Has anyone rebuilt a fan gearbox?

[Mikefromcny]

My 873 has a noisy gearbox, just at idle though. Its smooth when revved up. I realize surplus center sells the gearbox new for $100 however my 873 isnt listed in the application. I'm considering pulling mine and replacing bearings and seals..hopefully they are standard ones. Poking the fan with a stick shows what looks like normal gear backlash so I assume the gears are okay. Dont want my gearbox to die when I need it and then bobcat wants like $500 for it. Thanks for any input guys.

 

[Tazza]

I did one on a 751, it used standard bearings and seals. They are pretty simple.

 

[biggie]

R U Sure it's the gear box? It could be just the fan drive belt is worn/wrong. Or the ider pulley is worn or damaged. Lift the cab and see if the idler pulley bolt is hitting the drive belt housing.

 

[Mikefromcny]

R U Sure it's the gear box? It could be just the fan drive belt is worn/wrong. Or the ider pulley is worn or damaged. Lift the cab and see if the idler pulley bolt is hitting the drive belt housing.

Looked at it tonight, what it is, is the idler pulley arm doesnt seem to have much tension on it, and rattles at idle. It doesnt slip, but I can easily move the idler arm with 1 hand, and take the belt off. How much tension are these springs supposed to have?

 

[Tazza]

Looked at it tonight, what it is, is the idler pulley arm doesnt seem to have much tension on it, and rattles at idle. It doesnt slip, but I can easily move the idler arm with 1 hand, and take the belt off. How much tension are these springs supposed to have?

They don't have much tension on them at all, far less than you would expect.

 

[mahans7]

They don't have much tension on them at all, far less than you would expect.

Tazza, it shouldn't rattle should it? I replaced an idler pulley tensioner on my daugthers' Saturn a few months ago and it was making a terrible rattling noise. Not anymore.

 

[Tazza]

Tazza, it shouldn't rattle should it? I replaced an idler pulley tensioner on my daugthers' Saturn a few months ago and it was making a terrible rattling noise. Not anymore.

It shouldn't rattle, but the belt does wobble around quite a bit. I'd slip the belt off and give the idler a spin, see if it sounds crunchy and needs replacing.

 

[7LBSSMALLIE]

It shouldn't rattle, but the belt does wobble around quite a bit. I'd slip the belt off and give the idler a spin, see if it sounds crunchy and needs replacing.

back in the the day it was cheaper to replace an (ANGLE DRIVE) than to rebuild one now not so much, first belt lenghth on these is somewhat in the air s/n differances make this a make it work rather than this is my model this is my s/n thing, rather embarrisining i think. , so that being said a few facts. sevral changes have been made to both pulley size and belt length, as a genral rule first verify angle drive belt tenninoser spring and arm are good( belt off should snap back with no side to side play) backwards and fowards than verify it is not bottoming out on drive belt spring if it is go with shorter belt or bigger pulley (s/b i dont care # improved cooling etc) what you want is bolt that extends thru angle drive teninsoer arm to be about 1/2 inch off large spring, to reiterate this can be accomplished by a larger pulley or shorter belt.. now a couple of facts always going to be noisy on start up (takes a second to catch up wit eng speed a little knock normal. now to the heart of the matter the angle drive is a simple ring and pinion,! rear end on a smaller scale, take it apart clean it set backlash reseal and reassamble GRAVY parts avail at decent price be sure to ave shim kit, set it up at 2 to 5 backlash good to go,

 

[Mikefromcny]

back in the the day it was cheaper to replace an (ANGLE DRIVE) than to rebuild one now not so much, first belt lenghth on these is somewhat in the air s/n differances make this a make it work rather than this is my model this is my s/n thing, rather embarrisining i think. , so that being said a few facts. sevral changes have been made to both pulley size and belt length, as a genral rule first verify angle drive belt tenninoser spring and arm are good( belt off should snap back with no side to side play) backwards and fowards than verify it is not bottoming out on drive belt spring if it is go with shorter belt or bigger pulley (s/b i dont care # improved cooling etc) what you want is bolt that extends thru angle drive teninsoer arm to be about 1/2 inch off large spring, to reiterate this can be accomplished by a larger pulley or shorter belt.. now a couple of facts always going to be noisy on start up (takes a second to catch up wit eng speed a little knock normal. now to the heart of the matter the angle drive is a simple ring and pinion,! rear end on a smaller scale, take it apart clean it set backlash reseal and reassamble GRAVY parts avail at decent price be sure to ave shim kit, set it up at 2 to 5 backlash good to go,

Thanks for your reply 7lbssmallie. The angle drive seems to be good and tight, but I think I may need to buy a new idler assembly. The pivot is fairly loose and and theres a little play in the pulley bearing, but a new belt 1" shorter would probably fix it. Never thought of this, thanks again.

