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Allis Chalmers 312 Variable Speed Bgb Issues?


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#1 neverenough OFFLINE  

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Posted April 15, 2014 - 03:45 PM

I was looking for a decent tractor with a rear tiller attachment, to get one I ended up buying a lot of tractors at an auction.
One of the tractors in the lot is a 312 Variable speed which has issues with the variable belt drive or BGB. During the auction a few guys had looked over the machine, and all seemed to think the BGB was shot, but what gets me is that the tractor runs and cuts fine? It does slip when the variable lever is moved all the way down though. If I grab the BGB pulley, the outer sheave turns about half way before the shaft moves, the inner is fixed tight to the BGB shaft.

I really haven't figured out how this thing works, the belt is super loose all the time, I can turn the belt by hand without moving either pulley, yet it moves fine and mows grass well.

Is the drive pulley supposed to be two piece?

Along with this machine, I got a rough but functionally perfect 3410S with a rear tiller and deck, plus two older AC's, a B110, and a B1. The B1 looks decent but is missing its muffler and has no spark. The motor cranks and has strong compression. The B110 is complete, runs a bit rough but cuts grass and has a deck.

I'll probably sell off the two older AC's and keep the 312 and the 3410S.

I'd really like to set the 312 up as a snow plow only machine, I don't need the variable drive and would like to just toss it and convert it to a straight three speed if possible. I'm open to suggestions on this matter.

I like the B1 but I'm too big for it, and I really don't have room to store a tractor I can't use. 

 

 


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#2 New.Canadian.DB.Owner OFFLINE  

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Posted April 15, 2014 - 03:51 PM

http://gardentractor...-bevel-gearbox/



#3 petrj6 ONLINE  

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Posted April 15, 2014 - 04:45 PM

     Both drive pulley's are two piece, that is what allows them to be variable speed drive.  If you don't want to mess around forever with the variable speed then I would suggest removing it and putting a set of standard pulleys in place.  It should not be to much trouble on the bevel gear box end, just remove the variable speed drive and install a new pulley, I think!  The rear transmission will be different, the input shaft and seals are different, you will need to replace the seal with the correct one, I do have the part # here somewhere, I can get it if you need it.  I am not sure what can be done with the shaft, it will be to long and the key way will need to be cut in it for the pulley.  It would probably be easier to take the trans apart and replace the entire shaft with the correct one.

    I am basing this on the fact that your trans is the same as the older b-10 and b-110 machines as that is what I have here and they used them for a long time.  I have been messing with my variable drive on a b112 for about two years, slowly rebuilding everything one part at a time.  Good luck


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#4 neverenough OFFLINE  

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Posted April 15, 2014 - 06:26 PM

What does the rear shaft look like after the pulley is removed?

What makes the front pulley grab the belt or lock up?

 

I suppose that I could just push the variable lever all the way up and forget about it and run it as is.



#5 petrj6 ONLINE  

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Posted April 15, 2014 - 07:11 PM

    Should be just a 3/4" shaft sticking out of the trans about 3".  It will have a woodruff key way cut into it closer to the trans.  You will need to have a key way cut the length of the shaft to allow for the standard pulley, although I suppose you could just use the woodruff key to hold the new pulley.

   As for the belt grabbing I am not sure what you mean,  The belts on those should always be tight, when you step on the clutch pedal it pushes the belt upwards into the belt guide on the front pulley which in turn loosens it so the belt will slip on the pulley. 

   If you just want to use it my suggestion is to do exactly that, push the lever all the way foreward and use it.  If I remember correctly when I took the rear end apart on mine the rear shaft would not fit from one to the other, the snap ring grooves were wrong.  the variable speed rear end shaft was wider than the other, sot they would not interchange easily. 



#6 boyscout862 ONLINE  

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Posted April 15, 2014 - 07:11 PM

I picked up a 3310 Simplicity with the varidrive yesterday. It can be handy but is often a pita. It is necessary with a tiller or a blower to get the most out of it. Check our manuals section and www.simpletractors.com for info on adjusting. A new belt is almost $100. Good Luck, Rick



#7 makeitfit OFFLINE  

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Posted April 15, 2014 - 11:07 PM

I would think that I could just go to tractor supply and buy a pair of pulleys and a belt then?

The issue would be coming up with a clutch that would work as a belt tensioner. I'm not sure if its the same as a straight three speed?

The belt right now is loose till the thing starts, then the pulleys seem to close up and grab the belt. I haven't really dug into it to see what's going on, its dark in the back of the shed where their parked right now and I've been getting in late.
I really thought the BGB was toast because when I grabbed the drive pulley with my hand, I could rotate it a half turn before the input shaft tried to turn the motor, but I didn't realize in the limited light that the inner part of the pulley wasn't turning either. If I turn the input shaft, that inner half of the BGB pulley turns with no noticeable play at all.

