Repairing Bobcat 773

trouble007 said:

ya, i hope after this little problem my boss will get it through his head how important proper maintenance is this could probably been avoided if the plug had been opened every 250 hours like the manual suggests. o well, another lesson learned the hard way.

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LoL, it's rare for a boss to get anything in his head about maintenance.

This little Bobcat has to handle truckloads of attachments, hard for us to do without it, so we take care of it. With over 3,000 hrs, it still works great, engine is still in A-1 shape. But the chains were getting noisy from being stretched. When I took it apart, found a little wear on bearing cups. Well, we're in here, time to rebuild the drive system. She's ready for another 3,000 hrs.

What part of Ontario you from? I work with a fellow origionally from Cambridge.

ATCOEQUIP said:

LoL, it's rare for a boss to get anything in his head about maintenance.

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Now ATCO, we don't want to make generalizations....

CM1995 said:

Now ATCO, we don't want to make generalizations....

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Your right, point taken. :notworthy

ATCOEQUIP said:

Your right, point taken. :notworthy

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Just pullin' your chain. If I had a $1 for every time I saw an owner run their machine into the ground, either knowingly or in a case of ignorance, I would have enough to buy something expensive.

I,m from oshawa Ontario (45 min east of Toronto) ya I'm the maintenance man/farm hand so my boss never really gives me time to do maintenance chorus our bobcat 753 f series has 4000 hours on it i think and has had a lot of issues including having to have the pump rebuilt. we are have an issue with the parking brake solenoid randomly popping on not very fun ointhead i think i will have 2 take a volt meter and check the resistance. also, anyone have an alternitive to buying the $75 parts manuals. we have 2 different skidsteers the 753 and a s250 and my boss wouldn't be into spending the $150. I know he's kinda cheap


Thanks


Ryan G

CM1995 said:

Just pullin' your chain. If I had a $1 for every time I saw an owner run their machine into the ground, either knowingly or in a case of ignorance, I would have enough to buy something expensive.

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LoL...yep, I know, just practicing up on my modesty. You know, a guy from Tennessee telling a guy from Alabama they're right. Ahh, the TN - AL rivalry will live forever.

trouble007 said:

I,m from oshawa Ontario (45 min east of Toronto) ya I'm the maintenance man/farm hand so my boss never really gives me time to do maintenance chorus our bobcat 753 f series has 4000 hours on it i think and has had a lot of issues including having to have the pump rebuilt. we are have an issue with the parking brake solenoid randomly popping on not very fun ointhead i think i will have 2 take a volt meter and check the resistance. also, anyone have an alternitive to buying the $75 parts manuals. we have 2 different skidsteers the 753 and a s250 and my boss wouldn't be into spending the $150. I know he's kinda cheap


Thanks


Ryan G

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Yep, your in farm country Ryan. :yup

Yes sir, it's no fun when that parking brake locks while your driving. It's happened a couple times to ours, usually when the solenoid burns up. Ours has toasted a couple of solenoids, never have found a problem with the system, even sent it to Bobcat once, they couldn't find anything wrong with it. :beatsme. Don't know an alternative to buying parts manual. Bobcat's the only place I know to get parts info. I wish Bobcat would get with modern times and have parts lookups online like Deere and Case does. Worthless "billboard" information websites drive me crazy. :Banghead

agreed we get all are JD parts numbers online so when we go to the dealer it makes life easier for them but we still have them looking up the bobcat parts numbers and yep it hurts when the brakes lock any ideas as to my thread with the s250 fuel tank problem?

Thanks

Ryan

AndyGrevis said:

a few questions pop up, how much is too much stretch in chains?
Thanks!

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the exact figure for chain stretch is 3% limit. if you go to an MRO supplier you can get a chain stretch gauge. it is important to use the gauge properly so thoroughly read all instructions supplied with it. you need to use the portion of the gauge intended for roller chain, you must measure a loaded span of chain (no slack) and you need to know the pitch of the chain to measure it correctly. establish pitch of the chain by measuring from one pin center to the other on one outer link plate to establish pitch. measuring stretch will vary in technique from one gauge design to another, but you generally measure across a span of about a foot or more from one pin center to another and replace the chain when the second pin reaches the "no-go" mark on the gauge.

after 3% wear the load carrying capacity of the chain drops dramatically and so will the drive side wear transferred to the drive sprockets from pin spread.

very good information i will have to check the chain wear on the drive train of the 753 when i open it up to put in new hydraulic oil might as well just to get the boss mad. the people that drive this bobcat drive it a little on the rough side so i wouldn't be surprised at what i find

I'm repairing a BC 763. How do you set the end play for the axle? I have a shop service manual, but I can't find where it has any tolerences for that. I've repaired/refurbished several dozers under 50HP but first time on a Bobcat.
I thought maybe one would place the shim under outside tapered roller bearing? Just wondered how you do it.

