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1980 Bombi differential carrier preload and backlash?

T

trnak

New member
Hi guys, I bought a 1980 Bombi 5-passenger a while back. It has been quite a project and is nearly complete. Nearing the end of my list, I replaced the steering bands with kevlar from Tribco and had the steering drum bushings replaced at a local diff shop. Now to put it back in I need to know the specs for carrier preload and what to set the backlash to? I'm guessing one of you might know?

PS I have the original owners manual as well as factory parts manual if anybody ever needs copies for reference. But its just a parts-only manual, no specs, but has great exploded views of every component of the machine as well as part numbers.

Thanks guys!
 
From what I understand It is just a dana 44 ring and pinion.

search out the specs. I have them at home for a IH Scout.

I think the carrier preload is .025 shim.

back lash nte .009
 
Thanks redsqwrl, the backlash is probably close, I'm guessing its between .007 and .010, probably closer to .010 because its not new. There are no shims to use, this type of differential drops into a mount and the threaded adjusters are tightened to squeeze the bearings from both sides. See pics. I would like to know the torque specs for those adjusters once the backlash has been set.
 

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trnak said:
Thanks redsqwrl, the backlash is probably close, I'm guessing its between .007 and .010, probably closer to .010 because its not new. There are no shims to use, this type of differential drops into a mount and the threaded adjusters are tightened to squeeze the bearings from both sides. See pics. I would like to know the torque specs for those adjusters once the backlash has been set.
Click to expand...
based on your user name I'm guessing you are in ak where did you pick up your bombi from I ask because there wernt many of the 5man cabs sold and I have some history on one that spent it's early life at alexander lake lodge than wound up at big lake some time in the late 80's or early 90's
 
Ah yes,

The dana axle application has you drop it in no preload. Push it to and from the pinion while reading a dial indicator. (and use a pry bar to center it) Dividing and add the preload shim. I am sure the specs will turn up here shortly for the Bombi diff.
If not:
I would not be afraid to Zero out the ring side then tighten the pinion side until it zeros, then preload the ring side .025. Sounds crude but I bet it would work.

Mike
 
Typically, you would set up the pinion drag with a inch pound meter, then drop the carrier in, set you back lash,to your desired spec but paying attention to the pinion drag, make sure it doesn't increase, after your backlash is set, you would increase the side bearing preload slightly, a similar design is a Gm tracker or suzuki sidekick diff, it has the same style of side bearing preload,
 
Snowtrac, my bombi came from Talkeetna. Long story short, I bought it off Craigslist from Alaska Mountain Magic on the Parks Hwy. The parts manual says "Inland" on it, possibly referring to a company in Alaska. Whoever owned it before me must not have had a shop to work on projects because it was in dire need of maintenance in about every corner of the machine. It is finally ready to operate after a fresh engine rebuild and a lot of TLC.

My plan is to use it to freight some building materials to a remote cabin site for now, then possibly sell it when I no longer need to haul heavy stuff in the winter. Anybody know how many lbs one of these can pull on a sled without snapping an axle?
 
Hi trnak, we talked on the phone awhile back about your Bombi. I live in Trapper Creek and owned a couple of the Bombis many years ago. I kept one of my manuals and it has a "supplement" someone put in it about the specs and install procedure for the diff. I cannot guarantee the accuracy but it has hand writing on the top of page one that says Bombi.

Torque lbs-pl

Crown Gear Bolts 35-45
Side Case Bolts 25-30
Brake Drum Gear Bolts 15
Diff Cover Bolts 10
Bearing Adjuster 15-20
Pinion Nut 125-150
Carrier to Frame 35-40
Bearing Adjust Lock Bolts 20-25
Crown Gear Back Lash .003"-.006"

There is another two pages detailing Ring and Pinion tooth contact pattern from a Spicer/Dana manual. PM me you address and I can copy everything I have and mail it to you or maybe scan it and email it to you. I also have all the other manuals including the Ford Industrial Service manual for the factory engine if you need a copy of that.

Randy
 
Hey Randy, thanks! That should be exactly what I need. So when the carrier is dropped in place and the adjusters are tightened, I'm guessing the torque number I'm after is "Bearing adjuster" on your list and the "15-20" would be in inch-pounds, correct? Anyone else, does this sound about right?

I shouldn't need the contact pattern as I did not mess with the pinion so I should just have to set the backlash and torque the bearings on the carrier and be done. Is this right or is there more to do? This is my first diff project so I'm trying to be on the cautious side.

Thanks guys
 
I would think it is 15-20 ft/lbs? My smallest 1/4" torque wrench only goes down to 30 in/lbs and that is a very light torque. The "Torque lbs-pl" is what the data sheet has printed on it, never seen that measurement before.

I've never done a differential myself so I hate to give any pointers, but I think you are right about the "Bearing Adjuster"
 
15-20 ft lbs is a lot of torque on those as the threads are fine, which will put considerable preload on the bearings
 
caddyman said:
15-20 ft lbs is a lot of torque on those as the threads are fine, which will put considerable preload on the bearings
Click to expand...

I think that lb/ft are the units. These bearing are running in oil. If they were not, I think you may be right. I would assemble it and try it with ft/lbs, then turn the assembly by hand and see if there is a heavy drag while turning. I've done a Ski Dozer diff before, but I don't remember the torque specs. 15-20 inch pounds doesn't seem like enough to me anyway.

