Help with Bobcat 642 drive chain replacement

[ibbuckshot]

Greetings folks,
I have been asked by a friend of mine to help him replace the drive chains on his Bobcat 642. The left side chain seems to be jumping
the sprocket when the pressure is applied in turning or loading the bucket. Can anyone point me in the right direction to get to the disassembly of a 642. I will be getting the books soon but have been told the book is short on good information I have been told the chain size is 80 but I don't know if I should get the 80 H (heavy duty). I might be able to get both chains per side out of one box (10 feet) meaning I will need two boxes to complete the job. Any advice would be appreciated. I am not new to turning a wrench but am new to Bobcat 642 inner workings. Thanks in advance for you advice.
Have fun,
buckshot

 

[tonyq60]

Greetings folks,
I have been asked by a friend of mine to help him replace the drive chains on his Bobcat 642. The left side chain seems to be jumping
the sprocket when the pressure is applied in turning or loading the bucket. Can anyone point me in the right direction to get to the disassembly of a 642. I will be getting the books soon but have been told the book is short on good information I have been told the chain size is 80 but I don't know if I should get the 80 H (heavy duty). I might be able to get both chains per side out of one box (10 feet) meaning I will need two boxes to complete the job. Any advice would be appreciated. I am not new to turning a wrench but am new to Bobcat 642 inner workings. Thanks in advance for you advice.
Have fun,
buckshot

Is chain tight?

Use the bucket and lift the front wheels off the ground and see how loose the wheels are.

If they turn more than a tiny bit the chain is loose and to adjust if like our 825 you tighten large bolts that slide axle.

If tight and still tosses chain a sprocket may be bad.

A loose chain can jump a sproket.

 

[ibbuckshot]

tonyq60,
I have been told there is no drive chain adjustments that can be made on the 642. From what I understand when the chain is jumping the sprocket the only thing I can do is to replace the chain which has become stretched from years of use. I could not believe that Bobcat could not have built in a idler pulley as a slack adjuster......

 

[tonyq60]

tonyq60,
I have been told there is no drive chain adjustments that can be made on the 642. From what I understand when the chain is jumping the sprocket the only thing I can do is to replace the chain which has become stretched from years of use. I could not believe that Bobcat could not have built in a idler pulley as a slack adjuster......

Makes no sense....

Look closely at the axles where they exit the box and look for a large bolt between the wheels side of an axle.

The bolt pushes the axle outward to tighten chain.

To not have any adjustments would require perfection in all assemblies which is not likely.

Wait until you receive your factory service manual to be sure as we are speaking reference to our 825...

 

[ibbuckshot]

tonyq60.
I will be getting the shop service and repair manual some time this weekend. I am looking forward to finding what kind of
a ball of worms I am getting into. I will be looking for what you are describing tomorrow. I have an old 610 that I will be selling when I get the 642 up and in better condition. I have replaced clutches , drive chains and bearings not to mention changing out the hydraulic valve body in the 610. I was hoping for something a little less involved ? ? ? So much for "newer and improved. Thanks again.
Have fun,
buckshot

 

[laurencen]

there is no adjuster if similar to 743, you can replace chains, raise the arms and block, put loader on axle stands so wheels can rotate free of ground, remove the top chain cover to expose chains.

rotate wheels and see what play you have, if you are dealing with original chains you need to split the chain, when split use a connector to join new to old, carefully run machine to pull the new chain around the sprockets at the same time pull the old chain out, when the new chain comes over the front you can figure the link to break on the new chain, use the split link to join, check tension and if its more that one link remove another, you may have to use a half link,

now repeat another 3 times

its not difficult but take your time

 

[dfkrug]

there is no adjuster if similar to 743, you can replace chains,
raise the arms and block, put loader on axle stands so wheels can rotate free of ground, remove the
top chain cover to expose chains.

When the chains are worn out, do you need new sprockets, too?

I heard that some of these skidsteers require engine removal to get at some of the
hyd hoses. True?

 

[laurencen]

my guess is if the chain is stretched one would change sprockets however I have never changed sprockets, on one machine we removed a link in 2 of the chains and it worked

on the 743 we needed to remove the control valve for the lift and tilt, after hours fighting with shortened wrenches and tight areas, most lines are steel and wrap everywhere, we removed the motor to get access, in reality it was easier to work on with motor removed

 

[ibbuckshot]

Thanks again folks,
Laurencen, thanks for your input. Maybe it will not be such a buster after all. I will have to pick up a second pair of jack
stands for this.

 

[laurencen]

just put the machine on stands, if you want just a good runner rotate each wheel, if they are tight say a few degrees of rotation back and forth Id say good, on both I have owned only one chain was stretched, we removed a link and fixed it up

the last one we were keeping so we replaced all 4 chains, we used bulk chain and split links, I prefer the cotter pin type instead of the slide clip, that cotter pin is the hard part, not much room in the chain case

 

[laurencen]

you need all 4 wheels off the ground both to test and replace chain, lift arms and block, I recommend 2 people to replace chains, defiantly trust the fellow in control of the levers, it would be too easy to get hurt if the chain was pulled too fast while trying to feed it

 

[ibbuckshot]

What kind of homemade tools or tricks do you use to pull together the chain ends in order to insert the master link? There may only be a few thousands of an inch that keep the link from being connected............

 

[laurencen]

go get some strong zip ties, put then between rollers where the sprocket teeth would go and thro the other end of chain, use 2, pull each one tighter and it will bring chain together, there are tools for this but I could never get them to fit in the space, you may have luck putting each end on the sprocket teeth, need at least 2 teeth engagement, will work for the front chains but not the back chain, hard part is getting the split pins in the holes and spreading them between chain and side of case

 

[ibbuckshot]

How then would you get to connect the back two chains??? I spoke to the person who is to supply me with his now my shop manual and he cant find it...... Says he has it saved on his computer and can print it out.. I hope so. It looks like I am to be the proud owner of this 642. He has become disinterested in doing any additional work on it.

 

[laurencen]

the back ones are a real pain, I would first get machine on stands and try rotating the wheels one at a time and see how much rotation is in each,

if the 642 is same system as 743 I can email the pages for chain replacement,

 

[ibbuckshot]

Thank you Laurencen, your e mail pages have been printed out and in a binder to be out in the shop for the chain replacement. Wouldn't you know that this morning I got the previous owner to come up with a new copy of the three versions of the Bobcat 642 manual. This newly printed manual is a 384 pages and has " Dealer Copy - Not for Resale " printed on every page. I don't know where he obtained it but it sure is extensive. I want to thank you again for your assistance. Have a Merry Christmas and a Safe and Happy New Year..... Now I am out to finish my newly constructed backhoe thumb. I think it will work very well. I need all the help I can muster..in my old age.

Have fun,
buckshot

 

[enginespirit]

it often happens not to be a chain of a bearing camp on one of the hubs.