MF50 industrial grinding gear problem

[malightcommander]

Hello all,

I'm new here, so I think a small introduction would be good. A couple of months ago I have bought a 1971 Massey Ferguson MF50 industrial (backhoe) tractor, here in Sweden. The label actually mentions the type MF50R, but I think that might be the name the Swedish importer gave it (I can find no references to a model R on the internet and the serial number on the dashboard starts with MF50). It has a non-standard cab and lights, which were apparently done by the Swedish importer at that time.

The tractor is in a reasonably good condition, it has the Perkins A4-212 diesel motor which is running super smooth.

Now here is my problem: I have driven the tractor for the past few months without any issues at all. However, yesterday while I was driving it, all of a sudden a very loud grinding noise started to appear. I immediately stopped the tractor and that immediately stopped the noise as well. When after a few moments I started driving again, the noise was gone.
I then drove it for another half hour or so without issues, when all of a sudden the same thing happened again. Very loud grinding noise, I stop and the noise goes away, when I hit the gas pedal afterwards no problem.
Since the tractor was in a bad position, I had to drive it back to storage again, during that small drive, the same thing happened again and again and again. Sometimes after driving only a couple of meters.
Each time, I stopped the tractor immediately after the noise came up.

It must be noted that this tractor has the 'instant reverse transmission'. There is only a fork shaped gas pedal with reverse and forward directions (it serves as a clutch and accelerator in one).

Is there anyone that has a clue where to start looking for the problem? And possibly knows what is causing this exactly?

Something with the transmission seems logical.
So far, I have checked the oil level in the transmission, which was completely full, so that looks good at first glance.

/Hugo

 

[Dmacleo]

I have zero experience with unit like this but am wondering 2 things.
first is it possible to change tranny fluid and test for metal?
second does this unit run planetary gears on the axle ends and if so is fluid there contaminated?
pure shots in the dark, as I said I have no knowledge of these units.

 

[malightcommander]

Hi Dave,

Thanks for your reply. I will try to drain the transmission fluid and see what we get.
I only have a service manual for the MF50B, which seems to be quite similar to the MF50 in most aspects. It mentions that the instant reverse transmission holds 30,5 litres of fluid and that the torque converter holds another 9,55 litres of fluid. However, so far I have only found 1 fill plug on the side of the transmission, could it be that both share the same oil? I haven't been able to spot any additional fill plugs.
Does anyone know where another fill plug may be located? Hopefully not underneath the fibreglass floor in the cab...
Also, any recommendations on what sort of oil to replace it with? The service manual does not mention anything about it.

second does this unit run planetary gears on the axle ends and if so is fluid there contaminated?

It is my understanding that it does not. This tractor should have dry disc brakes (not working properly unfortunately), so there is supposed to be an oil seal between the transmission and the axles.

/Hugo

 

[malightcommander]

Alright, I have an update.

I found out that there is actually a somewhat hidden dipstick for the transmission fluid on the right hand side of the transmission (different location than the filler plug that I checked before, which as I have learned now is for the torque converter). The filler plug for the transmission is apparently hidden next to the gear leavers underneath the floor of the cabin.
Oil on that dipstick was low, so I changed the oil in the gearbox (I put in 20 litres of Q8 T2200 universal tractor transmission oil and it already shows full on the dipstick). The old oil was pretty dark, almost black, but did not contain any large metal debris. Only very minor metal filings (when sifting through the oil with a magnet, but that can be expected after so many years of use).

Unfortunately, did this not solve the issue, because the problem was still there after making a test drive.
However, I was able to do some more testing and also capturing the issue on a video, which you can see (hear) here:

I have found out that the problem mainly occurs when I accelerate quickly, or when I'm just driving around with full throttle. It happens in any gear. As you can hear in the video, the sounds gets less when I reduce the throttle and stops as soon as I take my foot of the accelerator pedal (even when the wheels of the tractor are still rolling).

After hearing the noise again today, I think it may even sounds less like gears grinding, but more like a screaming sound of some sort...

I am now actually suspecting the torque converter. There should be a bearing on the stator, could it be perhaps that this bearing has gone bad and that's what is causing the noise? Anyone got any ideas?