1930 Hudson pinion gear assembly setting round 2

[timecapsule]

I'd like some advise on setting up my pinion on my 1930 Hudson please.  Back in sept of '22 I asked a similar questions when I first approached the differential issues on this car.

But this time, I'm trying to reset my pinion setting.  The last time, after I had the pinion rebuilt on the differential, that was on the car when I bought it, I discovered that the right side of the differential housing was cracked in 4 places right at the attaching bolts to the left side.  So I fortunately came across a couple complete differentials.  The first one I pulled apart, was missing a couple key parts.  But the second one was in good shape, so with fingers crossed, I just bolted it in and it has been good for a year and a half.

However I recently posted a thread on here, where I was hearing a "clunk" noise.  I've gone over the car stem to stern and I've had a couple mechanics stand beside the car as I take off and they agree that it seems like the noise is coming from my differential.

I removed the differential housing/pinion housing assembly and mounted it on an engine stand.  I reduced the backlash to within specs but as I grab the splined end that bolts to the driveshaft and give it a quick twist I can still head a clunking noise.  So I've come to the decision that I need to bring the pinion gear closer to the ring gear.  According to the manual, it seems to be that to do that I need to remove one of the large diameter, brass shims between the differential housing and the pinion housing. ( see picture) I have 4 in there.  3 are 13.5 th.  and one is .010 th.  So I removed the .010th shim.  The manual says "Adjust pinion, so that backface of pinion teeth is flush with outside face of drive gear"

 

But I'm thinking that they mean the inside face of the ring gear and the end of the pinion shaft gear.  Because you can't even really see the other end (outside face).   Plus that end of the pinion gear has the teeth cut on an angle at the end, so it would be hit and miss to get an accurate reading, even if you could see it.  Where as the end of the pinion gear is a right angle cut on the end that you can see. ( see picture)  But as I held the pinion gear sort of in place by hand without the pinion housing so I could see both ends.  It looks like it is flush on both ends to the ring gear. So I think that part is good to go.

 

So now we're getting to my real question.  The smaller bearing has a couple pitted rollers, so I'm replacing it with a new one.  When I bolt the pinion assembly together and set my preload on that bearing, do I leave the bearing dry or do I rub a bit of the rear end oil (600W) all through the bearing?   

I've read that you have to put a monstrous preload on a new bearing in this case.  Something like 200 ft. lbs.  My next question is how do I accomplish that?  On the end of the pinion there are a pair of flat surfaces that a 11/16" wrench will sort of fit on it. (see picture)  Would I put that end in a vise so I can torque down the 1 1/4" but on the other end to set the preload?

 

My next question is do I use the same bearing shims that were in place on the pinion shaft for the old bearing?  Or would I add one or subtract one?  At the moment there are 5-.015 th. shims and 1-.010th shim totally .080th  I have a bunch more .015 shims.  Now I know that the splines on the end piece need to extend past the splines on the pinion gear, so that once the preload is applied, it doesn't bottom out before the required torque is applied.  So I'm thinking it might be obvious when you don't have enough shims in place, but how do you know if you have too many shims? The manual says there should be a bit of resistance when turning the pinion nut after the correct torque and shims are set.  Kind of a vague statement, to say the least.

 

On these old cars, as most of you may know, if you don't get both or either shim selection right, you have to disassemble the whole assembly and try again.  It's a real pain, especially since it takes a lot of persuasion, tapping on the side of the pinion assembly to remove it each time.  Like about 50 soft blows with a rubber dead blow hammer as you try and pull out on the assembly with your other hand.  Slowly after about 5 minutes it will come off.  The entire process is very time consuming. 

Edited December 13, 2023 by timecapsule (see edit history)

[Oldtech]

This could get complex. Do a search for how to set rear axle pinion depth using the contact patch on the teeth and follow the chart. It's not obvious how this works. 

Re the preload. It's not 200 lbs of preload you want. You want shims just enough so there is noticeable resistance to turning it by hand when the nut is Torqued to 200. I wouldn't go that high though.On an old axle. I'm thinking maybe 125 and some loctite.  Others?

Also... it's rare that you would get a clunk just from the ring and pinion. Most clunks are caused by slack in the diff gears and axle splines, or play in the pin for the spiders.  If they are all nice you may just have to live with it.

Edited December 13, 2023 by Oldtech (see edit history)

[timecapsule]

12 minutes ago, Oldtech said:

This could get complex. Do a search for how to set rear axle pinion depth using the contact patch on the teeth and follow the chart. It's not obvious how this works. 

Re the preload. It's not 200 lbs of preload you want. You want shims just enough so there is noticeable resistance to turning it by hand when the nut is Torqued to 200. I wouldn't go that high though.On an old axle. I'm thinking maybe 125 and some loctite.  Others?

