Cat 973 86G032xx - Hydrostatic Transmission and Brakes.

[Len220]

I have a Caterpillar 973, serial number 86G032XX, 07/97 in NSW, Australia. It is the second series of machines made in France. The previous owner had it sitting in a quarry for many years after a mechanic adjusted/serviced the hydrostatic transmission. They reversed up the machine and then it wouldn't go forward. It sat there for 5-10 years. A few people have had a go fixing it, to no avail. I picked it up for a bargain as the owner has lost interest. I want to bring it home and sort out the hydrostatic transmission. The motor runs okay and the implements and associated hydraulic pump works okay (except for some burst perished hoses).
At the time I didn't realise that the hydrostatic transmission had been drained (to use the oil elsewhere), but I only ran the engine for a few minutes to see how it sounded. Reading the owners manual, it appears I'll have to get the brakes off to move it onto a loader and get it home. I understand this can be done in 2 ways: by pressurising the hydraulic lines to the brakes, typically from the distributing manifold (on the left side of the machine ?) with a hand pump; OR taking the centre shaft out of the final drive sun gears.
My question is: can I take a simple hydraulic pump like a portable-power pump and attach it to the hydraulic lines to disengage the brakes? What sort of oil volume will I need to pump, to get both the brakes off ? I plan to put oil back in the hydrostatic transmission - Caltex Delo Gold Ultra - a multigrade 15W-40 oil, same as the engine, recommended for the 86G3000 and up. It'll be working in 10° - 40°C temps.
However can I get the brakes off by pumping oil into the brake lines regardless of the hydrostatic oil status - drained or otherwise ? What volume will the brakes (and the supply lines) take before they are disengaged ?
I'm hoping Bob/Ont and you other experienced CAT 973 guys, will pick this up quick.

 

[Len220]

I have been asked by a senior forum member to move the above request to a new thread.

Cmark has kindly and quickly responded with an E-mail as follows:

Yes, you can pump the brakes off without tranny oil, but your transmission may have the later type makeup/relief valves with the vent check valves deleted, in which case there will be internal plugs to remove. The transmission serial number would be needed to confirm either way.

It's far simpler to pull the sun gears/shafts. With brakes off you still have to spin the final drives and motors. With the sun gears removed it will freewheel easily. Very easily. Use caution.

 

[Len220]

Thanks Cmark. Hopefully there will be no frozen bolts or studs. I appreciate that the machine will not have any brakes to re-apply, if I take the centre final drive shaft out, so I need to be careful when loading and manoeuvring on any incline, else I'll have a runaway machine. Next time I'm at the machine I'll note the transmission S/N.
NB - I have a fairly thorough Service Manual for the 86G03000-up, with about 17 SENRxxxx publications as listed in SENR5362-02, including the Operation and Maintenance Manual .... purchased on E-bay from the States.

 

[Nige]

You may not have seen the comment I posted on your other thread ............... Hydrostatics are finicky about what oil you put in them.

G'Day,

I'm not sure that you want to be using engine oil in the hydrostatic transmission. Those systems are pretty finicky about what oil they use. The manual recommends a hydraulic oil, which for your climate would be an SAE10W. See below. Do you have an Operation & Maintenance manual BTW..?

View attachment 194273

Sorry to inform you that Bob/Ont passed away a couple of years back. He is still missed.

 

[Len220]

Thanks Nige,

Sorry to hear about Bob .... lot of experience and knowledge lost there.
You're in Sydney, I'm guessing ?

This is a cut and paste from the Op. Manual I have which is specific for the machine - 86G03000-up.
It has more oil options for the hotter climes. Says 15W-40 multigrade is suitable for -15°C to 50°C. We have 5°C (cold winter day) to 40°C (hot summer day), with a handful of days >40°C, with majority 10°C to 35°C.

View attachment upload_2019-3-24_22-22-36.png

Do you recommend 10W and ignore this guide ?

 

[Nige]

The list of "recommended" oils starts at the top with the "preferred" oil, a HYDO (hydraulic) and works down, in order of compatibility.

As he is considered one of the track loader gurus on HEF I'd like to hear what Cmark thinks about the oil. I was always under the impression that the hydrostatic loaders liked a good-quality hydraulic oil above anything else in the transmission. I understand that the engine oil is listed as an alternative, but if you are going to be battling with a power train that hasn't worked properly in a while, is it worth putting another unknown quantity into the system in the way of an oil that although it might work OK isn't exactly at the top of the manufacturer's preference list..?

As another comment, don't get too hung up on ambient temperature ranges quoted in the manuals, even for your stated high/low ambient range, an SAE 10W hydraulic in the hydrostat would work just fine IMHO.