555 Transmission Pressure

[ngilles]

Hi all,
Haven't been on the board for a while. Been a long winter in WI. I bought a 555 trackloader last summer. When I bought it, it seemed to function ok. Loader worked well, forward and reverse seemed to work, track worn but ok for my needs. The engine starts and runs very well, no noises. I've replaced the broken exhaust manifold, runs much quieter now! Now I'm tackling little things like replacing broken gauges etc. The tach and hour meter doesn't work, used farm tractors for years and years without those so not very concerned about those right away. Engine oil, temp and voltmeter work fine.
I've replaced all fluids and filters, engine, trans, hyd, and fuel. Cracked right off (much quieter now) after sitting all winter in the unheated shop.

My concern is this, I replaced the broken trans pressure and temp gauges today. Both seem to be working fine, however, my trans pressure gauge only reads approx 50 psi at idle and up to 90 at 3/4 throttle. I did let it idle and warm up for quite a while. When I shift from fwd 1 to rev 1 the pressure drops a little below 50 and then comes right back up to 90. This stays in the "red" zone for the gauge. It appears that the green zone begins around 175psi and goes up to 400 psi
Gauge Pic
https://drive.google.com/file/d/0B1E2y5 ... sp=sharing

1) Where do I start troubleshooting?
2) Would a person suspect the transmission pump first?
3) What else should I be checking?

I hope you all are doing well, have a great day!
Nick

[ngilles]

It appears that according to this doc https://drive.google.com/file/d/1Fqtbd4 ... sp=sharing
I should be getting around 255+ psi

[Jim B]

Hi Nick,

Your technical manual should have a diagnostic section for the transmission, and pressure checks, that would be a place to start. You may need to get another gauge to use for the testing. Going over all the linkage adjustments might be good as well.

Hopefully someone will have more on this for you.

Jim

[JWB Contracting]

I went thru a problem on one this past summer. The problem I had was marginal oil pressure but functioning well just slow shifts.

We were lucky enough to have one that was slightly burnt at the back. We were wrecking the machine so removed the loader and fuel & oil tank and got it running and moving.

I read the book to get an understanding on how the transmission worked. The torque pump supplies high pressure oil which then gets regulated down to operate the valving / clutch packs. I found the high pressure oil ports on both machines and found that the pressure was low on the working machine, so either had to be the relief or the pump. We decided to change the pump from the burnt machine and now have an excellent working 550 with the 36” widepad kit on it. The book did not show testing the high pressure oil at all from what I could find.

[ngilles]

Hi Jim and Jason,
Thanks for your replies. I do have a shop manual and will do some reading. I did see the test ports under the floor pan when I was hooking up the pressure gauge and running the wire for the new temp gauge. I'm online now, shopping for a pressure testing setup. Some pretty good examples to pick from on Amazon.

I've been looking for replacement pumps. New is crazy expensive! Found a rebuilt on Ebay for about $1000. Now I'm looking for hydro rebuilding shops to maybe send mine to if that's the issue. I'm just worried about what comes next when I get full pressure

On a machine this old I'm a little worried about going too far "down the rabbit hole". It's got a great loader and bucket, starts and runs excellent, tracks are worn appropriately for hours and age, but plenty of project life left.

Hope you are enjoying your weekend! It's a balmy 45 today in western WI, feels pretty good after a long winter.