I have a Cat 916 that will not take 1st gear. 2nd and 3rd are fine. While attempting to diagnose the problem you can occasionally feel it try to engage and one time it did in reverse .Cold or hot don't make any difference. All filters and fluids have been changed. Ideas ?????
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No 1st GEAR!
- Thread starter panlanrs
- Start date
Need to check trans pressures. I'd be checking the transmission neutralizer pedal (air valve) and air over hydraulic valve for the neutralizer whilst watching the P1.
That neutralizer dumps directional clutch pressure and if it hangs, it can drop it a touch - enough that if you have two leaky clutch pistons, you will lose gear.
I was tempted to suggest one leaky or failed clutch, but
1st forward uses clutches #2 (F) and #5 (Low speed)
the #5 clutch is also used in 1st reverse which is working fine
the #2 clutch is also used in all FWD speeds which are working fine
so, the issue may be partial leakage in both #2 AND #5... when they are both engaged the leakage adds up enough that neither stay engaged. again, a faulty neutralizer will make this happen earlier and more pronounced.
the seals on the pistons in those clutches may be leaking. a Cat tech with the right experience (grey hair) can watch the P1 and P2 pressure gauges and judge by how the gauge needles are reacting whether there is just too much leakage after verifying neutralizer not the issue and pressures generally ok (i.e. load piston, modulating relief and trans pump are working good).
Sometimes, a new transmission pump will add enough flow to buy you some time when clutch seals are just starting to show their age.
If you saved the old trans filter, cut and pry it open and look for friction material in the pleats, or any chunks of piston seal.
without gauges and the Cat experienced tech, what you can do, is disconnect the air line to the neutralizer valve, plug it off and retry...leave the air fitting on the neutralizer valve open to atmosphere.. just to verify air leakage or the air valve isn't the issue
That neutralizer dumps directional clutch pressure and if it hangs, it can drop it a touch - enough that if you have two leaky clutch pistons, you will lose gear.
I was tempted to suggest one leaky or failed clutch, but
1st forward uses clutches #2 (F) and #5 (Low speed)
the #5 clutch is also used in 1st reverse which is working fine
the #2 clutch is also used in all FWD speeds which are working fine
so, the issue may be partial leakage in both #2 AND #5... when they are both engaged the leakage adds up enough that neither stay engaged. again, a faulty neutralizer will make this happen earlier and more pronounced.
the seals on the pistons in those clutches may be leaking. a Cat tech with the right experience (grey hair) can watch the P1 and P2 pressure gauges and judge by how the gauge needles are reacting whether there is just too much leakage after verifying neutralizer not the issue and pressures generally ok (i.e. load piston, modulating relief and trans pump are working good).
Sometimes, a new transmission pump will add enough flow to buy you some time when clutch seals are just starting to show their age.
If you saved the old trans filter, cut and pry it open and look for friction material in the pleats, or any chunks of piston seal.
without gauges and the Cat experienced tech, what you can do, is disconnect the air line to the neutralizer valve, plug it off and retry...leave the air fitting on the neutralizer valve open to atmosphere.. just to verify air leakage or the air valve isn't the issue
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not necessarily, neutralizer valve will affect whichever combo of speed and direction clutch have the most leakage first, if only partially engaged.
1st FWD usually wears more than any other clutch packs, especially if the trans has ever been run with engine oil instead of the recommended TDTO spec oil. (but they all wear out eventually regardless of oil quality)
As the clutches wear, the pistons must travel further to engage them, and that's when shaky seals will be at their worst.
but I just mention neutralizer, because it is about the only testing/elimination you can do without gauges.
although checking linkage travel never hurts... a visual of everything you can see and watch move (engine off for safety)
1st FWD usually wears more than any other clutch packs, especially if the trans has ever been run with engine oil instead of the recommended TDTO spec oil. (but they all wear out eventually regardless of oil quality)
As the clutches wear, the pistons must travel further to engage them, and that's when shaky seals will be at their worst.
but I just mention neutralizer, because it is about the only testing/elimination you can do without gauges.
although checking linkage travel never hurts... a visual of everything you can see and watch move (engine off for safety)
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Nige
Senior Member
Does 1st speed reverse work OK all the time or not..? Your original post says one time it did engage, but does it engage correctly all the time.? If the answer is no you could be looking at a problem in the first speed clutch (Clutch #5 in the powershift).
