743 Major Repairs

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bluthunder

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Dec 14, 2009
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Guys I will be conducting repairs on the Surplus/ 2nd hand Bobcat 743/ 743B that my company recently bought. I will be documenting everything so that you guys could help me in giving me some hints/ points on how too's.
I am only using the manuals as my basis, thanks to southpaw and also to thetool as well as to tazza. It's my first time on everything. that's why the manuals and your ideas gave me a good picture on the problem.
I first checked everything and found out that the seals were broken and there's a large clearance with one of my axles and much worse its in the rear. Here is the game plan. Hydraulic System: Hydraulic Oil - Milky White Work - Bleed and Change old Hydraulic Oil need some advice on this - how to bleed and where to start Hydraulic pump.
Weak pressure work - new hydraulic oil and bleed. let air out am gonna try changing oil first before deciding to replace the pump. base on what i read.. how will i disconnect the return valve/ hose so that i could remove all dirty hydraulic oil.. do i need to replace my old hydraulic hose??
Chaincase Chaincase oil is also milky white Work - Change Oil Replace - axle Seals and Bearings Oil - What oil should I use? tools needed - ?? could i just use hydraulic jack to undo the axles unbolting the axles- what appropriate tools to undo them?
Reduction Gearcase Gearcase sounds terrible work - what work should I do. could the reduction gearcase be damaged? or the drive motor is the one making all the noise Replace - do I need to replace the oil seals and bearings?
Electrical rewiring of entire operator panel change new indications for fuel, oil temp, voltmeter, ignition switch, headlight switch. might rewire engine harness. GOOD thing is the Engine. its is in good condition/ but i might replace glow plugs. having hard starting.. plus white smoke when the engine starts.. gonna post some pics soon.. its 3:00 am Sunday.. gonna do the work on monday.. by the way.. I'm from the Philippines.
I already started working with the chain case yesterday. got it down for in 4 hours. One of the supports that we did for the front blocked the chaincase by a 3-5mm. right now my pump is supported since there is no chaincase.
How can i upload pics here?
 
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bluthunder

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Login and go here http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=EditUserProfile and put a check in "use html editor" and your paragraphs will work.
Read the faq here http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=67 about how to post pics.
Looking forward to your posts.
Ken
thanks skid but i tried using the html editor but.. the problem is i can't post any message.
 

Tazza

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thanks skid but i tried using the html editor but.. the problem is i can't post any message.
If you have the chain case out, you may need new bearings on the really sloppy axles. Replace all 4 axle seals while you are in there and seal the inspection covers really well when you are done and re-filled the chain case. Ensure you mop it all out to get the sludge from the bottom.
As for draining the oil, i always run the machine at idle and engage the aux hydraulics and drain it from the front couplers. When it starts to spit and growl, shut down and re-fill with oil, new filter, drive it around lift and tilt to get the new oil around. Repeat until the oil is a good colour. This will involve you removing a little oil and letting it sit. There will be air in the system so it will appear white, but its only air. Let it sit and check the colour.
Ensure you get all the end play out of the axles too. If you have access to a lathe, you remove a small amount from the inside of the washer that holds the sprockets on. Only remove from the part that touches the axle, not the sprocket. I measured how much end float i had, i then put them in the lathe and took the required amount off, worked a treat.
 
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bluthunder

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You don't use the editor,you just put a "check" in the box.
Follow the 4 steps in this thread.
http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=2445
Ken
yes skid I did all the instructions but still no luck.. i also tried it in the office yet still no luck.. try doing it if it works for you.. thanks
 

skidsteer.ca

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yes skid I did all the instructions but still no luck.. i also tried it in the office yet still no luck.. try doing it if it works for you.. thanks
Hmmm, thats a new one. Are you using Internet Explorer or another brouser like Firefox? This forum software does not play as well with Firefox.
Ken
 
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bluthunder

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Hmmm, thats a new one. Are you using Internet Explorer or another brouser like Firefox? This forum software does not play as well with Firefox.
Ken
I see i am using firefox as of the moment. haven't tried using IE. will try later. We already finished uninstalling the axles.. mud and water everywhere. looking for the replacement bearings and cups. today.. do I need to replace the wear sleeve? pls. pls note what do i need to replace. and how many.. i have taken out the cone bearings. looks like there are two. one for inner and one for outer side of axle.. plus the sleeving. thanks
 

bobbie-g

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Mar 15, 2004
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I see i am using firefox as of the moment. haven't tried using IE. will try later. We already finished uninstalling the axles.. mud and water everywhere. looking for the replacement bearings and cups. today.. do I need to replace the wear sleeve? pls. pls note what do i need to replace. and how many.. i have taken out the cone bearings. looks like there are two. one for inner and one for outer side of axle.. plus the sleeving. thanks
re using Firefox: I find that to do a post, I have to first click "preview" then click "return to editing" before I can type in the txt box. I can edit the subject, but not the text box. I also have turned "html editing" on, but still don't get paragraphs. Minor stuff. :) ---RC
 
