D6C with steering problems.
We have a D6C 76A with steering clutch problems. Pull both steer levers back, apply brakes, give it some throttle and put it in gear. The thing will take off unless severe brake pressure is used.
We bought this Cat in 1973 and had the transmission completely overhauled (after 12000 hours) in 2006 by local Cat dealer. Didn't use it much after that and in the fall of 2009 noticed steering problem.
My father said the Cat had same problem when we first got it and a Cat technician went under seat, opened a cover and added a few washers to something to change pressure.
In 2010 and 2011 we had 3 Cat technicians look at it. All say the pressures are at max and clutch packs don't appear do be leaking. But none of technicians are older than the Cat and don't really know what they are doing. None will boost pressure above the book which has 2 different max settings.
I would appreciate any helpful hints from this experienced forum.
You don't need to boost the pressure beyond the spec. They get full trans pump pressure(300 to 350 PSI) and all they need to release is around 100 PSI. Connect a 600 PSI gauge to the top of the trans filter, 9/16 fine thread STOP BOSS fitting. Watch the pressure as you pull each lever and then both together at low idle. If the pressure drops much you may have a leak down to the clutches or the linkage might be out of adjustment. As for linkage, lubricate it and make sure everything works freely. Then losen the rod ends, shorten the linkage as much as you can and still get the pins in with out forcing the levers on the valve forward and compressing the springs inside. Then lengthen the linkage one and a half turns and lock them up. Check your pressures again after adjusting linkage and compare. The pressure going down to the clutches can be checked at the 1/8 NPT plug holes in the elbows between the valve and the steering clutch case.
Steer Clutch Drag
if you are doing this test with COLD oil in a Cold climate this may be just oil drag, if so the problem should ease as the steer compartment etc warms up, also assuming you have the correct grade of oil for your current ambient temperatures.
A place known to leak is failed O ring seals on a tube that is inserted in the back face of the trans case where the oil line comes from the valves on the back of the Torque Convertor. This oil goes to the trans valves via the Flow Control valve that limits flow of oil to the trans so the Steer Circuit gets oil first for safety reasons.
Below is a copy from a Cat school hand out, sorry it is a copy and not too clear, on testing the Steer Circuits of the D6. As you suggest the pressures given here may not be the latest so a check via the Dealer maybe needed but, it should get you started on testing your circuits.
Hope this helps,
The D6C will drive through the brakes if first gear is selected, I know you had the steer controls pulled but from cold it is not a good test, what is the steering like after it is worked for 1/2 hour, I am thinking you dont find the steer clutches are working, with the engine set at low idle if you pull 1 of the steer control levers, you should hear a slight change in engine noise, when I sort steer faults, I always check and adjust the brakes first, test drive the tractor till hot checking for brake peddle dance, then finaly with a pressure gauge in the 1/8th test ports going to the slave piston, if the cross-shaft (bevel Gear shaft) bearings are failed or steer hubs are loose on the shaft, the gauge will soon make this fact clear, it would not be the common thing to have both sides showing a low pressure reading, if it does I would do a test as already said into the top of the trans' filter lid, then run a transmission performance test, please come back with your findings.
If you have any doubts about the clutch pressure loss, blank each elbow down to the clutches with of thin plate between the elbow flange and pipe down into the bearing carrier and check clutch pressures, this will prove that the tranny hydraulics are doing their job, or not,as the case may be.
1964 cat d6c s/n 74a1122
Ive recently purchased a 1964 cat d6c s/n 74a1122. I'm having steering problems. Well the problem is it started out steering and over time the left steering just ceased working and now the right does the same. It will steer with braking while pulling steering lever. Ive adjusted the brake and in the process of finding some gauges to measure oil pressures at taps. I bought a jensales service manual. Any additional info would be greatly appreciated. Also if I have too rebuild clutch packs does any have suggestions on where to get aftermarket parts. Thanks eric
The first thing I would do is to take off the round PTO cover on the rear of the tractor, take a pry bar and check the bevel gear shaft bearings. Pry the gear side to side, should have no movement. If so then take your fittings lines and gauges and connect them (600 psi gauges) to the 1/8NPT holes in the elbows from the steering valve to the top of the steering clutch cover. Pull the steering levers one at a time engine at low idle warm oil and record the clutch release pressure. Should be around 300 Psi. This oil pressure is from the trans pump, if it's low then hook gauge to the trans filter top 9/16NF stor boss fitting and record pressure at low and high idle, shouldn't vary much more than 10%. Come on back with what you get.
Originally Posted by southernmudcat
I will try that tomorrow and let you know what i find. Thanks
Originally Posted by bob
My service manual does not show a test port on the oil filter, have to get reading from port/plug on the pump itself. Says it's a 1/8" - 27 NPT plug.
Last edited by Old Magnet; 10-08-2012 at 10:03 PM.
hehei worked on a D6C that would stop driving when it got warm. I checked the cross shaft bearings and they were tight. Pulled the steering clutch and the clutch measured ok. The only thing I found wrong was the o-ring seals on the clutch release piston were hard as rock. i changed the seals and reinstalled the clutch and it worked perfect after that. I figure that the piston was cocking in the bore when the oil was hot and when it was cold the oil kind of acted as a bushing. It steered ok when cold but when warm and the clutch was released it would not drive. Just my two ents for what it is worth.
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