What pushed me to do the viscous coupler removal?
First of all when I made turns, for example, in a parking lot, I heard my tires scrub against concrete and one of the wheel stopped turning intermittently to relieve the stress on the drivetrain. Please note that my tires weren't squeaking but really dragging to the point that the truck would not roll while making a turn. Instead, it behaved as if the parking brake were applied. If your tires just squeal, especially on the slick kind of concrete found in shopping malls, then the VC (viscous coupler) is not your problem. Another way to find out if your VC is dead is to raise one wheel (tranny in N, transfer case in N). In the N/N position the wheel should move rather freely when you rotate it by hand. If you lock the center differential the wheel should not move (it might have play but you definitely can't make turns).
What can be the cause of the VC seizing?
The most often mentioned cause is running tires of different sizes. This causes the VC to operate all the time, heat up and seize permanently. I will not discuss the principles of the VC as this can be found in other threads and has already been explained extensively. In other words, the PO of my truck must have been a dummy and killed even such a friendly and simple device as the VC.
What can a seized VC damage?
First of all, a seized VC acts as a permanently locked differential. So when you drive in a straight line nothing happens but once you turn, even a little bit, the differences in tire rotation are not absorbed by the center diff but transferred onto all the drivetrain components. This puts enormous stress on your axles, driveshafts and all differentials. This, in turn, speeds up wear and sometimes may even break an axle or grind teeth in a diff. Such damage will surely cost you lots of time and $$$.
What does the VC give me?
It acts as a 'semi-locked' center differential. It means that if one axle loses grip, the engine torque is gradually transferred onto the other one. This is good not only for off road but also icy, snowy or wet roads. It's a kind of primitive traction control. Maybe 'primitive' is a bad word, as the VC is quite piece of engineering and craftsmanship, very simple but quite effective.
What will I get when I remove the VC?
I will simply get an open center differential. One can drive without the VC indefinitely and this will do no harm to absolutely anything.
PREPARATION FOR THE OPERATION.
You will need...
--- a garage where you have easy access under the truck.
--- 4 or 5 hours (if you do it alone)
--- a set of professional wrenches (very important, read further about it)
--- a 2ft steel tube to give leverage to your wrenches
--- a penetrating oil spray to loosen stubborn rusted nuts
--- gear oil if you don't plan to use the old one
--- RTV silicone or any kind of gasket material
--- a hard nylon sponge from your kitchen.
--- a file
--- a thread locker or at least dense paint if you want to lock the threads the redneck way (like me)
--- at least 4 kinds of snap ring pliers, you never know which will work for you
--- at least three flat screwdrivers of different sizes, including one which is very wide and hard
--- lots of paper towels or simply toilet paper
--- a camera or paper and pencil
--- a big syringe or pump to fill the differential with oil
--- patience
--- anything else that you will find necessary
1. Start with disconnecting the rear driveshaft. It is held by four screws, which you have to spray a bit to reduce friction and facilitate unscrewing. This is absolutely the point where you need the best quality wrenches. These nuts transfer big forces so they are really tight. The size of the nut is 14mm (as far as I remember) and you will probably have to use the steel tube for leverage. Chock the wheels to prevent the truck from moving. In my case, the small 14mm wrench had to withstand a 2ft leverage and a 160lb guy hanging on the end of it with full weight. A cheap wrench will snap right away causing danger or will deform itself and round the nut edges (say bye bye to driveshaft removal). So remember to use good stuff here.
2. Once the nuts are off you can pull the driveshaft away from the transfer case flange. If you have greased the shaft regularly it will probably be full of grease and won't retract. It this case you will have to remove the grease port on the shaft and use a big screwdriver to separate it from the flange. Use a file to scratch the flange and shaft joint to make sure you put it back in exactly the same orientation. Use a cord or wire to attach the shaft to the frame or exhaust tube, so that it doesn't hang around and make your work difficult.
Photo of rear of transfer case with driveshaft removed and attached to muffler.
