The infamous bombi clacking noise

Ok guys I posted in a previous thread about setting my backlash and preload on my 1980 Bombi. I had to do this because it had just come back from the diff shop with new drum bushings and freshly turned drums. I did all this in an attempt to eliminate the violent clacking sound coming from the diff when the steering levers are pulled hard. Well I got the diff set up correctly and tested the machine. The problem of the clacking sound coming from the diff remains. When you pull the steering lever the machine makes an awful clackaclackaclacka sound from the diff or axle area. I have been reading everything I can on this and other forums and some say its the bushings inside the inner gears of the 'chunk' of the differential. I have also read some posts that this noise is normal which I refuse to believe. If you rode in my machine you would swear the diff is going to grenade if it is driven like that. You feel the clacking sound in the handle as you pull it and it is definitely metal-on-metal.

So I did a test, I jacked up the machine and ran it on jack stands. The noise went away and the tracks spun normally with power transferring correctly as levers were pulled. I put it back on the ground and the noise persists. Another thing I noticed is if I push in the clutch and coast to a stop I hear a different noise that sounds like its coming from the axles, and this noise also does not sound very good and it feels like its trying to bind as it rolls to a stop. I have played with track tension to no avail. The sprockets are like new, bearings appear to be good, and I am fairly certain it is those bushings inside the core of the differential.

Anybody have any experience with this issue that was fixed?

Thanks again guys....

I think it is time to disassemble the "chunk" and look around in there. If it is trying to bind up when coasting, this could be issues in the chunk. It takes some time to take apart and reassemble, but it is not that hard to do.. Make sure you find the timing marks before you reassemble and fallow some good directions from the manual.

I have been into a Ski Dozer chunk to replace the ring gear, and if I am not mistaken this is a smaller version of the same. Minnisota outdoors has the bushings for the shafts in there. Boogie here on the forums here is the go to guy.. He can also help you trouble shoot this differential as well. You should contact him via a PM here or just call him on the phone...

Good luck,

Kirk

What oil are you using in there? I was just in Fairbanks three weeks ago. I would have loved to stop by and give a hand.

Did you time the 6 little gears inside the drums The guy I bought mine from redid the diff but didn't time the gears and thats what mine was doing horrible noise

My BR100+ made a similar sound mostly when letting off the gas, with mine it is the park disk brake pads rattling on the disk. I removed the disk and polished it and it is much quieter. It still makes the noise when hot but not like before. I am putting the same disk brake assy on my other J5, that I am converting to a TH350 automatic, if I ever get it completed i will see if it does the same. The disc is a std unit used for a park brake conversion on old vehicles that need a park brake.
Check it out, drove me crazzzzy for a bit until i fig' it out. Hope this helps!

300H&H, I think you're right. I drained the oil tonight in preparation for dis-assembly again tomorrow. I will take it as a unit to a local diff shop, they have the stuff to pull the bearings without destroying them. My bearing puller is a cutting torch.

Dr Zaugg, I am running ATF at the moment. I will be switching to Hy-Guard eventually but I bought 5 gallons of ATF and I figured I would run it through for this season, as I plan on changing fluid every season.

Snowcatt, when I took it to the diff shop he did not pull apart the internals, just replaced the drum bushings. I will ask him to check the timing of the gears, maybe that's the problem. Either way, something will need to be replaced. There's no way those gears aren't damaged at this point.

For anyone who has not heard this noise before, here is a youtube sample of my machine in action demonstrating the sound as the steering lever is pulled. https://www.youtube.com/watch?v=hV_EAQbaU2o

Thanks for the input guys.

The video helps a bunch.

I have a mercedes diesel powered bombi that had done a fair amount of work in its day.

It made that same exact noise. I had bent output tubes.
Outside the tub....
there was a flange bolted to the diff......
Loosen those bolts and see if there is tension there..

I Trued the output tubes and reinstalled them on the opposite side and my clack clack (your video) turned into a nonexistant clack. there was sometype of noise there like a burnished brake drum might make but that noise (your video) was gone.

$.02 Just a thought.

Mike

Redsqwrl, you seem to be on the right track, that makes a lot of sense as to the noises I am hearing. It does it on both sides but the left side is worse. If I gently pull the steering levers there is no noise but if I give it a sharp pull like you would steering on hard pack snow, it is the worst. It really sounds like something is hitting in there. You think those tubes are bent? How would they get bent? I still think some bearing or bushing has to be bad to give it enough slop to hit something in there but I do remember seeing some grooves where the axle slips into the differential that had to be caused by some rotational abuse. See attached photo. The grooves are deeper than they look in the picture.

Track tension changes during operation, or to tight to begin with bends axle tubes I would guess..

The grooves in the brearing suggest that the axle shaft has spun inside the bearing bore. Are those the grooves you refere too?

Regards, Kirk

Yes, I'm referring to those grooves. The axle and that scuffed sleeve which encompasses it are supposed to turn together, are they not? I dont see how it could have scored the inside unless somehow the axle is not spinning about its central axis. The axles don't appear to be bent, I had them both out and looked them over very carefully. Where should I go from here? I was ready to tear it all down today and remove the diff to have the 12 or so bushings inside replaced.

Thanks guys.

redsqwrl said:

It made that same exact noise. I had bent output tubes.
Outside the tub....
there was a flange bolted to the diff......
Loosen those bolts and see if there is tension there..

