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Originally I was "2caseB2" on this forum. The write up on the tech board of the cable shifted 1354 transfercase doubler is mine. I took that doubler out for some updates and repairs and I needed to replace my old 1350 transfercase with a 1354 so I could have a decent front driveshaft. Since the doubler was orginally built I have changed from a 2.9L to a 5.0L HO, I went from 33" tires to 35" tires, The rear 7.5" trac loc is now a Explorer 8.8 with a Electric locker, and the open Dana 30 Jeep straight axle has been replaced with narrowed D44 with cromo shafts and an electric locker as well. These are the problems and solutions I found in regard to the 1354 doubler in the last 8 years.
-The weak spot in these is the "spud shaft" that goes between the 2 units. I broke mine early on. My quick fix turned into an 8 year solution. The diameter of the input shaft that goes into the transfercase is just under 1" at the root of the splines, and that is where mine broke. My weld fix was just to weld the custom short doubler output shaft directly to the stock transfercase input shaft. It seems crude and it means you can't change the transfercase input shaft bearing or seal. But you end up welding a 1.6X" diameter shaft because you now get to use the outside diameter of the transfercase input shaft not the inside spline diameter. from 1" to 1.6" is a notable diameter and strength increase.
-The second problem I found was my vacuum shifted cable was not ideal, so I made a shifter to work on the end of the cable. Ideally I would not start with an electric shifted case again. A mechanical shifted case would be a better starting point, a cheap 1350 would work fine.
-I had oil leaks at many places and found careful cleaning and liberal use of Ultra Grey silicon to be a good fix.
-An interesting problem when used in the long term is the oiling of the doubler planetary. In the middle of the planet is a needle type support bearing that is spinning on the doubler output shaft when the doubler is in low. This bearing is normally oiled down the center of the shaft from a transfercase oil pump. The splash oiling system does not do a very good job of oiling this bearing, my shaft was turning color and the 80W90 gear oil around this area was burnt. My solution is a little complicated. But basically because I welded my doubler output shaft to the input shaft of my t-case I was able to leave the middle hollow as it was originally. I then knocked a hole in the transfercase output shaft plug (there is oil pressure inside the main shaft of these transfercases). The Rear transfercase oil pump now feeds down the center of the shaft and feeds the transfercase planetary and doubler case planetary. There is no longer a seal between the doubler and transfercase and I drilled some oil return holes in the lower edge of the front flange of the transfercase. So the doubler and the transfercase now share the same oiling system, and the both enjoy pressure lube to the planetaries.
-I also was worried about the forces being put into the actual cases and my way of hooking the doubler to the transfercase was not as strong as what is out there now, so I made a brace that bolts to the transmission mount point, then to the doubler to transmission mounting flange, then to the lower side of the doubler, and then finally to the transfercase under the output shaft to the front driveshaft.
This may be to much information but I see lots of ideas and projects on forums and am often courious how they ended up. So I figured I would update this one.
-The weak spot in these is the "spud shaft" that goes between the 2 units. I broke mine early on. My quick fix turned into an 8 year solution. The diameter of the input shaft that goes into the transfercase is just under 1" at the root of the splines, and that is where mine broke. My weld fix was just to weld the custom short doubler output shaft directly to the stock transfercase input shaft. It seems crude and it means you can't change the transfercase input shaft bearing or seal. But you end up welding a 1.6X" diameter shaft because you now get to use the outside diameter of the transfercase input shaft not the inside spline diameter. from 1" to 1.6" is a notable diameter and strength increase.
-The second problem I found was my vacuum shifted cable was not ideal, so I made a shifter to work on the end of the cable. Ideally I would not start with an electric shifted case again. A mechanical shifted case would be a better starting point, a cheap 1350 would work fine.
-I had oil leaks at many places and found careful cleaning and liberal use of Ultra Grey silicon to be a good fix.
-An interesting problem when used in the long term is the oiling of the doubler planetary. In the middle of the planet is a needle type support bearing that is spinning on the doubler output shaft when the doubler is in low. This bearing is normally oiled down the center of the shaft from a transfercase oil pump. The splash oiling system does not do a very good job of oiling this bearing, my shaft was turning color and the 80W90 gear oil around this area was burnt. My solution is a little complicated. But basically because I welded my doubler output shaft to the input shaft of my t-case I was able to leave the middle hollow as it was originally. I then knocked a hole in the transfercase output shaft plug (there is oil pressure inside the main shaft of these transfercases). The Rear transfercase oil pump now feeds down the center of the shaft and feeds the transfercase planetary and doubler case planetary. There is no longer a seal between the doubler and transfercase and I drilled some oil return holes in the lower edge of the front flange of the transfercase. So the doubler and the transfercase now share the same oiling system, and the both enjoy pressure lube to the planetaries.
-I also was worried about the forces being put into the actual cases and my way of hooking the doubler to the transfercase was not as strong as what is out there now, so I made a brace that bolts to the transmission mount point, then to the doubler to transmission mounting flange, then to the lower side of the doubler, and then finally to the transfercase under the output shaft to the front driveshaft.
This may be to much information but I see lots of ideas and projects on forums and am often courious how they ended up. So I figured I would update this one.
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