Foretravel Owners' Forum

Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: Old phart phred on December 02, 2017, 05:15:09 pm

Title: Differential level
Post by: Old phart phred on December 02, 2017, 05:15:09 pm
Went to check my differential lubricant level, and the oil gushed out. Manual says only a small amount goes to the axles. It hasn't been driven in weeks. You don't suppose some service guy would have been adding it through the vent tube opening do you?
Title: Re: Differential level
Post by: Pamela & Mike on December 02, 2017, 05:24:28 pm
You don't suppose some service guy would have been adding it through the vent tube opening do you?

OPP,

It wouldn't surprise me the least. Also it is a remote possibility that water has gotten in the vent and the gear lube is setting on top of the oil.  If this was the case the gear oil would be milky if it had been there any time at all and the oil has been agitated.

Pamela & Mike


Title: Re: Differential level
Post by: Old phart phred on December 02, 2017, 05:33:34 pm
Have not located the vent yet, clear oil, no evidence of it being in a flood on the coach anywhere. Looks like the carrier may have been changed, cause it's not painted, and silicone at the seam. Nothing in the service records, about it being changed.
Title: Re: Differential level
Post by: Pamela & Mike on December 02, 2017, 05:39:22 pm
If you are setting level it was most likely overfilled. This is one place that don't make oil from another component leaking into the differential.  On our GMC the trans. and diff. is bolted together and if the right circumstances happen the 2 will share oil which isn't good.

Pamela & Mike
Title: Re: Differential level
Post by: Old phart phred on December 02, 2017, 06:02:11 pm
Found the breather and it had an oil spill below it that had attracted dirt. Will loosen drain plug in the morning to see if any water come out. My guess is that water would milk up hypoid for quite some time.
Title: Re: Differential level
Post by: wolfe10 on December 02, 2017, 06:03:28 pm
Many differentials used in Foretravels have TWO "fill" plugs.  Correct one depends on angle of installation.  So, absolutely check for your axle model number to make sure which hole is the correct fill level.
Title: Re: Differential level
Post by: Old phart phred on December 02, 2017, 06:24:29 pm
Dana/Spicer J175. Appears to have only one fill hole slightly lower than the Centerline of the axle. Is there another one on the carrier side?
Title: Re: Differential level
Post by: craneman on December 02, 2017, 06:30:15 pm
They don't have one on the carrier side, but a lot of times there are 2 on the rear one for filling and a lower one for temp sensor.
Title: Re: Differential level
Post by: Old phart phred on December 02, 2017, 07:05:46 pm
Sensor hole is tiny and plugged
Title: Re: Differential level
Post by: craneman on December 02, 2017, 07:14:11 pm
Pretty obvious, but if it drains clean just lower the level. No need to change.
Title: Re: Differential level
Post by: amos.harrison on December 02, 2017, 09:16:29 pm
If the coach hasn't been driven in a while, I would not drain diff'l oil until it had been driven for a while-20mi.?  You want the wheel bearings to have adequate oil.  It will drain back over time.
Title: Re: Differential level
Post by: craneman on December 02, 2017, 09:20:29 pm
If the coach hasn't been driven in a while, I would not drain diff'l oil until it had been driven for a while-20mi.?  You want the wheel bearings to have adequate oil.  It will drain back over time.
Incase there is water in it you would not drive it, the water will settle to the bottom. See the first post.
Title: Re: Differential level
Post by: John44 on December 03, 2017, 05:46:30 am
You probably did this already but make sure the coach isn't leaning to the fill hole side.
Title: Re: Differential level
Post by: Protech Racing on December 03, 2017, 11:35:16 am
My book says to fill the axle ends separately.  I fill my diff by pulling the  axle, from the end.  With  one side of the axle  jacked up about 1in . The oil gets to the ends  when turning  , but Imake sure it starts with some in the end bearings.  My fillplug is under the axle  bearing  level by about 1in or maybe a little more.
 My full level is about 1/2 in over the plug  when I let it down  . Then I put the axle back in .
    I dont know what has happened in the 30 yrs of this bus and I dont trust the  fill plug to lube the axle ends , being so low .
Title: Re: Differential level
Post by: craneman on December 03, 2017, 01:10:27 pm
I have to pull my axles and hubs to do the brakes on my crane it has the same type rearend. There is always oil in the hub and I have over 600,000 mi. on it now. I fill to the threads on the fill hole. Axle bearings are original the carrier bearings were replaced when I did a gear change. If axle bearings were to be replaced, I would dip them in oil before installing. I have to be careful not to leave any oil on driveways when I do a lift so I wouldn't want any oil dripping from the vent from over filling.
Title: Re: Differential level
Post by: Old phart phred on December 03, 2017, 03:54:26 pm
Pulled the drain plug, and let about a pint out into a clean pan, no water or metal bits. Drained almost 2 Folgers 34 ounce coffee tubs full of hypoid out the fill hole. Between the eruption when I pulled fill plug yesterday, and not expecting anything to come out, and todays procedure, I've probably got a quart on the driveway to clean up. I can only guess someone filled to the breather hole. Previous owner did no mechanical work himself, and relied on a RV service facility.
Title: Re: Differential level
Post by: craneman on December 03, 2017, 04:06:17 pm
With all that gear oil it was probably running much hotter than it should. At least you know your axle seals are good.
Title: Re: Differential level
Post by: krush on December 03, 2017, 06:51:05 pm
  I dont know what has happened in the 30 yrs of this bus and I dont trust the  fill plug to lube the axle ends , being so low .