 

[KyMadMan]

back in the the day it was cheaper to replace an (ANGLE DRIVE) than to rebuild one now not so much, first belt lenghth on these is somewhat in the air s/n differances make this a make it work rather than this is my model this is my s/n thing, rather embarrisining i think. , so that being said a few facts. sevral changes have been made to both pulley size and belt length, as a genral rule first verify angle drive belt tenninoser spring and arm are good( belt off should snap back with no side to side play) backwards and fowards than verify it is not bottoming out on drive belt spring if it is go with shorter belt or bigger pulley (s/b i dont care # improved cooling etc) what you want is bolt that extends thru angle drive teninsoer arm to be about 1/2 inch off large spring, to reiterate this can be accomplished by a larger pulley or shorter belt.. now a couple of facts always going to be noisy on start up (takes a second to catch up wit eng speed a little knock normal. now to the heart of the matter the angle drive is a simple ring and pinion,! rear end on a smaller scale, take it apart clean it set backlash reseal and reassamble GRAVY parts avail at decent price be sure to ave shim kit, set it up at 2 to 5 backlash good to go,

Hi 7LBSSMALLIE, I've torn down the fan / blower gearbox on my 753 and it is obvious at least the bearings in the short housing need replacement. Also there seems to be the need for a couple more shims on one or both shafts. Before I get parts I want to check fitment of the bearings on the short housing. Are these bearings suppose to fit in the housing so tight as to need a press to remove and reinstall them or is it a snug fit on the tapered end side allowing them to be tapped out with a hammer and non-metal punch? I'm not sure if housing needs replacement or if I'm ok and good to go. I realize they need to be pressed on and off the shafts. The Service Manual states that the bearings may come out with the shaft but not sure what that actually means as far as needing a press to accomplish this. Thanks in advance for input suggestions etc. KMM

 

[bobbie-g]

Hi 7LBSSMALLIE, I've torn down the fan / blower gearbox on my 753 and it is obvious at least the bearings in the short housing need replacement. Also there seems to be the need for a couple more shims on one or both shafts. Before I get parts I want to check fitment of the bearings on the short housing. Are these bearings suppose to fit in the housing so tight as to need a press to remove and reinstall them or is it a snug fit on the tapered end side allowing them to be tapped out with a hammer and non-metal punch? I'm not sure if housing needs replacement or if I'm ok and good to go. I realize they need to be pressed on and off the shafts. The Service Manual states that the bearings may come out with the shaft but not sure what that actually means as far as needing a press to accomplish this. Thanks in advance for input suggestions etc. KMM

The seal on the outboard end (near the pulley) on my 763 is leaking oil. I need to tear the gear box down and replace that seal one of these days. I'm following this thread closely! ---Bobbie-G

 

[reaperman]

The seal on the outboard end (near the pulley) on my 763 is leaking oil. I need to tear the gear box down and replace that seal one of these days. I'm following this thread closely! ---Bobbie-G

IF you look at the dates on this thread its from 2012

 

[Tazza]

IF you look at the dates on this thread its from 2012

I did a blower on a 763 last year. The bearings are pressed onto the shafts, but not a real tight fit into the aluminium housings.
The ideal way is to note where the shims came from, you can adjust the side of the bearing that they go on to adjust the engagement of the gears. You don't want them too tight or too loose or they will have back lash. I am not sure what the correct figure is, but if you put it together and rotate the shaft, if it feels really gritty, you have too much engagement of the gears, install shims to pull the shaft out.
Bobby - if you just need to do the seal, drill a hole and use a self tapping screw to pull the old one out.

 

[bobbie-g]

I did a blower on a 763 last year. The bearings are pressed onto the shafts, but not a real tight fit into the aluminium housings.
The ideal way is to note where the shims came from, you can adjust the side of the bearing that they go on to adjust the engagement of the gears. You don't want them too tight or too loose or they will have back lash. I am not sure what the correct figure is, but if you put it together and rotate the shaft, if it feels really gritty, you have too much engagement of the gears, install shims to pull the shaft out.
Bobby - if you just need to do the seal, drill a hole and use a self tapping screw to pull the old one out.

Tazza, I figured it wasn't accessible with the whole gearbox/fan assembly in place. I'll have a closer look to see if I can remove the seal with the whole mess in place. But even if I have to remove it to get at the seal, that makes sense to just do the seal without tearing into the gearbox. Have you ever done a seal with the gearbox in place? Obviously the drive pulley would have to be pulled in place, unsure how difficult that would be. --- And by the way, my neighbor has a new Cat 262. He showed me the oil filter he was trying to change, egads! Bobcat does NOT have the sole patent on making things inaccessible!!! ---Bobbie-G

 

[Tazza]

Tazza, I figured it wasn't accessible with the whole gearbox/fan assembly in place. I'll have a closer look to see if I can remove the seal with the whole mess in place. But even if I have to remove it to get at the seal, that makes sense to just do the seal without tearing into the gearbox. Have you ever done a seal with the gearbox in place? Obviously the drive pulley would have to be pulled in place, unsure how difficult that would be. --- And by the way, my neighbor has a new Cat 262. He showed me the oil filter he was trying to change, egads! Bobcat does NOT have the sole patent on making things inaccessible!!! ---Bobbie-G

Sadly i have never tried doing one in place. If you can get the pulley off, there is no reason why you can't do it though. The seal shouldn't be too tight of a fit.
The biggest issue i had was getting the pulley off, the shaft got rusty and it took a lot of work to get it moving.