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bluthunder

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re using Firefox: I find that to do a post, I have to first click "preview" then click "return to editing" before I can type in the txt box. I can edit the subject, but not the text box. I also have turned "html editing" on, but still don't get paragraphs. Minor stuff. :) ---RC
Just got back from the shop. I've check the chains and manage to undo three because it has a lock pin so it's easy to break the chain. Can anyone tell me the the length of the chains per wheel. Cause one of the chains that I have is slightly longer than the other one. both are from the rear axles. I got a gear whose teeth are worn out. the one's sticking out from the reduction gears driving the chains. Axle Bearings are: LM 104949 - Bearing LM 104912 - Cup Reduction Gear Bearings are: LM 501349 - bearing LM 501310 - cup LM 506849 - Bearing LM 506810 - cup Just canvassed it this morning looks like i'm gonna have a hard time getting these.. Manage to get a timken LM506849 - set but no luck with the LM 501349. as for the axle bearings there are only 2 sets left (timken). Looks like i have to get them all, before it runs out. gonna buy them tomorrow. I also got the drive motors unassemble.. its really dirty.. found some plastics inside and i don't know where they came from.. gonna replace all the o-rings. good thing there's no sign of wornouts and scratches. by the way anyone has a drive motor manuals for the 743? really appreciate it if someone i can download it.
 

Tazza

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Just got back from the shop. I've check the chains and manage to undo three because it has a lock pin so it's easy to break the chain. Can anyone tell me the the length of the chains per wheel. Cause one of the chains that I have is slightly longer than the other one. both are from the rear axles. I got a gear whose teeth are worn out. the one's sticking out from the reduction gears driving the chains. Axle Bearings are: LM 104949 - Bearing LM 104912 - Cup Reduction Gear Bearings are: LM 501349 - bearing LM 501310 - cup LM 506849 - Bearing LM 506810 - cup Just canvassed it this morning looks like i'm gonna have a hard time getting these.. Manage to get a timken LM506849 - set but no luck with the LM 501349. as for the axle bearings there are only 2 sets left (timken). Looks like i have to get them all, before it runs out. gonna buy them tomorrow. I also got the drive motors unassemble.. its really dirty.. found some plastics inside and i don't know where they came from.. gonna replace all the o-rings. good thing there's no sign of wornouts and scratches. by the way anyone has a drive motor manuals for the 743? really appreciate it if someone i can download it.
You should replace the wear sleeves. If you are in that far, its a good idea. There is only one per axle. Cut an old bearing cup in half to knock the new seal in. Sit it around the axle and use a hose clamp to hold it together. Belt the axle in and it will seat the seal for you.
The chains, measure them by links not length. If the links are the same but one is longer, its stretched.
I found all the bearings to be easily found over here. Not super cheap, but not bad. I didn't touch the reduction boxes though, only axles. Two cups and cones per axle.
 
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bluthunder

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You should replace the wear sleeves. If you are in that far, its a good idea. There is only one per axle. Cut an old bearing cup in half to knock the new seal in. Sit it around the axle and use a hose clamp to hold it together. Belt the axle in and it will seat the seal for you.
The chains, measure them by links not length. If the links are the same but one is longer, its stretched.
I found all the bearings to be easily found over here. Not super cheap, but not bad. I didn't touch the reduction boxes though, only axles. Two cups and cones per axle.
check the wear sleeves next week.. if its ok.. i will not change it.. i have only little time to get everything done.. gonna check the chain to.. the length has a large difference. ... bearings for the reduction gear case. one side 2 pcs jLM 501349 - bearing LM 501310 - cup 1 pc - LM 506849 - Bearing LM 506810 - cup 1 pc - 4T-3780 - 3720
 
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bluthunder

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check the wear sleeves next week.. if its ok.. i will not change it.. i have only little time to get everything done.. gonna check the chain to.. the length has a large difference. ... bearings for the reduction gear case. one side 2 pcs jLM 501349 - bearing LM 501310 - cup 1 pc - LM 506849 - Bearing LM 506810 - cup 1 pc - 4T-3780 - 3720
Manage to post this.. more pics to come next week.. thanks skid. found out that mozilla does not support this.. that's why i can't post. now i'm using internet explorer.. merry christmas to all..


