Traction 4WD engagement

[svcguy]

Just wondering if someone has had the electric 4WD / diff lock systems on a TN75 series on the bench. I have a service manual as well as a user manual now, but can't find any reference to how they actually work. I am thinking they are activated with a solenoid triggered by either the switch (manual engagement) or system logic, probably 12V activated? The previous owner of my TN75F had a toggle switch installed that activates the 4WD after a module failed, which is why I am thinking 12V. I am just curious as to the engagement method, as the service manual only refers to a manual lever for 4WD and I can't seem to find the logic part of it as of yet. I will have the tractor in the shop this winter for a bit of an overhaul and am interested in giving some thought to all of this before hand.

 

[RickB]

Just go out and buy the correct service manual for your tractor. The traction management system is too complex for me to get into here. There are 3 MFD control systems on the various TN models, and you apparently have info on only one.

I will tell you that the MFD clutch on your tractor is spring applied and hydraulically disengaged via a 12V solenoid.

 

[svcguy]

I purchased the New Holland TN series manual, supposed to cover the TN55, 65, 70 and 75 tractors. It's an excellent manual (about 900 pages), but noticed it isn't specific to the TN75F itself. I will look for one specific to the F. Looks like I am going to need one as the tractor was not properly looked after. Is New Holland the best bet for manuals?

 

[svcguy]

Well that worked out pretty well. I looked all over the internet and to my shock found the TN75F manual is about $500 through a number of different suppliers. Thought I would check Ebay just in case and found someone had a New Holland TN75F service manual / binder in the original packaging for $180. It looks in the picture as though it's printed in about ten books, engine, hydraulics, etc. which makes sense. This should give me some good reading material. Not sure if this TN75F was a good decision or not, but at least I can fix it now if not. Don't know if anyone needs the TN75 service manual that I just bought previously, but I would be glad to send it on for $50, have both hard copy and digital. Didn't realize the F was so specific.

 

[svcguy]

Rick, I'm interested in the philosophy behind disengaging the clutch hydraulically using a solenoid. Is there an advantage to this type of clutch?

 

[Jbrink64]

Rick, I'm interested in the philosophy behind disengaging the clutch hydraulically using a solenoid. Is there an advantage to this type of clutch?

It's a safety thing. It will default to 4wd, maintaing 4 wheel braking

 

[svcguy]

Interested in getting this tractor in the shop and understanding how it all works. The concept of using 4WD for braking certainly makes sense using a diesel, just never having worked on one, it's hard to visualize. The previous owner had the dealership bypass the 4WD Auto switch, so I am trying to get my head around either going back to the module or maintaining manual switching. In the meantime, I am not using it much, although it seems to work fine manually. The diff lock hasn't been monkeyed with, so I am thinking its module is still intact. The tractor is a good tractor from what I can see, lot's of power, but needs some TLC. I tried chisel plowing with it yesterday and was quite impressed.

 

[Jbrink64]

Interested in getting this tractor in the shop and understanding how it all works. The concept of using 4WD for braking certainly makes sense using a diesel, just never having worked on one, it's hard to visualize. The previous owner had the dealership bypass the 4WD Auto switch, so I am trying to get my head around either going back to the module or maintaining manual switching. In the meantime, I am not using it much, although it seems to work fine manually. The diff lock hasn't been monkeyed with, so I am thinking its module is still intact. The tractor is a good tractor from what I can see, lot's of power, but needs some TLC. I tried chisel plowing with it yesterday and was quite impressed.

The auto 4wd and pto should be controlled by the module. Diff lock should be on it's own circuit.

 

[svcguy]

Mine may be slightly different because of the year it was made. According to the NH dealer, it was made in 1997, although my understanding was they were first made in 1999 (which is what it was sold to me as). My tractor has a manual lever to engage the PTO directly under the steering wheel below the guage cluster. It seems to be a manual linkage, but perhaps it engages a switch of some kind. It is so robust in size and how it levers though, I am inclined to think it may be manual linkage. This is unless you mean that the 4WD module can deactivate the PTO for some reason while in use. Very interesting tractors.

 

[RickB]

The auto 4wd and pto should be controlled by the module. Diff lock should be on it's own circuit.

Front HPL, Front PTO, and MFD are controlled by a single controller. Without Front HPL or PTO, that controller only serves the MFD system. Rear PTO on North American TN/F's are not computer controlled. As you say, the difflock is on its own circuit.