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MrSteele

BGB Questions

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MrSteele
Well, the free tractor I got in a ditch is becoming the money pit! First, the steering, then the engine, the deck, and today, the bevel gear box! Question. I have seen a lot of discussion here on the difficulty of repairing/rebuilding the bevel gear box. All of it seems to suggest that I take the box to the shop. I am my own shop. Is there anything that I need to know before I tear it down? I regularly take things apart that I have never done before, always watch what I am doing, take care to put parts removed in the order they were removed so they can be put back in the position they were in before I took them down. With that in mind, and with a parts manual breakdowm printed out, the manual showing all but the tolerances in the BGB, knowing from many experiences with other rear ends(this appears to be similar to the chunk in an automobile, with the exception of spider gears), is there going to be a surprise awaiting me anywhere in the rebuild? I can shim anything, having stock from .001 to ?, have a parts store within reach, and have rebuilt automobile rear ends from A models on up. IS there a tolerance that I have to work to? Or, do I do this like a lot of other projects, and adjust to what I think feels right? Tomorrow is the disassembly day, this week, after work, the rebuild time. I only know now, that the input shaft is terribly loose, so loose that it allows the gears to not mesh almost at all. I will let you know what I found, after tearing it down tomorrow.

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ReedS
There's nothing in the bgb that's incredibly difficult to work with. Hardest part IMO is splitting the tractor, removing the pulleys and removing the bgb. It's not uncommon to find that the entire guts are kaput. I had one that the front needle bearing race egged out the seat for the bearing, ended up replacing the entire bgb with a combo of new and used parts. If the input shaft is worn and walking around be sure to check the gears for wear that same bgb had that problem to the extreme where the gears were worn to points and some were chipped and broken. The early boxes had a vent hole in the vent plug which lets water right into the box so quite often you ended up with watered down lube which in turn led bearing failure etc. Replace all of the worn parts and assemble. On most of the ones that I have done reinstalling the original shims put the lash close. The lash should neither be loose nor tight. Somewhere in the past it's been said how much lash you should have but I can't remember whether it's about a 1/4 turn or an 1/8 but if you've set up rear diff's these are similar. Good luck, expect the worst and hope for the best.

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stevei46
Joe here is the link to repair imfo on this sight. i'm not sure if it will help you any or not http://www.simpletractors.com/club2/portal_articles.asp?catid=29&cattitle=Axles

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RayS
Just like Reed says the hardest part is getting out of the tractor. Once you get it on the bench you will beable to tell if you need to apply for a second mortgage or not. I can do them in 2 to 3 hours now if i don`t mes around much. If you have a repair manual for the large frame tractors they are a big help, if not you can download them from Simplicity publication.

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MrSteele
Well, it is almost out of the tractor, at least, the rear wheels are about 10 feet from the rest of the tractor. The setscrews are soaking as we speak, in hopes that they might move tomorrow night, as I have a business trip past the Simplicity dealer on Tuesday. I might be able to find the bearings at a local industrial supply, and will most likely need to shim the input shaft bearing, as the shaft is extremely floppy in the front of the gearbox. If I could just get the setscrew in the yolk to move a little... Will enjoy this, too, as it will make my new toy useable again, and I was just starting to really enjoy the nice racket it makes while cutting grass in third gear! Thanks for the encouragement. The job doesn't look too imposing, anymore.

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MrSteele
It is out, disassembled, looks like a set of gears, bearings on the input shaft, and for the heck of it, I'll most likely put a complete set of seals in it. Bearings on both sodes of the output shaft are in good shape, with no noticeable wear. I would have it back in the tractor, but a beach trip pending for the weekend kinda stripped me of useable funds. Thanks for the info. All fears were unnecessary, as this is much simpler than even a steering gear on this tractor.

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MrSteele
OK It is out, disassembled, being washed and cleaned up before reassembly, if I can afford a few things like gears! A question. I have seen a lot of discussion on the placement of shims in the BGB, however, mine had none when I took it down? The parts blowup shows "shims as needed", but the location of the shims will not have anything at all to do with gear lash, as they are located beyond the seal outside of the gear train. All I can see that the shims would be good for is to keep pressure on the transmission drive pulley sides. Is this correct?

