Sealed bearing in gearbox

Kvinnhering · Apr 5, 2020

Hi Gentlemens. I am overhauling the gearbox on my commando. New gears and bearings.
I wonder if the seal in the bearing should be facing the oil in the gearbox or should be out towards the sealing ring on the primary side? The bearing is pre lubricated from Andover. Anyone can come up with the correct answer?

concours · Apr 5, 2020

Seal out.

Tornado · Apr 5, 2020

Since the GB is spraying lube all around, having the seal on the bearing facing the spray side would prevent bearing getting constant lube. Makes sense to let the lube reach the bearings even if it is considered pre-lubed. I think Mick Hemmings mentions in his GB rebuild DVD the seals can/should be removed from gearbox sets.

ILLF8ED · Apr 5, 2020

Just did this same bearing on my ‘69 project and came to the conclusion mentioned. Sealed side outward.

ILLF8ED · Apr 5, 2020

Roller layshaft bearing while you’re in there?

Kvinnhering · Apr 5, 2020

illf8ed said:
Roller layshaft bearing while you’re in there?

Yes of course.

I agree that the seal should be towards the primary side. What made me unsure was that the bearing was pre-lubricated with grease from AN.

dave M · Apr 6, 2020

I’m sure Andover don’t make these bearings, so they are probably Sealed by the manufacturer as all sealed bearings are.

baz · Apr 6, 2020

We've had this question before about seals on bearings (if the bearing were sealed both sides)
One theory suggests the grease in the sealed bearing is sealed for life and suppose the bearings design life was say 100,000 do you really want to take the seals off and introduce oil?
IE the oil in an overstressed commando gearbox can have debris in that would enter the bearing?
Or would that oil make the bearing last longer / run cooler etc I really don't know
I guess you'd need to know the loading/design life of the bearing?

Peter R · Apr 6, 2020

Remove the seal at the inboard side of thr gearbox. I learned the hard way that leaving the seals in on both sides is a bad idea.

Fast Eddie · Apr 6, 2020

Peter R said:
Remove the seal at the inboard side of thr gearbox. I learned the hard way that leaving the seals in on both sides is a bad idea.

Why Pete, what happened ?

Onder · Apr 6, 2020

The bearing probably is speced out for stuff like rpm and heat. How hot can the 2RS bearings go? I know the specs for sealed bearings, or most anyway, is lower than unsealed.
Yes, what happened?

Peter R · Apr 6, 2020

Fast Eddie said:
Why Pete, what happened ?

After some time the grease disappeared from the bearing, and the bearing felt very rough, due to lack of lubrication, it lasted less than approx. 3000km.

baz · Apr 6, 2020

Peter R said:
After some time the grease disappeared from the bearing, and the bearing felt very rough, due to lack of lubrication, it lasted less than approx. 3000km.

Sounds pretty conclusive
Did you peel a side off to see it had no grease?

Tornado · Apr 6, 2020

Peter R said:
After some time the grease disappeared from the bearing, and the bearing felt very rough, due to lack of lubrication, it lasted less than approx. 3000km.

Sealed bearings are aimed at places like wheel hubs and such, as maintenance access is few and far between and outside contaminants a real issue. Hard to see how a sealed bearing that lasts for 50k+ miles in the wheel hub can't take 3k in a GB.

Peter R · Apr 6, 2020

baz said:
Sounds pretty conclusive
Did you peel a side off to see it had no grease?

Yes , bearing was dry inside, and felt rough, replacement bearing fitted with inner seal removed, and had no problems eversince.

baz · Apr 6, 2020

Peter R said:
Yes , bearing was dry inside, and felt rough, replacement bearing fitted with inner seal removed, and had no problems eversince.

Brilliant info thank you
I wonder how the grease got out?

seattle##gs · Apr 6, 2020

perhaps the bearing was sealed on both sides and the shop you purchased it from removed one side.

Triton Thrasher · Apr 6, 2020

Bearings in the gearbox are lubricated by gearbox oil. A sealed-in packing of grease will fail.

Madnorton · Apr 7, 2020

If the bearing seal is rubber with steel insert, remove it. If it just a rubber dust seal you can leave it. There is a difference between shielded and sealed.

Kvinnhering · Apr 7, 2020

Madnorton said:
If the bearing seal is rubber with steel insert, remove it. If it just a rubber dust seal you can leave it. There is a difference between shielded and sealed.

I have now installed the bearing with the seal out towards the primary. The bearing has only a rubber seal on one side.

Sealed bearing in gearbox

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