Ok I have 2 other threads, originally I thought wire harness was the problem I repaired it all lights and service codes went out . What's happening is machine is stopping locks up like brake applied every 5-10 feet in first gear only both foward and reverse 2nd and third machine runs fine and only after machine warms up about 15 minutes after starting . When machine is first started it runs fine . I really appreciate all the help I got so far thanks in advance
The R models had a electric switch in the brake pedal that would cause this
But wouldn't that stop it in all three gears in both directions and not just in 1st speed.?
It's only in 1st gear and only when warmed up
does it stop like drive you thru the windshield I had one that the harness to the transmission wore thru and it would engage in 2 gears at one time. it took putting it on the laptop and watching the shifting to find it
Yes but only when warmed up so you'd think harness would be any time and only when in first gear thanks
Talking about wire harnesses it might help if you knew the back story Dave. HeavyEquipmentForums HeavyEquipmentForums
Ok follow up had a mechanic come pressure test everything only thing he can find is when put in 1st gear the pressure drops from 370 down to 200 which the brake applies then all other pressure are good 2nd and third gear thanks were not sure what way to turn next short of pulling transmission
If the pressure drops the same way in both forward & reverse then the first speed clutch is on the point of failing and you will have no option but to pull the transmission. It might pay to look at the pump while you are at it, and also replace the transmission cooler.
We just went and changed clutch actuator valves around it still does it we're going to cut the filter apart yet and I guess the transmissions coming out
We cut filter apart nothing is there any possibility the control valve could be leaking we already switched clutch solenoids to rule out that thanks
If I remember right. The brakes are supplied oil from the transmission pump and there is a priority valve that ensures that the brakes are supplied with oil. If you had a problem with your brakes passing oil then you would lose pressure to the first speed clutch. But I can’t remember what the symptom would be if the problem was reversed. I would check the operation of the priority valve. Don’t ask me where it is it’s been too long to remember. Nige will correct me if I’m wrong and steering you in a wrong direction.
Thanks we want to rule everything out possible before we pull that transmission we spent all day today troubleshooting that when we cut the filter apart there was nothing in the filter you would think if the clutches were failing there would have been broken pieces in the filter
Have you pulled the magnetic screen at the bottom of the transmission to look for debris yet.? What colour is the oil.? Does it smell burned.?
One dumb question why does machine operate fine when cold this has me confused you think it should do it always my mechanic said maybe when the oil gets warmer it gets thinner I want to fix it properly but just don't understand why it's acting the way it is thanks again really appreciate your help
We cut the filter on the back of machine nothing it looks new has a couple hundred hours on it oil looks new smells fine
Where is screen located ?
In the suction line for the transmission pump inside housing #8. To get at it will require taking down the belly guard. #10 is the magnet assembly, #11 is the screen.
Thank you I'll pull the belly pan tomorrow
Just make sure you drain the transmission oil before you pull the end cover off ............
Is it possible that it could be priority valve I have a mechanic saying to check that first before pulling the screen I'm really getting confused thanks again
Where were the pressure readings taken from? You will need to take pressure readings from the transmission, park brake, service brake, and steering service ports. You will need at least two gauges so that you can get a better idea of what is going on. Three gauges would be ideal. It sounds to me that the park brake is being set. There are three pressure test ports where the final drive mounts to the frame. One is park brake, another is service brake and lastly is steering. I haven't touched a cat dozer in a long time. I probably forgot more than I knew about them. Is this a high drive dozer? If it isn't then forget everything I said.
There is always the possibility that something could be wrong with the priority valve. To eliminate that as a possibility before going any further try the test procedure (attached), and see what it throws up. Make sure to use the correct illustration for the pressure test ports on Page 1 of the document that corresponds to your particular machine Serial Number.
Another thought. You say the transmission works fine in 1st speed when the system is cold. Have you had the gauge on it cold to check whether or not the pressure is the same 200psi that you mentioned earlier or if it's closer to the 370psi that you measure in 2nd/3rd speeds.? Also to echo Paul's question can you indicate exactly where the mechanic is measuring the pressure.
IIRC the priority valve is on the left hand side of the TC casing, quite simple to pull off but watch the "o" rings. If the spring is old it may need the shims checked. I think Nige has the schematic and pictures to help
Ok follow up we pulled the transmission the first gear clutch seal was blown out and a couple of friction disc where bad on one side thanks to everyone for the help
Obviously sealing just enough to hold pressure when the oil was cold but not once it warmed up. Glad you got it fixed, pulling transmissions is always a PITA especially if you don’t find anything.
I want to especially thank you you where very helpful we have it torn down parts are expected today and reassembly on Monday I'll post an update when completed thanks again
I hope you are: - 1. Replacing the piston seals in all 5 clutches. 2. Replacing the friction discs/plates in the forward clutch in addition to the 1st speed clutch (they are the two clutches that siuffer the most abuse) Here are the specs for the transmission clutches. Probably best to look at all of them while it is out of the machine.