T-Case and Front Diff

[efialtis]

I have an '84 k10 6.2L which I really like...but I am experiencing two things...

I am having a really bad vibration while in 4X4H and going at freeway speeds.
I know my t-case is leaking, but I keep it full of oil, but I was wondering, if it only happens in 4X4, does that mean the vibration is coming from the t-case? Or could it be the front diff?
Is there a "rebuild kit" for the t-case, replacing the seals, gasket, bearings, and drive chain?

Also, I really hate the "hopping" that the truck does when turning while in 4X4...like the front diff isn't limited slip...
I have the auto-locking hubs, and wouldn't trade that for nothing, but I was wondering, is there a limited slip diff that I could swap out for this one to stop the 4X4 hop?

Thanks all!

[maverick_935]

you should not be in 4hi at highway speeds but if you have to and have a vibration check your u-joints especially in the constant velocity joint.

The hopping is the front diff trying to make a turn on dry ground. you are risking an axle shaft if it binds enough. 4x4 do not like this. If you have to turn sharp on dry ground then take it out of 4x4. It does not matter if you have a limited slip or detroit locker, they do not like to turn sharp on dry ground.

[trbankii]

What Maverick said x2.

Using 4WD at highway speeds leads to all sorts of bind-up and possible damage. If the conditions warrant 4WD, you shouldn't be driving at highway speeds. And if they don't warrant 4WD, you shouldn't be using it.

Even off-road, there are times I get too much traction and have to take it out of 4WD to make a sharp turn.

4WD, unlike AWD, needs some "slip" or drivetrain components bind up due to turning radius or even slight (or more) differences in tire size. Without the "slip" things bind up and will eventually lead to premature failure.

[arveetek]

These guys are right. It is normal for the front wheels to hop and bind when turning in 4WD. If it starts doing that, you have too much traction and need to shift out of 4WD. Those trucks were not meant to be driven at freeway speeds in 4WD. The front driveshaft would be my suspect for the vibration, not the transfer case.

Casey

[DmaxMaverick]

I disagree with most of the above. The 4x4 system is designed to operate at "highway speeds". Problem is, "highway speed" is rather subjective. The system, of any year model, will safely and reliably operate in the 45-55 MPH range. With enough snow/ice on the road to warrant 4x4 use, speeds above this is lunatic. One major problem with this is the owner's attention to the system. The TC and front diff are of the most neglected systems on the truck. Outa sight...Outa mind. If you use it on a regular basis, it should be serviced regularly. At least as often as the rest of the drivetrain, and more often, in many cases. 2 qts. of ATF in the TC is a 15 minute job, and should be done with every tranny service, or twice as often with heavy use. The front diff should also be serviced as often as the rear diff. When engaged, the front and rear are pulling the same duty, and the load on the TC is increased.

As said above, the "hopping" during turns is normal, and it is the nature of the beast. There are some 4x4 systems on some vehicles that don't do this, but they aren't "trucks". Also, just moving the lever from 4H to 2H doesn't necessarily mean it is in 2H. The older systems, especially with auto-locking hubs, require a few short moves in reverse and forward (once the lever is moved into 2H) in a straight line (no turning) to get it out of 4x4. It won't routinely disengage if there is any load or bind on the drivetrain.

Your vibration is most likely a TC output bearing failure, evidenced by the leak. As the bearings get more sloppy, the shaft wobbles in the seal and causes the leak. The TC can be overhauled easily yourself, or for not much more by a local shop (about a one hour job, not including R/R). Supplier exchange TC's will cost 2 or 3X as much, but that's because you are paying for shipping, and other's failed cases and internals your won't likely need (that's why the price is the same for a reman, no matter what is wrong with yours). Most of the time, a hardware kit will cure it. Only moderate wrenching skills are required. The box is very simple with very few parts. If you do it yourself with a hardware kit, be sure to include the shift fork shoes. They are nylon and almost always need replacement, but the last couple kits I got didn't include them. The chain may or may not need replacement, but replace if in doubt. Much depends on how much 4x4 was used, and the regular maintenance it received. If you've been running gear lube, it will likely need more than just a hardware kit. It requires ATF. Gear lube is too heavy and doesn't pump well (the pump is in the rear housing, and is plastic). Most of the TC's I've overhauled died because of the wrong lube used.

[efialtis]

Alright, I guess I get it... there isn't a way to fix the hopping, and yes, it isn't as noticeable in the deep snow or ice that ends up on our roads, but I was hoping for a solution... guess I will live with it, and try to go into 2X4 when 4X4 isn't needed...