Also... it's rare that you would get a clunk just from the ring and pinion. Most clunks are caused by slack in the diff gears and axle splines, or play in the pin for the spiders.  If they are all nice you may just have to live with it.

Thanks for that.  Thanks for clearing up my terminology. on that 200 lbs.  But can I do that to the pinion when it is not in the assembly?  By putting it in a vise.  I don't want to wait until I put it back in the car with the axles to do that.  If I don't get the shim selection correct d have to pull it all out again.

 

I haven't disassembled the differential assembly so I can just barely make out the spider gears and axle gears while the two halfs are still together, but as for the surfaces of each gear as I turned them and inspecting each one with a strong light, I didn't see anything that looked suspicious.  

Edited December 13, 2023 by timecapsule (see edit history)

[Oldtech]

Yes, you should be able to assemble it in a vice, but fitting the shims for the position is trial and error. 

[Bloo]

Moving the pinion in and out to fix backlash sounds like a recipe for disaster. You probably need to get some gear pattern compound of some titanium white artists paint to check the pattern. White or red lead was used in the past but is generally not available. The in/out of the pinion is set to get a reasonable pattern at a reasonable backlash, but the backlash itself would be set by moving the whole differential case (the part that spins) left and right.

 

Bearing preload in anything that old should be set with shims, and the nut is independent. This in contrast to modern stuff that has a crush sleeve and the torque of the big nut is involved in setting the preload. With shims, you'll have to check the bearing preload with tiny torque wrench after the big nut is tight. If it is wrong, you must shim differently. That tail on the pinion does look like it would be handy to help you torque the big nut. I don't see any reason you can't check preload on the bench. Hold that outer housing with something and turn the big nut and pinion with a tiny torque wrench. EDIT: re-reading @Oldtech's post, he pretty much nailed it.

 

Back to gear patterns: the deck is sort of stacked against you for several reasons. I would warn you to take any pattern reading instructions on the web with a grain of salt. Most rear wheel drive cars have had hypoid gears since the late 30s or early 40s, and therefore most how-tos assume hypoid gears. If your pinion intersects the ring gear at the center, you have spiral bevel gears, not hypoid. Also, you will notice a lot of those charts online contradict each other. Several years ago I found a Dana/Spicer document that told why. There are 2 methods to cut hypoid gears. The way the patterns move as you adjust in/out are different depending on which cutting method was used to manufacture them. I believe one type moved opposite on the coast side. I was working on a spiral bevel rearend at the time, and it didn't behave like either one.

 

Backlash and pinion position move the pattern, but in different ways. You'll just have to try a bunch of things to see how the pattern moves on yours with a change in pinion depth, and with a change in backlash (side to side adjustment).

 

What you want is a wide contact patch at the center of the tooth on both power and coast. You probably wont get it and need to settle for least bad. What you DON'T want, is contact on an outer edge or corner, or contact in the root. Anything that concentrates force on an outer edge will break teeth off.
 

On the Pontiac spiral bevel axle I was working on most recently, as you moved the pattern in toward the root, instead of making a nice oval like all the books show, it made more of a "D" shape, widening out to something closer to a narrow straight line across the tooth. I suspect the root of the pinion was "relieved" a little bit, causing this. Better than having contact at the root. Incidentally in that Pontiac rearend, The shop manual wanted the gears lined up like you show in your third pic. The gears were aftermarket and the pinion had about a bunch of extra metal there, and it was not even possible to set it like that. Trying gave a pattern that was almost off the edge of the teeth. I advise to not put a lot of stock in that method. If it gives you a good pattern, great. If not, throw that whole idea out and move on. 

 

I agree with @Oldtech that clunks are usually in the differential itself or splines. There might be some bronze washers under the side gears or spider gears that could be worn and replaceable, but you also might need to live with it.

 

Good luck.

 

EDIT 2:

 

5 hours ago, timecapsule said:

But the second one was in good shape, so with fingers crossed, I just bolted it in and it has been good for a year and a half.

Wow. I would check the pattern, but would be strongly inclined to leave the pinion depth set the same as it was.

 

 

Edited December 13, 2023 by Bloo (see edit history)

[timecapsule]

8 hours ago, Bloo said:

Moving the pinion in and out to fix backlash sounds like a recipe for disaster. You probably need to get some gear pattern compound of some titanium white artists paint to check the pattern. White or red lead was used in the past but is generally not available. The in/out of the pinion is set to get a reasonable pattern at a reasonable backlash, but the backlash itself would be set by moving the whole differential case (the part that spins) left and right.

