85' K5 4wd Question

Okay, finally got around to install the front drive shaft on my beast. It's been somewhat cold (down to 9deg at one point) and I haven't much wanted to do anything. :- )
It was somewhat of a task; the slip joint must be particularly nasty in there. The outside was nice and smooth, no pitting. But when I added grease to it, it hydro locked. All the grease that was coming out of the joint at the bottom was a nasty brown. (still is) I ended up taking off the grease nipple, and cleaning out the hole on the top as best I could. I put the CV joint on the ground and a piece of wood on the yolk at the top, and hit it with a hammer. 'Twas like a big nasty brown greasy zit. What came out of the top at first was very un-grease like. It finally did come out as grease, and nice 'clean' black grease. The grease that comes out of the sleeve end is still quite brown. I tried to take off the collar at the bottom with a pair of water pump pliers, with no success. I also tried lightly heating it - didn't want to burn the seal or make the grease explode out. Any tips would be nice, I'd like to clean out all the rust and dirt that must be in there. But I got it so it will expand and contract.
Questions: When I put it in 4hi and turn very sharp, it feels like its going over bumps at regular intervals. It gets worse (shorter intervals) in 4low. It feels like it's coming from the inside wheel (of the turn). A friend of mine (who has been relatively reliable thus far) said it's because the front diff is posi/locked and the wheels are spinning at the same speed as each other. It shouldn't feel like that if I were to take it out on dirt. This makes perfect sense, except for a few things.
A: As far as I know, this truck is basically stock. Also as far as I know, stock diffs weren't lockers (front or rear). My father remembers that you COULD get a ‘posi-track' (or whatever GM's flavour was named) rear-end, but nothing about a locking front. B: It doesn't do this when the wheels are locked, but in 2wd
My question, is something wrong or is this guy right?
Other Questions: I've asked this before, and I was told it was an art so I will write some very specific 4x4 use questions:
1: What happens if (for some reason) one wheel gets locked and the other does not? 2: How are you supposed to shift into 4wd? So far, I have stopped, put the tranny in neutral, and then shifted. 2b: Can it be shifted on the fly in some special manor? 3: Could someone explain, or show me a link, to a clearer explanation of t-case ‘wind up'? With what I have read, it seams like a myth. 4: Any do's and do-not's that you can think of? I mean basic – just how not to destroy the mechanics of my drive train, not how to be a pro rock-crawler.
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
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"Lonely G-Monkey" wrote

Nothing is wrong..."and"...that guy is wrong. What you are feeling is commonly called "crowhopping" It has nothing to do with whether or not the front diff is a locking diff. (I have never seen a stock GM truck with a locking front diff). It has to do with driveline windup that you get when you turn the front wheels on dry surfaces while in 4wheel drive. The front differential can handle the relative speed differences between the front wheels, but as soon as you engage four wheel drive, now you have a speed difference between the front driveshaft and rear driveshaft into the t/case (when turning corners). That's the binding you are feeling....and it often translates into crowhopping. If your truck has the solid front axle with regular style u-joints....they can also contribute to the feeling as they aren't quite as good at transmitting torque smoothly at a high angle the way a later CV type of joint is.

Yeah...it's just a myth. Seems to destroy a lot of 4x4 components though. That might be a myth too...but at least it pays me well.
Ian
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It is a U-joint

You explained it perfectly. It's when two things are trying to turn at 2 different speeds and attached to the same thing. But what I had read, had described "back up" to "unwind" the t-case, like it was a rubber band... and this was about a blazer of my general vintage. I suppose one could then understand why it seemed like a myth.
The reason the hopping seamed like a problem is because I would have thought that the wheels would have no problem turning at different speeds like a rear diff. So if the rear drive shaft were removed, this problem should lessen to next to nill? To the point where it's just a U-joint at it's extremes?? Just wondering - not planning on a front wheel drive blazer.
Also - why is "55" orange on my speedo? My two thoughts are "55 saves lives" and "max 4hi speed". I've also been told that no t-case is made to go faster than 45mph. Just wondering how fast my 4wd can be run in high? Speed in low?
~KJ~
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"KJ" wrote

Yes....I suppose so...I suspect you are listening to some folks that know just enough to make them quite dangerous and the purveyor's of wrong info and urban legends.
When people run worn out tires on one axle and fairly new tires on the other axle (which I've seen) and then throw it in 4x4...you can get severe windup....often so bad that you can't get the t/case to shift out of 4hi until you raise the vehicle off the ground.

Yes...if you did as you mention....there will be no crowhopping.

