The Quadratrac transfer case is a very unique piece of equipment. It was the first chain driven transfer case, which led to the development of all other such transfer cases. This led to the AWD craze in vehicles today.
The Quadratrac transfer case contains an internal differential that allows it to transfer power to either axle as is needed. (AWD) The switch found in the glove box is a vacuum switch that locks the differential forcing power to both axles equally. This should only be done off-road. in snow, in mud, etc. to prevent the damage of the internal of the transfer case. TCL-1 fluid is the only fluid to be used in the transfer case.
The Quadratrac is only found in
CJ7's from 1976 to 1979. FSL (full size Jeeps) had it during this time frame too. The
CJ7 was designed so that an automatic transmission could be an option for the first time in a CJ. From 1980 to 1986 a Chrysler transmission was used with the DANA 300 as the transfer case. '76 to '79 the TH400 was used. The first TH400's were either Chevy or BOP transmissions used with an adapter plate to bolt to the AMC engines. These were found mostly in the FSJ. In my case however, I have this setup in my
CJ7. Shortly after the first automatic transmissions came out the TH400 was produced specially for AMC with a different bell housing. For more information see my article:
http://www.jeep-cj.com/forums/f2/jeep-th400-technical-information-24384/
At some point Mile Marker developed a part-time kit for the Quadratrac. This removed the internal differential and replaced it with a solid gear. They also included lock out hubs for the front axle. This kit turned the transfer case from an AWD to a full / part-time case. It also allowed the use of ATF instead of the TCL-1 fluid. Moving the vacuum switch to the emergency mode locked the gearing into full time 4 wheel drive. Front hubs also needed to be locked in.
To use the part-time kit, lock front hubs, move the vacuum switch to the emergency position. You are now in 4 wheel drive. Do the reverse to go back to 2 wheel drive.
How do you know if you have the part-time kit installed. PO's can do some crazy things. Some put locking hubs on the front axle without the part-time kit. This only wears and damages the internal differential. So start by jacking the Jeep up and put jack stands on all four corners. Lock the front hubs. Make sure the vacuum switch is in the normal position. Start the Jeep up and give it a little gas. If only the rear wheels turn, you have a part-time kit. If however the front and rear wheels turn, you do not have the part-time kit. Please make sure your vacuum switch is working first.
You should also have a lever under the front of the driver's seat. This is for the low range unit. All the way forward is no low range, half way back is neutral, and all the way back is low range. This can be used in 2 wheel drive. You do not have to be in 4 wheel dive or the emergency switch engaged to use low range. If you do not have this lever, look underneath your Jeep. If you have the low range you should see this big round housing attached to the driver's side of the transfer case.
If you only have a round cover, you do not have low range:
There is only one supplier of USA made parts for the Quadratrac:
BJ's Off-Road All other chains and parts are made in China and are made from cheep steal. The will last maybe 15,000 miles. A good USA chain should last 30,000 to 40,000 miles with proper care.
Have you checked the amount of slack in your chain lately? Do What?
Put something under the transmission to support it. Remove the skid plate. On the bottom of the transfer case is a pipe plug. Remove this and drain the fluid. Not insert a screwdriver until you push on the chain. Measure the amount of travel. 1/4 to 1/2 inch is ok. Anything 1/2 inch and over requires a new chain. This is one of the biggest failure point in the transfer case. Keeping a good chain in is a must. But only a USA chain. Now replace the fluid you drained out with new fluid. If you have a low range unit, fill it first, then then main body of the transfer case.
Here are some links you can read for more information:
Jeep QuadraTrac
Removal, disassembly, assembly and re-installation of a Quadra-Trac transfer case in an SJ series truck.
Quadra-Trac Transfercase Rebuild - Jp Magazine
QuadraTrac BW1339-BW1305 Parts
Good luck and be sure to ask questions. This was a lot of information to absorb at one time. Rod