Welcome to the forum country53. :usa

Good question. I was looking for shims for bearing load when I disassembled the axles, wasn't a shim anywhere. Appearantly, Bobcat has the components machined so when you tighten the bolt that retains the sprockets on splined shafts, the sprocket presses the inner axle bearing cone in place. You tighten the sprocket retainer bolt until it's washer bottoms out on end of axle that bolt screws into. At that point, the load is proper on the bearings, the axles were just slightly snug to turn by hand, but not excessive.

Bobcat help

I have a broken mount for the center piston for the bucket. Do they make repair parts for this mount?

ATCO
Great thread. I did the same rebuild on my 743 last year. Bobcat has 3 different size washers for the end of the axel. They each have a different amount of play that they will take up on the bearings. I still cant figure out how Bobcat expects you to torque sprocket retainer bolt. I just used a wrench and a big cheater bar. Bobcat is also really proud of their tool kit for doing that job $800. I modified all the tools i needed for the job and saved alot.

I'm getting all sorts of issues with my 773. Sorry to jack this thread, but I can't start any new posts yet. Getting codes: 04-21, 05-21, 07-21, 08-21, 09-21, 11-06, 12-21. Any ideas? I have about 1500 hrs on it.

JAZZY5 said:

I have a broken mount for the center piston for the bucket. Do they make repair parts for this mount?

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Hi JAZZY5. Sounds like you might have a 743 or 753 with the single bucket cylinder in the middle of the bucket. Those machines were really bad for cracks at the pin boss where bucket cylinder attaches to loader frame. Anyone who has one of these machines needs to watch for cracks and repair/re-inforce them before they get bad. I don't know if Bobcat offers repair parts to fix a broken one, you may have to repair the unit with new steel plates. I think I'd rather have the loader arms off the machine to do that.

LBTCon said:

ATCO
Great thread. I did the same rebuild on my 743 last year. Bobcat has 3 different size washers for the end of the axel. They each have a different amount of play that they will take up on the bearings. I still cant figure out how Bobcat expects you to torque sprocket retainer bolt. I just used a wrench and a big cheater bar. Bobcat is also really proud of their tool kit for doing that job $800. I modified all the tools i needed for the job and saved alot.

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Yep, it's quite a project LBTCon. I can't figure out how Bobcat expects you to do anything to their machines. Painful little critters to work on. Bobcat is an appropriate name for them, by the time your done, your scratched and cut in numerous places. I looked closely for shim washers when I took this one apart, never saw one. But I did make sure to re-install axles from the tubes they came out of just in case there were something different about them.

bcat773t said:

I'm getting all sorts of issues with my 773. Sorry to jack this thread, but I can't start any new posts yet. Getting codes: 04-21, 05-21, 07-21, 08-21, 09-21, 11-06, 12-21. Any ideas? I have about 1500 hrs on it.

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You can start a thread now bcat773t, and, welcome to the forum. :usa

Don't know the codes on one, can't help you much with that. Maybe bobcatmechanic will show up here and help you out.

ATCOEQUIP said:

Hi JAZZY5. Sounds like you might have a 743 or 753 with the single bucket cylinder in the middle of the bucket. Those machines were really bad for cracks at the pin boss where bucket cylinder attaches to loader frame. Anyone who has one of these machines needs to watch for cracks and repair/re-inforce them before they get bad. I don't know if Bobcat offers repair parts to fix a broken one, you may have to repair the unit with new steel plates. I think I'd rather have the loader arms off the machine to do that.




Yep, it's quite a project LBTCon. I can't figure out how Bobcat expects you to do anything to their machines. Painful little critters to work on. Bobcat is an appropriate name for them, by the time your done, your scratched and cut in numerous places. I looked closely for shim washers when I took this one apart, never saw one. But I did make sure to re-install axles from the tubes they came out of just in case there were something different about them.




