Technical Which way around?

[cinque500]

Evening all. I’ve got a new pinion bearing for my gearbox and I don’t know if the writing should face inwards or towards the diff?

 

[bugsymike]

Evening all. I’ve got a new pinion bearing for my gearbox and I don’t know if the writing should face inwards or towards the diff?

I know this data is for a different part number, but it gives a picture that may show the wider part of the outer as a guide.
I work on the principle that the thicker part of the outer bearing ring goes into the hole up to it's stop as with that design normally the inner race can be slid in afterwards and the locking nut is in effect holding the inner bearing tight into the ouiter race if that makes sense.
So if looking at the picture below with this design I would say the locking nut goes on the left side where the capital D is.
I have used this method on ball bearing races as well as tapered in wheel hub bearing applications and none have failed.
Looking at your photo of new bearing it looks like it has a circlip holding it togethe, so implying that the inner race is pushed into the outer from that side, similar to the photo /picture below.
Again looking at my picture, I would expect your bearing to be driven into the casing up to a stop machined in the housing and that the shaft wwith it's gears , thrust washers etc. would come in from the right hand side, the the axle pinion in your other post would be on the right hand side of this picture.
Obviously confirmation from another source would be helpful.
Are you able to look at the old bearing or is there doubt as to if it was fitted correctly before.

 

[cinque500]

I know this data is for a different part number, but it gives a picture that may show the wider part of the outer as a guide.
I work on the principle that the thicker part of the outer bearing ring goes into the hole up to it's stop as with that design normally the inner race can be slid in afterwards and the locking nut is in effect holding the inner bearing tight into the ouiter race if that makes sense.
So if looking at the picture below with this design I would say the locking nut goes on the left side where the capital D is.
I have used this method on ball bearing races as well as tapered in wheel hub bearing applications and none have failed.
Looking at your photo of new bearing it looks like it has a circlip holding it togethe, so implying that the inner race is pushed into the outer from that side, similar to the photo /picture below.
Again looking at my picture, I would expect your bearing to be driven into the casing up to a stop machined in the housing and that the shaft wwith it's gears , thrust washers etc. would come in from the right hand side, the the axle pinion in your other post would be on the right hand side of this picture.
Obviously confirmation from another source would be helpful.
Are you able to look at the old bearing or is there doubt as to if it was fitted correctly before.
View attachment 475758

Thanks Mike. I’m still not sure though, the bearing has a circlip on both sides and the inner and outer races are the same respective thickness both sides visually, albeit I haven’t got my gauge on it yet. The other thing is the bearing does rattle a bit - so going back to fundamentals am I still right to assume it is indeed a taper bearing that needs preloading, which I know you also think, as unfortunately on previous post no one confirmed?

 

[fiat500]

Thanks Mike. I’m still not sure though, the bearing has a circlip on both sides and the inner and outer races are the same respective thickness both sides visually, albeit I haven’t got my gauge on it yet. The other thing is the bearing does rattle a bit - so going back to fundamentals am I still right to assume it is indeed a taper bearing that needs preloading, which I know you also think, as unfortunately on previous post no one confirmed?

I've a feeling that this bearing "floats" in the housing, and is plain rollers. So, notwithstanding the good advice above, it's probable that the orientation is irrelevant in this case.

It all goes back to the back that each pinion shaft and gearbox housing had to be set up at the factory, and would normally need a number of shims behind that bearing. These "push" the pinion forward to the exact location for perfect alignment with the crownwheel. Consequently, the bearing can't be in a fixed position, and finds its correct location once all the gears and bushes are fitted to the shaft, and the front bearing is locked in place with its plate, and the external gears are locked up with the nut.

I don't think it matters which way the bearing faces.

 

[bugsymike]

I've a feeling that this bearing "floats" in the housing, and is plain rollers. So, notwithstanding the good advice above, it's probable that the orientation is irrelevant in this case.

It all goes back to the back that each pinion shaft and gearbox housing had to be set up at the factory, and would normally need a number of shims behind that bearing. These "push" the pinion forward to the exact location for perfect alignment with the crownwheel. Consequently, the bearing can't be in a fixed position, and finds its correct location once all the gears and bushes are fitted to the shaft, and the front bearing is locked in place with its plate, and the external gears are locked up with the nut.

I don't think it matters which way the bearing faces.

Sorry I didn't get back, I tend to go to bed early.
I agree with you , if a circlip both sides it would indicate not a thrust bearing, so not like the picture I sent, sorry to mislead.
Surely if the bearing can find it's own position, then to a certain extent shims would not function in giving correct depth of pinion in crown wheel of diff, so when the gears are under load they must thrust in a direction depending under power or on the over run and in so doing put end load on those bearings.
It is frustrating not having original data from the gearbox builder.

