I'm new here, been looking for a site like this for some time, and I think I found a good place to ask some questions, and maybe answer a few. Our snowmobile club in Western NY has 2 bombi's. One is original with the 1.6 and 4 speed ford pinto setup, the other is a repower with a chevette 2.0 maybe with a hydramatic. I'm looking for a couple things. One would be a procedure for properly adjusting (although I don't believe it to be rocket science) the steering brakes, general maintenance procedures for the finals and lubricant specs. Next would be an overhaul description with exploded views for the finals. We have one that wreaks of gear oil in the cab, I think there might be a top cover that has a leaking gasket that may be the cause, and I would like some accurate service information before I become big, brave, and bold, and open this sucker up without some information to help me backtrack my way out of a disaster. Forwarded files would work, or I could PM someone with a fax number to send it that way. Any help would be appreciated.
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Bombi final drives. Info wanted.
- Thread starter dieseldr
- Start date
Sarge
New member
Our ford powered bombi is fine, it is the chevette powered one with th odor.... I know the finals in that machine are filled with gear oil. Guess I need to drain, flush and refill with hygard or tactor/hyd. I may try the positrac friction modifier if I don't get the response I want. Thanks for the post. PS I don;t think ours has a filter, I know it doesn;t have a cooler..... either machine.
Alaska Snow Cat
Member
Hi guys, welcome to the best snowcat forum you will find!
I have had a couple of Bombis and think they are a real good cat for what they were designed to do. I think Sarge is on the right track with your tranny problems and no, it is not normal to spew fluid out of that tranny in any condition or slope angle. Like with any gear box application too much fluid can cause as many problems as too little fluid so that is always something to check.
Regarding the differential, it would be advisable to drain it completely and do a refill if the machine is new to you or the fluid has not been changed in a couple of seasons. I used to change mine every year but I was working it hard grooming steep slopes in deep snow. The differential will get very hot and the factory cooler set up helps out a lot. It is a fairly easy cooling system and could be retrofitted to one that does not have it already.
Any leak could becoming from an overfilled diff, which could be contaminated with water causing the overfill. The pinion seals as well as the axel seals are the other locations for leakage. There is a vent on top of the diff access plate that vents inside the cab but shouldn't give off a real strong gear oil odor. Because the Bombi is not tightly sealed from the engine and drive train and it is a small tub type chassis they do tend to smell more than other cats do.
As far as fluid type I would recommend you do a search on this site on the subject as it has been discussed in detail and there is a lot of good information to be read. I used a synthetic gear oil made by TRC for years because that was what the Bombardier Dealer used on all their cats they sold or leased to North Slope companies at the time.
Eventually I switched to HyGaurd tractor fluid made by John Deere for hydraulic systems and wet brake differential systems. It was a lot cheaper, easier to get and I used it on several snowcats for well over 10 years with no problems. I liked it too because I could simplify my fluids by using it in both the gear box applications and hydraulic systems. Others use ATF, Caterpiller fluids or just regular old 80-90wt gear oil. I personally wouldn't use the friction modifier but am in no position to not recommend it either.
I have all the manuals that were ever available for the Bombi including the complete manuals for the Ford industrial 1.6l engine. I am happy to answer any questions but I stopped coping and send out manuals after doing it about a dozen times over the years. I used to have several extra manuals too but gave them away and this last set I am keeping to help provide information to others. I recommend you get ahold of Prinoth as they are the current supplier of parts and manuals for Bombardier snowcats. There are also several private dealers on this site that might be able to sell you manuals. Check the Forum site as some manuals are available for download.
The steering band adjustment is very simply to have 3-5" of free play at the handle. There are jam nuts at the base of the steering levers where they attach to the treaded rod coming out of the differential. The important thing is to not have them too tight because the brakes will drag and heat up the diff real fast and you will loose steering capability rather quickly. It is best to steer with quick application of the levers and avoid dragging the brake through turns. If you are grooming a lot then there is a steerable hitch assembly you could make or buy that makes steering much easier and greatly reduces brake wear.
