DonW wrote:The front input shaft bearing is now getting expensive. There is an alternative which is just as capable as the original, and also allows a standard 25 x 40mm front seal to be used instead of the factory 26.5 x 40mm seal. I can give you details if you're interested. I used an aftermarket Viton front seal as it copes with the heat better than nitrile does. Nitrile is the seal material most bearing houses sell, and it's designed to work to a 120C limit. Regular exposure to that limit shortens the seal's lifespan, while Viton is good to 180C.
I'm interested... Also interested in the source for Viton seals
thanks,
don
OK Don, there's a lot of numbers and dimensions coming your way. Here goes . . .
The following photo shows the standard OEM setup in three steps. On the left is the input shaft complete with the helical gear and bearing outer race, the middle shaft has the standard bearing inner race, and the shaft on the right is bare.
The next photo shows the standard OEM bearing on the right, with the inner race beside the outer race. On the left is an SKF NJ204E C3 with it's inner race beside the outer race. The outer races are identical with each other, but the inner races are different.
This photo shows the difference in length between the OEM inner race and the SKF inner race, as measured with my metric micrometer.
This last photo shows the inner ring which is used as a spacer to position the input shaft correctly. The OEM inner ring has a 26.5mm OD, which is why the front oil seal has a 26.5mm ID. The inner ring I use has a 20mm ID and a 25mm OD. It is available in different lengths for various applications, but I've found the 20.5mm length to be the most readily available in my neighbourhood. The shorter the better, as that means there's less to grind off the end. The desired length is 9.50mm based on my measurements, but you'd be advised to double-check this for yourself.
Why would anyone bother doing this? The reason is that the aftermarket NJ204 bearing is between a third and a quarter the price of the OEM bearing, and that's the prime reason for me. The advantage of being able to use an off-the-shelf oil seal is appealing too, especially because 25 x 40 x 7mm seals are available in Viton as mentioned earlier. Subsequent gearbox rebuilds will only require the bearing to be replaced, not the spacer. The cost saving doesn't create any compromise in terms of function, durability or lifespan IMHO.
I've noticed that the r/h part of the photos have been cut off, but I've also noticed that if i right-click and select "show image", the complete photo is shown. Bit of a PITA, sorry.
