Technical Differential expert's ! Weird pinion gear

Ford 9" is the differential in question. It seems this could also happen with a "new set of gears" per specs I mention further along on this thread. For now this is what I have. Used 3:25 gears therefore the pinion has 12 teeth. Now here's is the weirdness. Every third tooth at exactly 90 degrees apart and always the same four teeth is giving me .002 less back lash than the other remaining 8 teeth and I can hear the 4 seemingly proud teeth in question scrub when the gears are dry and free of lube. The more I shim the pinion away (within the acceptable wear pattern allowable) from the ring gear things get better as far as showing a good contact on all 12 pinion teeth and the scrubbing sound is next to near gone and has very very short in duration. Is this something that happen's from time to time ? Because specs say a backlash reading of plus or minus .003 is acceptable when going around the ring gear! I'm going to run it none the less to see what happen's as far as noises are concerned because these gears ran fine before.

 

I'm no 9" expert. But, I am definitely interested in what you find here. Since the ring gear has an odd number of teeth it doesn't seem that it is a mating surface problem. I would guess that it was a machining error on the pinion.
I would bet that if you set the backlash @ .003" leaving the 'high' teeth at .001" you will never know it in the finished unit.
Then again, i might be completely wrong.

 

Partially non hunting gears...did you align the marks? usually lines ground on the inside of the ring gear, and between two pinion teeth, there may or may not be yellow paint there.

 

shop manual...see paragraph 9

 

pictures

 

Neat

 

Super Squirrel to the rescue, with actual information, again!!!

 

I'm 74 years old , Ive been around cars ever since they put horns on them...but til today I never had heard of"hunting " or non-hunting " gearsets !!!....What a place this is..Learn something new nearly every time ...
Thanks Squirrel....
Stan

 

Now I know; who not to line up against in the staging lane!
Good stuff there!

 

Awesome Jim ! Unfortunately those marks are gone due to cleaning and the unawareness of timed dif gears . Today I'll go with my alternative plan and start back at base line with the stock pinion shim and concentrate more on the wear pattern on the pinion. Meaning, I will read off the pinion rather than the ring gear. Because as I mentioned at the top of the page. The more I moved the pinion out the better things got and that was evident visually also because the other remaining pinion teeth began to have contact with the ring gear.

 

Turn up the stereo, you won't hear it

I don't know if this is what's causing the issue or not. I have had pretty good luck with used Ford gears, they don't seem to be too picky about the pattern, I haven't had a noisy set for years. And I've run 7 different sets of gears in my 55 and 62. The pic is of my 3.25 gears, I've put a lot of miles and at least a dozen drag strip passes on them.

btw the 3.00 gears are the non-hunting type, as you should be able to guess. 13 and 39 teeth.

 

Just went back and looked at your reply Jim. I missed the marking that doesn't wash off. I'll be looking for that stamped mark on the pinion .

 

some of them have ground lines on both gears, some have only paint.

 

Along those lines of no remainder in math. That's what had me scratching my head yesterday ! Thanks for your help.

 

It must be one of Ford's "better ideas"

 

Lol. I really have to laugh at the majority of people that think a 9" is stronger because of the 3rd bearing that support's the pinion. What most people don't know is by Ford placing the pinion so low from the ring gears CL actually put's an extra load on the pinion. Therefore they made it weaker, with more drag, then had to make it stronger to combat the issue they designed into it ! Shall I go on about the 2 extra spider gear's with their stubby pinion shafts and a cross block that's suppose to make up for the side load !

 

Just a check..spin the pinion with an indicator on the out board support bearing area just to see if it is spinning true in the bearings..

 

Maybe...So why is it in such wide spread use? Must have some kind of reliability credit or is there that many people to laugh at? Early Fords have a pinion support bearing and the pinion is on center..

 

There's this thing called "belief" and if it's said it must be true ? Even you question it by saying "Maybe". As far as wide spread use. Marketing my friend and marketing is about making claims that ones product is better than the other's product which leads back to "believing".

 

Hey Jim, I'm with Turbo26T, I hadn't heard of the "hunting"/non-hunting factor. I read the quoted manual section but I'm still wondering what the difference is? Non-hunting gear set are lapped together and hunting set aren't? Is that all? I'm a little foggy this morning, I guess it's a 2 cup morning........

 

I'll jump in for just a second and I'm sure Jim will agree. Non hunting would mean a tooth isn't searching (hunting) for a new spot. It will always return back to the same tooth every time on the opposing gear. In this situation the gears are mated, timed, go back together in the same spot over and over and can never run in any other way.

 

Makes perfect sense, thanks JG.

 

No I question your statement by saying Maybe..Nascar uses them..Drag racers use them..I use them and you have at least one..Lot of people on here use them..Must be more than just marketing, even before the internet...

 

Some have or had the paint at one time to make the mark easier to find on assembly.

 

seb fontana said;"I question your statement by saying maybe"
Makes me wonder too. I know of several GM rears that failed and were subsequently replaced with Ford's that were considered "bullet proof" and wouldn't, couldn't, didn't fail despite the punishment sustained. Come to think of it, I've never heard of one failing in street use. (don't know about drags)

 

Learn something new everyday.

 

I"ve seen a few pictures of 9" third members split open, the front comes right out. I've seen the Trac Lock differentials split in half.

The 9" is really strong, if you replace almost all of it with aftermarket parts

.

 

Yep..Build to suit..

 

The 5 bolts didn't cut it !

 

And from a guy that started building QCs because Ford 9 inchers were too expensive for my intended use:

They are very strong. Like everything else, there were compromises made in the design. They lasted almost forever in their original applications. When you start testing the limits, you find the weakest link. That is different for the drag racers and the oval track guys.
None of the above applies to the OP's situation.