Best of luck, Randy
I have had a couple of Bombis and think they are a real good cat for what they were designed to do. I think Sarge is on the right track with your tranny problems and no, it is not normal to spew fluid out of that tranny in any condition or slope angle. Like with any gear box application too much fluid can cause as many problems as too little fluid so that is always something to check.
Regarding the differential, it would be advisable to drain it completely and do a refill if the machine is new to you or the fluid has not been changed in a couple of seasons. I used to change mine every year but I was working it hard grooming steep slopes in deep snow. The differential will get very hot and the factory cooler set up helps out a lot. It is a fairly easy cooling system and could be retrofitted to one that does not have it already.
Any leak could becoming from an overfilled diff, which could be contaminated with water causing the overfill. The pinion seals as well as the axel seals are the other locations for leakage. There is a vent on top of the diff access plate that vents inside the cab but shouldn't give off a real strong gear oil odor. Because the Bombi is not tightly sealed from the engine and drive train and it is a small tub type chassis they do tend to smell more than other cats do.
As far as fluid type I would recommend you do a search on this site on the subject as it has been discussed in detail and there is a lot of good information to be read. I used a synthetic gear oil made by TRC for years because that was what the Bombardier Dealer used on all their cats they sold or leased to North Slope companies at the time.
Eventually I switched to HyGaurd tractor fluid made by John Deere for hydraulic systems and wet brake differential systems. It was a lot cheaper, easier to get and I used it on several snowcats for well over 10 years with no problems. I liked it too because I could simplify my fluids by using it in both the gear box applications and hydraulic systems. Others use ATF, Caterpiller fluids or just regular old 80-90wt gear oil. I personally wouldn't use the friction modifier but am in no position to not recommend it either.
I have all the manuals that were ever available for the Bombi including the complete manuals for the Ford industrial 1.6l engine. I am happy to answer any questions but I stopped coping and send out manuals after doing it about a dozen times over the years. I used to have several extra manuals too but gave them away and this last set I am keeping to help provide information to others. I recommend you get ahold of Prinoth as they are the current supplier of parts and manuals for Bombardier snowcats. There are also several private dealers on this site that might be able to sell you manuals. Check the Forum site as some manuals are available for download.
The steering band adjustment is very simply to have 3-5" of free play at the handle. There are jam nuts at the base of the steering levers where they attach to the treaded rod coming out of the differential. The important thing is to not have them too tight because the brakes will drag and heat up the diff real fast and you will loose steering capability rather quickly. It is best to steer with quick application of the levers and avoid dragging the brake through turns. If you are grooming a lot then there is a steerable hitch assembly you could make or buy that makes steering much easier and greatly reduces brake wear.
Best of luck, Randy
As an off highway equipment, portable service tech for over 30 years, I can understand the value and worth of the manuals. As for the 80-90, I find it very hard to fathom putting anything more than a GL1 in this application, and I will explain why: Eaton/roadranger makes the most popular truck transmission in the world. The range shift mechanism (lo to hi, hi to lo) utilizes an air cylinder, fork clutch collar with a synchronizer making the shift seamless and quiet. This synchronizer is nothing more than a lined friction surface (brake) that contacts a cone on the gear, so that when contact is made, the friction material grips the cone, the speed of the shaft and gear are now matched, and the shift is completed. One surefire way to destroy the function of this synchronizer is to add a lubricant with a service classification of anything higher than GL1. 80-90 is a GL4, and when subjected to the friction and wiping action of the synchronizer, the Extreme pressure additives oxidize, burn, or carbon up the friction surfaces on the synchro, eventually carboning or burning it until it either flakes off its backing, or just can't match the speeds anymore. In extreme cases, the loads from not being matched in speed shears the pins in the synchro and it slam shifts. So utilizing the 80-90 in a wet brake system subjected to that much heat, brings my little peabrain to thinking that it is only a matter of time before the oxidation on the band will limit its ability to function. Just the way I see it, so I will be draining the gear oil out (which is what I assume is in it given the odor in the cab) and refilling with chevron 1000 thf, since I have scads of it on hand. As for friction modifiers, I realize that a posi additive will make it worse, as its purpose is to take the clunk out of a posi, which is caused by a non releasing clutch pack (or brake), but somewhere over the years I saw a friction modifier for lock up torque convertors that would make them bite tighter, taking the shudder out of them. Sorry for being so windy, but there it is in a nutshell, IMHO. And, folks, this is a great forum, and the knowledge of the people helping us all out is top notch. I hope not to wear out my welcome.... everyone-- best wishes your new year turns out great.
