I have read numerous posts advising it was ok to lock you hubs when not in 4WD, some even touting that it helps keep the works from freezing up by helping to lubricate them. Others say NEVER do this.

I did this on Monday when I drove my truck to work (35 miles) since it had been a long time since using 4WD.

The result, my gear oil boiled over due to the heat and dripped all over the place - scaring the crap out of me.

After being chastised by my mechanic, I will NEVER do this again.

Maybe it is just my truck, but thought I'd share my experience.

 

As one who has periodically driven my 1980 F-350 4x4 auto with the hubs locked while in 2 wheel drive since 1981 - as recommended - with no boiling over gear oil, I would suggest that you might want to find another mechanic who is skilled at repairing/replacing malfunctioning front hubs. That's what is sounds like you have.

 

I agree - your mechanic is clueless. There's NO WAY you could have boiled gear oil by locked the hubs in, unless you were driving 300mph.

Locking your hubs in will not cause any harm -- guaranteed -- given that everything is functioning properly in the front end, i.e. you have enough gear oil, u-joints in good shape, transfer case has enough fluid and isn't fubar, etc.

 

Actually only driving 65-70 mph for about 35 miles on dry pavement, and that is exactly what happened. Hubs work fine, it was definitely gear oil that had heated up.

I confirmed this with a second mechanic. I'll take their word on this.

 

Driving 65 to 70 will obviously result in the front hub gear lubricant heating up, and may even result in possible lubricant "boiling" over and gushing out of the hub assembly if the first mechanic put too much lubricant in the hub - won't be the first time that's happened. Still, running in 2 wheel drive with locked hubs occasionaly, assuming you don't regularly go 4 wheeling, is a recommended procedure to properly lubricate the hubs. You might want to check with a third mechanic, preferably one who is FORD certified.

 

As a mechanic and someone who has been driving 4x4s since 1965 here is my take on this subject. You should lock in your hub every once in awhile to lube front differential, In cold weather I will lock in my hubs a few miles before I plan on using 4x4. The other day I locked in my hubs to use four wheel drive which I did, after coming back on the pavement I left the hubs in and drove about 25 miles at 65 to 80 MPH when I got home I had blown out some oil from the vent tube, checked the transfer case and it had plenty of oil. You must remember that ATF expand when HOT as much as a quart in an auto trans. Finally, it is best to lock in your hubs in 2 wd. when driving in town.

 

I don't believe it.

Does the gear oil in the rear 'boil over' when you drive at 70 miles an hour?? nope.

I've driven my beater back and forth from my folks house (~35miles 50-60mph) and I never had a problem.

You are probably seeing your fluid expanding (like other said) and puking out the vent. If this is a problem, I'd switch to a synthetic lube, which won't expand as much.

 

Apparently, the "puking out" is what occurred.

 

The only way I can see the possibility of this happening to the front diff and not the rear, is the oil level must have been seriously low or too high, the vent tube being clogged would do it. If there was water in the front end it may have boiled out. That is unless we misunderstood you, and you were talking about wheel bearing grease spewing out from the hubs. If that's the case having the hubs locked, is not reason for the grease spewing out. I have heard of this happening for a few reasons: lack of maintenance ( not repacking the wheel bearings) The grease breaks down and the seals go bad, and you lose your grease. Another would be contamination of bearing grease...water. They both lead to expensive repairs later on down the road, it cost me $120 just for the bearings. I run with my hubs locked all winter long in my 84 F150 up here in Michigan. I will unlock them if the roads are clear and dry to save on tire wear. My truck sees it's fair share of off roading...deep mud, water, sand, trails, etc...so maintenance is ESSENTIAL for what I do. If I don't do a whole lot of serious 4 wheeling, I repack my bearings once a year; along with changing the fluids in the diffs, tcase, and trans. If I get stuck in mud and or deep water past the hubs, or just came back from playing in the dunes, I repack and change all fluids immediately as soon as I get home. I recently installed a Trak Loc limited slip diff in the front (to compliment the locker in the rear), so I can't drive with the hubs locked on hard surfaces. You can barely steer the beast with em locked because it rips the wheel out of your hands! A properly maintained 4x4 can be driven for miles with the hubs locked in 2wd and not hurt a thing... accept maybe tires.

 

If you're driving a part time manual hub 4x4 in any slippery conditions, the only way to easily go from 2 to 4 wd is to lock the hubs in ahead of time. On the Ford D44, you can leave the hubs locked in. I drove to work one day 1 hour each way like this because it was icy. I just clicked the transfer case from 2high to 4high when entering an icy patch - it works well. This is a standard operating procedure for part time 4wd systems in general. It is beneficial to the seals to lock the hubs in every now and then as long as the transfer case is in 2high. The only thing you shouldn't do is engage 4wd when on dry pavement. It sounds like your front differential had too much lube, or maybe some water in there on top of the gear lube.

 

my father ran his 1990 f-150 with hubs locked from november until april for nearly 10 years and never had any problems from what I know so the guys must be right...

 

I kept the hubs locked in on my 1979 F150 from November to April also. I would put on about 350 miles a week, and would drive 100+ miles non-stop two times a week and never had any problems. That was my first truck, but all of the ones have owned since then, I keep the hubs locked in all winter, then lock and unlock throughout the summer. In the last 15 years, I have done this with two 1979 F150s, a 1984 Ranger, a 1989 F250, and I currently have the hubs locked in on my 1985 F150.

 

I don't know if anyone else mentioned this, but you said in your first post that it had been a long time since using the 4wd. How long? Maybe the gear oil went bad in a matter of 10 years or whatever the case may be? Then shocking it by one day running it for 35 miles at highway speed caused it to boil over. I'm thinking some new oil is the trick here.
Mike

 

definatly need a gear oil change and well, at least you know you front axle vent is no longer clogged. A clogged vent is most likely why heat buildup forced the oil out.