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Gear Box Rebuild-Cross shaft


dextyr

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Hi Folks - I'm rebuilding my Simplicity 725 gear box.  I took the box apart and inspected all the parts.  Things looked good so I replaced the seals and put everything back together.  Problem I have is for some reason the cross shaft moves laterally and the cross shaft gear doesn't stay in contact with the drive shaft gear (input shaft from the engine).  I've looked at the parts diagram and can't see what I did wrong.  The gear box is mounted between the steel plates that connects it to the transmission.  Does anyone know what keeps the cross shaft from moving and allowing the gears to not mesh?  I can't see anything apparent in the diagram and I put things back the way they came apart (near as I can tell).  I must have missed something, but what???

Thanks in advance - Dick

 

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On the RH/clutch side of the BGB, the cross shaft bevel gear shoulder sets up against the ball bearing inner race, the ball bearing outer race sets up against the oil seal, the oil seal sets up against the shim stack and the shim stack sets up against side plate. When the nut that holds on the clutch pulley is tightened to 45-55 Ft-Lbs, it pulls everything tight and the gear lash is set. The original oil seal thickness is 0.452/0.422" thick and is NLA. The Simplicity replacement oil seal does not work because it is not the correct thickness. I suspect either the oil seal and/or lack of shims is the issue.

To correct the oil seal issue, machine a spacer out of 1-3/4" OD X 1.510" ID X 0.120" wall to 0.406" long and use with a Timken oil seal P/N 471733 like pictured. Make sure the lip on oil seal will allow the spacer to go into the oil seal.

When re-assembling, make sure half the thickness of the thick shim protrudes out past the BGB machined surface.

Sm BGB RH Seal Pic 1.jpg

Sm BGB RH Seal Pic 2.jpg

Small BGB Seal Assy.jpg

Edited by Bill725
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Thank you both for the information.   My gear box is currently mounted between the plates attaching it to the transmission.  I have about 1/4" play and I'm thniking you both are correct.  I replaced the seals, but don't remember if the one I took out was an original or replacement.  I had only 2 shims and probably spaced it thinking the side plate would move the gears together without realizing there might be play when I got done if the seal thickness didn't match up with the original seal thickness.  I recall thinking the spacer and pully when tight would take care of the play. 

I have everything (transmission, BGB, and forward frame) on my work benchGuess I'll take the plate off of the clutch side of the BGB and see what gives.  I don't remember a spacer between the seal and bearing.

I watched the referenced video and don't recall an o-ring ever being in place when I took the BGB apart.  It doesn't show in the parts diagram either.  Maybe it was a later item than my 1962.  Absolutely necessary??

Thanks again - Dick

 

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1 hour ago, dextyr said:

I don't remember a spacer between the seal and bearing.

The original seal was thicker (I measured an old one at 0.437") and didn't require a spacer.  The old design is no longer available and you are forced to use a spacer.  Simplicity first used this same "fix" for the "large" BGB's and supplied the spacer and seal as a "kit".  

1 hour ago, dextyr said:

I watched the referenced video and don't recall an o-ring ever being in place when I took the BGB apart.

The o-ring is another "improvement" on the newest large BGB's.  If you want to use an o-ring, I'd suggest a #16 standard (0.754"OD x 0.614"ID, 0.70"Thick)

 

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Thanks - I pulled the pulley off the clutch side of the BGB.  Removed the spacer and peeked inside.  With the shaft pushed back to mesh with the input gear I could see there is no spacer, but room for one.  I looked in my parts boxes holding everything I pulled off and found nothing resembling a spacer.  I must have had old seals and not paid close enough attention putting the BGB back together.

I'll try to get the seal out without taking the whole transmission off to remove the gear box.  If I can't, guess I'm removing the BGB and starting over.

Do you think an o-ring like you suggest would also work as a spacer?  Problem is, I only have a space of .21 inches (7/32) between the seal and meshing with the gears.  Shaft in was 2 5/32" and shaft out was 2 12/32".

Dick

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20 hours ago, dextyr said:

Do you think an o-ring like you suggest would also work as a spacer?

IMO, no - it's soft and would just compress and not stop the movement of the bearing in the case.  

As an alternative, since the seal is already installed, I would think you could drive the seal all the way in tight against the outer bearing race.  Then you'd have to fill the outer space above the seal with a much bigger (ID & OD) spacer to fill the larger "outside" gap to the side plate.  

NOTE:  The above alternative won't work, see @Bill725's post below

Edited by PhanDad
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6 hours ago, PhanDad said:

As an alternative, since the seal is already installed, I would think you could drive the seal all the way in tight against the outer bearing race.  Then you'd have to fill the outer space above the seal with a much bigger (ID & OD) spacer to fill the larger "outside" gap to the side plate.

The replacement oil seal does not have enough column strength and will collapse when tightening the clutch pulley nut. Someone tried stacking (2) oil seals and they crushed while torqueing the nut.

The purpose of the o-ring is to ack as a seal between the ball bearing inner race and the clutch pulley spacer.

@dextyr, I happen to have (1) oil seal spacer and a set of shims. You will have to provide the oil seal. PM me if interested.

Edited by Bill725
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1 hour ago, Bill725 said:

The oil seal does not have enough column strength and will collapse when tightening the clutch pulley nut.

The old seals must have been thick wall or some other manufacturing enhancement.  

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36 minutes ago, PhanDad said:

The old seals must have been thick wall or some other manufacturing enhancement.  

Pictures of the old NLA seal.

20221025_155238.jpg

20221025_155227.jpg

20221025_155222.jpg

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  • 3 weeks later...

Thanks to all for your ideas.  I was able to pull the seal after taking the clutch side plate off connecting the Bevel Gear box and tranny.  Used a couple screws to assisst in pulling the seal out.  Installed new shims and new seal.  Problem solved.

Dick

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