You can start a thread now bcat773t, and, welcome to the forum. :usa

Don't know the codes on one, can't help you much with that. Maybe bobcatmechanic will show up here and help you out.

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Thanks ATCOEQUIP

ATCO
Hey I just signed up here after doing some research and I found this thread using a google search for how to adjust chain tension on my 773. I am posting this in a separate thread but I see you may have the knowledge to answer my question. I just bought a 2003 773g with around 900 hrs(supposedly) and I am in the process of rebuilding the running gear with new bearings, seals due to a very bad maintenance program by the previous owner. As far as I can tell the previous owner got some wire wrapped around the axle and it ripped the seal out letting about half of the oil out of the chaincase and then it proceeded to destroy the bearings so that is why I am replacing the bearings but now I have come to a standstill until I find out weather or not my drive chains are stretched beyond the limit ( this is were I hope you can help) I have put one side together and I noticed that the chains are so close to rubbing on the chaincase I can actually push down on the chains and they hit the bottom of the chain case making me think that they will really rub or slap the case when it is running. I can move the carrier shaft back and forth about a 1/4 to a 3/8 of an inch and it will tighten one chain or the other up but it also makes the opposite loose. The manual does not go into any detail on how to adjust or how to tell if your chains are wore and I cant believe at 900 hours that they would be that far stretched. Visually the chains look in great shape, sprockets look new, its just that I can push the chain down by hand and rub the bottom of the case that concerns me. When I put the carrier so that both chains are equal in slack I can pull up on the chains and get about an 1 3\4 slack. Any suggestions would be great you had a great wright up on this so I am hoping you can help. Thanks

Welcome to the forum jrrhotrod. :usa

As for the stretch spec, didn't bother finding out myself. Our unit has over 3000 hrs on it, and it's still a daily used machine, the boss decided it was just time to go through the drives to keep it in good shape. I'm curious about what you said about the carrier shaft, that you can move it fore and aft and make one chain taught and the opposite loose. The bearings in the motor carrier shouldn't let that shaft move at all, have you got a problem with the carrier bearings? As for chain adjustment, Bobcat didn't make a provision for adjustment, the fabrication dimensions of the machine simply have proper length chains to be at proper tension. And you mentioned wire (uggh) wrapped around the axles tearing out seals, did it do any damage to axle housing so new seals won't fit proper? Wire wrapped around axles is recipie for #%&$ :Banghead. Hope you get everything sorted out. Keep us posted with the repairs, and do post some pics.

new chains arent going to break the bank, as atco suggested the carrier shaft is where you should be looking first but 900 hours of operation (i might question that number on a 2003 unit) with no lubrication is plenty of time to cause all kinds of havoc including stretched chains. price the chains out, they wont be that expensive as they are a regular MRO supply item.

Hey that was quick
I will start with the carrier and how it mounts to the side of the chaincase there are oval slots in my caincase (hopefully not just mine) allowing the carrier to move forward and backward slightly but it travels no more than 3\8 of an inch if that it maybe more like a 1\8 inch of movement you can definetly tell the holes are stamped in a oval shape in the case I do not think it is wore like that(hope not).I replaced motor carrier bearings and seals while I was in there so carriers are good. Long story short the bad outer axle bearing disinigrated and once the cage broke it proceeded to allow excessive endplay and it destroyed the axle tube itself so I had to get good at my pipe welding skills and weld on a new axle tube about 3 inches in and also had to replace an axle. as near as I can tell there was something wrapped tightly around the axle as it scarred the tube pretty good and my guess was that it pulled the seal out . I will be detailing that in a post for others when I find out if my weld job is going to hold up( hope it will). Back to the chain, I do feel a little play in the rollers but not much and there is hardly any play in the pins or rivets pinning the links together. it is my inexperience with these machines that is probably making me wonder more than anything it seems that they put those sprokets so close to the bottom of the case that there isnt much room for the slack at all. any idea how close your chains were to the bottom of the case or how much slack you had it seems more like the rear is the closest to the bottom just cause it is longer and has a more gradual slope to the back.normally I would just go and buy new chains but man everything looks new sprockets chain pretty much everything but those worn out bearings I replaced. Maybe I can get a pic tomorrow and post for a decent visual of it. Thanks for your help