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ReedS
Once the bgb is installed the shims end up between the side plate. Without the shims, the seal/bearing/gear could walk out toward the side plate. All the nut on the end of shaft does is to clamp the pulley, the bearing and bevel gear to the shaft, unlike the nut on a pinion shaft. With the cross shaft installed (with the gear and bearing)install the seal tight to the bearing, at that point you can check the lash and see what will be needed for shims. Shim flush to case. Clear as mud right? It boils down to this; the depth of the gear/bearing/seal/shaft is set by those shims which in turn sets your gear lash. Hopefully this will make sense.

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MrSteele
It makes good sense, actually. I started washing the case and the bearings on the cross shaft. Then, I did find one shim. The shim makes the edge of the case flush behind the pulley arrangement. What the shim really appears to do with gear adjustment, though, is nothing. The locknut on the end of the shaft, crushes the gear on the shaft in a location that is not affected at all by the shim, but the shim will protect the end of the seal, should any play come into the gear shaft. However, if any play does become present, the gears would self destruct, quickly.

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MrSteele
I have almost sold enough aluminum cans to afford the parts for the BGB! Now I have a question, again. The gears look identical, except for the shoulder on the output gear. The shoulder does nothing as far as I can tell, as the gear is in an open housing, with nothing resting on the shoulder or bearing on the shoulder. The gears have the same number of teeth, the same diameter, same bore, same keyway, are cut the same otherwise. There is a distinct difference in price for them. Is it possible to use 2 input shaft gears, or has anyone tried such? If not, why will it not work? If I can do this, I have sold enough cans to pay for the rebuild, already!

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MrSteele
I am finally in the assembly stage, nearly. That second mortgage would have been a good thought! I am waiting on an input shaft, and a Simplicity seal for the transmission pulley side of the gearbox. And, I found out exactly what the difference is in the gears. Basically, nothing. There is a step cut on the outside of the output gear. I suppose this cut is to allow the gear to 'miss' the inside of the BGB housing as it turns. However, in my housing, there would have been enough clearance for either gear to work. As I have already bought the complete set from Simplicity, I'll keep it, but, I will also make a note that if I ever need another set, or am working on one for anyone, I'll put both gears in that are the same, the input gears, as they are cheaper.

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maxtorman1234
Hello, I wish you could use 2 input gears, but you have overlooked 2 important differences that do not allow you to use 2 input gears. First of all, youre right about the cut out in the back of the output, but youll also notice that the teeth point opposite directions so they mesh. Also, the output gear has a indent in the front to retain the clip on the shaft, so the gears mesh properly. Thats why the output is more expensive, [img]http://www.simpletractors.com/club2/attach/maxtorman1234/DSCF0969.jpg[/img] [img]http://www.simpletractors.com/club2/attach/maxtorman1234/DSCF0970.jpg[/img]

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BrianP
Nice to know I'm not the only one who is his own shop. I rebuilt a BGB a couple of years ago, and not only is the biggest job breaking the tractor in half as others have said, but the re-build is quite straight forward if you're mechanically inclined. I picked up a factory repair manual that served as a good step-by-step guide. I also replaced all the seals and bearings (when you're in it that deep, why not?) when I did the gears on mine, just to be on the safe side. I definately had metal shavings in one ball bearing, so I went whole hog on the thing. When you re-assemble the PTO pulleys, tighten the side opposite of the cone clutch first, that places the gears into proper contact with each other. I didn't know this at first and tightened the cone clutch side first. When I started up the machine, it sounded like it had a rod knock. I shut it down immediately and did a lot of staring at the old BGB that I kept as another guide to reassembly before tumbling to the cure. My repair manual neglected to mention this, either that or I missed it, either way, I wanted to pass along my experience.

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MrSteele
On my tractor, there is only one nut to tighten on the shaft, and it tightens against a spacer, which crushes against a step on the shaft. The seal on the output side wears on this spacer, not the shaft. The shims that seem to concern folks here do basically nothng except help to keep the seal in place on the output shaft. From what I can tell, there is no adjustment whatsoever in the gear lash on the gearbox, if it is assembled properly. The input shaft has a retainer ring that keeps it from working out of place into the gearbox. The output shaft has no adjustment to take up end play. If the rope pulley is installed properly and the nut on the end of the shaft tightened according to any spec, there is absolutley no way to adjust end play. I haven't begun the reassembly as yet, and am still painting, but, when my input shaft arrives, it will be a short job to put it all back together. I'll try to post a pic or two showing reassembly.

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