HMMWV (not H1) Helical Hubs oil level

[T9000]

If I had to put $ on a theory for the overfill, that's the horse I'd bet on. Bench fill is possible also, but seems less likely. The vent lines are probably a long shot if the fluid doesn't look thin and the transmission fluid level hasn't changed.

Agree, that's why I asked about the bolt above the spindle, which also looks like it could be a fill port. Another telling thing towards the overfilling theory is that both hubs seemed to have about the same amount of oil, which would be less likely to be equally distributed if it came down the vent lines (plus is wishful thinking as I prefer that scenario - will check if there is any oil residue in the vent line).

 

[Retiredwarhorses]

Agree, that's why I asked about the bolt above the spindle, which also looks like it could be a fill port. Another telling thing towards the overfilling theory is that both hubs seemed to have about the same amount of oil, which would be less likely to be equally distributed if it came down the vent lines (plus is wishful thinking as I prefer that scenario - will check if there is any oil residue in the vent line).

ive literally seen pics of folks filling the hub from the upper plug on the GH, no one bench filled anything, I’ve rebuilt hundred of GH’s, I’ve always filled after the hub is on, if it falls over the GO leaks out of the vent.
If you want to know if the rear diff cooler is cracked and filling the rear differentia, open the fill plug, you should have the same issue at the Differential as you do at the geared hub, over full and contaminated G.O.
In a sense, it’s the same as the vampire issue, just using power steering fluid “ATF” instead of it killing the transmission via the transfer case cooling loop failure.
My geared hubs were over full with absolutely new golden clear Gear oil…unlike a Glycol cooled rear diff I have that is a milkshake from a probable cracked cooled loop in the REV B truck.

REV=Reliability Enhanced Vehicle

 

[Mogman]

Just check/replace all the fluids, drive it and then re-check after some miles instead trying to second guess what someone else did.

 

[Mogman]

Also the reson the rear diff is hotter is it may have actually been heated by the coolant, whereas you did not drive far enough to actually heat up the gear hubs and front diff.

 

[juanprado]

I understand and appreciate your feedback, I don't have much experience myself. On my truck the power steering line is not connected to the rest of the vent system and it is routed by itself to the top of the air intake stack, it was built like that from the factory, maybe to solve exactly what you described:

View attachment 862156

When I replaced some of the fuel lines, the vent line by the fuel pump broke and I used high temperature silicone tape to temporarily fix it.
I will open it to see if there are any oil traces inside.

The hard line on the intake is for the fording kit.

The gm Saginaw pump takes a new cap with a nipple for the vent tubing on the fording kit but that is for the older models.
You must have the remote reservoir pump?

If so that might explain the additional line.

 

[T9000]

ive literally seen pics of folks filling the hub from the upper plug on the GH, no one bench filled anything, I’ve rebuilt hundred of GH’s, I’ve always filled after the hub is on, if it falls over the GO leaks out of the vent.
If you want to know if the rear diff cooler is cracked and filling the rear differentia, open the fill plug, you should have the same issue at the Differential as you do at the geared hub, over full and contaminated G.O.
In a sense, it’s the same as the vampire issue, just using power steering fluid “ATF” instead of it killing the transmission via the transfer case cooling loop failure.
My geared hubs were over full with absolutely new golden clear Gear oil…unlike a Glycol cooled rear diff I have that is a milkshake from a probable cracked cooled loop in the REV B truck.

REV=Reliability Enhanced Vehicle

I will check the rear differential if it’s overfilled. It sounds like my truck should have glycol (SN over 300,000) but the only coolant I did put in is the green

Also the reson the rear diff is hotter is it may have actually been heated by the coolant, whereas you did not drive far enough to actually heat up the gear hubs and front diff.

I drove it about 12miles when I took that infrared shot, not sure if that was far enough?
From what I read, the helical gears are very efficient running around 94%-98% so I can see why they would not get as hot as the differentials.

 

[T9000]

Just check/replace all the fluids, drive it and then re-check after some miles instead trying to second guess what someone else did.

Agree, I am checking everything and I also get many good ideas about what to look for from you guys.