Either way, this machine was sort of a bonus that came with the lot, Its by far the nicest looking one of these I've seen in a while.
The 3410S is rough looking but it works fine. My guess is that it sat under the lean too where I found it for the past 40 years or so.

The AC machines were all inside the shed and garage.

 

I'm sort of debating on what to do with the B110, maybe its the better of the two machines? Its a straight three speed and it runs as is, its just smaller overall. Being as tall as I am, its a tight fit.

When i went to the sale I had no intention of buying four tractors, but I didn't expect them to group all the garden tractors and attachments together in one bid. I was willing to go $500 for a running tiller and tractor, and I got it but the bid didn't come anywhere close to that. I figure I can sell or part out the rest for as much as I paid. All but the B1 will start with a jump and go.

The B1 will run with a new coil, I was just going to hook up a battery ignition to it and get it running as is.

 

 


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#8 boyscout862 ONLINE  

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Posted April 16, 2014 - 09:26 AM

How about some pics? The seats on the tractors can usually be moved farther back by drilling some extra holes. You have some real good tractors there and there are plenty of attachments around for them. I have about 10 AC/Simplicity tractors and more than 25 attachments. You may want to keep them all. Good Luck, Rick

#9 petrj6 ONLINE  

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Posted April 16, 2014 - 05:06 PM

:picsoritsnotyours: :wewantpics:



#10 skunkhome OFFLINE  

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Posted April 16, 2014 - 08:52 PM

Sounds like to me the variable pulley shifting forks have slipped out of the "carrier" . We had a brand new 312d in 1971 that wouldn't pull in the low range but would pull like an ox in any gear with the vari drive running in the high range.

#11 neverenough OFFLINE  

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Posted April 16, 2014 - 10:26 PM

The Variable speed works, it slips only if the lever is pushed all the way down, which I don't understand because the lower the lever goes the tighter the belt feels.

If I run the thing at idle with the seat up, the belt is flopping all over the place with the lever up, as I move the lever down the belt gets tight and runs dead true.
If I turn the motor by hand, the BGB pulleys move instantly, if I turn the outer pulley, it takes a 1/4 turn before it catches and starts to lock up and turn the inner pulley half and the shaft. The inner pulley half is tight to the shaft and the BGB itself doesn't seem to have any backlash that I can feel by hand. It makes no noise, unless I back up, then I get a steady gear whine and it'll only back up with the variable lever nearly all the way down. Who every had it before marked the lever and guide with a black arrow and the word 'Reverse' where it doesn't slip in reverse.

What doesn't make sense is that it appears that the front pulley fork moves the inner half of the pulley in and out to tighten up on the belt, I'm not sure how the two halves of the pulley can spin separately?



#12 makeitfit OFFLINE  

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Posted April 16, 2014 - 10:47 PM

I've got two tractors with the variable drive, both have a bit of play in the outer half of the pulley, but what gets me is that the inner pulley is what appears to move?

I've also got a few parts machines with the variable drive so I may tear into one and see what's there once all the variable stuff is gone.
I'd just as well toss the Variable on both of mine as well.

 

Keeping them all' is great but only if he's got room, I've got a shed and a big tarp, with about 15 tractors under the tarp. I'm running out of yard space. With mine, I store them here but use them to cut and garden a piece of property about a mile from here. Depending on the machine, sometimes I trailer them, some just get driven there. My 416 is the best on the road but I hate tearing up good ags. The 416 really moves in fourth gear.
I've got a running 310 parts machine that someone swapped out the front pulley for a 7" pulley, it barely clears the fender pan but the thing is too fast for its own good. Its great for pulling a wagon but stopping is an issue if I load it up too much. Its fast enough that I have some concern as to how well the transaxle and bearings will hold up going that much faster. I do know that if you let the clutch out too fast with a trailer on it'll stand up and throw you off the back. A buddy hopped on it one day and pushed the throttle open and stepped off the clutch real quick and it reared up till he fell onto the tongue of the trailer as it sat there and bucked till I shut it down. He had about 3 tons of wood on a 20' trailer hitched to a ball on the rear.

If it were my 3410S or the 312, it would have just slipped the belt. 



#13 neverenough OFFLINE  

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Posted April 17, 2014 - 10:25 AM

Well, I sort of solved the issues I had with the 312 this morning, I bought a 410 with a tired motor, I just got done swapping the motor over from the 312 into the 410 with a three speed. All fixed, now I've got a rock solid 3 speed 410. I bought a 5" pulley at the local hardware store and moved the tiller to the 410. It works great.

I gave the tiller a few passes in the garden and what seems to work best is to put the tractor in neutral and let the tiller push the tractor along. The 410 came with a Simplicity snow plow and a mid mount grader blade.






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