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bombi rumbling noise

aknopp

New member
I bought a bombi last year. I've been running it a little and noticed a pretty loud rumbling noise, sounds like it's coming from the differential area. Only does it when the road speed is up, 3rd and 4th gears only. There seems to be quite a bit of play in the ring and pinion. Just wondering if I should pull it apart and inspect or if I'm just being paranoid.
 

snowcatt

Member
there should only be like 3 to 5 thou play in the ring and pinion . But if its rumbling its most likely a bad bearing . Best thing pull the cover off .That is a standard rotation Dana 44 gear set easy to get . Does it make any noise when you turning
 

aknopp

New member
A bearing was what i was thinking as well. Without the cover off I'm not able to get that accurate of a reading on gear lash. Just an observation at first glance. Only get noise in hard turns. I was looking around under the floor and noticed the pulley on the different pump is loose on the shaft, somebody installed it and didn't tighten the set screw so the bore is worn out causing the pulley to be off balance. That could be my noise since it's out of balance and spinning so fast at that speed. I suppose I will fix that and go from there. Don't hesitate to keep the ideas coming in the mean time.
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
It's not uncommon for the Bombis to make noise in a hard turn some of the contributing factors is the rigidity of the stiffners in the differential case it's self
The original side to side integral stiffner is marginal and in a hard turn there is some deflection that occurs. The next most common contributor to that noise is the play in the drum bushing has become excessive and when you pull hard on the steering arm it is canting the drum causing the brake drum gear (sun gear ) to run out of alignment with the internal pinions (planet gears )there is three on each side. Causing a temporary chatter.

I have had about 70 Bombardier Bombis through the shop over the years and I would say most made a noise in a hard turn.

What type of fluid are you running in the differential? I would not run the ATF
That Bombardier recommended for a number of years it allowed rapid ring and pinion wear.

30 weight fluid if cold or 50 weight if summer use AMSOIL power shift fluid or
The cat T-04 they both work well
 

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aknopp

New member
I have not replaced the fluid yet, but it is on my list, in the manual I got with the machine the previous owner listed a bunch of compatible fluids, mobile, 76, John deere, etc. I don't have the info in front of me at the moment.
 

aknopp

New member
Is there something I can do to add more strength to the stiffeners? Would be nice to avoid excess wear in the future.
 

MNoutdoors RIP

Gone But Not Forgotten
GOLD Site Supporter
Is there something I can do to add more strength to the stiffeners? Would be nice to avoid excess wear in the future.

I the photo you can see the factory stiffener in the front of the differential
What you can do is build another stiffener that goes on the top the carrier right above the lower one that's in there it seems to help I just finished one but I did not take any pictures and now it's all buttoned up covers on and the cab is on again.
 

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aknopp

New member
Took the belt off the driveline for the pump and ran it through the yard and back, much quieter. Working on finding a new pulley for the pump. It still makes noise, but it just sounds like a planetary gear set at high rpm's, will work on some insulation for the cab to dampen the sound.
 
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