 

[T9000]

The hard line on the intake is for the fording kit.

The gm Saginaw pump takes a new cap with a nipple for the vent tubing on the fording kit but that is for the older models.
You must have the remote reservoir pump?

If so that might explain the additional line.

Not sure if I have what's called the remote reservoir pump, but it looks like this, with the vent line connected at that brass piece:

 

[T9000]

ive literally seen pics of folks filling the hub from the upper plug on the GH, no one bench filled anything, I’ve rebuilt hundred of GH’s, I’ve always filled after the hub is on, if it falls over the GO leaks out of the vent.
If you want to know if the rear diff cooler is cracked and filling the rear differentia, open the fill plug, you should have the same issue at the Differential as you do at the geared hub, over full and contaminated G.O.
In a sense, it’s the same as the vampire issue, just using power steering fluid “ATF” instead of it killing the transmission via the transfer case cooling loop failure.
My geared hubs were over full with absolutely new golden clear Gear oil…unlike a Glycol cooled rear diff I have that is a milkshake from a probable cracked cooled loop in the REV B truck.

REV=Reliability Enhanced Vehicle

I will check the rear differential level, was planning to change the GO to synthetic.
If indeed there is glycol leaking into other components, then the coolant level should be dropping, correct?
Or if I run the engine (not the truck) with the rear differential drain plug open, there should be coolant coming out if there is a crack?

 

[juanprado]

Not sure if I have what's called the remote reservoir pump, but it looks like this, with the vent line connected at that brass piece:

View attachment 862279

Yes, That is what I would call the remote resovoir. Might have a different official name. Interesting that they did not tie that line into the others as done previously with the fording kit instead of running a seperate vent to the intake stack?

 

[T9000]

Just check/replace all the fluids, drive it and then re-check after some miles instead trying to second guess what someone else did.

I still have to change the front hubs oil, which should be done in the next few days and the only two fluids that I didn't replace are the steering and brake. Both have the right levels, didn't even have to top it off and they look good. I will eventually get to it, but it didn't seem a priority, like the engine oil, transmission, transfer case, geared hub fan and hub oils.
Is it OK to use the original steering and brake fluids for now if everything looks good?

 

[TNDRIVER]

I thought the oil is dark because it was very old, maybe from 2012, or maybe even factory fill from 2009 as the truck had only 7k miles and maybe they didn't change it. Yes, I do thermal testing using an infrared camera and the hubs look OK, one thing that seems to run hotter is the rear differential. I changed the oil to Lucas 80W90 and now I am switching to Lucas 75W90 synthetic to see if it makes a difference in operating temperature (there is some marginal thermal transfer from the brakes):

View attachment 862152

Actually I don't know if 75C is too hot, it just seems high to have an almost 50C rise on a let's say 27C ambient. I wasn't pulling anything, it was just the empty truck itself, so I am just getting some data-points for now.

I think 75C is like in the mid 100s or so. I wouldn't worry about the diffs until you see 250 deg. or more. Most here would never work one hard enough to get them that warm. Just my 2 cents.

 

[Mogman]

I will check the rear differential if it’s overfilled. It sounds like my truck should have glycol (SN over 300,000) but the only coolant I did put in is the green


I drove it about 12miles when I took that infrared shot, not sure if that was far enough?
From what I read, the helical gears are very efficient running around 94%-98% so I can see why they would not get as hot as the differentials.

The diffs have helical gears also, IIRC on that truck you have coolant going through the rear diff cover, if you just let the truck warm up it will be 200ish

 

[T9000]

The diffs have helical gears also, IIRC on that truck you have coolant going through the rear diff cover, if you just let the truck warm up it will be 200ish

Yes, you are correct, it does have cooling, the two cooler green tubes in the thermal image (running at about 65C/ 150F):


I will take another shot next time, right when exiting the freeway after driving 70-80mph or maybe even while driving it, will try to make some adapter to install the infrared camera underneath. The one above was taken after I already went thru a few stop lights, so it could have cooled down by then.

 

[Mogman]

I would not spend too much time worrying about it.