CAT 518 Transmission Air Cylinder

mills · February 25, 2020, 12:26:45 PM

Does anyone know how to take this little sucker apart? It's the safety air cylinder that bolts to the top of the transmission valve. It keeps the transmission from shifting out of neutral unless you have sufficient air pressure to release the parking brake. It's had a small leak for years, but opened up to where the compressor is struggling to keep up. CAT shows a parts list, but I can't get it apart. I'm thinking the ring around the outside is threaded, but a 2" pipe wrench didn't budge it. Any ideas before I open it up with a four lb. hammer? :D

Autocar · February 25, 2020, 01:30:54 PM

Just looking at your picture it looks like there's a few 3/8 inch bolts around the rim . If that's the case wrench them out and it should split right apart.

mills · February 25, 2020, 01:49:26 PM

Sorry, should have taken another picture showing the bottom of the cylinder. The two bolts on the sides are just studs coming out of the case. The one in the center is attached to the diaphram inside the cylinder, and the threads is where the yoke screws on.

Autocar · February 26, 2020, 07:24:03 PM

Mills I figured someone would gave you a direction by now you may just have to break down and go to the dealer and see what they cost new. I am sorry I can't help you I have a treefarmer and a timberjack the only peace of equipment I ever had that had a cat name was a Autocar that had a 425 cat engine in it. My Autocar I have now has a cummin's the cummin's is a lot better on your pocket book ;D

mills · February 26, 2020, 07:48:16 PM

"Mills I figured someone would gave you a direction by now you may just have to break down and go to the dealer and see what they cost new."

Lol, yep I'm guessing these things aren't real common. It's soaking up penetrating oil right now, so by morning it might break free without busting apart. If not, then I'll call CAT. You never know, some of the old guys back in their shop may know something about it. They've bailed me out before. It's simple to bypass around it if needed, but you better be certain the parking brake is released.

Thank you sir.

mills · February 27, 2020, 12:37:42 PM

For those with inquiring minds. I guessed right and the air cylinder came apart fairly easily after a night of soaking in penetrating oil. Looking at it I can't believe it worked at all. Of course there has been a revision, so you can't buy just the diaphragm. Have to buy the cap as well. :

Still under $90.

dgdrls · February 27, 2020, 12:55:32 PM

Nice work mills,
how much is a new one?

D

mills · February 27, 2020, 03:57:46 PM

"how much is a new one?"

:D :D :D Don't know. Too scared to ask. :D :D :D

coxy · March 01, 2020, 01:30:51 PM

dang wish I would have seen this earlier we just did the one on ours in November there a pain to get off the newer 518 but my 81 its right out in the open you can get a new rubber its like 100 bucks

coxy · March 01, 2020, 01:31:50 PM

they also have a revived kit but I just got the rubber

mills · March 01, 2020, 05:31:53 PM

I knew I should have hollered at you.:D I was putting so much pressure on it to get apart that I just knew I was going to bust the housing. Prices weren't too bad. New diaphragm and the revised cap were $88. Probably the cheapest call I've had with CAT in a long time.

Fairly easy to get to, but had to take the lever off the shifter to get it out. Thanks for responding.