Snowcat Pat
Active member
http://www.lubegard.com/~/C-230/Dr.+Tranny+Instant+Shudder+Fixx
This stuff?
This was discussed on the Astro/Safari forum supposed to help the auto trans. I haven't tried it in anything yet.
-Pat
This stuff?
This was discussed on the Astro/Safari forum supposed to help the auto trans. I haven't tried it in anything yet.
-Pat
Hey Pat-
Thanks for the interest in the thread, after talking to a few other techs in the area, and looking at the add for this product, I think I can safely say that my previous statement was all wet. Indirectly, this product won't do the trick either, as you can see on the add, it says not to use with type F, or CVT fluid, so this tells me that is a "slippery enhancer", because type F is a "bite" enhancer. SOOOOOooooooooooo, that being said, I am going to fill the brake compartment of our Bombi with Hygard equivalent (THF), and if I can't get bite enough, I am going to add a quart of type F to get more bite. Will let you know where this gets me. ( probably a broken band!)
Thanks for the interest in the thread, after talking to a few other techs in the area, and looking at the add for this product, I think I can safely say that my previous statement was all wet. Indirectly, this product won't do the trick either, as you can see on the add, it says not to use with type F, or CVT fluid, so this tells me that is a "slippery enhancer", because type F is a "bite" enhancer. SOOOOOooooooooooo, that being said, I am going to fill the brake compartment of our Bombi with Hygard equivalent (THF), and if I can't get bite enough, I am going to add a quart of type F to get more bite. Will let you know where this gets me. ( probably a broken band!)
Alaska Snow Cat
Member
dieseldr,
You may already understand how the controlled differential works in the Bombi and other snowcats and I not trying to imply that you don't but there is a real good description of how they work posted somewhere on this site. I'm a mechanic and equipment operator by trade too, and I know how it works in my mind but not well enough to explain it if you know what I mean?
Some folks have a misconception that it is a brake skid steer mechanism when it is a gear reduction or gear ratio changing steering system that is initiated by slowing one side down. Again not saying you or others don't know that already but just letting you know that information is out there and is a good read. I should probably find it and reread it again before I look like an idiot trying to explain it.
I went and found one of the old buckets of the gear oil I used early on in the old Bombi days and it was a 75w synthetic gear oil. I like the Hygaurd but I would say more people swear by a fluid made by/for Caterpillar. Maybe someone reading this will chime in with the number.
You may already understand how the controlled differential works in the Bombi and other snowcats and I not trying to imply that you don't but there is a real good description of how they work posted somewhere on this site. I'm a mechanic and equipment operator by trade too, and I know how it works in my mind but not well enough to explain it if you know what I mean?
Some folks have a misconception that it is a brake skid steer mechanism when it is a gear reduction or gear ratio changing steering system that is initiated by slowing one side down. Again not saying you or others don't know that already but just letting you know that information is out there and is a good read. I should probably find it and reread it again before I look like an idiot trying to explain it.
I went and found one of the old buckets of the gear oil I used early on in the old Bombi days and it was a 75w synthetic gear oil. I like the Hygaurd but I would say more people swear by a fluid made by/for Caterpillar. Maybe someone reading this will chime in with the number.
Sarge
New member
Hey JimVt going to change oil in my diff was just wondering how the amsoil is making out. and what type/grade is it. I have a 76 Bombi and was just wonedring. And so...is 32 wieght hydraulic fluid ok for front diff oil? I've looked through a ton of posts but have not seen 32 wieght mentioned.
