are nearly always the result of a pinion issue (loose yoke nut, worn bearings, or some other reason for the pinion to be allowed to move). On a rear axle, when coasting under a load, the pinion is being overdriven and if, for any reason, can move, the ring gear will push it and cause noise. If the problem is indeed in the rear differential, it will most likely be directly related to the pinion.
Problem here is two different pinions, same noise. Yoke nut is tight as can be (no movement on the yoke that I could see with the dial indicator, the pinion bearing spacing is shimmed correctly). Plus, it's two different sets of brand new bearings between the two axles.
JAB wrote:
Wed May 19, 2021 6:11 am
If the straps are rubbing, the there's got to be a problem with one, or both, of the carrier bearings (improper preload). A cracked case could cause this but then there'd be a leak, and this is the 2nd rear end with the same problem, so something clearly isn't right here.
We set those bearings for the carrier perfectly. No left and right movement whatsoever on the carrier. Nice and snug when it went in, but still turns freely. (this is on both axles, but I'll just focus on the second one since we really checked everything) When we did the grease tests, we checked for proper grease scraping on the ring teeth. We got it as center as center could be, and it was wiping away the grease meaning a nice fit with the pinion teeth.
jnissen wrote:
Wed May 19, 2021 6:27 am
Same guy setup both? Not pointing fingers but I’m waiting to see what the slack is in the pinion. A dial indicator and a breaker bar to help move it fore and aft will be very telling.
We used a dial indicator the entire way and checked all movement. I rebuilt both the axles, but I used my friend, who's restored more Jeeps (and is an expert mechanic) than most of us have ever laid hands on. I completely trust him as he's the guy all the local people bring their Jeeps to for restoration help. Besides, when we set this second axle's ring and pinion, I had another person I'd consider to be a Jeep expert having worked on them for over 35 years! He happened to be there the day I brought up the axle and he concurred with the other person the whole way. They are just as frustrated at this as I am.
Wolfman wrote:
Wed May 19, 2021 6:38 am
May be getting close, Jeff & Jim. The pinion teeth spiral, not straight. When going forward under load, this would force the pinion to try and move one direction and in reverse or during deceleration in gear, this would try to move the pinion in the opposite direction. Fore and aft. Closer or farther away from the differential carrier. There is not much room between the rear face of the pinion and carrier. Pinion depth on set up too far back ???
But the grease test, which we did under a simulated load as the manuals/tutorials online often say, shows a centered pinion with nice even contact on the ring gear. We also set the front axle the same way with the same tests/grease pattern. No clackity from that.
Wolfman wrote:
Wed May 19, 2021 6:38 am
What appeared to be a very, very slight fore/aft movement of the pinion yoke in the Go Pro video during acceleration and deceleration ???
Be hard to see the rear face of the pinion in the differential but by now, after all the clanking, you would think there would be evidence of contact on the carrier or maybe the spider gear cross shaft a little too long. Sticking out of the diff. carrier ??? Parts that were moved from one differential to another differential ???
Keep in mind it's a different carrier, ring, pinion, housing, bearings/races, shims, pinion spacer. Axle shafts swapped out made no difference. The only things the same are the brake plates, drums, and the yoke.
Wolfman wrote:
Wed May 19, 2021 6:38 am
Still think it is time to pull the rear diff. cover.
Wonder if you would get a clank if the jeep was backed up a step grade aggressively, in two-wheel drive ???
There is a pretty good hill next to my street here. I could park the Jeep and try to reverse it on the hill if you think that would be worth testing? This weekend I'll drain the axle and take a look inside the housing.
Wolfman wrote:
Wed May 19, 2021 6:58 am
Now that I think about it, I have seen spider gear cross shafts that have had the ends of the shaft dressed smooth with the carrier surface.
Never gave it much thought. If contact was made, that would give a knock once or maybe twice for each carrier revolution. About where we are.
I've now used three different sets of spider gears in two different carriers (two sets in the first axle, no difference in sound, and a different set in this second axle). I also replaced the main shaft and thrust washer with new ones from Ron. No change in sound. That was one of the first thoughts we had that it was spider gear related, so it was the first thing I tackled.
Britt
1944 Ford GPW #208102 undergoing restoration!
Follow the progress: http://www.facebook.com/1944gpw or on the Blog: https://1944gpw.warbirdphotos.us

