Transmission does not want to go into neutral. Also, the hydraulic tank is pressurized even after I make sure the blade is down and pressure relieved. (Obviously not)
"1971 D6". Model years don't really mean a lot. It is a D6C by any chance and do you have the Serial Number.? The hydraulic tank always will have a certain amount of pressure in it after you shut down hot, even if you attempt to relieve the pressure in the hydraulic system as best you can. Try unscrewing the cap slowly before the first start in the morning when the machine is still cold. Even then it would not surprise me if there was a small amount of pressure still in the tank. Pretty much the nature of the beast.
First off welcome to the forum, second a s/n for the Cat D6 might help get info. As for the hydraulic tank having pressure might also help to have numbers off the tank, there should be a tag on the tank. Many variations depending on how the tractor was spec'd when new. Tag would probably show a three digit number like 150, 163, or 172 something like that then a serial number. EDIT: Looks like Nige replied while I was thinking. To be honest I had very little experience on Dozers but we did see some. Do not recall of there was a breather or pressure vent on the D6C we saw from time to time.
Can you elaborate a bit. Do you mean the transmission control lever will not go to the neutral position in the gate, or it goes to the neutral position but even when it does the transmission remains in gear.?
I have a D6C . 3 years older than yours. My powershift linkage is worn enough that when I move it to the neutral position it tends to stay in gear, if I slap it into neutral it usually goes in but if I just move it there it usually stays in gear. If you remove the floor board you can view the linkage and determine if that may be your issue. I need to do a rebuild of my linkage and it will cure my problem, you may be just as lucky. Your hydraulic issue has been covered.
Good point on the shifting, can never understand why Cat did not build that linkage to last over 50 years without needing repairs, like rod ends and bushings!
Lol, I know...they just don't make em like they used to.
If I move it out of gear, say reverse, to the transfer gate it goes into forward. I just move it, have not tried "slapping". I would think I should have an "over toggle" moving to the forward and reverse position. This is just the forward and reverse position. I am not even moving the lever to the speed selector.
I don't have a D6 sitting here to be sure but if you take off floor boards or whatever needs to come off to see the shift linkage. Shift from forwards to reverse and look at where the linkage attaches to the transmission case. Then disconnect the linkage at that lever and put that lever in the center position which should be neutral. Start engine. With engine running at idle shift from neutral to forwards then reverse and watch the driveline from the converter to the transmission. In neutral with engine running it will be spinning. Then when shifted into gear it should stop probably pretty fast. If it does that then I would say your problem is in sloppy linkage, a little slop at a few points will add up to a major amount. PS: I and I'm sure others are still waiting to see what the s/n number is and the numbers off the hydraulic control.
With a Serial Number I can upload a procedure for checking, and adjusting if necessary, the transmission control linkage. Without the S/N it is no more than a guess what is the correct one if there are small differences between them.
So basically you can't find neutral when you move the lever left to right or vice versa across the "neutral" gate.? Has this problem started suddenly or was it getting worse for a while until it got to the stage where it is now.?
My problem is like Nige describes above, if I slap the shifter to the neutral position it will go into neutral but if I just shift it easily into the neutral position it with jump to reverse and visa versa. The pins in the linkage and probably what the pins go through are worn, I have checked it and know that to be my problem, yours could be something altogether different but it's not much work to remove the floor boards and check that first.
I will get the serial number off the controls when I return to the farm as well as "slap" the lever to try to get the transmission's attention. The farm is 65 miles away. Plan is to go there this week. The Internet there is nonexistent.
Get the one from the machine while you're there.
I would write down any numbers you see on the machine especially any that are stamped in! I know we are not "working" on the engine or other things but someday you will be needing those numbers. Not positive but think there might be a tag on the side of the transmission near the top on the left side. Also seems that the S/N tag for dozers of that vintage are located on the very back of the frame over to the left side. If the tag is not there there should be numbers stamped near where the tag would have been. Usually something like 10K or some other combination of two digits followed by a letter then followed by four or five digits.
Well, I made it back. S/N on dozer: 10K4955 S/N on hydraulic tank is more of an issue as it was not that clear: 3068761 or 3G68761. I got the request for the number on the transmission a bit late. (Like today) Linkage adjustment was the issue. I found it strange that I only had 2 positions for forward or reverse. The linkage never allowed the transmission to fully shift the spools. I have not started it yet as it has a fuel problem. I would have thought the fuel sediment bowl gasket would have been sort of standard. But NO. I had to order a Cat part. Pick it up tomorrow, then back to the farm late next week.
I think you got close but no coconut. There is a 163 hydraulic control that would have been fitted to a D6C of your era where the prefix is 38G. So I think your hyd control S/N could possibly be 38G8761. If you ever need parts for the hydraulic system and cylinders for the blade that number will be essential. Glad that you got your shifting problem sorted out BTW. Take a look at the last page of the attachment, it may serve to confirm that what you did was right.