3. Disconnect anything that connects to the back of the T-case. These will be...
a) speedometer cable which is in the middle of the photo below. This is a socket, so don't try to rotate anything, just lower the rubber boot, press the tab and pull.
b) grounding cable, seen below speedometer cable and a bit to the left.
c) two electrical plugs on top of back of T-case, not seen on the photos but easy to find. Mine snapped off with ease (remember to press the locking tabs) and probably yours will also be easy.
d) there might be some other stuff connected by previous owners so inspect the back of the transfer case.
Here you can see speedo cable, ground cable, drain plug on bottom, fill plug on upper left.
4. Drain the T-case. On the very bottom there is a plug (24mm). Put a socket wrench and loosen it. Loosen it further by hand. Negative pressure will prevent ani oil from leaking, so hold the plug firmly. When the thread ends it will pop off, and together with it a stream of oil, so have a container ready. Make sure the container is near to the opening as the oil is dense and it could drag itself in different directions. It will drain like this for at least 10 minutes and some dripping will continue for the next 4 hours (it means it's going to spill oil until you close the T-case again). Let it drain and have a break, dring a juice and eat a sandwich.
5. Loosen and remove the bolts that surround the T-case. You will have 9 bolts of different sizes, so remember to put them on the floor in order and take a note of them or take a picture like I did. This is to ensure that if you accidentally move the bolts around, you will be able to retrieve their original position.
Photo of bolts in the right order.
6. Now you have to separate the back of the T-case from the rest. You can use some sophisticated pullers and try to separate it, but you can also go the 'brute-dummy' way and simply point a flat screwdriver to the edge and bang it with a hammer. You will end up with a few dents on the mating surfaces, but you can tap them back to flatness with a hammer. Wiggle the screwdriver around to make sure you gave a gap everywhere. Remember to do it alternatively on both sides (left-right-left-right...) of the case. At this point you should be careful as the oil pump inside the case has a round metal spacer which might fall off. Do not lose it. Mine stayed sticked to the transfer case all the time but yours could fall, so be careful. See photo.
Left upper side shows the pump with the metal ring sticked to it in my case. In your case it could be on the other half of the pump or even on the floor, so be careful.
7. The photo below will show the back of the T-case. The big brown disc inside is the VC. Be careful while pulling the back of the case, as it is quite heavy due to the VC. The other half of the pump (with rotor) is also visible.
8. Now comes the most frustrating part !!! There is a C-clip that holds the VC on the shaft. Too bad the clip is surrounded by the VC flange, too bad the clip is quite hard, too bad the clip has no holes like most C-clips, too bad you have to remove it. You will be my guru if you do it in 20 minutes. I bet it will take you longer. I had to bend mine pretty badly to remove it, see below.
So once you remove the C-clip you can slide the VC off with ease. Damn heavy...
9. Make sure you wipe the mating surfaces with a paper towel. Use a nylon sponge (the hard type) to remove any gasket residue on the mating surfaces.
10. Apply gasket material (RTV silicone or similar) to one of the surfaces. Make sure to make a continuous path of silicone. Do not surround the bolts but make it on the inner side of the bolt holes, you don't want oil to leak through the bolt holes.
11. Put the case back on and tighten the bolts with little force. Before that make sure you align the pump rotor (tab) with the groove on the other half of the T-case. After a while tighten the bolts with proper force. Do not tighten them one by one in series but tighten them across the case to avoid any stress. Do not use too much brute force. Remember that you are working on aluminum and you don't want to snap any threads.
12. Put back all the electrical connectors.
13. Put back the driveshaft.
14. Use thread locker (Loctite or similar) on the driveshaft screws and nuts. I had no Loctite ('ve lost it somewhere) so I soaked the threads in paint. A worse solution (redneck-like) but better than nothing.
15. Plug the bottom of the T-case
16. Unplug the filler hole.
17. Fill with gear oil. You will have to use your intelligence here, as it is not so easy to fit a bottle over that hole. Use a special syringe or some other method. Feel free to experiment.
Inspect everything to make sure you have not missed any screws.
Enjoy.
I hope you enjoyed the tutorial.
Feel free to ask any questions.