IMG_8241.jpg picture by bluthunder_36
 
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bluthunder

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Manage to post this.. more pics to come next week.. thanks skid. found out that mozilla does not support this.. that's why i can't post. now i'm using internet explorer.. merry christmas to all..
18122009003.jpg picture by bluthunder_36

Remove Steering Linkages, And Foot Brake
18122009002.jpg Under Operator Cab picture by bluthunder_36

Remove Hydraulic Pump Bolts, And Remove Lift Linkage Nut under Hydraulic Pump.
18122009004.jpg pallet jack under chaincase picture by bluthunder_36

Support Chaincase with a floor jack or like the one we used here. a 3 Ton Pallet Jack
18122009001.jpg Uninstalling Hydro Motor Lines picture by bluthunder_36

Uninstall all bolts that link the chaincase and the body. Front Bolts are Easy to unbolt. Rear right bolts are quite hard due to the location of the hydraulic contol valves..
IMG_8243.jpg support for hydrualic pump picture by bluthunder_36

Don't Forget to Put a support for your hydraulic pump.. in this case we used a 25mm/1" Deformed Bar and some Tie Wire.
IMG_8244.jpg picture by bluthunder_36

For Safety Purposes We used a 3 ton Chain block to support the fron as well as jack stands under it.. We used a Modified jack stands in this case.. 2 inch Tubular Galvanized Steel Pipe.
IMG_8241.jpg Chaincase 1 picture by bluthunder_36

Voila.. We disconnected the chain case.. Remember to Put indications for the Hydraulic motors with its respective hoses..
 
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bluthunder

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Dec 14, 2009
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Remove Steering Linkages, And Foot Brake

Remove Hydraulic Pump Bolts, And Remove Lift Linkage Nut under Hydraulic Pump.

Support Chaincase with a floor jack or like the one we used here. a 3 Ton Pallet Jack

Uninstall all bolts that link the chaincase and the body. Front Bolts are Easy to unbolt. Rear right bolts are quite hard due to the location of the hydraulic contol valves..

Don't Forget to Put a support for your hydraulic pump.. in this case we used a 25mm/1" Deformed Bar and some Tie Wire.

For Safety Purposes We used a 3 ton Chain block to support the fron as well as jack stands under it.. We used a Modified jack stands in this case.. 2 inch Tubular Galvanized Steel Pipe.

Voila.. We disconnected the chain case.. Remember to Put indications for the Hydraulic motors with its respective hoses..
IMG_8372.jpg cleaned chaincase 2 picture by bluthunder_36

the cleanest i can get. any suggestion guys? used sandpaper with this grit 800
IMG_8376.jpg cleaned chaincase 4 picture by bluthunder_36

suggestions any one?
gearcase6.jpg gearcase 6 picture by bluthunder_36

gearcase
gearcase2.jpg gearcase 2 picture by bluthunder_36

gearcase internals
gearcase5.jpg gearcase 5 picture by bluthunder_36

damaged gears... slightly..
chaincase.jpg chaincase internals picture by bluthunder_36

chaincase internals
hydraulicmotor.jpg hydraulic motor1 picture by bluthunder_36

hydro motor.. checking internals
hydraulicmotor2.jpg hydraulic motor 3 picture by bluthunder_36

damaged O-RING
hydraulicmotor3.jpg hydraulic motor 4 picture by bluthunder_36

in this hydro motor. there isn't a lot of things damaged but the only problem here was there are hardplastic that circulates in the motor. good thing there aren't any damages in the wall but one of the spring is broken.. need to replace it. the other motor in the other hand need lapping.. got get it to the machine shop.. on monday.. till next time guys.. gonna take pictures on the damaged motor.. a lot of scratches.
 

Tazza

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Dec 7, 2004
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the cleanest i can get. any suggestion guys? used sandpaper with this grit 800

suggestions any one?

gearcase

gearcase internals

damaged gears... slightly..

chaincase internals

hydro motor.. checking internals

damaged O-RING

in this hydro motor. there isn't a lot of things damaged but the only problem here was there are hardplastic that circulates in the motor. good thing there aren't any damages in the wall but one of the spring is broken.. need to replace it. the other motor in the other hand need lapping.. got get it to the machine shop.. on monday.. till next time guys.. gonna take pictures on the damaged motor.. a lot of scratches.
Impressive job so far!
The way i'd clean the rust off the chain case is with an angle grinder and wire buff. Use an air die grinder and small wire wheel for the hard to get to places.
With that said, if you clean all the gunk off it, which you havw, there isn't a whole lot more you can do. Its a LOT cleaner than it was, i know you don't want to have to do the job again. The oil that will splash around in the chaincase should coat all the walls so it won't rust again. Ensure the covers are sealed with silicone sealant, this includes the bolt threads. You shouldn't have to do the job again.
 
