bobcat drive motor seal and fan gearbox gears

[taggarsind]

hi everyone. i bought a used bobcat753g series a month ago.its a 2001model with bics and has 5500hrs on it. It seems quite a lot maintainance work is to be done. initially there was problem with creeping in neutral but with help from threads by tazza, fishfiles and few others i solved that problem. THANKS TO ALL OF THEM. NOW i have a few more problems. firstly the fan gearbox bearings had gone but i have a replacement for them but its the helical gears inside that is driving me crazy. one of it is worn out and the dealer is charging a whopping $2000 here. i want to know whether anyone has any idea for a substitute gear or any other solution for the gear. i don't why that gear is so costly and what is it made of. Secondly the hydraulic oil is going into the chaincase. i had replenished the oil around 6litres after i bought it. and within 3hours of running the machine all the 6litrs is in the chaincase. i have now cleaned both case drain filters. do i have to change the carrier seal also before using the machine again or can i run it as it is for the time being. thanks.

 

[ZANMAN]

Seals bad behind the drive motors. Get price for the complete gear box from bobcat, should be around $500.00

 

[OldMachinist]

Seals bad behind the drive motors. Get price for the complete gear box from bobcat, should be around $500.00

Surplus Center has the fan gearboxes for $99.
http://www.surpluscenter.com/item.asp?item=13-1422&catname=powerTrans

 

[ZANMAN]

Surplus Center has the fan gearboxes for $99.
http://www.surpluscenter.com/item.asp?item=13-1422&catname=powerTrans

WOW, I almost freaked when I seen how cheap that was, great job.

 

[OldMachinist]

WOW, I almost freaked when I seen how cheap that was, great job.

I know, if I had one on my machine I'd buy one just to have a spare because you never know how long Surplus Center will have them available.

 

[taggarsind]

I know, if I had one on my machine I'd buy one just to have a spare because you never know how long Surplus Center will have them available.

thanks for the link. but i want only the spiral bevel gears inside it. please help me with the motor carrier seal. i have cleaned and refitted both case drain filters. now should i change the motor carrier seal or can i run it for now and check whether the oil goes into the chaincase. please somebody tell me how to remove the seal. thanks.

 

[ZANMAN]

thanks for the link. but i want only the spiral bevel gears inside it. please help me with the motor carrier seal. i have cleaned and refitted both case drain filters. now should i change the motor carrier seal or can i run it for now and check whether the oil goes into the chaincase. please somebody tell me how to remove the seal. thanks.

It's good that you changed your case drains, they protect your pump after one or both of your drive motor fails. They will not stop the oil from getting into your chaincase. Your motor is pressured up and the chaincase has no pressure, once your seal blows, you need to change out that carrier seal. First remove your side covers, easier with tires removed. Then drain your hyd. fluid, remove both main hyd. hoses and the small drain hose off the drive motor. Now before you remove your drive motor, the chain case fluid should be drained down below your seal, especially if it's filled to the top. Below your engine is a plate with 3 screws , remove it, clean out all dirt, there are 2 plugs in there with rubber bushings, 1 is for the fuel tank, the other is for the chaincase, have a few pans ready, as normally a chaincase holds 20 gallons, overfilled may be 30 gallons, then pop your plug and start flipping pans. When your all done, reinstall your plug, suggest new rubber bushing, you don't want a tiny leak . Also while your down there, good idea to drain out a gallon of fuel, in case you have any dirt or water build up in there. , re-install your cover plate. Next remove your drive motors, your carrier seals are now exposed, they are tough to get out, I usually drill 2- 1/8' holes oppsite each other, and use a screw type slide hammer puller, pop them out. Next, buy new seals, and try to borrow the seal installer from bobcat, I tried to install them without it once, never could get them straight. Re-assemble, don't forget to install new o'rings on the drive motors. You should also put in a new hyd filter, even your fill cap is a breather filter, top off fluids and start and check for leaks. To fill that chaincase, you need to remove that front center cover between your feet and fill to fluid comes out the front center plug in the front of your machine, use the same hyd oil as your machine uses. I may have written this fast and may have forgotten something, but this should get you through it.