Mike
First of all when I made turns, for example, in a parking lot, I heard my tires scrub against concrete and one of the wheel stopped turning intermittently to relieve the stress on the drivetrain. Please note that my tires weren't squeaking but really dragging to the point that the truck would not roll while making a turn. Instead, it behaved as if the parking brake were applied. If your tires just squeal, especially on the slick kind of concrete found in shopping malls, then the VC (viscous coupler) is not your problem. Another way to find out if your VC is dead is to raise one wheel (tranny in N, transfer case in N). In the N/N position the wheel should move rather freely when you rotate it by hand. If you lock the center differential the wheel should not move (it might have play but you definitely can't make turns).
What can be the cause of the VC seizing?
The most often mentioned cause is running tires of different sizes. This causes the VC to operate all the time, heat up and seize permanently. I will not discuss the principles of the VC as this can be found in other threads and has already been explained extensively. In other words, the PO of my truck must have been a dummy and killed even such a friendly and simple device as the VC.
What can a seized VC damage?
First of all, a seized VC acts as a permanently locked differential. So when you drive in a straight line nothing happens but once you turn, even a little bit, the differences in tire rotation are not absorbed by the center diff but transferred onto all the drivetrain components. This puts enormous stress on your axles, driveshafts and all differentials. This, in turn, speeds up wear and sometimes may even break an axle or grind teeth in a diff. Such damage will surely cost you lots of time and $$$.
What does the VC give me?
It acts as a 'semi-locked' center differential. It means that if one axle loses grip, the engine torque is gradually transferred onto the other one. This is good not only for off road but also icy, snowy or wet roads. It's a kind of primitive traction control. Maybe 'primitive' is a bad word, as the VC is quite piece of engineering and craftsmanship, very simple but quite effective.
What will I get when I remove the VC?
I will simply get an open center differential. One can drive without the VC indefinitely and this will do no harm to absolutely anything.
PREPARATION FOR THE OPERATION.
You will need...
--- a garage where you have easy access under the truck.
--- 4 or 5 hours (if you do it alone)
--- a set of professional wrenches (very important, read further about it)
--- a 2ft steel tube to give leverage to your wrenches
--- a penetrating oil spray to loosen stubborn rusted nuts
--- gear oil if you don't plan to use the old one
--- RTV silicone or any kind of gasket material
--- a hard nylon sponge from your kitchen.
--- a file
--- a thread locker or at least dense paint if you want to lock the threads the redneck way (like me)
--- at least 4 kinds of snap ring pliers, you never know which will work for you
--- at least three flat screwdrivers of different sizes, including one which is very wide and hard
--- lots of paper towels or simply toilet paper
--- a camera or paper and pencil
--- a big syringe or pump to fill the differential with oil
--- patience
--- anything else that you will find necessary
1. Start with disconnecting the rear driveshaft. It is held by four screws, which you have to spray a bit to reduce friction and facilitate unscrewing. This is absolutely the point where you need the best quality wrenches. These nuts transfer big forces so they are really tight. The size of the nut is 14mm (as far as I remember) and you will probably have to use the steel tube for leverage. Chock the wheels to prevent the truck from moving. In my case, the small 14mm wrench had to withstand a 2ft leverage and a 160lb guy hanging on the end of it with full weight. A cheap wrench will snap right away causing danger or will deform itself and round the nut edges (say bye bye to driveshaft removal). So remember to use good stuff here.
2. Once the nuts are off you can pull the driveshaft away from the transfer case flange. If you have greased the shaft regularly it will probably be full of grease and won't retract. It this case you will have to remove the grease port on the shaft and use a big screwdriver to separate it from the flange. Use a file to scratch the flange and shaft joint to make sure you put it back in exactly the same orientation. Use a cord or wire to attach the shaft to the frame or exhaust tube, so that it doesn't hang around and make your work difficult.
Photo of rear of transfer case with driveshaft removed and attached to muffler.
