Cat hydrostatic transmission overhaul.

[Bob/Ont]

The story I heard was the 943 and 53 was very profitable and dependable. The 963 was less so and the 973 was a very Expensive Learning Curve. If you look at the four HPCU's side by side and then look at the horsepower going through them you can understand why. Heat is the problem and the 73's had two speed motors. The rotating group was mounted on trunion bearings with swivels carrying the oil. If the bearings flexed the swivels would leak and trans overheat. That was one problem that was overcome but motor leakage was biggest problem next to shock loads breaking the internal drive shafts.
Later Bob

 

[overworked]

Bob, we used to see alot of 973's here in the northeast, mid eights till mid 2000, used in stripping overburden in bluestone quarrys, operators would bang back and fourth peeling cap rock, worn trunions and broken shafts were the common, they were real money makers if you liked crawlin through the mud and oil from blown drive hoses, once the belly pans were smashed in.

 

[overworked]

Cmark, very well presented, nice work,

 

[nzpatch]

Hi , just wondering , what sort of cost is it to do a full overhaul like this?
Thanks for the full rundown on this , it's really good to see .

 

[Cmark]

Hi , just wondering , what sort of cost is it to do a full overhaul like this?
Thanks for the full rundown on this , it's really good to see .

Bearing in mind this is a public forum, out of respect for our customer I'd rather not discuss costs if that's OK with everyone.

However if anyone wants to discuss price of repair from a business point of view, they can certainly PM me.

 

[nzpatch]

Ok all good, we don't see many track loaders over here, a few older ones 955/941 and a few 953/943s ,so haven't had much to do with rebuild prices of the hystat system , often thought about a 943 but as they are getting older now worry about the cost to keep going( to a good state not just "going") .

 

[Cmark]

That's the thing about the hystats. They either go (with little problems along the way) or they don't....bigtime.

Their biggest downfall was the high pressure drive lines from the HPCU to the motors. The entire thing is crowbarred into the chassis with maybe 3/8" to spare either side to remove and install hoses like iron bars. Difficult enough to replace in a clean machine but in the field, keeping dirt out of the system was much like the recreational pursuit of walkng through mountains. Impossible.

If you happen to buy a used one that runs for a few hundred hours without trouble, you've probably got a winner. If you blow a hose however, be ready to spend an extra hour cleaning things down before you even begin to remove the old one. It will be time well spent.

(This applies to all hydraulic systems of course, except most hydraulic systems don't take an hour of cleaning)

 

[Plant Fitter]

Looks like a very professional overhaul. I presume from this and your other previous posts that you work for a Cat dealer?

Are these type of jobs just given to anybody who works there and expect them to follow the book and produce a reliable rebuild? Or are they only given to the best techs who are capable of doing as good a job as you have here?

The reason I ask, is I have worked with some Cat trained mechanics and some ex-Cat trained mechanics who would not be capable of doing a job like this, and it has always made me wonder what standard of repair I would get if I ever sent a component to a Cat dealer for a rebuild.

 

[Cmark]

Looks like a very professional overhaul. I presume from this and your other previous posts that you work for a Cat dealer?

Sorry to dissapoint PF, I'm an independent contractor. However father ran an earthmoving business all his working life. I left school in '83 and have worked a steady 50+hrs/week purely as a HE mechanic since then (That's a lot of bolts tightened. ) and I've spannered everything for Aveling-Barford to Zamboni.

I've worked for Cat dealers, TEPS dealers, contractors, subbies, dreamers, wannabes, chancers, carnies, gyppos and myself.

I'd be lying if I said access to SIS wasn't essential to doing a good job on Cat equipment, but bear in mind the yellow/black stripe over the door doesn't guarantee a good job if the people sitting under it aren't up to scratch.

 

[Plant Fitter]

Sorry to disappoint

No disappointment at all.

bear in mind the yellow/black stripe over the door doesn't guarantee a good job if the people sitting under it aren't up to scratch.

That's what I was getting at. I guess that means I am not the only one who is concerned about it.

 

[Extractorfan]

Yair . . . Excellent comprehensible thread and pictures Cmark.

A beautiful bit of gear but you would really have to wonder about the designer who first got his head around the concept and put it down on paper . . . it makes my head ache just thinking about it.

Cheers.

My thoughts exactly, some clever people out there, wonder how many hours it took to iron the bugs out of the prototypes?
Ex tractor fan

 

[Jdr]

that was a brilliant layout an explanation..i wish i had a Cat

 

[sealark37]

What Cmark has to say is spot on. Your local Cat dealer has field mechanics, shop mechanics, truck mechanics, and specialized mechanics. The guys who do overhauls like these are the ones who have the knack and special training, not to mention the equipment to do the job correctly. However he got it, Cmark has this training, and the facilities required to do this work correctly. When a shop or field mechanic removes this transmission, he delivers it to the specialization shop for overhaul. I'm not saying that this work cannot be performed in your garage or shed, but you do need the proper tools, information, parts, and cleaning capability before you start. Oh, did I mention money? Regards, Clark

 

[basicequipment]

Very informative thread Cmark! There are still quite a few of these old machines running out there and many of us who own them appreciate the time and information you have shared here! Thanks!

 

[Dickjr.]

I'll second that , great thread. Cmark along with a few others are full of valuable information. I appreciate the fact that they take time to share.

 

[Thomas c Knight]

Over the next few days, I've got the job of overhauling a Cat 953B HPCU. The 943, 953, 963 and 973 B series and earlier are all much the same.

Anyway, due to the fact that these machines are getting scarce in front line work nowadays, and the relatively high cost of repair I think this may be the last one I ever get to do.

If anyone has any interest, I'll post some photos showing the the insides of one of these mystery boxes and what goes into rebuilding them.

I would also like to see the internals of one too please

 

[Tommyc]

Cmark, did you have to use the proper CAT tools to adjust the linkages or is there another way