Millions of trucks on the road running millions of miles. Do you think they use your method, or just fill to the bottom of the plug?
Title: Re: Differential level
Post by: wolfe10 on December 03, 2017, 08:14:33 pm
Please post a link to other than "fill plug" fluid level for a rear axle.

Again, some axles have TWO fill plugs depending on angle of installation.
Title: Re: Differential level
Post by: stump on December 03, 2017, 08:15:34 pm
Millions of trucks on the road running millions of miles. Do you think they use your method, or just fill to the bottom of the plug?
I full to bottom plug drive around turn left right a couple times, recheck too off if needed, shoot for the moon. Recheck next oil change
Title: Re: Differential level
Post by: krush on December 04, 2017, 01:12:14 pm
I full to bottom plug drive around turn left right a couple times, recheck too off if needed, shoot for the moon. Recheck next oil change

I like that method.  Some like to over-analyze.  Which is fine, as it is their equipment.

But let's look at this with practical eyes. Have any of ya'll seen inside a gear case, or rear end when the gears are moving?  Oil is flung EVEYWHERE!  I'd bet a lot of money that there are thousands of rear-ends riding around the roads that are significantly low on oil.  Yet, no damage is being done to the bearings or gears.  As long as enough oil is in the sump to get flung around, components are probably going to get proper lubrication.

Roller bearings (anti-friction bearings) require very little oil to keep from failing.  I haven't installed windows on any rear ends, but I'd guess that the oil splashing around also dribbles down the spinning axles to the hub bearings.

Another bit of anecdotal evidence: when rear axles are removed for towing, and cardboard is bolted over the hole, we don't see hub bearing failures.  I've seen brand new trucks being towed thousands of miles from the factory with axles removed and nothing but cardboard covers bolted in place. No bearing failures.  I guess there's enough oil in the hub to keep it all lubed.
Title: Re: Differential level
Post by: Protech Racing on December 05, 2017, 08:23:28 am
  I'm sure you guys are correct .  I have serviced vehicles  for 40 yrs and this one is the only diff with the fill level substantially lower than the axle tube.  Knowing several vehicles with fill levels different then the fillplugs, I simple went with known good value. At the axle tube. 
 When I serviced the brakes, diff etc. i realized that when you change the diff oil, you do not also change the axle bearing oils.  The hubs need to get removed and tipped on end to get the old oil out.  I would much prefer a weepy axle or pinion seal than an axle/wheel  bearing failure. . The diff noise seems to have reduced also .
 Thanks . MM