User avatar
JAB
G-General
G-General
Posts: 9588
Joined: Fri Dec 13, 2002 5:25 pm
Location: under the jeep in North Prairie, WI

Re: Return of the Rear Axle Clackity Sound

Post by JAB » Wed May 19, 2021 1:35 pm

OK, it sure sounds like it's coming from the rear differential, but "we" looked it over, twice now. What do the axle splines look like? Is one of them so worn it's flopping around when it's not under load? Going further out, despite that the sound seems to be coming from the differential, what do the rear brakes look like? I'm looking again at your earlier post that shows what was used in each case where the noise existed and am coming up with minimal new ideas.
-Jeff

GR8GPN2U!!!

Image

Image

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6880
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Wed May 19, 2021 1:58 pm

I am not talking about the spider gears.
The shaft that goes through the rear diff. carrier that the spider gears are on and the length of this shaft is what I am referring to.
First, what is the pinion shaft bearing pre-load ?
The nut that holds the yoke on the pinion can be over tight, but that has nothing to do with the pinion bearing pre load.
This is getting complicated. But, that's OK..
When you set up the differential, using new bearings and races in this example.
First. you set the pinion gear depth in the case.
This is adjusted by adding or removing shims between the rear pinion bearing race and the diff case bore the race fits in.
Moves the pinion gear fore or aft in the diff. case.
Takes a special depth gauge that most people do not have. Most people just go by the tooth pattern on the pinion & ring gear teeth and that leaves some leeway.
Once you get the pinion depth set, you go to pinion bearing pre-load.
To set this you add or remove shims between the step on the pinion shaft, behind the splines, and the front pinion bearing inner race.
No differential carrier in place at this point and before the front pinion oil seal is installed.
When you think you have this set, you install the pinion yoke and retaining nut, set to the proper nut torque.
This next step is real important. Turn the assembled & torqued pinion assemble several turns before checking the pinion bearing preload.
This aligns the rollers to the races. What at first may be too tight will loosen up after you rotate the pinion assembly a few turns.
Now check the pinion bearing preload with an inch pound torque wrench by putting the torque wrench on the yoke nut and turning the pinion.
It should take several inch pounds of torque to turn the pinion at this point. ( help) maybe 30 or 40 inch pounds.
The yoke should not just spin freely, even though there is no perceptible fore/aft movement. If it does, you do not have enough bearing pre-load and it is possible, under high torque loads, the pinion shaft is moving "slightly" fore and aft.
"POSSIBLY", if the pinion depth is slightly too deep. The pinion bearing pre-load is too low. The ring gear backlash was adjusted to make up for pinion depth by moving shims from side to side on the diff. carrier.
Everything might look OK but now the rear pinion face is closer to diff. carrier/ spider gear shaft than it should be and on deceleration the pinion might be moving just enough to make contact. Slightly.
Not talking a major lock up. Just a bump. clackity clack.
Like the general opinion seems to be moving, it is going to be something weird like this.
????
See what you find this weekend.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

User avatar
YLG80
G-Lieutenant General
G-Lieutenant General
Posts: 4095
Joined: Fri Aug 05, 2011 9:45 am
Location: near Namur, Belgium
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by YLG80 » Thu May 20, 2021 12:04 am

A last suggestion:
Attach your camera as shown on the drawing, just to try to pickup the clackity sound by contact from the shaft inside the long tube.
I don't know if you can put the camera housing directly in contact with the tube without having Velcro in between. Perhaps temporarily with a tape.
We don't really need images.
clackity_last_measurement.jpg

Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
serial 164794

User avatar
W. Winget
LTC, U.S. Army
LTC, U.S. Army
Posts: 4448
Joined: Mon Dec 16, 2002 10:37 am
Location: USA, Virginia, Carrollton
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by W. Winget » Thu May 20, 2021 4:36 am

Could it be axle shaft lengths, :idea: one being just a tad too long for the spider setup perhaps?
V/R W. Winget
Looking for 1918 Standard B 'Liberty' truck parts

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6880
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Return of the Rear Axle Clackity Sound

Post by Wolfman » Thu May 20, 2021 4:36 am

Your up early, Yves.
I like it. Goes back to my earlier suggestion of using a mechanics stethoscope to track down the noise location.
That would not be easy on a moving jeep.
One more thought.
If the cover is removed to look for damage, there may not be much, with my last suggestion.
This would not be two objects making hard contact that causes severe damage..
Just two hard, smooth, well oiled surfaces bumping.
No pile of metal shavings.
Just a shiny spot on the rear face of the pinion gear and on the diff carrier around the spider gear cross pin.
Where the bump occurs.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

harve
G-Major
G-Major
Posts: 838
Joined: Fri Mar 03, 2006 5:21 pm
Location:

Re: Return of the Rear Axle Clackity Sound

Post by harve » Fri May 21, 2021 11:48 am

That noise is coming from the engine. Pull the oil pan for a close inspection , sounds like the bottom end wasn’t set up right . Keep us posted

jnissen
G-Sergeant Major
G-Sergeant Major
Posts: 150
Joined: Sun Dec 16, 2018 9:43 pm
Location:
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by jnissen » Fri May 21, 2021 2:25 pm

See Videos. Not engine noise.


Sent from my iPad using Tapatalk
Jim Nissen
1955 M38A1
Patent Plate MD74784
Engine Plate MD85578
BS Hood Number 20974784

jnissen
G-Sergeant Major
G-Sergeant Major
Posts: 150
Joined: Sun Dec 16, 2018 9:43 pm
Location:
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by jnissen » Sat Jun 05, 2021 7:54 pm

88 posts then crickets? Any update?


Sent from my iPhone using Tapatalk
Jim Nissen
1955 M38A1
Patent Plate MD74784
Engine Plate MD85578
BS Hood Number 20974784

User avatar
warbirdphotog
G-Sergeant Major
G-Sergeant Major
Posts: 176
Joined: Wed Oct 03, 2018 10:54 pm
Location: Southern California
Contact:

