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AGCO ALLIS 918H BEVEL GEAR BOX


johno107

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Hi guys need your help.  I have an Agco Allis 918H garden tractor that needs to replace a bevel gear box

Does anyone have instruction on how to remove the bevel gear box?  I have almost all the bolts out and still it won’t drop down.

Does the bolt #157273 stud for the handle to tighten the belt from the rear have to come off, I put a wrench on it and I could not budget it?  May have to use heat!

I purchased a used bevel gear box and will install this one.

 The last gear box broke the shaft # 1685054 (shaft Driven) in 6 months with very little hours on it.

Price new tractors and they are out of sight will not spend that kind of money at 83 years of age.

Any help would be appreciated

I had this box rebuilt by a dealer and it lasted 11 months so I had him rebuild it again and that lasted 6 months so now I picked up a used bevel gear box from a Allis Chalmers so far I have $1500 into the dealer.  Not that many hours on any of the rebuilds 

Thank You

John

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3 hours ago, johno107 said:

Does the bolt #157273 stud for the handle to tighten the belt from the rear have to come off

Yes, it’s one of the bolts that holds the left side plate to the tranny - if you're removing the left side plate.  

I usually leave the left side plate attached to the tranny and using a furniture dolly to support the tranny rotate the tranny assembly away from the BGB as seen in this pic:

IMG_9440.thumb.JPG.45e34974269e782ba6348a6eaaccc2a0.JPG

The front half of the tractor is supported from overhead or by jack stands under the footrests:

IMG_9427.thumb.JPG.3352368ebd3e97e1b3394ae5334e2eb2.JPG

IMG_9442.thumb.JPG.8d33a237a396e2dd07c8f121f3014173.JPG

 

Edited by PhanDad
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When you get yours off, you might want to rebuild it yourself for future use.  It isn't that difficult if you take your time and do it right.  There are posts on here that go thru the process.  There might be a video on youtube about it as well, if ZippoVarga has one he is the guy I would look for, he does it right and his videos are good.

Not sure on part availability for rebuilding, I know they are not cheap, but that dealer sure did something wrong for it to last less than a year.  My 918H has the original and is still going.

 

Steve

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Here is an excellent tutorial on rebuilding the gearbox by @GLPointon.  It does not explain the removal process however.  If you become a dues paying member, it will allow you access to the "Downloads" section which has the large frame repair manual which will explain how to remove it.  It will also give you access to the "Videos" section which has a Simplicity Tech video on rebuilding the gearbox & the orbital valve for power steering if equipped.  It really is the best $10.00 per year you can spend.

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

 

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Either a part was of defective quality or something was done incorrectly with the rebuild or installation. 

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13 hours ago, Chris727 said:

Either a part was of defective quality or something was done incorrectly with the rebuild or installation. 

I agree with you.  Did not realize the tractor had to be split, great information, I will replace not rebuild with another used BGB just afraid my box may be something wrong since it was rebuilt by the dealer twice or as you said he did something wrong

Thanks for the info I have all summer to work on it and get it ready for the winter I hope, a little at the time

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Did the shaft break on the PTO side or the side which drives the transmission?  Were you doing anything unusual?  It is unusual for a shaft to break.  After very many hours they will pound  out a key or keyway.  Or they might wear out  the gears or input needle bearing but this is often aggravated by low oil level.  

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Tom45 thanks for responding the shaft broke part way in from the PTO side.  I was using the vacuum like I always do, nothing unusual and this rebuilt box only had several hours on it. Both BGB rebuilt by the dealer only had several hours on them each. My original box lasted 20 years and I used it a lot harder than I used both of these boxes.

What type oil do you use the manual say's light oil the dealer put in transmission fluid which I think may be a little light, don't know for sure?  

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If you look at

https://reliabilityweb.com/articles/entry/torsional_fatigue_failure_-_identification_diagnosis_and_prevention

you likely will find the type of fracture you experienced.  If your usage was the same as before it is quite possible the rebuild was done with used gears/shafts and the accumulated fatigue resulted in a short remaining life.  Sometimes the fracture results from the stress at the sharp edges of the keyways.  Reversing back and forth adds stress.  If the rebuild used new components they could have had internal flaws or been installed with interference.

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PGL-It-SCIR-Tom45-Chris 727

Thanks guys did not want to start another and did not know how to add but I took a good look at the shaft (PTO side) and the end is blue from heat so I must of had a catastrophic bearing failure.  There is not that many hours on this rebuild that is what bothers me and I did not have that many hours on the first rebuild either

Thanks for all you input 

broken shaft from PTO side (Custom).JPG

from end (1) (Custom).JPG

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2 hours ago, johno107 said:

There is not that many hours on this rebuild that is what bothers me and I did not have that many hours on the first rebuild either

After seeing the above pics of the broken shaft, I have to ask the obvious- when you got the tractor home from the dealer did you check the fluid level in the BGB to make sure the dealer filled it?  I'm surprised the dealer used ATF vs the latest recommended "Multi-Purpose Hydraulic/Transmission Oil" - the same fluid recommended for the Sundstrand hydro.  