Regards, Kirk
 
trnak said:
I shouldn't need the contact pattern as I did not mess with the pinion so I should just have to set the backlash and torque s
Click to expand...


I have set up a pile of rear diffs in (Scouts Dana 44s) and the marks on the pinion set the orientation to where the factory ran them in together. If you are like me that didn't get captured when you pulled it out.

Look close at the end of the pinion, there are markings there.

take a peek at the pattern just for grins, it will help you sleep at night.

A nice oval will be there. If it not, rotate the ring/crown 90 and drop it in again. If it takes three drops and you get no change in pattern.

Start over.

I never had a ARB install come back, I was trained by a really crappy sawed of Norwegian....

BTW the mark you want to align is the big blotchy looking one. Look close they are there.
 
My ignorance is showing :unsure:

My brother came over last night and he strongly recommended checking the pattern as its easier to do now and would help verify the integrity of the pinion bearing as well. This thing is going far out in the boonies and he reminded me how much easier it is to inspect things properly now than out in a ravine 20 miles from help after its broken.

So your post this morning buries the hatchet, I will get some of that blue stuff and check the pattern tonight. I might even take pictures. Thank you all.
 
Pics of the Bombi as I received it. I added the Rigid led light bar right away thinking the machine was already good to go. I was wrong. Yanked the old motor, rebuilt from the ground up with new everything. Added 100 amp alternator, changed distributor to fully electronic Pertronix, cut tub under engine for access to oil drain and fabbed a skid plate of 1/4" steel. Rebuilt track tensioners, brand new Zenith carburetor. Replaced one drive sprocket, added pintle hitch to the rear. Finally on to the front diff, brand new Kevlar lined shoes from Tribco, new steering drum bushings, old drums turned. I was going to run ATF due to the extreme cold weather we get here but I think I will switch to HyGuard.

I have been trying to eliminate the clacking sound these seem to make. I think its play in the diff causing the noise as the power is diverted when you steer. It could be slop in the bushings or the actual gears in the chunk of the diff but I am hoping it was the bushings on the drums as they had a bit of wobble in them. I'm headed to the shop to finish the differential setup right now.

**note***
These pictures arent the newest and not all changes to the Bombi are shown here (Pertronix distributor and possibly others)

Enjoy
 

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the noise is very common in bombi differentials. most will make it, you are right on top of diff so it is louder than most machines
 
Alaska Snow Cat said:
Hi trnak, we talked on the phone awhile back about your Bombi. I live in Trapper Creek and owned a couple of the Bombis many years ago. I kept one of my manuals and it has a "supplement" someone put in it about the specs and install procedure for the diff. I cannot guarantee the accuracy but it has hand writing on the top of page one that says Bombi.

Torque lbs-pl

Crown Gear Bolts 35-45
Side Case Bolts 25-30
Brake Drum Gear Bolts 15
Diff Cover Bolts 10
Bearing Adjuster 15-20
Pinion Nut 125-150
Carrier to Frame 35-40
Bearing Adjust Lock Bolts 20-25
Crown Gear Back Lash .003"-.006"

There is another two pages detailing Ring and Pinion tooth contact pattern from a Spicer/Dana manual. PM me you address and I can copy everything I have and mail it to you or maybe scan it and email it to you. I also have all the other manuals including the Ford Industrial Service manual for the factory engine if you need a copy of
Click to expand...

Alaska Snow Cat said:
Hi trnak, we talked on the phone awhile back about your Bombi. I live in Trapper Creek and owned a couple of the Bombis many years ago. I kept one of my manuals and it has a "supplement" someone put in it about the specs and install procedure for the diff. I cannot guarantee the accuracy but it has hand writing on the top of page one that says Bombi.

Torque lbs-pl

Crown Gear Bolts 35-45
Side Case Bolts 25-30
Brake Drum Gear Bolts 15
Diff Cover Bolts 10
Bearing Adjuster 15-20
Pinion Nut 125-150
Carrier to Frame 35-40
Bearing Adjust Lock Bolts 20-25
Crown Gear Back Lash .003"-.006"

There is another two pages detailing Ring and Pinion tooth contact pattern from a Spicer/Dana manual. PM me you address and I can copy everything I have and mail it to you or maybe scan it and email it to you. I also have all the other manuals including the Ford Industrial Service manual for the factory engine if you need a copy of that.

Randy
Click to expand...
How do I pm you to get manual to help install differential in my Bombi, also I will like to get the Ford Industrial Service manual, thanks
 
Check out Bombardier "Keeping them alive" , a group on Facebook. They have a ''1975 Bombi maintenance manual'' PDF in the File section.
J5 Bombardier
 
muscleman said:
The think after I download I can't open it, it doesn't give the option for pdf file, weird
Click to expand...
I just downloaded it and it opened. Pretty slim on the diff section , like most of Bombardiers manuals. When you get to the backlash don't be surprised if the numbers differ 180 degrees apart on the crown. Some of Mr Bombardiers diff housings have some serious run out , but they get the job done.
J5 Bombardier
 
Can someone tell what does screw are for on the 1975 bombi differential?
 

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