2008 Farmall 35 with bad HST pump

[zzjvf8]

Hello. New member here.
I have a 2008 DX35 tractor with 501 hrs, bought new in 2009, that barely moves forward or backwards. Took it to the dealer and they said the HST pump output is only 325psi when is should be 4500psi. They are recommending installing a new pump for $12,250. Any thoughts ? Tractor is in almost new condition.

 

[ptsg]

Not sure I would trust that. That tractor has a dry clutch used for the PTO that could very well be slipping for one reason or another, since it shares the same power shaft, it would affect the HST as well. Have you noticed any loss of power at the PTO?

 

[LouNY]

After checking the pto output for dry clutch slippage, if still needed.
Usually the hst is a combined unit pump and hydraulic motor which would make your tractor almost new again.

 

[zzjvf8]

The PTO will not turn either. The tractor will creep if I give it just a little pedal. Any more pedal than minimal, the tractor will stop. The pedal will vibrate sometimes like a hydraulic cavitation.
They said the pump is $7k.

 

[ptsg]

Can you tell if you have any free play in the clutch pedal?

 

[oldnslo]

The PTO will not turn either. The tractor will creep if I give it just a little pedal. Any more pedal than minimal, the tractor will stop. The pedal will vibrate sometimes like a hydraulic cavitation.
They said the pump is $7k.

From this description I would suspect clutch is slipping and requires adjustment or worst case replacement.

Like PTSG asked is there any freeplay in clutch pedal travel.
I find it easier to check clutch free play pushing on the pedal with my hand vs foot.

To check free play with tractor engine off and brakes on or parked on flat ground so tractor can not roll.

Push on clutch pedal until you feel resistance change from spring load to starting to disengage the clutch. Should be approx one inch free movement before feeling resistance change. On tractors I have owned there is some form on length adjustment in the pedal linkage.

 

[zzjvf8]

Yep... there is about 3/4" free play on the clutch.

 

[zzjvf8]

They said the pump is only has an output of 325psi where is should be approx 4500 psi

 

[LouNY]

If the dry clutch is shot it may not be turning the hst.
With the tractor idling if you engage the pto does it rotate with no load?
How is your pto engaged a switch or a lever?
Does the loader lift properly?

 

[zzjvf8]

The PTO is engaged via a lever and will not rotate. The loader and 3-point work as they should.

 

[dieselscout80]

Not sure I would trust that. That tractor has a dry clutch used for the PTO that could very well be slipping for one reason or another, since it shares the same power shaft, it would affect the HST as well. Have you noticed any loss of power at the PTO?

I don’t own a Dx35 but it is basically a TC35 NH.

When I pull up the parts diagram it looks like it has wet PTO clutch like my TC45DA has vs a dry one.

https://www.messicks.com/catalogs/c.../03-transmission/03-04-03-clutch-assembly-pto

So hydraulics could be the issue.

Have you replaced all the hydraulic filters and cleaned the suction screen back by the right rear wheel?

 

[ptsg]

I don’t own a Dx35 but it is basically a TC35 NH.

When I pull up the parts diagram it looks like it has wet PTO clutch like my TC45DA has vs a dry one.

https://www.messicks.com/catalogs/c.../03-transmission/03-04-03-clutch-assembly-pto

So hydraulics could be the issue.

I believe there might be some confusion between models. Checking TractorData, the DX35 model was only made up to 2006 and the OP says he owns a 2008. Wondering there was a typo somewhere. Could it be a DX34? Farmall 35?

 

[zzjvf8]

My apologies... it is a Farmall 35.

 

[zzjvf8]

I changed the HST filter, after the issue started, with no change. Have not looked at any inlet suction screen.
Told the part number I need is SBA322800221 which is a $7k part.

 

[ptsg]

Ok, being a Farmall 35, it does indeed have a dry clutch, so my theory may still make a little bit of sense. If it slips, the HST and PTO won't work.

 

[zzjvf8]

Could that cause a 350psi reading on the pump ? I am not sure how or where they took the reading.

 

[ptsg]

If the clutch disc is slipping, the hydrostatic pump will stop spinning under load, so it won't build any pressure. Since the shaft powering the hydrostatic pump is the same as the PTO, the PTO won't spin either.

I believe the key here is that the PTO won't work either and that's only caused by a clutch slipping. Well, there are other issues that it could be but would only affect the PTO, not the transmission. The PTO is purely mechanical though.

 

[zzjvf8]

Not sure if this helps diagnose but it will move very slowly if I barely depress the pedal. I pushed in the clutch, as it was creeping, it stopped and then would not move at all when I released the clutch.

 

[LouNY]

I'd have to wonder where and how they tested that pressure;
most HST systems have what they consider a charge pressure often that comes from the tractor hydraulics. The charge line is there to make up for fluid looses in the pump/motor loop. It is often 300-600 PSI.