3. Disconnect anything that connects to the back of the T-case. These will be...
a) speedometer cable which is in the middle of the photo below. This is a socket, so don't try to rotate anything, just lower the rubber boot, press the tab and pull.
b) grounding cable, seen below speedometer cable and a bit to the left.
c) two electrical plugs on top of back of T-case, not seen on the photos but easy to find. Mine snapped off with ease (remember to press the locking tabs) and probably yours will also be easy.
d) there might be some other stuff connected by previous owners so inspect the back of the transfer case.
Here you can see speedo cable, ground cable, drain plug on bottom, fill plug on upper left.
4. Drain the T-case. On the very bottom there is a plug (24mm). Put a socket wrench and loosen it. Loosen it further by hand. Negative pressure will prevent ani oil from leaking, so hold the plug firmly. When the thread ends it will pop off, and together with it a stream of oil, so have a container ready. Make sure the container is near to the opening as the oil is dense and it could drag itself in different directions. It will drain like this for at least 10 minutes and some dripping will continue for the next 4 hours (it means it's going to spill oil until you close the T-case again). Let it drain and have a break, dring a juice and eat a sandwich.
5. Loosen and remove the bolts that surround the T-case. You will have 9 bolts of different sizes, so remember to put them on the floor in order and take a note of them or take a picture like I did. This is to ensure that if you accidentally move the bolts around, you will be able to retrieve their original position.
Photo of bolts in the right order.
6. Now you have to separate the back of the T-case from the rest. You can use some sophisticated pullers and try to separate it, but you can also go the 'brute-dummy' way and simply point a flat screwdriver to the edge and bang it with a hammer. You will end up with a few dents on the mating surfaces, but you can tap them back to flatness with a hammer. Wiggle the screwdriver around to make sure you gave a gap everywhere. Remember to do it alternatively on both sides (left-right-left-right...) of the case. At this point you should be careful as the oil pump inside the case has a round metal spacer which might fall off. Do not lose it. Mine stayed sticked to the transfer case all the time but yours could fall, so be careful. See photo.
Left upper side shows the pump with the metal ring sticked to it in my case. In your case it could be on the other half of the pump or even on the floor, so be careful.
7. The photo below will show the back of the T-case. The big brown disc inside is the VC. Be careful while pulling the back of the case, as it is quite heavy due to the VC. The other half of the pump (with rotor) is also visible.
8. Now comes the most frustrating part !!! There is a C-clip that holds the VC on the shaft. Too bad the clip is surrounded by the VC flange, too bad the clip is quite hard, too bad the clip has no holes like most C-clips, too bad you have to remove it. You will be my guru if you do it in 20 minutes. I bet it will take you longer. I had to bend mine pretty badly to remove it, see below.
So once you remove the C-clip you can slide the VC off with ease. Damn heavy...
9. Make sure you wipe the mating surfaces with a paper towel. Use a nylon sponge (the hard type) to remove any gasket residue on the mating surfaces.
10. Apply gasket material (RTV silicone or similar) to one of the surfaces. Make sure to make a continuous path of silicone. Do not surround the bolts but make it on the inner side of the bolt holes, you don't want oil to leak through the bolt holes.
11. Put the case back on and tighten the bolts with little force. Before that make sure you align the pump rotor (tab) with the groove on the other half of the T-case. After a while tighten the bolts with proper force. Do not tighten them one by one in series but tighten them across the case to avoid any stress. Do not use too much brute force. Remember that you are working on aluminum and you don't want to snap any threads.
12. Put back all the electrical connectors.
13. Put back the driveshaft.
14. Use thread locker (Loctite or similar) on the driveshaft screws and nuts. I had no Loctite ('ve lost it somewhere) so I soaked the threads in paint. A worse solution (redneck-like) but better than nothing.
15. Plug the bottom of the T-case
16. Unplug the filler hole.
17. Fill with gear oil. You will have to use your intelligence here, as it is not so easy to fit a bottle over that hole. Use a special syringe or some other method. Feel free to experiment.
Inspect everything to make sure you have not missed any screws.
Enjoy.
I hope you enjoyed the tutorial.
Feel free to ask any questions.
Mike
