What Happened?

[PineCreek]

I drive a 78 3/4 ton 4x4 GMC Sierra .I was about an hour and fifteen minutes away from a problem free 3200 mile trip and all of the sudden boom a weird sound and the steering wheel was shaking bad and the truck was hard to control, I almost lost it luckily I slowed the vehicle down to a stop without incident. I get out expecting a flat but there wasnt one but the front passenger hub sure was smoking and hot too. So I get back in and as I am pulling the vehicle safely into the ditch my drive gives out and and I cant get the truck to move at all. Just a slight grinding noise as I move the shifter lever through the gears. The CAA tow truck driver says he thinks the bearings have piled up and may have done some damage in the axle . Does this sound right? If the bearings are piled up in the hub then how would that effect the transfer case?  

[roundedline]

Without looking at it, it is hard to say, but if you have fulltime 4x4, that would definetly cause the problem.  What is the drivetrain we are working on?  Transfer case, trans?  Have you jacked the front tire off the ground and tell if it is locked up?

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[PineCreek]

So if it is full time 4 wheel that sounds reasonable? Its got the turbo 400 trans, I'm not entirely sure about the transfer case but it is stamped 344268 GM on the side and it is big. When it was on the tow truck I spun the wheel and it seemed to turn about as well as the other front tire. I'll have to wait til pay day before I take it to a mechanic.

[roundedline]

It is fairly reasonable.  Like I mentioned, it is hard to tell without looking it over.  Are the hubs lock in/ lock out?  

Does the T-case have gear selections of Low Range Lock, Low Range, Neutral, High Range, High Range Lock?

Or is it: 4Low, Neutral, 2 High, 4High?

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[PineCreek]

The hubs are non adjustable(capped), does that mean its full time? The TC gear selection is 4 low, neutral, 2 high, 4 high. Sorry, I wish I knew more about it. Thanks for the help roundedline much appreciated.

[roundedline]

4 low, neutral, 2 high, 4 high indicates it is Part time, but it should have hubs that are locking.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[PineCreek]

I double checked and it does have low range loc, low, neutral high and high loc my mistake.

[roundedline]

That makes sense then.  It is full time 4x4.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[PineCreek]

The mechanic tells me that the spindle shaft is broken and that I'll need to take it to Mister Transmission after he fixes that because they figure the shaft between the tranny and transfer case is broke as well. All in all $525 Cdn.+ taxes.  It should be on the road by Friday.

[Blazin]

I would tell them both that you want to see the broken parts when you pick it up, not ahead of time. That way they don't have time to find an old broken part to snow job you with. The broken spindle sounds O.K. but the shaft between the trans and transfer is shaky. The problem with the full time 4 wheel is that if the front drive saft is not turning the truck will not move, I am not an expert of the full time crap, but if there is a problem in the hubs or front end it could posibly make the truck not move?? Your tranfer case should be a
NP 203. Also now would be a good time to switch to manual hubs. It would help your gas milage and cut down on front end wear etc.

[PineCreek]

I got my truck back today, it turns out they replaced the front spindle and hub and also had to put in a new axle shaft wow the old parts were fried. That fixed it. No transmission work necessary after all. The mechanic was talking about a bearing that give up the ghost which is when things snowballed and done all the damage. Thanks for the reply Blazin, I would like to put manual hubs on eventually for sure maybe in the new year. I also am considering putting a diesel under the hood. What diesel would line right up to the 400 turbo transmission? I'm just considering it, I was originally going to put a fresh 350 in it and build the motor up but with the price of fuel and I travel alot hunting and what not I'm considering diesel.

[Blazin]

Not an expert on diesels as I have only owned one ( 6.2, still have it, parts truck, would like to sell the motor, ) but it is my uderstanding that the 6.2s & 6.5s share the bell bolt pattern with the gas jobs.  

[PineCreek]

Hmmmmm. That would make for a fairly straight forward switch. I'm in Saskatchewan otherwise I'd come over and take a look at that engine. I'll look locally and see what I can come up with. Another thing that has crossed my mind is changing the axle gears when I do the engine change. I'm not sure what gears they are now but when I'm doing 60 -62 mph my rpm's are at 2500. I'd like to keep the transmission if possible so I was thinking that changing the gears would give me a little more highway speed and better fuel mileage? Is that whats normally done?

[Blazin]

I would bet you have 4:10 gears beings its a 3/4 ton and the vintage. I have seen them with 3:73s and 4:56 gears as well but the 4:10s are far more common. Higher gears will drop your RPMs at speed. Would also get a bit better milage, if you do mostly highway driving. If you only hit the highway once in a while you probably wouldn't notice any difference. You might also consider a gear vendors under/overdrive unit. Thay are not cheap about $1,000, but they split all you gears 1st low, 1st high, 2nd low, 2nd high, etc.