How to rebuild a Bush Hog Rotary Cutter gearbox.

[HCJtractor]

I just replied to your PM. I was looking online. Surplus Center has some 6 hole gearboxes listed for under $300. I’m sure they’re Chinese made but aren’t they all? Might be worth a look. Look at item number 13-1590 and several others in that range.

In case you didn’t see my message, mine is a Woods Brush Bull 720X. They sell boxes at Messick’s, Coleman’s, German-Bliss etc. Current cost is $750 range. Don’t confuse it with BB 72 which is lighter duty 4 hole.

 

[HCJtractor]

Looked closer at the Supply Center. Have 2.25 shaft. Assume yours is a 2”.
Sorry. Thought that was too good to be true. Good luck.

 

[beemerphile]

Looked closer at the Supply Center. Have 2.25 shaft. Assume yours is a 2”.
Sorry. Thought that was too good to be true. Good luck.

Mine is 2" x 15-spline output and 1-3/8 x 6-spline input.

 

[Dave M7040]

Comer has some good video's on you tube. Not likely your exact gear box but will give you some ideas

Some video's explain the way to use the different thickness of gaskets as shims.

I think the recommended clearance is - i.e. negative, so you first have to adjust to get a little clearance and then select a gasket which will bring the clearances to a negative value.
In other words their design calls for some preload on the bearings.

You may also find good contact info for Comer from the Video's

When changing bearings on Model HP gearboxes up to 12", always double check the bearing looseness. - YouTube

Comer Gearbox Suppliers - Why Buy From Us - YouTube

Comer is not some fly by night operation. They have a presence world wide. The trick is getting to the best support people.

Dave M7040

 

[beemerphile]

Comer has some good video's on you tube. Not likely your exact gear box but will give you some ideas

Thank you much. I will try again to contact Comer. My request to their web site contact was not answered (likewise for Bush Hog). Both have ignored the contact. My box is not shimmed by gaskets though. It has no bolted bearing flange on either shaft. There is a top cover, but it does not have a through shaft. The output shaft has shims below the gear to adjust backlash. The only instructions I have gotten so far (through Messick's) says .005-.015 clearance.

 

[Dave M7040]

Thank you much. I will try again to contact Comer. My request to their web site contact was not answered (likewise for Bush Hog). Both have ignored the contact. My box is not shimmed by gaskets though. It has no bolted bearing flange on either shaft. There is a top cover, but it does not have a through shaft. The output shaft has shims below the gear to adjust backlash. The only instructions I have gotten so far (through Messick's) says .005-.015 clearance.

I am pleased my post at least enlightened you a little. Far too often, owners and mechanics buy expensive parts and then waste them by not providing design pre-load or clearances. Because the usual approach is to replace the complete gearbox, no one is getting educated on how to do a proper rebuild. What is proper for one brand may be completely wrong for another.

Good luck on your quest for information.

Dave M7040

 

[beemerphile]

Well, it is clear now how to disembowel the beast...



In addition to the parts I had on order, the input shaft bearings, seals, and end cap will need to be ordered. I also had to order a 55mm 6 point socket to remove the output shaft nut.



I opened up the box of parts I got from Messicks to find this surprise for the condition of my new output shaft, so back it goes....



I still have some level of uncertainty about the reassembly. I'm told that the shims won't change with new bearings and can go back where they were. A Bush Hog tech told me to pre-load the output shaft by tightening the 55mm nut until the moving torque on the shaft was 6-8 ft.-lb. without the shaft seal. That is straight-forward. Less obvious is how one would ever set the preload on the input shaft bearings. It is entirely by shims. I'll just hope that my guidance was correct and that no shim changes are necessary.

 

[DieselBound]

Holy smokes! That's really putting the OLD in New Old Stock!

 

[beemerphile]

Holy smokes! That's really putting the OLD in New Old Stock!

The Messicks rep said they had problems with some Bush Hog parts because they don't put any kind of rust preventative on them. I am used to precision parts being wrapped in VCI paper. Not so these clowns.

 

[1010]

That is pitiful,, He'd be getting an ear full on that shaft..