8N rear axle bearings.

[Southernspeed]

I need some advice from those in the know!
I’ve just installed new axle bearings ( ‘51 8N), both sides and setting the preload.
I shimmed it right to the point where one axle stayed stationary when I turned the other ( it didn’t rotate in the same direction as the book suggests). It seemed so tight I didn’t want to go tighter to find the point where they both turned in the same direction. I then added shims until they turned in opposite directions but they are still ( seemingly) very tight to turn. I can only just turn them by hand ( holding onto bare axle shaft, no extra leverage from hub etc)
Does this sound right?
I realise that with a big diameter, heavy wheel on, they’ll turn easily but I don’t want to burn the bearings out. I’m used to taper roller bearings typically having some free play.
Your wisdom please!

 

[D'oh]

8N rear axle Seals leak easily, I have replaced many, but 35 years ago. But I don;t ever recall tightening the Bearing Nut any tighter than the bearing rolling in the Housing. Not hard turning or resistance. Like any other Wheel Bearing

Mind you, we did it with a Homemade Spanner Wrench

 

[John0829]

The final spec for the bearings are .002 - .004 of clearance. You are probably within that spec if you can turn them by using your hand. If it really concerns you add a thin shim, this is a low speed application and a tiny bit of extra clearance won't hurt a thing.

 

[EdGooding]

You are actually aiming for zero load here and that's hard to gauge. I'm with John - you are better off if it is a tad loose than tight. Too tight will destroy the axle bearings. I also recommend that you reassemble with some Permatex Ultra Blue silicone RTV on all flange faces and wherever grease could leak out. The Permatex No.2 non-hardening form-a-gasket works fine, too. Don't goop it on, just use it sparingly to seal the surface.

 

[John0829]

Ed is right about adding some sealant to the mating surfaces, I prefer #2 Permatex. Make sure you use the thinnest of thin coats.

I stay away from RTV, it has its uses like valve covers, oil pan, ect. but I do not like around things with close tolerances. If it cures the least little bit before you get it reassembled the skim it creates can/will change your shim pack clearance you have worked so hard to get. Granted only by a few thousands, plus most people use to much, so it gets places it does not belong.

 

[EdGooding]

Ed is right about adding some sealant to the mating surfaces, I prefer #2 Permatex. Make sure you use the thinnest of thin coats.

I stay away from RTV, it has its uses like valve covers, oil pan, ect. but I do not like around things with close tolerances. If it cures the least little bit before you get it reassembled the skim it creates can/will change your shim pack clearance you have worked so hard to get. Granted only by a few thousands, plus most people use to much, so it gets places it does not belong.

Agree on the #2 Permatex. I know a number of people who have used the blue RTV and been satisfied with the result, but I've been a fan of #2 since my days working on air-cooled VW engines. I used #2 to seal the case (block) when reassembling and never had a leak.

 

[Southernspeed]

Well after several dry test assemblies I put sealant on the shims last night and bolted them down. It was as the factory said "when they turn opposite directions, the clearance is correct" (words to that effect) but checking it this morning and barely being able to turn it by hand, I'm going to pull it apart and add another shim. I really don't like the idea of the bearings being that tight. I'll see what one more does and report back. Thanks for the comments.

 

[Southernspeed]

I took one side off (the first side I did that only had the two necessary shim/gaskets in. Of course, one tore and I only had one spare new one but luckily one of the original steel shims was still usable. Now there is a light drag when you turn but much smoother and easier and no perceivable end play. I think that'll do. I'll see what it's like with the wheels on but I have to fit new tires first.... not today though as it's 100 degrees and very humid!