L4850 hydraulic pump

[clinter36]

Gentlemen! Been a while.

I have to say that my L4850 has been a champ the last 5 years or so with no issues to speak of.

Recently, it seems like my hydraulics have slowed down a bit. Particularly noticeable with the loader going up and down. I will admit that the loader control lever has quite a bit of slop so its "possible" that its not toggling the valve all the way, but my gut tells me something is going on with the hydraulic pump. I have had an annoying buzzing noise coming from near the front of the engine, mostly when the engine is cold or at certain RPMs. I have had this noise for years.

I starting looking through the hydraulic section of the parts book to get an idea of what we had going on. (I have not yet opened up my service manual). So after some lengthy time perusing the parts list and digging through my old Everclutch notes.... I think I have a handle on what I have in my particular tractor (everclutch). For those of you who have not memorized the parts diagram... let me explain that there seems to be various pumps and "assy hydrualic pump" (read secondary pump) options for this machine.

Here is what I think I have so far:
Machines with the manual shuttle (not hydraulic) get pump part number 33740-82202
Machines with the HDT and HDT-W (hydraulic shuttle and everclutch) get pump part number 32550-76100
- this pump appears to have a different shaft and end plate because....
Machines with Hyd. shuttle and everclutch get a secondary hydraulic pump bolted to the end of the main pump
- This is called "assy pump hydraulic"
- I assume the assy pump hydraulic runs the shuttle or everclutch.

I would much prefer not to spend $900 on a new pump and I see there are many aftermarket hydraulic pumps on ebay, including one listed as for the L5450. If I remember correctly the 5450 has a bit more hydraulic flow, which would be nice running my backhoe.

Does anyone think the pump from the 5450 would fit the 4850?

Does anyone have any experience with this dual pump setup?

Has anyone had issues with their pumps?

Is there a place that can rebuild this pump? Can I rebuild this pump (I do rebuild lots of stuff).

Any other thoughts or words of wisdom?

and yes, I have considered that the pump could be sucking air making that strange buzzing noise. And no, I have not attempted to remedy it, simply because my life does not work that way....it will be the worst possible scenario every single time. So I have learned not to waste my time grasping for $10 solutions. I go straight for the good stuff! (I suppose it could be sucking air because the shaft has worn and the shaft seals are no longer sealing = new pump)

Thanks
clint

 

[rbargeron]

Hi Clint - Before you dive deep, check the hydraulic junction block (low on right side) Its diverter valve should be turned full CW to send flow to the loader. There are other things that can affect flow too - like the priority valve, relief valve, cushioning valves, hyd oil filter, etc.

My WSM for the L5450 covers the L4850 too - shows the 2-pump arrangement. The L5450's pump is mounted on the front of the engine, where the L4850's pump(s) are on the side.

The pump currently on eBay is a front pump for an early S/N L5450 - might work but would require some adapting.

Would you say the problem is volume or pressure? If it's both, haven't heard of anybody re-building a Kubota pump. Take care, Dick B.

 

[clinter36]

That is interesting. I just looked up the 5450 diagram. Looks like you also have two pumps. One in the front which must be the main pump for hydraulics and one on the front side of the engine which must be for the shuttle.

I think the problem is volume not pressure. I seem to be able to lift OK, but its slow. There is a funny feeling like a sticky or a detent upon raising the loader that I haven't notice until recently.

 

[rbargeron]

I didn't know my L5450 had a separate shuttle pump but you're right it does. The WSM only covers the front pump in the L5450 sections. In the sections on the L4850/L4350 there's a picture of 2 pumps.

The shuttle circuit is isolated from the main system - wouldn't affect loader motion. The main system pulls oil thru the filter and supplies the steering controller first before anything else branches off. Is the steering notchy? Recent filter?

 

[oldnslo]

If your pump was bad you would typically have full speed empty and then slow down more with a load. Depending on how bad the pump is you typically would also lose pressure / lift capability. Do you have any way of of flow testing the pump?

 

[art]

After time things do wear in and your tractor is not new and certainly is broken in and for the time you have owned it you might not be too amazed anymore with what it can do. I'd be checking pressures before anything else!