Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

Sign in to follow this  

Bevel Gear Box

Recommended Posts


Hi, I got my BGB off of my Allis 312 today. I tore it apart and found that the woodruff key that holds the driven gear on the cross shaft had fallen out. There was also a whole lot of play in and out, like 1 inch or more in the cross shaft. Anybody know what happened? I dont quite see how this happened. Gears are quite worn, sharp and pointy on the top, and the driven gear has some chips in it, possibly from the woodruff key. So, my question is, should I be able to get away with new seals, bearings, shims and gears? And would gears out of another model of Allis/Simplicity work?

Or would it be more cost effective to find a used BGB and swap it in? Does anyone have one they would be willing to part with for a reasonable price? It is a 312 Hydro is that makes a difference. Will try and get some pics up of the box and internals.


  • Like 1

Share this post

Link to post
Share on other sites

The gears in the bevel gear boxes are the same in all of them other than the bore sizes. The bgb gear bore sizes in the early tractors were 3/4" and latter bore sizes were 7/8". Your 312 may have 3/4" or 7/8" bore in the gears. I think they changed gear sizes at a certain serial number but I would have to check a parts manual. I have a 300 - 400 series Allis gear box. I will check the condition. I would definitely change gears and shafts if I were to rebuild. If the woodruff key fell out it will do so again. Usually the needle bearing wears out on these over time do to hours or because they were ran low on oil. Once that needle bearing wears on the input shaft and makes shaft tolerances out of spec. the other end starts to wobble and where out the gears and cross shaft causing worn keyways, ect.

Share this post

Link to post
Share on other sites

I'm pretty sure, in your BGB,  there's a retaining ring used to keep the cross shaft from moving. But probably the nut on tranny pulley came loose allowing the shaft to move left so the key could come out.  See this post for discussion:


IMO, you need to find a good replacement  BGB, that should be a much more cost effective solution based on your description of the damage to your box. 

And id also replace the needle bearing and seals before installing the replacement box.  Maybe the roller bearings too.  

Edited by PhanDad

Share this post

Link to post
Share on other sites

Ok , thanks for the replies. I am a little leary of buying an unknown BGB, but that seems like the only viable option.

PhanDad - Where should I look to find a good used BGB?

RayS - I would be interested to know the condition of the box. Let me know when you get a chance to check it out.

Share this post

Link to post
Share on other sites

There were a few variations on these BGBs but you should be able to find a number of models that used the same one.  Check the part number and search on that to find other models that used the same one.  If the shafts are still good but only the gears worn you can search for any BGB that uses the same gear part numbers.
Some models had different length shafts but the same gears.

The rebuilds on these are pretty easy if you have no unusual wear.  The teeth on your gears seem to be in pretty rough shape.  If they still mesh well together or can be cleaned up to do so, and the shafts are not in bad shape you could rebuild the box you have and use it.  Keep in mind that those worn teeth will not match as nicely as they once did and will cause faster wear against each other and so will not last as long as a rebuild on one with good teeth.
There are plenty of tractors out there to get replacements from but it sometimes takes time to find one for a good price and then you end up thinking you have most of another tractor you should fix up and use.  That goes on forever.

Share this post

Link to post
Share on other sites

Ok, will check out the part #s. Yeah, they arent the best, the drive gear has chips out of 2 or 3 teeth. They could work if I needed to reuse them however. I dont know if the shafts are worn. I havent measured yet, and I dont know what the spec is for the shafts. Anyone know?

I have a local guy who may have 1 or 2 gearboxes and if they are good I may pick one of them up and be done with it.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Who's Online (See full list)

    • ecarter
    • littlemarv
    • casinojim
    • s_stephen
    • Trailer Monkey
    • Bill725
    • AC710
    • lt-scir
  • Today's Birthdays

    No users celebrating today
  • Recent Status Updates

    • Paul M.Murphy

      Paul M.Murphy

      Hello glad I got on this site. I hope to upload a couple of photos of my Simplicity Broadmoor 
      Model 707 Tractor. I have replaced all the belts on it and installed a new ignition switch.
      Have a mower deck which was in poor shape , repaced a couple of bushings and welded the
      deck where there was some holes. The tractor and mower deck came from a friend and the 
      mower deck metal was getting pretty thin. Some new metal was put in it and we also undercoated the underside of the deck. This was done by my friend Greg Toulman.
      I have not put the mower deck on the tractor yet, waiting for Greg to come home and give me a hand. Can you please tell me if there is a manual for the mower deck and where I could get one.
      I would also like to get some moon wheel discs as well.
      I will try and down load some photos of the tractor when my wife shows me how to. 
      I really love driving this tractor and also how well it is made compare today's tractors, especially the flexible rear end and the rollers.
      Tell the next time 
      · 8 replies
    • jbrooks

      jbrooks  »  Talntedmrgreen

      folowing  this from a link at the downloads.  I just rescued an AC 920 with the lambodini diesel. I can' t download  yet .  Where did you find the PDF copy you posted. . I would like to figure out how to adjust the injection pump. 
      I assume it's a bosche, correct
      · 0 replies
  • Adverts