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Question of the week regarding BGB


Horvik

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Hello;

My tractor is a 3416 H , had a "clunking" sounds in the BGB. After removing the BGB entirely, then the cover, I found a couple teeth gone from the drive bevel gear, and about the same damage on the driven gear.

These were used gears that looked good upon install, although to be honest the BGB they were removed from had seen better days.

So my question for you members is what causes this to happen?

I have rebuilt them before with good lasting results and they are cleaned exceptionally well  prior to reassembly.

All the best

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It sounds possible there was interference due to some misalignment, maybe wear of shaft, bearings.  I haven't tried rebuilding though, are there shims?  Did it turn easily upon reassembly and all teeth meshing well?  Did the teeth break off at their base - could be stress failure of long used ones.

Edited by PGL
spelling error
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On 11/16/2021 at 7:59 PM, Horvik said:

how are the shims used, and how many, to correctly set up the rebuilt BGB?

Shims are only used on the outside of the gearbox case to fill the void above the right side cross shaft such that the seal/ball bearing assembly is kept tight against the housing lip (the side plate holds the shims in the space).  No shims are used inside the case, all clearances are set by the part/case dimensions and the tightening of the nut holding the tranny drive pulley on the BGB cross shaft.  

@GLPointon wrote this excellent "How To" post:

https://simpletractors.com/forums/topic/46509-bevel-gear-box-rebuild/

And there's a video about rebuilding the BGB in the site's video forum:

https://simpletractors.com/videos/view-64-simplicity-service-video-power-steering-rotary-valve-and-bevel-gear-box/

Note the BGB rebuild starts at the 33 minute mark.

 

On 11/17/2021 at 10:11 AM, PGL said:

This link to repair manual may help.

On 11/17/2021 at 10:12 AM, PGL said:

Sorry, that link doesn't work.  Anyone else know where it is?

https://simpletractors.com/files/file/21-simplicity-large-frame-repair-manual/

 

 

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Hi Phandad,

 

After i read your fine suggestions I though I would mention the facts on what I am encountering.

In assembling the BGB with new gears and bearings, with the input pinion all assembled...then moving on to putting the crossshaft in place. I put the clip on the shaft, insert gear sliding the  circlip until it is correctly located. Then push to left, inset the woodruff key, then push into the gear.

Here in lies my problem.

Although the ball bearing is ALL the way seated in the bore housing, the gear is free to travel say 1/2" left to right and I know this  is not kosher.  Also, when you "completely assemble" that right side with spacer and pulley, it does noting to alleviate this problem. At the end of the day, that gear can have some free play, but not like this. While in the overview i am aware that the spacer and seal keep the bearing "in alignment" for end play, that is not at all what I am looking at.  It "acts" as though either the casting is not right, or I have to fabricate a hardened spacer between the ball bearing and gear. Honest. I rebuilt one of these 6 years ago with Al Edens and didn't run into this headache before that is for sure.

 

Have a good day.

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1 hour ago, Horvik said:

Although the ball bearing is ALL the way seated in the bore housing, the gear is free to travel say 1/2" left to right and I know this  is not kosher. 

I’m guessing this BGB is not completely OEM and the spacer isn’t matched to the cross shaft - there are different length spacers depending on the tranny type. I’m not sure how many different types there are, but there is more than one.  
 

@SmilinSam may know. Including their lengths. 
 

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The spacer you refer to , is this on the inboard side of the ball bearing, or the outer? The way I see it, an inboard spacer would take up the play.

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4 hours ago, PhanDad said:

I’m guessing this BGB is not completely OEM and the spacer isn’t matched to the cross shaft - there are different length spacers depending on the tranny type. I’m not sure how many different types there are, but there is more than one.  
 

@SmilinSam may know. Including their lengths. 
 

To my recollection(flawed as it very well may be) the Gear boxes for the variable speed tractors were the only ones that used different cross shafts than the rest.

 Starting with the 3400 series, there were no more variable speed tractors offered. The shuttles, gear drives, and hydros all used basically the same gear boxes. Only thing different between them was the transmission drive pulleys....and I think the straight 3 speed used the same pully as the hydro, but not sure on that. I dont recall any of the spacers between the pulley and the bearing being different.

The only thing that changed in the gearboxes after the 3400 series was from the early 7000 series to the late 7000 series they did away with the long keyway and the stub shaft on the pto end and went to  all woodruff keys and a full diameter nut on the pto side just like used on the trans drive pulley side. The 6 speed tractors , again, just used a different drive pulley.

I'm not really following how there could be 1/2" of play in the cross shaft gear. The back of the gear should be up  against the bearing inner race and the other side of the gear is held in place by a retaining ring in a groove on the cross shaft.. All this is drawn up tight when you tighten the nut against the drive pulley & pulley spacer.

I feel like I'm missing something here....

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1 hour ago, SmilinSam said:

To my recollection(flawed as it very well may be) the Gear boxes for the variable speed tractors were the only ones that used different cross shafts than the rest.

Thanks for refresher (again). 
 

6 hours ago, Horvik said:

The spacer you refer to , is this on the inboard side of the ball bearing, or the outer? The way I see it, an inboard spacer would take up the play.

