Posted by Clint Dixon on Friday, April 15, 2005 at 1:21PM :
For 25 years now I have been dealing with a transfer case in my '47 WDX that leaks terribly. For the first 12 years, the original leather oil seals were still in place. They leaked bad enough that I wanted to replace them, but not bad enough to drench the underside of the truck.
In 1992, I completely rebuilt the case with new bearings, seals, and wear sleeves on the companion yokes. I used Chicago Rawhide single lip seals and they lasted for about two years. I am no longer a fan of single lip oil seals, especially the wimpy ones from Chicago Rawhide. The seals gradually leaked worse over time until last year when they got so bad that gear lube was entering the cab under the seat. I replaced these with NOS neoprene seals dated from the middle 1970's. These seals were very heavy duty and looked to be an exact replacement for the old leather ones and the wipers were supple. The wear sleeves were still very good, showing no visible wear, and were not replaced. These NOS seals worked perfectly for about 6 months. Now, they have failed and gear lube leaks steadily from the transfer case even while the truck sits for a week at a time. Gear lube is entering the cab again.
Local companies really don't want to sell National Seals. They all try to push Chicago Rawhide. I have had good success with National double lip reinforced oil seals in other applications in the past, so I researched these for use in the NP200 transfer case. I found several possibilities that are sized properly for the companion yokes and housing bores:
470308N is a double lip non reinforced seal made from Polyacrylate high temperature material. It has a width of .005 compared to the .687 of the original Dodge leather seal. Unfortunately this is not a stock item and generally not available in small quantities.
410308 is a double lip reinforced Neoprene seal with a .500 width.
473468 is a double lip non reinforced Neoprene seal with a width of .375.
I ordered eight of the 473468 and plan to stack two of these in each housing bore. The combined width will be only 1/16" greater than the original Dodge seal.
All bearings in this case are still very good, and the preloads are correct. It has always run hot enough that I can touch it but not hold my hand on it for any length of time.
Would anyone else have any comments/concerns/advice on what I plan to do?
Thanks,
Clint
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