The 3 reverse gears all work fine. Forward 1st gear only works 25% of the time and it hesitates to go into gear when it does go in. Forward 2nd gear works about 40% of the time and it also hesitates to go into gear about half the time. The fluid is black looking but clear. Next i will do a fluid change but I'm not optimistic. Thoughts? Haven't had this dozer long but I'm suspecting a transmission rebuild. Could it be a gearbox issue or transmission fluid pump issue or something? What is the best way to remove the transmission? I've seen a youtube video where the guy removed it out of the top, but heard it should be removed as one unit with the engine, (which the guy on youtube did not do) and the whole thing (with engine) weighs 1600 lbs. Any advice appreciated.
If someone can tell me if this is for sure the transmission (requiring rebuild) or might be something else, and how to check, I'd appreciate it.
Why don't you try something simple like getting the transmission control linkages correctly adjusted followed by pressure-testing it first.? See the attached. Start at the bottom of Page 8 in SENR3806 for a 5KG-prefix tractor like yours.
I don't think anyone can tell you exactly what's wrong on a forum. Have you checked the trans. filter for debris and do you know what oil is in the trans.? D3 transmissions are generally pretty bullet proof but anything can be abused. The wrong oil could affect operation too. The fact it works sometimes could be an indication it doesn't need a major rebuild. When I had my engine rebuilt, the shop checked the trans. screen (3F/1R) when they took the trans. off the engine. They said it looked good and there were no black particles. Black particles are a tell tale sign of the clutches deteriorating and needing to be replaced. The 3F/3R trans. has a filter. First thing to do is check that filter for black or other particles. Dozers are much easier than loaders to pull the engine and transmission as a unit. Still a bit of a pain though because of the tight fit. I don't think there's enough room to pull the trans. by itself. I'm pretty sure you need to remove the trans. mounts in order to the pull the engine and trans. as a unit. You do on a D3B and a D3C is very similar. First check the trans. filter. If it looks OK then do as Nige says above. If it's full of black particles then you have to think about pulling it but check the linkage and pressures first.
Have you checked pressures my guess is forward clutch is out
I forgot to mention that 3rd gear forward seems to work all of the time.
Do you mean the screen? I have not yet. I found the diagram where that is, and was planning on doing that this Wednesday. I can't actually do anything myself since I had shoulder surgery and have 1 arm temporarily, have to wait for buddies to become available. I signed up for SIS2GO online manuals, waiting for approval. It has whatever oil was already in there when I bought it, and I added some TO-4 SAE 30 when it got low. Here is a video where a dude pulled the transmission without pulling the motor: Although he has a D3C XL and different generation too I think.
Adjust linkages & check pressures, then you'll know instead of hypothesizing.........
If it has a screen you can check then do that. If it has filter, check the pressure instead of cutting the filter apart. The filter can be inspected after you've determined low pressure or other obvious problems. The video is pretty lame and doesn't show the trans. removal at all. It's based on the trans. after it's pulled out and doesn't show it being put back in. I'm guessing he never looked at the Cat service manual. It does show he had to pull the cab off and take the dash out. Cat will have a detailed procedure on how to pull the transmission and an educated guess is it comes out with the engine. I didn't have to pull the dash out. I think that would be a pain to pull and put back in. I did it on a flat grass field. I bought a cheap engine hoist and took the wheels off so I could slide it on the grass. There are lifting lugs bolted on the engine. Once I had it lifted enough to clear everything, I used my skid steer to pull the hoist backwards. I did have to take the nose off with the rad. but it wasn't a big deal. The rad. is mounted to the nose so just had to take the hoses off. The engine and trans. was too heavy to lift with my skid steer so I took the bucket off to get it closer to the skid steer and then was able to lift it to put in my truck. When putting the engine and trans. back in take the oil filter off. It's way too easy to dent it. If I did it again I'd wrap a small towel around the filter base to protect from an accidental bump. You need to empty the hyd. reservoir when pulling the engine and trans. There is a drain plug but I used a rotary barrel pump with a hose on it to pump most of the oil out.
so I changed the fluid and cleaned the screen. It looked NASTY. There were a couple bits of flat metal too. The first day it seemed to work better, like 80% good. The second day, first gear didn't want to work at all, in forward or reverse. I'm hoping it is the linkage. The shifter feels VERY loose. The plan is to have my mechanic (with the directions, thx Nige) try to adjust the linkage and check the pressures. He said he would try. It is a little beyond me. Maybe after I've seen it done once.
Did you find bits of black material in that sludge? I don't know how much metal filings and other crap is normal on the magnetic screen. I also don't know if the trans. can be flushed with diesel or something to clean the crap out. I guess it's worth trying an oil change but wouldn't be surprised you need to pull the the trans. and overhaul some or all of it.
The sludge was pretty soft and not too gritty, although I was wearing thick nitrile gloves. What looks like iron filings in the photo would disintegrate into a soft sludge when it was touched. The sludge was magnetic and wouldn't come off the magnets without a pressure washing. The fluid had many small black particles that you could see. There was that piece of rusty flat metal that apparently I didn't get a photo of but it was about 3/4" x 1/2" and looked like it was part of a gasket or other circular metal object. I forgot to mention that 5 gallons of waste oil came out, and I was never able to find a filter, making it the 3F/1R.
Filter housing circled And filter assembly
You couldn't tell by the gear indicator what transmission you have? It's pretty obvious. 3F/3R has the shifter in a U pattern with the shift lever travel the same in forward and reverse. 3F/1R the shifter only travels about half way in reverse. 3F/1R only has a screen behind a cover with 3 bolts. 3F/3R has a filter like heymccall showed. I'm not sure if the magnetic screen you pulled out is the screen for the 3F/1R trans. or if both transmissions use a similar magnetic screen.
Oh, I thought that was some mysterious code. Now I see that F means Forward and R means Reverse. Doh. OK so obviously I have the 3F/3R transmission and there must be a filter where heymccall has pointed it out to me, so kindly. CAT sold me a transmission filter but it looks like an oil filter and I don't think it is the right one....
The 2P-5834 has been superceded. The updated one...1R-0746
Yup, 3f/3r has same style screen.
I found where the filter is. Thank you. CAT website not totally helpful, as usual. "Unable to verify" I'll just order it. Searches of the filters available for my serial number never lead me to this part number. Maybe if I did call them.......
Installed the new filter. The old one was metal. After installation, the dozer was behaving a bit better. On this day, would go into 1st gear 80% of the time, after fiddling with the shifter. Sometimes it would like to go into 1st after first going into 2nd gear and then downshifting. Sometimes you could put it into 1st, and if it wouldn't go, then monkey around with the (very loose) shifter a bit and then it would go. I'm starting to wonder if this could be mostly a problem requiring linkage adjustment?
It sure sounds like it. Each of the gears should have a bit of a detent to hold the shifter in the gear chosen. I could see the detent's/linkage getting worn over many hours of fast back and forth shifting. I think throttling down when changing direction is not only easier on the trans. but also on the shifter linkage and detents. I think some operators don't bother throttling down when changing direction, especially with 2 seperate controls. I have the optional twist grip throttle on the gear shift. Some people don't like it but it makes it very easy to throttle down and change direction at the same time. A decelerator pedal, usually found on larger machines, also makes it very easy to throttle down and change direction at the same time.