Can you describe the first failure?  I'm curious since I also had a BGB failure and I'm suspecting what @Chris727 said above:

"a part was of defective quality"

My BGB failure wasn't catastrophic - at least I don't think so, I haven't opened the box yet.  

In July 2017 I rebuilt the BGB in a Sov18 purchased for my daughter/SIL (I knew the BGB was hurting, but not to the extent it was).  I installed a new cross shaft, a set of good used gears, and all new bearings and seals; I reused the input shaft.  The cross shaft was ordered in from Briggs, my local dealer didn't have one in stock.  

In this past January while blowing snow with the Sov18, an "oil" spot trail was noted on the driveway; further Facetime video investigation showed the leak was from the PTO side of the BGB.  Not quite 90 hours on the rebuilt BGB.  

Last month, the Simplicity Repairman made a house call (with a "good" 7018 BGB in tow).  With the tractor running without the PTO engaged, no leak; PTO engaged, leak).  No unusual noise from the box regardless of the PTO position).  Compared the amount of radial movement of the shaft to their other non leaking Sovereign BGB.  A lot more movement on the leaker.  So a BGB switch was made.     

Pics of the leaking box shaft movement:  

IMG_0928.thumb.JPG.724099d00f6275c26fb52c70feef8d12.JPG

IMG_0927.thumb.JPG.adca9e275d3062d51fa7925109000f32.JPG

 

And there is unusual wear at the PTO spring retainers, especially the outer one:

IMG_0924.thumb.JPG.c2c2b3f2cc9e284a70f9608d1b1b7ab0.JPG

I'm suspecting the needle bearing has eaten into the shaft rather than the needle bearing being bad.  Is the shaft supposed to be hardened at the bearing area?  Also at the PTO spring retainer area?  

Thoughts?

 

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The shafts that I have looked at I would not consider hardened.  I believe that they are a material with more hardness than mild steel, such as 1144 or pre heat treated 4140, Rc about 30.  If the oil level is low such as the front needle bearing is not flooded I believe the input shaft and needle bearing run dry and fail.  

The output shaft breakage failures are a mystery to me.  

 

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On 6/1/2022 at 7:06 PM, Tom45 said:

The shafts that I have looked at I would not consider hardened.  I believe that they are a material with more hardness than mild steel, such as 1144 or pre heat treated 4140, Rc about 30.  If the oil level is low such as the front needle bearing is not flooded I believe the input shaft and needle bearing run dry and fail.  

Thanks for the reply.  

I decided to get the key out of the tranny drive side of the cross shaft and do some further examination without opening the box.  A pic of the tranny drive side before I drove the shaft left; it looks fine (minimal radial movement) as I expected: 

IMG_0931.thumb.JPG.ca2a2d8b134dc57e64860def573c1867.JPG

You can see the sealing O-ring against the ball bearing inner race; since it's still intact, I don't think there's an issue with the shaft surface where the ball bearing race contacts it.  

 

And the PTO side is also as I expected:

IMG_0934.thumb.JPG.426a143b094c9475fe0427002dbe17c3.JPG The needle bearing contact area is definitely chewed up and to my eyes there appears to be some blue on the shaft to the right of the worn area.  The issue wasn't lack of lubrication since the seal was leaking and the box was properly filled.  

It's always possible that the new needle bearing was defective or I damaged it when I seated it.  I used the same method to seat both needle bearings and the front one is fine.  And I agree with your opinion that the front needle bearing is the more easily damaged one.   

Based on the appearance of the shaft, I'm thinking there's going to be metal bits in the needle bearing so I'll never know for sure what caused the failure.  I still suspect a faulty part.  If the shaft isn't hardened in the bearing area, maybe the wrong shaft material?  

 

 

Edited by PhanDad
corrected axial to radial
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Gotta believe that the shaft should be hardened at the bearing wear surfaces.  If you are pressing on a ball bearing it doesn't need to be hardened, but with that needle bearing running on the shaft it would almost have to be hardened.  Maybe these parts missed the heat treat process?

Steve

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No I did not check the fluid level when I got it back the dealer has always been good by checking different things and lubing everything in sight so NO probably should have.  My new/used BGB is out of 7018 also and it seem good and tight.  I took the oil seals out and will replace them in the next couple of days and start the assembly over again

Could he snowblower be causing my problem it appears that since I got the snow blower a several years ago my trouble started??????? I only use the blower 3 or 4 times a years but I have a lot to do??????

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