In my '91 F-150 I get a squeaky, rotational noise when I put it in 4x4 HI.

In an attempt to find out where it is coming from, I checked the fluids in
the transfer case and also the front diff. They are full. I checked the
driveshaft... there doesn't appear to be any grease zerks on it.

The noise seems to match the speed of the engine, and not the wheel
speed. When I lift off the accelerator, the noise fades in frequency (rotational
frequency, if that makes sense).

Manual hubs, and usually they are locked this time of year. I get no noise
when not in 4x4 mode, but when I shift into 4x4 mode the noise starts.

Other than that, it seems to work OK. And yes, the 4x4 mode is DEFINITELY
NEEDED here in my part of Idaho!

Any ideas?

 

Unlock your hubs until you need them. Your gonna damage them if you dont.

 

I need them every 10 minutes...

 

What it's gonna hurt? I have never head of any problems with doing this. What exactly goes wrong and why? Enlighten me if you can. My hubs stay locked pretty much Nov-April. I live in northern MN and I can have 4x4 engaged 4 different times in a 2 mile trip. I have had no problems whatsoever.

If the squeek is at engine speed, it is probably on the driveshaft side. Squeeky U-joints could be the culprit. You could eliminate any axle parts by putting it in 4Low and listening. If it is not at road speed and slower than engine speed, then your front axle beyond the pinion is probably ok.

 

Ditto. I'd like to hear what gets damaged and why.

 

I'll keep looking... the more I think about it, it could be squeaky U-joints, but what to do
if there are no grease fittings? Just live with it?

 

Squeeky U-joints means the joints are going...

 

I agree with everyone else, Just squeaky axle joints. I had the same deal with mine and when I replaced the ball joints, I went ahead and replaced the axle u joints cause I had them out already. Noise is gone now!

 

locking your hubs just locks the wheels to the front axle, so basically all that happens is the axle and the gears spin in the front, and they turn the drive shaft, cause the transfercase is in neutral, you cannot damage anything.

I have a slight vibration when my hubs are locked in, but nothing serious.
and yes, in idaho this time of year, you need 4wd if your not crazy.
or if you are. who knows. its nasty out there sometimes.

 

Correct me if I'm wrong, but when you engage 4HI, the TC will put 50% of the power to the front and 50% to the rear. However, when your are driving (especially during turns) each tire turns at a different speeds. But since you are pushing 50% into the front and rear, two of the tires have to turn at the same speed. This will cause stress on your drivetrain and wear it out faster. I am not entirely sure what makes that noise, but I bet if you drive 4HI in loose dirt, it won't make that noise at all.

 

Yes thats true, but the front ends on these are not locking differentials (I dont believe). If you Jack the the whole truck up off the ground and put the truck into drive or 1st or whatever, you can stop one of the front or rear tires with your hands (might not want to try that one) but the other tire will keep spinning. I think basically that although vehicles are considered 4 wheel drive, only two will spin at once (On the the front, one on the rear.)

Thats why if you go to a mudrun and see a chevy thats buried, While hes still giving it hell, only one front and one rear tire is spinning. Usually on opposite sides (Front left and rear right might spin and vise versa.) I could be wrong though. In my truck, all 4's spin, but I've never had it buried to where one side of the truck is in different terrain than the other side.

 

All four of your tires spin because it has equal amount of traction on your tires. If you had locking diffs (or LSD) in the rear, both L and R tires will spin at the same rate, which is what you want when one tire is up in the air (or has no traction). Open diffs will give the power to the wheel that has the least traction. This is exactly what you want on the street, but not off road.

In this case, I am assuming that the author of the thread turned on 4HI while on a paved road or on a maintained dirt road. He has too much traction which keeps the tires from spinning on the dirt.

 

I wasnt disagreeing with you in your last post, Willf. You are probably right. I mean my truck with the wore out axle joints (one was siezed up) it made a squeek and clunk when I turned. I'm guessing thats what his problem is. Just wanted to make sure that you knew that I wasnt trying to prove you wrong at any rate buddy.

 

Heh, sorry. I didn't think you were either. I was just commenting. There was some "I think", "I believe" so I wanted to comment on it a bit more, if anything for other people who might not know...

I'm coming off real badly on this site, heh. People must be sensing that I really am a GM guy You guys are good!

 

Yes, you're right, but there's a good reason why it's bad to engage 4x4 on dry pavement.

I got thinking about this because of another thread where a guy claimed you won't damage anything by keeping it in 4x4 on dry pavement. Why that's wrong...

Think about what happens to an 18 wheeler when it makes a turn. The front end goes through the turn fine. The rear, if the driver isn't paying attention, will take out anything on the inside of the turn. They run over sidewalks and whatnot on tight streets all the time. This is because the rear wheels cannot follow the same track as the front wheels. They will always follow a tighter radius circle than the front wheels.

The same thing happens to a pickup truck. When you make a turn, the front wheels follow the arc of a circle. The rear wheels also follow a circle, but the radius is shorter for that circle. If you were to drive around in a circle, the front wheels would follow a larger circle than the rear wheels would. This means the front wheels travel further - bigger circle = more feet travelled.

When you're locked in 4x4, the front wheels are locked to the rear wheels. They do not allow for the possibility of different sized circles. So something has to give. Either the tires will skip, or something will break. When you have a 5000 lb truck sitting on four tires, the wheels do not like to skip. It won't take long for something to break.