I Trued the output tubes and reinstalled them on the opposite side and my clack clack (your video) turned into a nonexistant clack. there was sometype of noise there like a burnished brake drum might make but that noise (your video) was gone.

Mike

Click to expand...

Since the Differential is installed I would check this out first, then go to the Diff if you need to.

Mike is pretty darn good mechanically, and I think you should heed his advice, as he has been there done that...


Regards, Kirk

Just thinking out loud here....

But bent axle tubes would cause the axle shafts to not run true through the bearing inner race.... It could explain the grooves we see in the bore? I am thinking you should check those axle tubes over very closely..

Regards, Kirk

You guys rock. I think Mike hit the nail on the head. I tore it all down this afternoon and by the way the axle sits in the tube I can see its bent towards the back of the machine. I measured from the tips of the sprocket to the tub at the points where the bend is the most and least and theres a difference of 3/4". The axle rides hard against the side of the tube without the hub cap on. When the hub cap is on the axle has to bend to line up the bolt holes. This bow was most likely slapping the wall of the tube causing the noise.

Now I just gotta straighten it. Tomorrow's project.

One more thing, I included a pic of the ring and pinion and theres some numbers on the pinion and a matching number on the ring gear. I did not notice them before I took this picture, does the "880" on the pinion need to match the "880" on the ring gear?

Thanks again guys.

The 880 is not it. ( i need to dig out a manual)

I think it is the 0 looking mark, straight above it. there was a (or still should be) a single tooth marked on the ring. mostly I saw them marked with a paint mark. I can usually feel when they are in the right spot, ( I know that sounds funny, but the contact pattern and high and low spots feel wrong when the run in marks are ignored) O would not worry about it as that pinion contact looks a little high and on the heel.

as far as how they get like that.
Stumps
Rocks
snow banks
tension on the track

I have a picture of mine opened up but I don't think it will help much.
jim

I don't know a bombi from a bombsea, but I would check the inner axles too for straight.

Well I got the whole axle hub assembly off the machine today and tore it down. I decided to write up a step by step guide so anybody else who's never done this can eliminate the guesswork.

Note: I wrote this for someone in the future who needs to remove the axle tube assembly. To replace the bearings at the drive sprocket the track must be removed but the axle tube can remain on the machine.

Step 1: Release track tension by sticking a sharp pointed object into the ball of the track tensioning grease zerks in between the rear 2 wheels. Do one side, go do the other side, then come back and do each side once more as the track tensioners are connected and have to work together.

Step 2: Remove drive sprocket hub. 6 bolts and a pry with a chisel should get it off. If gasket tears don't sweat it, RTV Silicone can make a new gasket.

Step 3: Pull out drive axle.

Step 4. Remove track of machine by removing nuts holding each half of track guide in place. The track overlaps 2 sets of guide bars, 3 nuts for each long bar and 2 for the shorter inner guides, for a total of 10 nuts. The track should separate with some application of a prybar between the two parts of the track at the overlap joint. Since the drive axle is removed the top part of the track can be pulled towards the back of the machine and clear of the drive sprocket.

Step 5. Remove the 2 nuts on the U bolt that holds the axle tube to the frame of the vehicle.

Step 6. Remove the 6 bolts holding the axle tube to the tub of the vehicle. With some application of a hammer the tube should now come free.

Tearing down the sprocket and bearings....

Step 1: Remove the 10 nuts on the face of the sprocket. Remove the steel bowl that they held in place. Now you can remove the sprocket.

Step 2: Take a chisel or punch or flat head screwdriver and tap the seal inward, causing the opposite side to come popping out. Remove seal, make sure to get a new one. Federal-National-Mogul 471341.

Step 3: Now you can see the lock nut. Using a punch and hammer in the square notches, drive the lock nut counter clockwise until it comes off.

Step 4: Remove the castle lock washer.

Step 5: Hammer and chisel again. Remove lock nut same as step 3.

With the last lock nut removed everything else on the axle tube should slide right off.

Well I put the stripped down tube in the vise and put some heat on it. I put a cheater bar inside the tube and put all my weight into it and it didn't budge. So I guess I will take it to a local machine shop tomorrow and see about having it straightened.

That last picture says it all.... Yup it is BENT...

I have to believe that this issue is presant in many Bombi's I would think anyway. At the age these machines are, they have had plenty of encouters with rocks, stumps, hard landings on road ways from snow berms ect..

Good work, especially sharing your results for the future owners of these machines!

Regards, Kirk

trnak, I have an old Bombi chassis that I think has those tubes still. They are at at a property a few miles off road from my house and I'll go see if they are still on the tub if you are interested.

Randy

Another cause of bending can be snow and ice build up, usually wet snow, on the tracks that causes the track to become extremely tight. We have had build up to the point that the machine walked out of the rubber tracks. If you combine that with any of the causes described above, you could bend a brand new housing. We had a local company, Axlemasters, which repaired an axle for me when it broke clear off right at the root of the inner bearing shoulder on a full floating axle on my 500 Tucker. The local co. is no longer here but maybe there is a national chain. They did a lot of class 8 truck axle repairs. Warning to steel pontoon folks, the same build up can happen on the steel rails on the old machines with the right temps and snow conditions.

and back on point, My thought is that constant twisting on the axle shafts (which will fight to stay straight), will load the inner planetaries, Mine got quieter but still had the under your feet feel there.

Great right up.

Mike