 

Bearing preload in anything that old should be set with shims, and the nut is independent. This in contrast to modern stuff that has a crush sleeve and the torque of the big nut is involved in setting the preload. With shims, you'll have to check the bearing preload with tiny torque wrench after the big nut is tight. If it is wrong, you must shim differently. That tail on the pinion does look like it would be handy to help you torque the big nut. I don't see any reason you can't check preload on the bench. Hold that outer housing with something and turn the big nut and pinion with a tiny torque wrench. EDIT: re-reading @Oldtech's post, he pretty much nailed it.

 

Back to gear patterns: the deck is sort of stacked against you for several reasons. I would warn you to take any pattern reading instructions on the web with a grain of salt. Most rear wheel drive cars have had hypoid gears since the late 30s or early 40s, and therefore most how-tos assume hypoid gears. If your pinion intersects the ring gear at the center, you have spiral bevel gears, not hypoid. Also, you will notice a lot of those charts online contradict each other. Several years ago I found a Dana/Spicer document that told why. There are 2 methods to cut hypoid gears. The way the patterns move as you adjust in/out are different depending on which cutting method was used to manufacture them. I believe one type moved opposite on the coast side. I was working on a spiral bevel rearend at the time, and it didn't behave like either one.

 

Backlash and pinion position move the pattern, but in different ways. You'll just have to try a bunch of things to see how the pattern moves on yours with a change in pinion depth, and with a change in backlash (side to side adjustment).

 

What you want is a wide contact patch at the center of the tooth on both power and coast. You probably wont get it and need to settle for least bad. What you DON'T want, is contact on an outer edge or corner, or contact in the root. Anything that concentrates force on an outer edge will break teeth off.
 

On the Pontiac spiral bevel axle I was working on most recently, as you moved the pattern in toward the root, instead of making a nice oval like all the books show, it made more of a "D" shape, widening out to something closer to a narrow straight line across the tooth. I suspect the root of the pinion was "relieved" a little bit, causing this. Better than having contact at the root. Incidentally in that Pontiac rearend, The shop manual wanted the gears lined up like you show in your third pic. The gears were aftermarket and the pinion had about a bunch of extra metal there, and it was not even possible to set it like that. Trying gave a pattern that was almost off the edge of the teeth. I advise to not put a lot of stock in that method. If it gives you a good pattern, great. If not, throw that whole idea out and move on. 

 

I agree with @Oldtech that clunks are usually in the differential itself or splines. There might be some bronze washers under the side gears or spider gears that could be worn and replaceable, but you also might need to live with it.

 

Good luck.

 

EDIT 2:

 

Wow. I would check the pattern, but would be strongly inclined to leave the pinion depth set the same as it was.

 

 

Thanks for that info.  Since this is my second go round of setting up the rear end, I pretty much did everything you suggested on the first attempt.  That being before I found the broken diff. housing half that is on the original differential.  So even though I didn't use that assembly, it was a good practice run for this time around.  I had actually forgotten about using the in. lb. torque wrench on the big nut to check on the drag. So thanks for the reminder.  The last time I did it, I slowly spun it 360 degrees and I had a reading of 15 in. lbs.

 

Regarding your first sentence, I wasn't taking about moving the pinion in and out to set the backlash.  I'm just doing that before setting the back lash to get it as properly aligned as possible.  By using those large shims.  I'm guessing that design of using those large shims between the differential housing casting and the pinion housing casting is to make up for any casting irregularities in the manufacturing.  So that the pinion gear is lined up pretty much with the ring gear, before setting the backlash.  

 

I went through the "painting" procedure last time so I know how that is done.

 

As for shims on the differential gear and spider gears. I have the original assembly all apart and I didn't see any in it.  I have another spare assembly that I think I'll take apart today to see if there are any in it.  I'll also check the parts book, but I don't remember seeing any mention in the parts book about shims for any of those gears.  It would almost make sense that there would be shims for those gears,  but then again, when they are all assembled between the two halves, you really can't see very much of the gears so I don't see how you would know if you had then set accurately, so they were not meshing too loose or too tight. 

[timecapsule]

I think I have corrected the clunking issue.  I reduced the amount of shims between the differential housing and the pinion housing by .015th.  I reduced the shims between the pinion spacer and the smaller bearing in the pinion assembly by .020th. But that part really isn't significant because I have a new bearing in there now and I'm using a different companion flange, then was in there before. 

I've set the backlash at .010th.  and I increased the drag on the pinion nut from 15 in. lbs. to 30 in. lbs.

Everything looked and felt good while the differential housing was mounted on an engine stand. I've put maybe 60 miles on the car since the changes and there is no clunking noise.  Most of my drives are around 30 minutes before stopping.  I drive at all speeds up to about 60 mph.  I check the pinion housing and the differential housing with a digital laser temp gauge, and the differential housing is around 100F.  and the pinion is around 130F.  I'll keep monitoring the temperatures and listening for any strange sounds.

Thanks for the help and suggestions guys.