I will pull the front shaft, and replace the u-joints... they prolly need it. This truck was my grandfather's and he had it serviced regularly, but u-joints are only about $15, and that little bit of work is no biggie.

I will check the front bearing on the TC while I have the shaft off, and see if it looks like it needs replacing...

The TC has only ever had ATF in it. I have a book and I find it cheep and easy to replace fluids, so I do it every couple years.
I am not sure when the TC was last serviced, but the guy who did it didn't put in the gasket between the halves and used RTV only... this is where it is leaking, from around it's seam...

This truck is great, and I want to keep it running for a long time yet... with over 400k miles (only about 100k on the "new" engine) and a new Stage 2 Transmission (700r4 rated at 400 lbs torque) It should be on the road for a long time to come...if I can get these minor things fixed...

Thanks for the advice and info, now its time to go futz with it some more... ;)

[DmaxMaverick]

There is no gasket between the TC halves. It is sealed with only RTV. If it leaks there, the surfaces weren't properly prepared, it wasn't torqued properly, the case is damaged (pitting at the mating surfaces), or a poor quality or wrong formula sealer was used.

Try to wobble the front shaft output. If it wobbles, the bearing is shot. Also check the front diff pinion and the half-shafts (during a brake job is a good time for this). Probably not the U-joints, but they are cheap and easy to replace once the driveshaft is out. With 25+ years on them, replacement isn't a bad idea, in any case.

[6.5 Detroit Diesel]

the TC to tranny surface can be a pain to seal. really make sure the surface is dry and that there is no oil at all on it. like D-Max said, a good RTV is used in there. I have done it plenty of times, and the extra 10 minutes of prep beats an hour spent pulling it.

FWIW, up here in Canada, my trucks spend thousands of kilometers in 4hi doing mountain highway speeds, (90KMH) and I have had no issues. have towed and hauled in 4hi with no problems. the owners manual has a section on 4 wheel about top speed being 50MPH in 4hi.

wondering if the vibration is from gears not meshing properly? when was the last time the front diff oil was checked? being a solid front, popping the cover shouldn't be to much of a hassle.

[DmaxMaverick]

He/I was referring to the TC case halves not having a gasket. The TC to tranny adapter surface has a gasket listed, but is rarely used after R/R (they didn't always come from the factory with one, either). The most important part is a clean surface before applying the RTV. I use brake cleaner, which allows for very good adhesion (too good, sometimes). With the transfer case, after cleaning and applying a small bead of RTV, I'll place the TC on end (shafts up/down, in a vice or blocked on the ground/bench), align the bolt holes and install the bolts just barely hand tight. Let it set for about an hour, then torque the bolts in a cross pattern (like heads or wheels). I've never had one come back with a leak. I also use a smear of RTV on the shaft seal shells.

If you do an overhaul yourself, the bearings will be free needles (as in, not encased like wheel bearings). DO NOT clean the grease from them. The heavy grease will eventually dissolve into the ATF (harmless). If you clean and break them apart, it is many times more difficult to install. Leave them in strips (held together by the waxy grease), wrap them around the shaft and push them in with a rolled piece of cardboard or plastic sheet (there is an expensive tool for this, but not required). Shop temp should be between about 60-90°F, or the grease will be too tacky, or too stiff. You can warm them with a blow dryer to soften them a bit if they are too stiff. A smear of ATF on the shafts and races helps to slide them in. I've never had a kit with too many or too few bearings, so be sure to use them all, and don't lose any.

[6.5 Detroit Diesel]

He/I was referring to the TC case halves not having a gasket. The TC to tranny adapter surface has a gasket listed, but is rarely used after R/R (they didn't always come from the factory with one, either). The most important part is a clean surface before applying the RTV. I use brake cleaner, which allows for very good adhesion (too good, sometimes)..

My bad. I was thinking of the NP241 hooking up to a tranny. i have split open a few of them, and used RTV on them as well. may have to try brake cleaner on the next one. i usually use a bit of emery cloth to scour the face.

[DmaxMaverick]

I know of several folks who rough up the surfaces. I prefer it as smooth as possible, and rely on good adhesion. Fewer leaks later on that way, and cleaning up the old material (be it gasket or RTV) is easier when it's parted again (quick swipe with a razor blade). There is very little basic difference between the 208 and 241. Most practices apply to both.