• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Cat 931b brake replacement

Aaron McGrew

New Member
Joined
Oct 16, 2018
Messages
3
Location
Georgia
No turn to the right,

Got rt clutch assembly out, found slave cyl. Piston and push rod laying in the bottom, explains no turn scenario. That bay was full of hydraulic fluid from blown slave cyl.

Brake looks new but has been soaked with hydraulic fluid? Replace or not?

I know how to redo brake pads from doing airplanes, who sells new liners?

Bearing is done in rt side so back to cat for that!

Pulling lt side while in there to look at it!

Anyone know what thickness a new pad is so I know whether or not to replace lt brake!

Thanks in advance!
 

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,260
Location
Canada
A local heavy duty brake and clutch shop should be able to do the linings for you. It was about $120/side if I recall. Cat also sells the bands and rivets I believe but probably more expensive or you have to do it yourself. I'm guessing you have dry brakes that aren't supposed to have oil in the compartment. Wet brakes were optional though and I think there was even a kit to convert to wet brakes. Bob/Ont was the expert on these smaller cats but sadly we lost him a little while ago. It was a few years ago but I think the new linings were about a 1/4" thick (approx. 6mm like OM suggested). While you're at it, you can get the metal clip and rivets that the adjustment bolt ratchets on. I would get them first and ask the brake shop to put them on. I had them but got them in a bag from the independent repair shop that did the steering clutches. I saved a little money by taking the brake bands to the brake shop myself. Why pay 20% mark-up if you don't have to. The steering clutches were about $3000/side to do so the shop wasn't suffering. The shop never bothered to mention taking the clips for the adjusters to the brake shop and have them riveted on at the same time, so I used the old ones and returned the new ones. They could have been done when the brake bands were done but I discovered this after the fact. Here's who did the brake bands on mine.

http://www.sifbrake.com/

Having said that, it may be possible to cook the oil out of the brake bands depending on how badly soaked they are. I only say this because I had almost new brake pads on a 3 ton truck soaked with oil reclaimed by putting them under heat lamps at another brake shop. The brake shop would be better equipped to tell you if they're salvageable but $120 isn't too bad for crawler repair.
 
Last edited:

Aaron McGrew

New Member
Joined
Oct 16, 2018
Messages
3
Location
Georgia
Thanks Nige, OM, & WD! I got the rt clutch out real easy, left one is hung up and I cannot move it, it’s hitting the tank.

upload_2018-10-21_22-20-45.jpeg

Any suggestions?

For 3k per side I’m not doing clutches just brakes!

Who or how do I get new slave cylinder pistons? Is that the correct name? It’s what moves the yoke to disengage the clutch. The pistons that are in them are pitted. Need to replace them.
 

Welder Dave

Senior Member
Joined
Oct 11, 2014
Messages
12,260
Location
Canada
I was told loosening the bolts on the tank lets it tilt enough to get the clutches out. I did this but it barely moves. I used a 1" wide x 3' long double loop lifting sling to pull the clutches out. I lifted from the ROPS but moved the chain holding the come-a-long more towards the center. The sling was long enough I could yank on it enough to tilt the clutches so they would come out. I may have had help to tilt it while I lifted. You need a special press to do the clutches but I seem recall they can look at how much the fiber discs have notched to get an idea what shape they are in.

You can get new hardened bushings (and I think ball ends) to go in the frame where the ball end of the clutch arms fit. They say heating around them helps to get them to come out and it's too hard to try and weld a bead on it to shrink it. I tried heating and all it did was melt the plastic plugs they put in accessory holes for a ripper. I ended up putting a big tip in my torch (cleaning the tip so It had a perfectly straight cutting jet) and cutting the bushing in 2 places 180 deg's from each other. I didn't quite cut all the way through the bushing. I left maybe 1/16" so I wouldn't cut into the outer housing. I did the cuts in the 3 and 9 o'clock position so I could use a chisel in the notches to try and turn them. It worked. Getting the new ones in was a royal pain. I'd suggest getting some dry ice to freeze them so they're easier to pound in. Also the shop suggested not to lube them with grease as it attracts dirt and grime. Use aerosol dry graphite lube.

Adjusting the brakes is where Bob really helped me. Cat has an extensive adjustment procedure involving measuring the length's of all the linkage rods, etc., etc., etc. Bob said to put the brake bands tight and then shorten the linkage from the pedals to the clutches as short as you can and still get the pin in. Loosen the bottom support bolt for the brake band ( I think 1 1/2 turns), then back off the brake adjusters till you get the right foot pedal movement. I think it was about 1 1/2 to 2 turns and they click every 1/4 turn. This guarantee's the free play is at the brake bands and not in the linkage. Brake bands too tight can bind up and wear out fast. Machine should coast when put in neutral and taken out of gear with no brakes or roll back on an small incline.
 
Last edited:
Top