2003 TC40D jerky hydraulics and dropping out of high gear

KingLu · May 31, 2020

Good day everyone.

Recently when I start my 2003 TC40D the hydraulics on the loader are very jerky. After about 20 or 30 minutes of use they are fine. Is this air in the line? I do hear squealing from what I am assuming is coming from the pump.

The oil and filters where changed about 100 hours ago.

This may be linked but I am not sure, the tractor will on its own drop out of high gear then back. Yesterday it struggled going up a slight incline and at one point would not move. I let it sit and was able to complete moving topsoil by keeping the revs low and in 2wd.

Any help would be greatly appreciated.

rScotty · May 31, 2020

It sounds like a clogged hydraulic suction filter or air leaking into the line from the sump to the hydraulic pump. Are you sure that filter got changed? Sometimes tractors will have several hydraulic filters. Our old Yanmar had two hydraulic filters , and I think our current Kubota has three....not counting the engine oil filter.
What transmission do you have? if it is HST then losing power is another clue pointing at the hydraulic suction filter clogged, or a leak in the line/hose to the hydraulic pump, and all the associated connections.

None of this is rare or unusual. Mechanics begin to expect it as a normal maintenance item in the 500 to 1000 hr. range.
rScotty

KingLu · May 31, 2020

Thank you rScotty, it is a HST. I will pick up a filter and give it a try.

rScotty · May 31, 2020

KingLu said:
Thank you rScotty, it is a HST. I will pick up a filter and give it a try.

Good. That might not be the problem, but with those symptoms any mechanic is going to insist on a filter change.
It could be an air leak in the line from sump to pump. If so, it would suck a tiny amount of air into that line when running, and leak a little bit of fluid when it is not running. So look for drips, too.
rScotty

dlctcg · May 31, 2020

KingLu - your TC40D definitely has two filters for the hydraulic system - the first will be on the right rear just under the operator platform it is the larger of the two & the main filter for the hydraulics (should be a NH #47408372). The second is on the left front just forward of the operators platform; just in front of the brake pedal assembly & to the inside of your loader arms, its tucked up so look up from below. That is the filter of the HST Hydraulics (should be NH #47671640).

Also when the hydraulic fluid was changed do you know what was used? Was it NH-134 or an equivalent?

KingLu · Jun 2, 2020

Thank you dlctcg, I have ordered both filters and will be installing them this weekend. As for the Oil it was changed by my NH mechanic who comes out to my cottage to service my tractor, so I want to say yes. I did notice a small leak on one of the smaller hydraulic hoses for the loader, I will have that changed as well. Do you think that may be letting air into the system?

Regards,
Lu

rScotty · Jun 2, 2020

KingLu said:
Thank you dlctcg, I have ordered both filters and will be installing them this weekend. As for the Oil it was changed by my NH mechanic who comes out to my cottage to service my tractor, so I want to say yes. I did notice a small leak on one of the smaller hydraulic hoses for the loader, I will have that changed as well. Do you think that may be letting air into the system?

Regards,
Lu

It could be that hose or an improperly fitting filter gasket letting air into the hydraulic system, but it's a long shot. If it was either one you would see it as a very slow leak - more like a slow seep - with the engine turned off.

So the good news is that it is pretty obvious. Other than the base of the filter - which almost never leaks - there is only one hose that can pull air into itself and cause those specific problems. And it is between the transmission and engine block. That hose doesn't go up to the loader valve.

That would be the hose that goes from the hydraulic reservoir in the transmission to the input of the hydraulic pump on the engine. That is the only hose in the whole system that is under suction instead of pressure, and as I said..... it doesn't go up to the loader control valve. It is usually a fairly short hose or line that typically runs from the lower part of the transmission case up to the side of the engine.

I doubt that is your problem. But I would expect that your mechanic has probably seen suction leaks in hoses and filters happen before - it's not an uncommon problem and a simple one to remedy. When you mention the symptoms he will check both that as a matter of course.

Leaks in that suction side hose will eventually happen because of the hot hydraulic fluid degrading the rubber at the end connections - but this takes thousands of hours typically. It can also happen by abrasion or damage like running over a stick.
So we expect to see suction hose problems in big tractors with thousands of hours and in small garden tractors that are low enough to the ground to run over sharp sticks.
I doubt if that it the problem, but it's so simple it is always worth mentioning.
rScotty.