 

[fiat500]

Sorry I didn't get back, I tend to go to bed early.
I agree with you , if a circlip both sides it would indicate not a thrust bearing, so not like the picture I sent, sorry to mislead.
Surely if the bearing can find it's own position, then to a certain extent shims would not function in giving correct depth of pinion in crown wheel of diff, so when the gears are under load they must thrust in a direction depending under power or on the over run and in so doing put end load on those bearings.
It is frustrating not having original data from the gearbox builder.

I think the roller bearing just takes the radial load on the pinion shaft. The thrust, or axial load is handled by the front bearing, which has a double row of ball bearings which can swivel in their race. That outer race is flanged, and sits in a recess, so is unable to be moved towards the differential. It is trapped in place by a strong housing that is screwed tightly in place. Once all of the components that are external to the main gearbox are locked up with the castellated nut on the end, the entire shaft is now fixed. Depending on whether the diff is being driven, or is on overrun, one or other of the rows of ball bearing will take the load.
Then again, I'm only interpreting what I see, I admit, I could be wrong.

 

[bugsymike]

I think the roller bearing just takes the radial load on the pinion shaft. The thrust, or axial load is handled by the front bearing, which has a double row of ball bearings which can swivel in their race. That outer race is flanged, and sits in a recess, so is unable to be moved towards the differential. It is trapped in place by a strong housing that is screwed tightly in place. Once all of the components that are external to the main gearbox are locked up with the castellated nut on the end, the entire shaft is now fixed. Depending on whether the diff is being driven, or is on overrun, one or other of the rows of ball bearing will take the load.
Then again, I'm only interpreting what I see, I admit, I could be wrong.

That sounds hopeful, once thrust shims are in, giving correct engagement of pinion in crownwheel.
What are your thoughts about the original bearing failure?

 

[fiat500]

That sounds hopeful, once thrust shims are in, giving correct engagement of pinion in crownwheel.
What are your thoughts about the original bearing failure?

I'm beginning to wonder if the end nut had come loose, or there were insufficient shims, or if there was a mismatched crownwheel and pinion. It's also possible that the crownwheel and pinion had
been dismantled, and then reassembled without care to check the meshing or backlash.

It looks a simple gearbox, but is actually very cleverly designed, and despite the low power output involved, the setup involves precision.

 

[bugsymike]

I'm beginning to wonder if the end nut had come loose, or there were insufficient shims, or if there was a mismatched crownwheel and pinion. It's also possible that the crownwheel and pinion had
been dismantled, and then reassembled without care to check the meshing or backlash.

It looks a simple gearbox, but is actually very cleverly designed, and despite the low power output involved, the setup involves precision.

Just another thought that occured to me.
The shims that control the pinion depth in the crown wheel, are they just spacer shims or are they thrust washers that fit one way only and have a bearing material on them similar to crankshaft thrust washers to take lateral loads, thus doing away with the need for thrust bearings as such?

 

[fiat500]

Just another thought that occured to me.
The shims that control the pinion depth in the crown wheel, are they just spacer shims or are they thrust washers that fit one way only and have a bearing material on them similar to crankshaft thrust washers to take lateral loads, thus doing away with the need for thrust bearings as such?

They are true shims,in fractions of a millimetre increments, and placed where they should rotate in synch with the inner bearing race.

 

[bugsymike]

They are true shims,in fractions of a millimetre increments, and placed where they should rotate in synch with the inner bearing race.

So they couldn't work as any form of thrust support anyway.
It is a strange system.

 

[fiat500]

So they couldn't work as any form of thrust support anyway.
It is a strange system.

FIAT!

 

[fiat500]

FIAT!

After an interesting (to me ) bit of research, I think the front bearing of the pinion shaft would be called an angular contact ball bearing. This type is listed as being typically used in gearboxes, and is designed to handle both axial and radial loads, which is exactly what is is doing here.

I can't wait to get my new, insulated garage built, so that I can waste spend my retirement time on this sort of trivia.

 

[bugsymike]

After an interesting (to me ) bit of research, I think the front bearing of the pinion shaft would be called an angular contact ball bearing. This type is listed as being typically used in gearboxes, and is designed to handle both axial and radial loads, which is exactly what is is doing here.

I can't wait to get my new, insulated garage built, so that I can waste spend my retirement time on this sort of trivia.

I have a garage that I could fit two cars at least in if it wasn't so full of my other junk, so I usually work out of doors like, most of my working life.
Strangely my Doctor is suggesting I need more Vitimin D for my bones, the suggestion is sunlight and milk for calcium etc. Milk is another thing I get plenty of. I suspect the bone issue is more to do with a lifetime of lifting heavy objects, fitting gearboxes etc. on my own.

 

[cinque500]

After an interesting (to me ) bit of research, I think the front bearing of the pinion shaft would be called an angular contact ball bearing. This type is listed as being typically used in gearboxes, and is designed to handle both axial and radial loads, which is exactly what is is doing here.

I can't wait to get my new, insulated garage built, so that I can waste spend my retirement time on this sort of trivia.

