2120, 4wd, Front drive reduction drop box building pressure

dasimmons24 · Jan 12, 2015

Has anyone else encountered this issue? I have a 1989 Ford 2120 4wd, 12x12 shuttle shift and after operating the tractor with loader for 6 or 8 hours both front drive drop boxes started pushing oil out the axle seals. I opened the fill plugs on the drop boxes and they were pressurized, obviously causing the seals to leak. The level was correct and I am using multi G-134 oil. The ambient temp was around 40 deg. I have had this tractor for 21 yrs. and have only seen a small amount of oil seep from the axle seals. I have always done the recommended maintenance, the machine is in excellent cond. with only 1310 hrs. This is probably the longest continuous running time it has seen, normally I only run it for a couple of hours at a time. I am thinking the drop boxes should have some sort of pressure relief venting.

dave1949 · Jan 12, 2015

It's possible that worn parts (bearing maybe) are generating heat from friction.

dasimmons24 · Jan 12, 2015

There is always some heat generated from friction of the moving parts and everything expands (as temp. rises) including the oil. That is why it should be vented to prevent pressure build up. Worn bearings have increased clearances thus creating less heat.

dave1949 · Jan 12, 2015

I was thinking more along the lines of damage due to wear, like gaulding and scoring.

40F or 40C?

PILOON · Jan 12, 2015

Are you sure there is not some sort of venting that is possibly clogged up? I'd be surprised if one did not exist somewhere. Sometimes a small hose that reaches up into the chassis?
If no vent then make one. Filler is probably NPT (1/4", I'll bet) so you could use a NPT hose adapter and add a short tubing length that would tuck up under the cowling placed that the opening faces downwards. That would effectively make for a vent.

dasimmons24 · Jan 13, 2015

Galling and scoring usually come from lack of lubrication, that is not the case here. I have many years experience working with industrial machinery and gear reduction units and lubrication.

dave1949 · Jan 13, 2015

Until you open up the final drive, you have zero knowledge of what is actually the state of things inside. You are assuming it was correctly assembled with all parts in good condition and remained so. Maybe it was and maybe it wasn't. You say it has seeped a little bit of G-134, that should not be the case.

The symptom of becoming pressurized after longer than normal use, although that shouldn't really matter, could be explained by heat build up.

What are the possibilities?
If your fill port is like mine, it would be impossible to overfill the gear box by pouring into a funnel without tipping the tractor or parking on a slope.
Since you are asking about adding a vent, I'll assume your tractor, like mine, does not seem to have one.
40C is hot weather, perhaps beyond the range anticipated by the designer. Maybe it should have had a vent for those conditions but doesn't.
40C combined with operating in 4x4 on surfaces that don't provide enough tire slippage could generate excess heat in the gears.
Excess friction between rotating parts is generating heat.
The seals are 26 years old and may have deteriorated.

kirkawilson · Jan 14, 2015

First, I would check the front axle oil level to make sure it is not overfilled, which can cause pressure build up. My Ford I&T shop service manual (FO-46) says the oil level in the front wheel drive housing should be maintained between the mark on the dipstick and the lower end of the dipstick. If it's overfilled, you can drain some from the plug on the bottom of the final (wheel) drive housing.
If oil level is fine, you might try this mod I read from another site; "I fitted a commercial breathing filler cap to the gearbox I have just built for an IC engine model loco. The filler has what amounts to a spring loaded rivet which seats on an O ring. The cap can burp, but cannot suck air back in. I thought it would help me avoid the sort of trouble you are having."

fried1765 · Jan 17, 2015

For: DAVE1949:
An "ambient temp" of 40C would be 104F.
That is NOT likely, unless in Saudi Arabia!

I was thinking more along the lines of damage due to wear, like gaulding and scoring.

40F or 40C?[/QUOTE]

dave1949 · Jan 17, 2015

fried1765 said:
For: DAVE1949:
An "ambient temp" of 40C would be 104F.
That is NOT likely, unless in Saudi Arabia!

I was thinking more along the lines of damage due to wear, like gaulding and scoring.

40F or 40C?

[/QUOTE]

Welcome!

Well, I asked and didn't get an answer. :laughing:

I don't know when this problem occurred. Summer/winter? I also don't know for sure where "ambient temperature" refers to. The outside air temperature, the air near the final drive gear box? 104F is certainly possible there. I went with Centigrade thinking the OP sounds very technically oriented. So sue me. :laughing: