Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors


BGB free play

Recommended Posts


I've never seen an "official" Simplicity description of "excessive" BGB backlash.  

The most definitive comments that I can remember posted on this site were by @RayS; his comments:

I have rebuilt with all new bearings and shafts and backlash on the gears is 1/16" to 3/32" with all new parts.

The 1/16" to 3/32" is rotational at the cone clutch that I am talking about.

At the outer diameter of the cone clutch.

His opinion of a measurement of 1/8":

I wouldn`t mess with it. That is only .032 difference. My numbers were on all brand new parts. Not used parts and there is nothing written in the repair manual on what I came up with. Simply what I have observed in the ones that I have rebuilt with all new parts.

If you had a 1/2". Then there would be an issue somewhere.

Above from this post:



Share this post

Link to post
Share on other sites


This is too much:


What I found:

Many times the cause of lash is a worn key if you're lucky:


And probably if the key is in that bad of shape, you're a little lucky if you find just shaft damage:



Unlucky is gear keyway damage:


If just the key way is damaged, you can have a keyway cut 180 deg and salvage the shaft.  If it's worn as was the case with the pictured shaft, you'll need a new shaft.  And if the gear keyway is damaged, a new gear too.

The BGB that the above parts ran quiet but was leaking fluid from the tranny drive pulley side.  

Hopefully you'll be lucky when you investigate.  


  • Like 2

Share this post

Link to post
Share on other sites
4 hours ago, Gary said:

I'd agree with the 1/32 - 1/16, maybe even up to 1/8" backlash.  Any more than that, and there's probably damage to a gear/shaft/key, et all.

where are you measuring the backlash? I am measuring 5/8ths on outside edge of 5 " pulley

Share this post

Link to post
Share on other sites
On ‎2‎/‎8‎/‎2019 at 12:44 PM, deebig said:

5/8ths on outside edge of 5 " pulley

This equates to 1/8" at 1" from the shaft's center.  I agree with @deebig in that 1/32 to 1/16 would be better.  In other words 5/32 to 5/16 at the 5" edge.  1/16" is .0625 or 60 thousanths - - -that is a lot of gear lash.

Edited by wwbragg

Share this post

Link to post
Share on other sites

Wait a minute - - I might be confused - - - maybe not???  :S 1/16" lash 1" from the center is 60 thousandths.  1/16" on a 5 " center is only 12 thousands (on a 1" center) which is a reasonable amount of play.

Edited by wwbragg

Share this post

Link to post
Share on other sites

Backlash isn't the only thing to judge.  There should be basically no end play on the cross shaft.  I don't know if there is a Simplicity spec for end play on the cross shaft, but it should not be enough to really see.  Obviously it can't be set up too tight, otherwise there will be gear problems, but I was always taught that it needs to spin freely, but have minimal end play.   The input shaft shouldn't wobble - the needle bearing on input shafts is a notorious wear point.  As for your backlash, how does it feel?  This is difficult to explain, but often times when the problem is a worn out key/key way, there will be a small amount of normal very free backlash, but then you can keep turning the shaft more when a little effort is put into turning things.  Again, hard to explain, easy to feel once you have some experience.  Make sure it isn't just a shot pulley or key outboard of the gearbox that you are feeling.  

Edited by TimJr
  • Like 1

Share this post

Link to post
Share on other sites

@TimJr is spot on. Those variable speed pulleys have play in the pins, even when dealing with nearly new parts. Check at the inner half of the pulley instead. These units will operate still with quite a bit of wear. On my first B-110, the pulley can be rotated probably an inch or more and its still going but the likelihood of being able to re-use any of the parts will decrease. 

  • Like 1

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

  • Who's Online (See full list)

    • dince
  • Today's Birthdays

    1. mjbarbero
      (64 years old)
  • 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