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bluthunder

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Messages
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Impressive job so far!
The way i'd clean the rust off the chain case is with an angle grinder and wire buff. Use an air die grinder and small wire wheel for the hard to get to places.
With that said, if you clean all the gunk off it, which you havw, there isn't a whole lot more you can do. Its a LOT cleaner than it was, i know you don't want to have to do the job again. The oil that will splash around in the chaincase should coat all the walls so it won't rust again. Ensure the covers are sealed with silicone sealant, this includes the bolt threads. You shouldn't have to do the job again.
ok. thanks tazza. most of the rust that builds up in the surface was already taken off.. looks like this Bobcat We bought survive Typhoon Ketsana... LOL.. The rust that is embedded in the steel plates can't easily taken off.. i guess i'd rather settle with what i have as long as i seal everything out.. have you seen the picture with the axle? the axles should be zero in/ no gap between the housing and the hub? if not how many inches/mm does it need to be?
 

Tazza

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ok. thanks tazza. most of the rust that builds up in the surface was already taken off.. looks like this Bobcat We bought survive Typhoon Ketsana... LOL.. The rust that is embedded in the steel plates can't easily taken off.. i guess i'd rather settle with what i have as long as i seal everything out.. have you seen the picture with the axle? the axles should be zero in/ no gap between the housing and the hub? if not how many inches/mm does it need to be?
The gap between the housing and hub is determined by the bearing. Fully seat them and just ensure you take out any end play when they have been installed with the sprockets inside. There should be no end float. With new bearings and cups, there should be no play anyway. I had to machine the washer on one axle when i installed new bearings. You can't adjust the gap between the end of the axle tube and hub.
Remember you need to install your new seal. Remove the bearings, replace the wear sleeve if you decide. Sit the new wear ring on, slide the seal down on to the wear ring, make sure its the right way!, slide the bearing on and seat the bearing. This will in turn seat the wear ring in the correct place. Its too thin to tap in place with a brass drift, the bearing does a perfect job.
To seat the seal, i assume you don't have an installation tool, get an old bearing cup, cut in tinto two sections, slide the wo halves over the axle between the hub and seal, use a hose clamp to hold it to gether. Hit the end of the axle hub to seat the seal. When its seated, remove the make shift installation tool. Install the bearing in the inside and check for end float.
Ensure you grease the bearings when you install them, it does all run in an oil bath, but you don't want to run them dry before you get oil on them.
I'm sure most of that you already know, you're doing a really good job so far! if you need more info, just yell.
 
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bluthunder

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The gap between the housing and hub is determined by the bearing. Fully seat them and just ensure you take out any end play when they have been installed with the sprockets inside. There should be no end float. With new bearings and cups, there should be no play anyway. I had to machine the washer on one axle when i installed new bearings. You can't adjust the gap between the end of the axle tube and hub.
Remember you need to install your new seal. Remove the bearings, replace the wear sleeve if you decide. Sit the new wear ring on, slide the seal down on to the wear ring, make sure its the right way!, slide the bearing on and seat the bearing. This will in turn seat the wear ring in the correct place. Its too thin to tap in place with a brass drift, the bearing does a perfect job.
To seat the seal, i assume you don't have an installation tool, get an old bearing cup, cut in tinto two sections, slide the wo halves over the axle between the hub and seal, use a hose clamp to hold it to gether. Hit the end of the axle hub to seat the seal. When its seated, remove the make shift installation tool. Install the bearing in the inside and check for end float.
Ensure you grease the bearings when you install them, it does all run in an oil bath, but you don't want to run them dry before you get oil on them.
I'm sure most of that you already know, you're doing a really good job so far! if you need more info, just yell.
wear sleeve and wear ring are the same? did checked the chain links yesterday.. remember i mentioned before that 1 is longer than the other.. both has the same number of links.. so i checked the connections. the longer one has bad connections. there's a lot of play in every links thats why its longer. I have good news found the remaining bearings.. now i need to follow up on the chains. got 10w30 for the chaincase.. yahoo.. bad thing is i didn't started the hydro pumps. and lines yet..
 

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