Matthew
Matthew
JimVT
Bronze Member
I cant say how it making out. I run it in the grass about 100yds to my barn and it sets parked.
last season it wanted to veer to one side so I gave it the change thinking it will help.
amsoil 75-90 synthetic gear lube is the stuff. it says on it that it is compatible with conventional and synthetic gear lubes and most limited slip differentials.
I just play and don't tow much so it doesnt get hot . My diff. oil cooler works good.
last season it wanted to veer to one side so I gave it the change thinking it will help.
amsoil 75-90 synthetic gear lube is the stuff. it says on it that it is compatible with conventional and synthetic gear lubes and most limited slip differentials.
I just play and don't tow much so it doesnt get hot . My diff. oil cooler works good.
Tahoeskier
New member
Maybe someone can answer me about a couple problems I am having with the final drive on my '81 Bombi. I started getting a clacking noise in the dif. when I made turns to the right or the left. I could feel it in the steering bars like a jumping or grabing feel and this clacking noise. I thought that it may be worn out brake bands so I got into the dif and took them out to see whats going on. The brakes showed some wear but not real bad the cross hatches still there and not down to the rivets. The drums though are pretty rough on the surface they may need to be turned. I really don't know how to remove them or if they really are the problem. I also noticed that the oil in the dif. is cloudy so there is water getting in there and mixing with the oil. I noticed that the oil was mixing with water the last time I changed the oil but didn't have the clacking problem then. The gears and bearings all look real good with no real signs of unusual wear or metal in the oil. Has anyone had this kind of problem? Do I really need to turn the drums or should I just change the oil and reline the brakes? Any help you could give would really be great.
Hey Alaska Snow Cat-
I am going to assume from your last post that the bombi uses a planetary steering system of sorts? I can grasp that when the brake is applied the planetary shifts to a lower speed, initiating a turn. Now what I wonder, is can the brake be applied hard enough to stop the inside track? I would think that it is possible, and being diff steer, as soon as the inner track is stopped, the outer track will now turn at twice the speed. I have a T340 IH crawler loader with diff steer of sorts, as I recall it has a disc that when the steering lever is pulled, the brake is released, the track can freewheel (when going down a steep grade the released side will go faster than the engaged side), and when the lever is pulled all the way back the external turning brake is applied, the inside track is stopped, and the outside track does not turn at twice speed, it maintains the original speed. That's what I like about original operators manuals and service/maintenancemanuals, at least one's that are well written, you get a good explanation of how the system was designed to work, and it takes all the guesswork out of knowing what it is supposed to do when someone says it isn't acting right. Having not been inside one of these to actually see what is going on, I can only make assumptions on what might be happening inside. But someday when it gives up the ghost, I will know then how it is supposed to work. Ideally, the aim is to keep it from giving up the ghost by understanding how it works- not the other way around! This thread will go on long enough that eventually we will all know how it's supposed to work- wether we want to or not! Thanks for the info.
I am going to assume from your last post that the bombi uses a planetary steering system of sorts? I can grasp that when the brake is applied the planetary shifts to a lower speed, initiating a turn. Now what I wonder, is can the brake be applied hard enough to stop the inside track? I would think that it is possible, and being diff steer, as soon as the inner track is stopped, the outer track will now turn at twice the speed. I have a T340 IH crawler loader with diff steer of sorts, as I recall it has a disc that when the steering lever is pulled, the brake is released, the track can freewheel (when going down a steep grade the released side will go faster than the engaged side), and when the lever is pulled all the way back the external turning brake is applied, the inside track is stopped, and the outside track does not turn at twice speed, it maintains the original speed. That's what I like about original operators manuals and service/maintenancemanuals, at least one's that are well written, you get a good explanation of how the system was designed to work, and it takes all the guesswork out of knowing what it is supposed to do when someone says it isn't acting right. Having not been inside one of these to actually see what is going on, I can only make assumptions on what might be happening inside. But someday when it gives up the ghost, I will know then how it is supposed to work. Ideally, the aim is to keep it from giving up the ghost by understanding how it works- not the other way around! This thread will go on long enough that eventually we will all know how it's supposed to work- wether we want to or not! Thanks for the info.