The neutralizer valve dumps direction clutch pressure. Direction Clutch Forward is #2, Direction Clutch Reverse is #1. Therefore a neutralizer problem would give the same symptoms in all speeds, forwards or reverse.
As WWZ says above, need to check pressures. Neutralizer valve operational check is that P2 should drop like a stone to zero psi when you press the neutralizer pedal, and return to full pressure just as fast when you release it.
These are the pressures you should be getting if the machine is within specification. See photos for locations of pressure taps.
Pump Pressure (Test Point A) - 310psi minimum at Low Idle RPM. 390+/-17psi at High Idle RPM.
Transmission Lubrication Pressure (Test Point C) - 1psi minimum @ Low Idle RPM. 20psi maximum at High Idle RPM.
P1 Speed Clutch Pressure (Test Point E) - 300psi minimum at Low Idle speed with transmission engaged in any FORWARD speed. 370+/-10psi at High Idle RPM under the same conditions.
P2 Direction Clutch Pressure (Test Point F) - 55+/-8psi LESS than P1 at both Low Idle & High Idle RPM with the transmission engaged in any FORWARD speed.
The neutralizer valve dumps direction clutch pressure. Direction Clutch Forward is #2, Direction Clutch Reverse is #1. Therefore a neutralizer problem would give the same symptoms in all speeds, forwards or reverse.
As WWZ says above, need to check pressures. Neutralizer valve operational check is that P2 should drop like a stone to zero psi when you press the neutralizer pedal, and return to full pressure just as fast when you release it.
These are the pressures you should be getting if the machine is within specification. See photos for locations of pressure taps.
Pump Pressure (Test Point A) - 310psi minimum at Low Idle RPM. 390+/-17psi at High Idle RPM.
Transmission Lubrication Pressure (Test Point C) - 1psi minimum @ Low Idle RPM. 20psi maximum at High Idle RPM.
P1 Speed Clutch Pressure (Test Point E) - 300psi minimum at Low Idle speed with transmission engaged in any FORWARD speed. 370+/-10psi at High Idle RPM under the same conditions.
P2 Direction Clutch Pressure (Test Point F) - 55+/-8psi LESS than P1 at both Low Idle & High Idle RPM with the transmission engaged in any FORWARD speed.
Thanks for all the good info guys. Here's what I found. When the machine is first started ,1st will engage forward and reverse and will barely move the machine. After it warm's a little it won't move either way. 2nd & 3rd work either way, warmer the better. Bought this machine pretty cheap and it has a fairly fresh engine overhaul and know very well the previous owner so I am probably gona be having some tranny work done. What am I looking at $$$$ for a rebuild ?
Nige
Senior Member
I would stick my neck out and say you have a #5 clutch failure. If you're lucky it'll be what I call a "soft" failure and have just taken the clutch out. #5 is the clutch that takes all the hammer because you spend most of the time in 1st gear.
To double check I'm correct it will need transmission pressures taking as per the numbers above.
A quick & dirty check would be to pull the screen from the bottom of the transmission drop box (drain the oil first!) and see if it is clogged with what look like charred bits of cardboard. If it is that's what's left of the facing material for the plates of #5 clutch.
Price for a rebuild..? It's a "how long's a piece of string" job because you never really know if any of the high-dollar items inside the transmission need replacing until it's disassembled. You cross your fingers and hope that you just need clutch discs/plates and a bag full of seals & gaskets.
Final thought. Make sure the transmission hydraulic control valve (under the cover on top of the powershift) gets well cleaned out, because you can bet some particles will have got up that far and they'll bite you in the ass one day unless they are completely cleaned out.
To double check I'm correct it will need transmission pressures taking as per the numbers above.
A quick & dirty check would be to pull the screen from the bottom of the transmission drop box (drain the oil first!) and see if it is clogged with what look like charred bits of cardboard. If it is that's what's left of the facing material for the plates of #5 clutch.
Price for a rebuild..? It's a "how long's a piece of string" job because you never really know if any of the high-dollar items inside the transmission need replacing until it's disassembled. You cross your fingers and hope that you just need clutch discs/plates and a bag full of seals & gaskets.
Final thought. Make sure the transmission hydraulic control valve (under the cover on top of the powershift) gets well cleaned out, because you can bet some particles will have got up that far and they'll bite you in the ass one day unless they are completely cleaned out.
grandpa
Senior Member
(Drain the oil first),,,,, bet you only have to remind them once....bwah ha hahahha