Probably because of the stupid max speed laws that you Americans had back in those days.
Stop listening to whatever "t/case experts" you might be listening to. I think they are leading you down the garden path.
Ian
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Yes the internet can be a dangerous place. I've read almost all of that online, on sites suggested by the perpetrators of this forum.
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
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"Lonely G-Monkey" wrote

The internet is probably one of the worst places to get advise and also maybe one of the best....you just have to have a bit of discernment.
Ian
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"shiden_kai" wrote

typo corrected.
Ian
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I try as best I know to route out the truth. But <on coming jab> when _someone_ says "your guys an idiot about XXX" and leaves the question of XXX still hanging (yes it's a yolk (yes it's a pun)) then it dunen't help much.
Father says T-case can go as fast as the truck can go, long as it's a low-traction situation? Is it ever advisable to use 4wd during the snow? From what I understand, no. What happens if one wheel doesn't lock, for whatever reason?
~KJ~
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"KJ" wrote

Yes, I realize that I do that sometimes. It's either an indication that I'm too lazy to answer the real question...or perhaps...I just may not know the answer. There are many, many.....automotive...GM...etc... things that I do not know about. I try to only tackle questions that I'm certain that I have some valuable or pertinent information about.
> Father says T-case can go as fast as the truck can go, long as it's a

All things being equal, you should be able to go as fast as you want even in high traction conditions. But, it's not recommended with a part time t/case. Which is why the newer auto t/cases were developed. The yuppies driving all the new SUV's have no clue how to properly use a part time t/case without blowing compenents up...so the auto t/cases were developed to hopefully allow full time 4x4 usage without doing too much damage.

I don't think that I understand your question. If you can't use 4wd in the snow......I'm not sure what other better condition you could find to use 4wd in.
Ian
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Kinda silly, because you say he's wrong because you don't know it :-)

Again, what would this usage curtail? I'd assume going down the highway, or anywhere where the turning isn't tight....

It's actually supposed to help you loose traction, according to "most" driver's ed teachers. I've never taken driver's ed, so I don't know what the argument is exactly. One thing I can tell all the little kiddies:
EVERYONE HAS 4 WHEEL BRAKES
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
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"Lonely G-Monkey" wrote

Now you are being silly. Go back and look at my original post. When I said your buddy/friend was wrong, I gave an explanation of why.

If you aren't losing traction, don't use 4x4.

And how do these two sentences make any sense. You are quoting "most" drivers ed teachers, but you've never actually heard even "one" drivers ed teacher utter those words?
You are getting too much second hand info.
Ian
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I forget what I was thinking that night, and glancing back over the thread I can't remember exactly what it was. It made sense at the time though.

Your right it is second hand, but I've seen alot of people go through driver's ed (and didn't think it helped a lick)
-The Lonely Grease Monkey 1985' K5 305CUI TH700R4 NP208 KJ's successor
"Ignorance is preferable to error; and he is less remote from the truth who believes nothing, then he who believes what is a wrong." - Thomas Jefferson
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On 12 Nov 2003 07:03:15 -0800, pde_on snipped-for-privacy@hotmail.com (Lonely G-Monkey) wrote:

the auto xfer cases have clutches and/or a center differential in them to allow differentiation between front and rear drive shafts, otherwise you still have the same drivetrain windup problems. one of the times I was at the local tranny shop I saw a jeep NP231J xfer case that shot the chain *through* the case because of driving in 4wd on a high traction surface.

4wd drive in snow is great if you remember the cardinal rule:
don't go faster than your brakes can stop you.

if one of your hubs doesn't engage, all that will happen is the little spider gears will be whirring around like mad in the front diff. the effect... no 4wd.

what it does is not allow the front tires to turn at the speed they need to, causing them to slip relative to ground speed causing the front end to plow. this can be overcome by juicing the gas. your arguement for brakes isn't relative as the brakes don't lock the tires together.
-Bret
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The cause of the brown is, more than likely, due to rust. If everything is clean, possibly a different color of grease... As for the hopping when you turn sharp on dry, high traction ground in 4WH(naughty) and 4WL(BAD, BAD boy), it is the axle u-joins trying to work at an extreme angle. NOT where they work best. Just a quick note, don't use 4WD on any high traction surface unless you need to pull something that the rears cant handle on their own and even then be careful. Please don't turn in 4WD, high OR low on anything with good traction. You might as well take a jack hammer to all the u-joints in front of the t-case and the t-case itself!

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it's not the axle angle that causes the 'hop', it's that the front and rear wheels are describing circles of different radius, and therefore one driveshaft is trying to turn more revolutions than the other
they can't, of course, being connected by the transfer case internals
so one wheel will 'hop' when the torque applied to the axle shaft overcomes the tread's gripping power

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I wasn't about to go running over peoples (frozen so no different) yards. I wanted to feel if it was shaking, just to test if things were wrong. Now that I know better, I can stop doing it.
As you can see from the end, I don't know everything - so I asked the questions.
~KJ~

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