Over the last couple of days I’ve been doing a few experiments and it doesn’t make a difference which orientation that roller (not ball) bearing goes in at the pinion end. Suggests it’s NOT a taper then, which it’s good and make sense as the outer bearing casing floats.
So having established all these lovely things, I’m now looking to set the pinion to the correct distance. Pinion and crown are a correct set for a 126 box, 8x39.
On setting the distance the Haynes manual says:
”On the end of the pinion shaft will be found two sets of figures.
The upper ones are the matching numbers repeated on the crownwheel while the lower ones indicate the differential (+ or -) between. the nominal distance of 2.95 in (75 mm) from the centre-line of the differential to the shoulder at the back of the pinion gearteeth.
Compare the lower sets of figures on the old and new pinion shafts and by simple calculation, increase or decrease the thickness of the shims required. Shims are available in thicknesses from 0.0039 to 0.0059 in (0.10 to 0.15 mm).“
I can’t find any numbers on the pinion shaft, but that shouldn’t matter, that seems to be just as an aid to work out the new shims. At the end of the day it needs to be 75mm from the pinion shoulder to the centre line of the diff. I’ve got 81.28mm!!
To arrive at this I have measured the pinion gear length from the shoulder to the end of the pinion which is 24.14mm. Then I measure from the end of the pinion to the casing which ought to be the exact centre line of the diff. Not sure what I’m doing wrong but it ought to be close to spec out the box as the shims are only 0.10 or 0.15mm, don’t think Fiat use 30 shims!
The floating bearing is located correctly into the casing because its position is governed by the gear cluster which is all tightened together by the castlelated nut at the other end.
I tried some experimental washers just for a proof of concept and I can get the pinion close to 75mm but it means the bearing is protruding a long way outside of the casing, which can’t be right. So I can only conclude my theory on how to measure is wrong somewhere, meaning I’ve got what I think is the shoulder of the pinion wrong or I can’t use the casing as a true Centre line of the diff but surely the latter can’t be wrong?!

 

[bugsymike]

Over the last couple of days I’ve been doing a few experiments and it doesn’t make a difference which orientation that roller (not ball) bearing goes in at the pinion end. Suggests it’s NOT a taper then, which it’s good and make sense as the outer bearing casing floats.
So having established all these lovely things, I’m now looking to set the pinion to the correct distance. Pinion and crown are a correct set for a 126 box, 8x39.
On setting the distance the Haynes manual says:
”On the end of the pinion shaft will be found two sets of figures.
The upper ones are the matching numbers repeated on the crownwheel while the lower ones indicate the differential (+ or -) between. the nominal distance of 2.95 in (75 mm) from the centre-line of the differential to the shoulder at the back of the pinion gearteeth.
Compare the lower sets of figures on the old and new pinion shafts and by simple calculation, increase or decrease the thickness of the shims required. Shims are available in thicknesses from 0.0039 to 0.0059 in (0.10 to 0.15 mm).“
I can’t find any numbers on the pinion shaft, but that shouldn’t matter, that seems to be just as an aid to work out the new shims. At the end of the day it needs to be 75mm from the pinion shoulder to the centre line of the diff. I’ve got 81.28mm!!
To arrive at this I have measured the pinion gear length from the shoulder to the end of the pinion which is 24.14mm. Then I measure from the end of the pinion to the casing which ought to be the exact centre line of the diff. Not sure what I’m doing wrong but it ought to be close to spec out the box as the shims are only 0.10 or 0.15mm, don’t think Fiat use 30 shims!
The floating bearing is located correctly into the casing because its position is governed by the gear cluster which is all tightened together by the castlelated nut at the other end.
I tried some experimental washers just for a proof of concept and I can get the pinion close to 75mm but it means the bearing is protruding a long way outside of the casing, which can’t be right. So I can only conclude my theory on how to measure is wrong somewhere, meaning I’ve got what I think is the shoulder of the pinion wrong or I can’t use the casing as a true Centre line of the diff?

It does seem to be down to their definition of the centre line of diff, do they have any pictures of their method?
I thought crown wheels and pinions had to be supplied as a matching pair.
When it is in place, is there any way you can check contact areas of teeth engagement using engineers blue or similar and check for "lash"?
Is there any measurement given for a preload figure, or with no thrust bearings maybe that is irrelevant.

 

[cinque500]

It does seem to be down to their definition of the centre line of diff, do they have any pictures of their method?
I thought crown wheels and pinions had to be supplied as a matching pair.
When it is in place, is there any way you can check contact areas of teeth engagement using engineers blue or similar and check for "lash"?
Is there any measurement given for a preload figure, or with no thrust bearings maybe that is irrelevant.

No pics in Haynes manual unfortunately just what they say above. I think you’re right about the pinion the crown coming as pairs although they give guidance how to work out the differences on shims should there be a replacement.
At the moment I’m miles away from checking teeth contact and preload etc as the pinion is 6.28mm away from where it should be