Re: Return of the Rear Axle Clackity Sound

Post by warbirdphotog » Sun Jun 06, 2021 12:25 am

jnissen wrote:
Sat Jun 05, 2021 7:54 pm
88 posts then crickets? Any update?
Apologies! Life got pretty busy the last two weeks. But, I did some more tests during that time, just haven't had a bit of time to post about it. It takes a good chunk of time to reply to everyone on this thread, so I often wait until I have enough time to really sit down and give a proper update!
harve wrote:
Fri May 21, 2021 11:48 am
That noise is coming from the engine. Pull the oil pan for a close inspection, sounds like the bottom end wasn’t set up right . Keep us posted
As posted in reply, the noise is 100% not from the engine. It's for sure the rear axle. GoPro videos prove this as multiple angles from the engine area have no indication of the sound. You might be hearing the noisy valves my engine has. I've tried to adjust those things 3 times now, and they are still noisy!
Wolfman wrote:
Thu May 20, 2021 4:36 am
I like it. Goes back to my earlier suggestion of using a mechanics stethoscope to track down the noise location.
That would not be easy on a moving jeep.
I have the stethoscope, but the problem is 1) I need someone else to drive the Jeep so I can listen (waiting for that), and 2) I'm afraid the sounds of the Jeep moving will overpower what I could hear in the stethoscope. So it might be a moot point, sadly.
Wolfman wrote:
Thu May 20, 2021 4:36 am
One more thought. If the cover is removed to look for damage, there may not be much, with my last suggestion. This would not be two objects making hard contact that causes severe damage.. Just two hard, smooth, well oiled surfaces bumping. No pile of metal shavings. Just a shiny spot on the rear face of the pinion gear and on the diff carrier around the spider gear cross pin. Where the bump occurs.
I opened up the differential and checked everything. See the next post for a more in-depth post, but basically, found only light metal shavings (typical of a newly set ring and pinion) and no strike marks.
W. Winget wrote:
Thu May 20, 2021 4:36 am
Could it be axle shaft lengths, :idea: one being just a tad too long for the spider setup perhaps?
V/R W. Winget
The problem with that is the axle shafts are GPW (and came with the original GPW rear axle I tried, and I borrowed rear MB axles from a friend and threw them in mine with no change in the sound.
YLG80 wrote:
Thu May 20, 2021 12:04 am
Attach your camera as shown on the drawing, just to try to pickup the clackity sound by contact from the shaft inside the long tube. I don't know if you can put the camera housing directly in contact with the tube without having Velcro in between. Perhaps temporarily with a tape. We don't really need images.
That's pretty much where I had it mounted (on the axle directly) on the last videos I posted. I can put it back on that spot, but not sure what you mean by direct contact? Like literally resting the camera lens on the axle itself? That might damage the lens/internals if there's a lot of vibrations.
Wolfman wrote:
Wed May 19, 2021 1:58 pm
The shaft that goes through the rear diff. carrier that the spider gears are on and the length of this shaft is what I am referring to.
I've been through three of those shafts now. The first one I used was 'okay' with the first GPW rear axle. The second one was a repro from Ron. The third one is the current one which came with the second GPW rear axle.
Wolfman wrote:
Wed May 19, 2021 1:58 pm
First, what is the pinion shaft bearing pre-load ?
The nut that holds the yoke on the pinion can be over tight, but that has nothing to do with the pinion bearing pre load.
I tightened it the same way I tightened the front axle pinion nut. I made sure (with a dial indicator) there was no forward and back movement with the pinion and the nut, and it's tight enough that if I spin it with my hand, it freely spins but the second I let go of it, it stops immediately. So a bit of resistance, but not too much.
Wolfman wrote:
Wed May 19, 2021 1:58 pm
Takes a special depth gauge that most people do not have. Most people just go by the tooth pattern on the pinion & ring gear teeth and that leaves some leeway. Once you get the pinion depth set, you go to pinion bearing pre-load. To set this you add or remove shims between the step on the pinion shaft, behind the splines, and the front pinion bearing inner race.
Yes, I know exactly what the pinion pre-load is, I've done it a few times now! Ha ha. All of this was done using a dial indicator, a master Jeep mechanic (who's done many many axles and also did my front one which is working just fine). We used the grease test on the teeth to measure how the pinion presses on the ring and did indeed have to change things several times until we got a perfect centered pattern. We did it by the book, and I trust the mechanic's knowledge and experience with installing ring and pinions. Especially for this second GPW rear axle, he was just as frustrated as I was with this sound, so when we did the second one two months ago, we spent several hours going back and forth making slight changes/tweaks with the shimming, testing it, feeling it out, etc. Honestly, that has to be one of the best put-together axles out there. Ha ha.
Wolfman wrote:
Wed May 19, 2021 1:58 pm
Everything might look OK but now the rear pinion face is closer to diff. carrier/ spider gear shaft than it should be and on deceleration the pinion might be moving just enough to make contact. Slightly. Not talking a major lock up. Just a bump. clackity clack.
The problem with this is I'd say it's unlikely that this would happen twice with two rear axles. I could see this happening with the first axle... but since the sound is exactly the same between the axles that have totally different parts internally with no change in pitch, pattern, volume, etc... that tells me it has to be something different.
Britt
1944 Ford GPW #208102 undergoing restoration!
Follow the progress: http://www.facebook.com/1944gpw or on the Blog: https://1944gpw.warbirdphotos.us


Post Reply

Return to “MB GPW Technical Knowledge Base”

Who is online

Users browsing this forum: Jim Thomason, Oakapple98 and 85 guests