 

[taggarsind]

It's good that you changed your case drains, they protect your pump after one or both of your drive motor fails. They will not stop the oil from getting into your chaincase. Your motor is pressured up and the chaincase has no pressure, once your seal blows, you need to change out that carrier seal. First remove your side covers, easier with tires removed. Then drain your hyd. fluid, remove both main hyd. hoses and the small drain hose off the drive motor. Now before you remove your drive motor, the chain case fluid should be drained down below your seal, especially if it's filled to the top. Below your engine is a plate with 3 screws , remove it, clean out all dirt, there are 2 plugs in there with rubber bushings, 1 is for the fuel tank, the other is for the chaincase, have a few pans ready, as normally a chaincase holds 20 gallons, overfilled may be 30 gallons, then pop your plug and start flipping pans. When your all done, reinstall your plug, suggest new rubber bushing, you don't want a tiny leak . Also while your down there, good idea to drain out a gallon of fuel, in case you have any dirt or water build up in there. , re-install your cover plate. Next remove your drive motors, your carrier seals are now exposed, they are tough to get out, I usually drill 2- 1/8' holes oppsite each other, and use a screw type slide hammer puller, pop them out. Next, buy new seals, and try to borrow the seal installer from bobcat, I tried to install them without it once, never could get them straight. Re-assemble, don't forget to install new o'rings on the drive motors. You should also put in a new hyd filter, even your fill cap is a breather filter, top off fluids and start and check for leaks. To fill that chaincase, you need to remove that front center cover between your feet and fill to fluid comes out the front center plug in the front of your machine, use the same hyd oil as your machine uses. I may have written this fast and may have forgotten something, but this should get you through it.

See the previous image in the folder... See the next image in the folder...

 

[taggarsind]

See the previous image in the folder... See the next image in the folder...

left drive motorcarrier

leftdrive motorcarrier

leftdrive motorcarrier seal

leftdrive motor

right drive motorcarrier

rightdrive motorcarrier

rightdrive motorcarrier seal

rightdrive motor

motorshaft ring damaged on both motors

 

[taggarsind]

left drive motorcarrier

leftdrive motorcarrier

leftdrive motorcarrier seal

leftdrive motor

right drive motorcarrier

rightdrive motorcarrier

rightdrive motorcarrier seal

rightdrive motor

motorshaft ring damaged on both motors

these are a few pics that i took of both the drive motors that i took apart today. can anyone tell me whether the seals are good or bad. do i need to change them.
in another forum i read the motors need timing adjustment before they are fixed back. what is this timing all about and how is it done. i have service manual that doesnt tell anything about timing of motors.

 

[Tazza]

these are a few pics that i took of both the drive motors that i took apart today. can anyone tell me whether the seals are good or bad. do i need to change them.
in another forum i read the motors need timing adjustment before they are fixed back. what is this timing all about and how is it done. i have service manual that doesnt tell anything about timing of motors.

Those motors do not need timing. I don't know if that blue seal does much. The main cause of leakage is the carrier seal that you took pictures of.

 

[taggarsind]

Those motors do not need timing. I don't know if that blue seal does much. The main cause of leakage is the carrier seal that you took pictures of.

but do i need to change those carrier seals tazza. how can i find whether whicht seal needs replacement. is there any way of testing the seals. i don't find any point in replacing both the seals together. the bobcat service engineer suggested that i fit the motors back, then drain the chain case fully. then he told that ishould remove the front chaincase cover and start the machine. then to see from which side of the drive is the oil leaking. i think this method is good for testing the seals. but is it safe to start the machine with an empty chaincase and without the case cover. what do you peaple suggest.

 

[Tazza]

but do i need to change those carrier seals tazza. how can i find whether whicht seal needs replacement. is there any way of testing the seals. i don't find any point in replacing both the seals together. the bobcat service engineer suggested that i fit the motors back, then drain the chain case fully. then he told that ishould remove the front chaincase cover and start the machine. then to see from which side of the drive is the oil leaking. i think this method is good for testing the seals. but is it safe to start the machine with an empty chaincase and without the case cover. what do you peaple suggest.

For the price of a seal, i would just shange them out. The motors are already off.... I think they ran me all of $20 each from the dealer. You may be able to get them cheaper after market.
I'm not a fan of running the machine without oil in the chain case, but i believe there would be enough lubrication from the oil residue in the axles and motor carrier/chain for a short test.