There is no inside spacer, just the outside spacer that is designed to be clamped between the bearing inner race and the back of the drive pulley.  If the spacer is too short, the spacer won’t be clamped when the nut is tightened  to the bottom of the threads. This will let the shaft move to the left and the gear will no longer be tight against the inside race of the bearing so the gear is floating on the shaft.  The same thing happens when the drive pulley nut becomes loose.  In this condition the gears are no longer ruining with their design clearance. 
 

As to gear movement, I don’t see how it can move 1/2” since it is trapped between the input gear and bearing inner race. The shaft however can move freely. 
 

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Hello SmilingSam;

I did a rough check of the side to side play and it is just over 1/8" (not 1/2" as I mentioned)  To try to be clear, when that cross shaft gear is against the circlip, and then the spacer over the shaft is added, along with the seal and spacer, then the hydro drive pulley, the gear is then pulled "out of mesh" and instead of the two bevel gears true to one another, they only "meet" about halfway. I know i is nuts, but that is what I am dealing with. I too feel I am missing something here, because the other one I did years ago still runs fine, and i don't remember having this problem. With new gears being installed also, I want to make it right to avoid damaging my investment.

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Also wanted to add as a clarification, when those two bevel gears are in mesh, the crossshaft bevel gear (backside)is NOT in contact with the bearing. Bearings are new, checked and fully driven into the bore till it sits on the stop. The new bevel gears check against the damaged ones i took out. it is my speculation that whatever is causing this caused the other gears to fail. I am about ready to fit a shim in there to take that slop out. Either that or go fly a kite!

Appreciate the help

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9 hours ago, Horvik said:

Also wanted to add as a clarification, when those two bevel gears are in mesh, the crossshaft bevel gear (backside)is NOT in contact with the bearing. Bearings are new, checked and fully driven into the bore till it sits on the stop. The new bevel gears check against the damaged ones i took out. it is my speculation that whatever is causing this caused the other gears to fail. I am about ready to fit a shim in there to take that slop out. Either that or go fly a kite!

Appreciate the help

The assembly is as Bill stated:

21 hours ago, PhanDad said:

Shims are only used on the outside of the gearbox case to fill the void above the right side cross shaft such that the seal/ball bearing assembly is kept tight against the housing lip (the side plate holds the shims in the space).  No shims are used inside the case, all clearances are set by the part/case dimensions and the tightening of the nut holding the tranny drive pulley on the BGB cross shaft.

Like indicated by Bill if anything the spacer between the drive pully and the inner race must bee to short. It would though have to be short enough to allow the nut to bottom out on the threads and still leave that 1/8 gap between the gear and the inner race.

 

Theres only two to three possible things wrong here. Either the spacer is considerably too short, or there is damage to the cross shaft like a burr or something that prevents the shaft from freely sliding through the race till the gear is up tight against the race. Those or the retaining ring on the tooth side of the gear is coming out of its groove on the cross shaft.  I have run into that a couple of times trying to  re-use old rings..

 When assembled that retaining ring on the tooth side of the gear on the cross shaft is the only thing that prevents the shaft from being pulled all the way through the race as you tighten the nut against the pullley.

...There is one other remote possibility, if the ball bearing is not oem, the inner race could be too narrow. Really , logically this makes the most sense, as in the above instances, there would still not be the 1/8 gap.

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The BGB cross shaft used on all of the 3400 series tractors was P/N 173966 which has been superseded to P/N 1685054SM which was used in the last BGB tractor built in 2000 which is the Sovereign. The cross shafts physically look different but are interchangable. As mentioned before the 173966 has a long keyway and smaller threads on the PTO end. The only other 7/8" big BGB cross shaft is the 3300 series, P/N 172207. The 3300 series was the first big BGB but still used the mid-PTO mule drive. The 3400 series is the first tractor to use the cone clutch PTO.

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To SmilingSam and all interested....The problem with the excessive side to side play was that the bearing was china made and off specs. And it took a bit of my time to figure that out. Anyhow, here I am on reassembly, with pictures...

So I seated the large seal with accompanying  shim, and used the square end of the pipe in foreground to drive until it dead headed home. Then I took a straight edge and the two .006 shims was all that is needed to make them level with the case frame. Does this sound kosher? I ask as I have a used one here that uses BOTH the .006 AND a .040 shim assembly to get square.

Thank You to all that are helping out.

 

BGB_Rebuild.jpg

BGB_Rebuild_1.jpg

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Use any many of the thin shims needed so half the thickness of a thick shim sticks out past the machined surface. Use grease to hold them in place while bolting on the side plate. Torque nut to 45-55 Ft. Lbs.

Edited by Bill725
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1 hour ago, Horvik said:

the bearing was china made and off specs.

Interesting that the face of the inner race was ~1/8" recessed compared to the outer race.  Must have been a special spec bearing of some sort - I'm only familiar with ball bearings where the inner and outer race faces are on the same plane.  

  

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More questions:

1. Since the 2 of the .006 shims are even with the machined surface of the BGB, with that being said, would I put on a .040 shim first, then  2 of the  .006?

2. Is it normal for the mounting seal(with spacer) to be "almost or a little below level with the casting, only then to have the entire shim pack 2- ..06 and one .040 shim "Pull" the seal down into the bore when finish tightened against the plate?

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