May be a dumb question, but can anyone explain to me how to go from forward to reverse in a D7F dozer without "banging" the transmission? I've a friend who has a D7 on his farm and we're a little scared we might damage something. Once when I was about 18 I tried to do it and the foreman screamed at me that he could hear " the tranny banging like Christ" but wouldn't explain to me what I was doing wrong. Don't want to make the same mistake again. Can anyone spoon feed the procedure to me?
Come to a complete stop prior to changing directions. You wouldn't (shouldn't) go from reverse to forward in a car without completely stopping. But remember that your car has a gas pedal, while your dozer is usually chugging away at full RPMs, so is a lot more forgiving of the procedure. Give the torque converter and the tranny a chance by stopping all movement.
Does it have a decelerator pedal? If not reduce throttle when changing direction after coming almost to a stop.
If it's a power shift,most people push deaccelerator at end of push. Then reverse But Caterpillar always said the power shift could take hi idle 3rd gear forward to high idle 3rd reverse the way the tran is set up speed clutches engage first as they are lighter clutches The direction clutches are heavier and take up the load The old 977s had no deaccelerator it was common practice to dump them into reverse at high idle
Thank you both SLKOO1 and Dave. It was a long time ago; I'm fairly sure I came to a complete stop, but now you mention that decelerator that makes me think a bit. Maybe(maybe) this is what I did wrong---- treated it like an accelerator in a car and let it rev up instead of down before moving the transmission lever from forward to reverse. It was my first time on a dozer and I was nervous, and this foreman in question had a reputation for screaming his head off at a lot of his employees. It was the early 1980s, they got away with that sort of thing then. I'm fairly sure I had pulled out the steering clutch levers and had my feet on the track brakes, so the machine would have been at a stop, but I think I forgot that it is a DEcelerator pedal not an ACCelerator, and maybe this is what he meant by me "banging" the transmission. Will have to keep constantly in mind that it is the opposite of a car. Thanks for the heads up, I should have thought about that regards tomcoq '
In the manual for my Cat 931B it says the trans. can be shifted between forward and reverse at high idle but reducing throttle will give longer service life of the components. A lot of operators of 955's and 977's ran at about 3/4 throttle. Possibly because a loader is pretty much stopped when the bucket is loaded from a pile or the load is dumped is why they never had a decelerator. Dozers on the other hand can do a push and be jammed into reverse without having to curl or dump a bucket.
Thank you too, Pittsburgh cat man. Interesting that Caterpillar says that but I"ll still err on the side of caution and try to remember that decelerator pedal.Wish I had learned a bit more about these things when Iwas younger
When you're on flat ground, there's no excuse not to decelerate. When you're half way to vertical, you do what you have to. The high tracks are orders of magnitude more forgiving.
Personally I always use the deaccelerator, only takes a second and yields nice smooth forward/reverse transitions…
The very definition of a “powershift” transmission is that all shifts, including directional, can theoretically be made under full power. That being said, a big dip on the decelerator pedal when changing direction can lead to much smoother shifts.