Attention: TDR Forum Junkies 
WARNING Cast Iron NV4500 Rear Housing
If you have one of the cast iron rear housings for the NV4500, you have cause for concern. I don’t know if they are all machined off location, but the three I bought and the fourth that came on a rebuilt transmission were all the same distance off-center. On my transmission, it caused it to pump the oil from the transmission into the transfer case, burning up the gears in the transmission and pumping all of the metal chips through the transfer case.
The four covers I checked, were from . 028” to . 036” off location. This causes a severe bind in the rear transmission bearing and the front transfer case bearing. This translates to excessive heat, which causes failure of the seals in both the transfer case and the NV4500, pumping the oil from the NV4500 into the transfer case.
My transmission ran about 6,000 miles total before this happened. At the end of a 900 mile highway run, it generated enough heat to cause total seal failure. Because of my problem, we pulled the cover from a truck with 3,000 short trip miles on a freshly purchased rebuilt from a company that advertises here on TDR. The cover was found to have the same defects, but there was no apparent harm done other than the oil in both the transfer case and the transmission showing signs of extreme heating.
I repaired these housings by boring the alignment bore ¼” oversize and inserting a ring, then re-boring that to the correct diameter and location. I also had to re-bore the seal diameter. The seal diameter was machined to mate with the alignment bore and was basically off the same amount. I corrected this with a larger seal in a new hole bored correctly.
There is another issue with three ribs on the input seal holder of the transfer case, which prevents the transfer case from being completely pulled into position against the face of the cast iron adapter. The last ¼” of these three ribs contacts the flat area at the bottom of the bore and if not removed, they will be flattened (crushed) by tightening the six nuts that hold the transfer case in position.
This problem is not something you can see without setting the housing on a bare transmission case, finding the location of the rear bearing bore, then bolting the housing to the back of the case and indicating the transfer case alignment bore.
Please see the link at the end of this post so you can see an AVI movie of the way I check for the defect. If you have dial up, these files are very large and will take a long time to download. These movies clearly show the errors in the original machining of these units. You can see in the second movie, that in addition to having the bore done off location, there is severe taper to the bore. This makes the cast cover extremely difficult to mate to the transfer case.
It is likely that all of the NV4500 cast iron rear housings came from the same point of origin. Do yourself a favor and check your transmission if you are using the cast iron housing. If you have one installed, make sure you check the transfer case to ensure no leakage of gear oil into it. If this happens in the cold weather, you not only risk damage to your transmission, but also destroying the transfer case due to failure of the delicate oil pump…(which is not designed to pump anything but ATF. )
http://users.rcn.com/jvssyn/DSCF0167.avi
http://users.rcn.com/jvssyn/DSCF0168.avi
You can click on the links above to view the videos.
If you have one of the cast iron rear housings for the NV4500, you have cause for concern. I don’t know if they are all machined off location, but the three I bought and the fourth that came on a rebuilt transmission were all the same distance off-center. On my transmission, it caused it to pump the oil from the transmission into the transfer case, burning up the gears in the transmission and pumping all of the metal chips through the transfer case.
The four covers I checked, were from . 028” to . 036” off location. This causes a severe bind in the rear transmission bearing and the front transfer case bearing. This translates to excessive heat, which causes failure of the seals in both the transfer case and the NV4500, pumping the oil from the NV4500 into the transfer case.
My transmission ran about 6,000 miles total before this happened. At the end of a 900 mile highway run, it generated enough heat to cause total seal failure. Because of my problem, we pulled the cover from a truck with 3,000 short trip miles on a freshly purchased rebuilt from a company that advertises here on TDR. The cover was found to have the same defects, but there was no apparent harm done other than the oil in both the transfer case and the transmission showing signs of extreme heating.
I repaired these housings by boring the alignment bore ¼” oversize and inserting a ring, then re-boring that to the correct diameter and location. I also had to re-bore the seal diameter. The seal diameter was machined to mate with the alignment bore and was basically off the same amount. I corrected this with a larger seal in a new hole bored correctly.
There is another issue with three ribs on the input seal holder of the transfer case, which prevents the transfer case from being completely pulled into position against the face of the cast iron adapter. The last ¼” of these three ribs contacts the flat area at the bottom of the bore and if not removed, they will be flattened (crushed) by tightening the six nuts that hold the transfer case in position.
This problem is not something you can see without setting the housing on a bare transmission case, finding the location of the rear bearing bore, then bolting the housing to the back of the case and indicating the transfer case alignment bore.
Please see the link at the end of this post so you can see an AVI movie of the way I check for the defect. If you have dial up, these files are very large and will take a long time to download. These movies clearly show the errors in the original machining of these units. You can see in the second movie, that in addition to having the bore done off location, there is severe taper to the bore. This makes the cast cover extremely difficult to mate to the transfer case.
It is likely that all of the NV4500 cast iron rear housings came from the same point of origin. Do yourself a favor and check your transmission if you are using the cast iron housing. If you have one installed, make sure you check the transfer case to ensure no leakage of gear oil into it. If this happens in the cold weather, you not only risk damage to your transmission, but also destroying the transfer case due to failure of the delicate oil pump…(which is not designed to pump anything but ATF. )
http://users.rcn.com/jvssyn/DSCF0167.avi
http://users.rcn.com/jvssyn/DSCF0168.avi
You can click on the links above to view the videos.
Last edited by a moderator:
:-laf ) and she had heard of the issue and said it has been fixed for sometime now and had actually sold about 30 of those cast pieces just this week. None have called with any issues, but I am kinda weary of this as, I think they are just trying to sell the product and those whom have recently purchased it haven't reached the problem yet since it isn't exactly and external leak that can be caught. 
