hi we have a 1975 cat 988a and we was pushing a pile of coal up with it, and went from forward to reverse. and have nothing now. it wont go into forward or reverse. so, we thought it was the declutcher vavle acting up. we took the valve off and took eveything off of the valve. we found some pieces of an o-ring in it. we got it clean up and put it back on, and we still have nothing. we tested the psi and we have 360 or so psi. it acts like it is stuck in neutral, but eveything seems to work. does anyone have any clue what it could it be? it's also a late modle 988a. thank you for any help
hey... is your directional forward/reverse cable broken by chance?... where is the 360psi from? clutch? torque? trans pump?
Beck, Can you feel the detents as you shift gears??? Think you have the F N R shift with the 1234 Roll of the wrist shift not the earlier F R shift and the N1234 shift of the earlier ones. First check your cables are well connected to the trans valve. If you have cable/linkage problems and get into gear before start up you will never get any drive. Make sure you can get into and out of neutral. Watch the pressure gauge as you shift and come back with what you find. Later Bob
Hi people here have been good to me so figured I might try to help anyhow. I have a 988A, last fall we had a similar issue. It indeed was linkage. They don't have cables (or at least not ours) but direct linkages. a 3/8's fine thread nut backed off of a swivel knuckle and the threaded stem popped out of the hole. All of the sudden we had nothing. We hunted and could find nothing wrong.. It was hiding under the floor on the left side under the brake pedal. We could also partially access and see it from the ground while the machine was turned alll the way to the right. Then peek up from the ground to under the floor area and you'll see the linkage. Maybe have someone wiggle the shifter while you look and you should find it. Hope it is that simple for you also. At least it was the issue in our case. Thanks
no the rod linking is not broken.we tested the declutcher valve that is in the tran. and it tested bad so we got another valve and that got the machine to move and we put everything back to together and i ran it around the job and i hit the brakes and i lost everything in tran again. i hit just the brake not the declutcher brake pedal. so we are right back where we started. we tested about every valve that is for the tran. what got me is that the brakes have nothing to do with the tran. other than the declutcher and it had good psi. cant feel anything in the tran. with the shifter but everything is working in tran it almost feels like rod linking fell off, but its not. its stuck in neutral so it has to be a valve, right? thanks for any help.
Beck, your taxin my memory rather high here but I think the Neutralizer valve uses Brake hyd oil to cut out the Directional clutches. Now get back into the brake peddal linkages and pivot pins. Clean and lube all pins so everything workes free and only the LH peddal works the neuralizer valve. I suspect the neutralizer is stuck. Later Bob
Am I dreaming or could there be an issue related to the accumulator? When the brakes are applied pressure drops too far for an instant therefore kicking it into neutral? Those old 988A's have a brake applied pressure gauge in the cab. maybe it is something to look at. Again, I am Polish and have a degree in nothing. Sorry.
Matt, if there was an accumulator problem(under charged or not charged) there would be no reserve brake oil under pressure but the charging valve should keep up enough supply to keep the parking brake off. The brake oil pressure is sent into a valve on the back of the trans pressure control pack to neutralize the trans when the LH brake peddal is applied. I feel something is wrong at that valve or it's oil supply. Later Bob
Like I said, I'm Polish
Naustravia Later Bob
One thing to check real close that many will not think about is how clean is cab? If there is any dirt build up under the brake peddles, well the left one at least, it can hold the brake depressed just enough for the neutralizer to keep trans. in neutral. Also make sure the peddles are nice and free. I was asked to rebuild a transmission in a 966 Cat once because it had "failed" a quick pull up on the left brake and I was driving around the guys yard. A good soaking with penetrating oil and it was nice and free. I think I made $50 for 5 minutes easy work. Back to your problem, Have you actually had the valves out of the transmission? Not a fun job! Is this one of the ones with the batteries under seat? I had one of these with a similar, no move problem, that turned out to be a small piece of gunk stuck in an orifice in one of the valve spools. You say you have good pressure, somewhere, so I'm guessing your pump is not the problem. One common problem we had back when we had several of these machines was the large suction pipe from the transfer case to the pump would have a hose rub in it and wear a hole in it causing a suction leak. One time had to replace a hose on a 988 that was driving just fine but when new hose was installed it would not move. Forget how I determined the problem was this large tube but pulled it off brazed on a patch and put it back on then everything was fine again.
The 988's also have a valve that keeps the transmission in neutral if you start it in gear. . I don't know if could cause your problem but it's possible if it's stuck. When the machine is off or the pressure goes too low the valve is pushed into the neutral position by a spring. The spring isn't that strong if I remember correctly. Our loader would go into neutral at times shifting from forward to reverse. You then would move the shifter to neutral and it would go into gear again. I finally figured out what was going on. Our pressure was good as yours is but would drop during shifting enough to let the valve shift into neutral. I replaced the spring with a much weaker one. It's been working fine for over 10 years now.
Yes that is right. The problem that we had with the plugged orifice I mentioned might have been that valve. I'll have to see if I have records from way back then!
I'm going through the same thing as this guy was. But I see a resolution was never posted. Anyone have any more insight?