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View Full Version : More gear pattern opioins. Long post



JRouche
02-18-2011, 10:46 PM
What I have here is my 62 Nova. Ford nine inch rear. And I posted a story about my problem on another site so Ill just copy and paste. If anyone has any thoughts Id love to hear them. Thanks ahead of time. Solly, its a long read... JR





Ok, here is the deal. Way back in 1996 I bought a drop out center section for my ford 9" from Reider racing. It is a nodular case with a 31 spline Auburn LSD, Precision gear ring and pinion, daytona pinion support, Timken bearings, solid spacer (non-crush type) for bearing pre-load. Basically a decent street drop-out, and I trust Reider racing to assemble it correctly.

Fast forward to two months ago I finally got to use it. Yeah, it sat in the housing the whole time while I worked on the other parts of the car. And its kinda sketchy as to when I filled it up with lube and friction additive. Im thinking I did it back then.

But anyway, I finally drove it two months ago, rechecked the fluid level first, it was right up there.

I had a whine from the get go. And it was a speed induced whine, not a load dependent whine. At any speed above 30mph I could hear it. My dad couldnt, but his hearing has never been great.

So that was a concern. Specially because my car isnt that quiet anyway. So for the gear whine to be that noticeable I knew it was for real.

So I was thinking gear lash was the issue, or some really rough gears. And in the back of my mind bearing noise was a possibility due to the way the noise wasnt dependent on load but more about speed. It seems to me if it was the gears there would be a noticeable change in the sound when I was on or off the gear.

But I was willing to drive it and see what poped up, or poped OFF!!..

So 200 miles later I get a new noise. One that I dont like. If Im driving with even the slightest load all is good. But if I have a slack in the load, like say driving really slow through a parking lot (thats when its really noticeable). I will give it a lil gas to get to 10mph then let off and I would hear (and sorta feel) a knock as I lift the throttle. Idle and coast a lil till I needed some more forward go then lift and the knock would happen again.

To be honest its embarrassing. It sounds like the engine is knocking its that loud. And no, its not the engine.

And I can create the same knock at 50mph if Im on a level street with no load. Ill blip the throttle (lightly not alot) then release it and it will knock once. I can make it happen every time.

Its like the ring and pinion have a major gap now and the knock is the pinion rolling back off the ring on a no load condition and hitting the back side of the teeth as it hits because the rear end is moving faster than the drive shaft. But I dont get ANY knock when I apply a forward (on the throttle) gear mesh.

It seems to me if I have a backward knock when the ring is the load I should get a forward knock when I throttle up and it takes up the slack and the pinion is loading the gears up. I dont.

Baffles the heck out of me.

I dont have any noise from the LSD on turns, its tight and quiet. So I dont suspect the LSD.

The U joints are also "new". Old but not used. And I raised the rear and checked the joints. They are solid and dont have ANY play.

I called Auburn and they didnt want to talk much. Like they thought I was trying to get some warrantee issues. LOL I made it clear I was just looking for tech advice, this drop out is WAY beyond any of that. I just wanted some expert advice so I could go ahead and pull the unit and know what to look for. Like if it was gonna be a simple rebuild for me or if they thought the LSD was shot.

Anyway.. Any thoughts????

Oh, and I did check EVERY link I have under the rear. Its a parallel 4-link, watts link and roll bar. I triple checked ALL the links thinking it might be a link making the noise. They are all good to go.

Any thoughts would be cool. Even if its to say yeah, been there done that, its the bearings, or its the pre-load. I am just looking for justification for dropping the center out and rebuilding it. Id hate to rip out all the "new" old parts just to replace them and have the same thing happen...


Ok, so I dropped the pumpkin today. Fairly simple after the axles were clear. U-joint clamps (four bolts) then the case bolts. Problem was some idiot glued (gaskacinch) the gasket to both the case and the housing. Wait a second!! Guess that idiot is ME. Yeah, it took some wedging to get it loose. But to be honest, Ill glue the new gasket in also. Talk about a leak free joint. And it does make it a lil easier to keep the gasket in place for under the car installs.

Here are the pics. Click on the pic if you want to see the large pictures of the ugliness :)

https://static1.pt-content.com/images/pt/2011/02/dropped-1.jpg

So I tossed it on the bench, cleaned it up of all the remaining lube and just took a looksee. Nothing looked out of place. All the paint markers for the fasteners from the assembler were still lined up, nothing came loose.

The ring gear looked brand new. Although even without any marking compound on the gear I could see a pattern on the coast side. Its more evident eyes on. But here is a pic of what it looks like.. See its way out on the heel (kinda wiping the edge of the heel) and up on the face too much?

https://static1.pt-content.com/images/pt/2011/02/patternnomarker-1.jpg

So I sprayed it all down with solvent and dried it off and checked the backlash. Even before I checked it I rotated the ring gear back and forth and it seemed like alot of play. But, after checking it at six spots on the ring it was within specs. I got constant readings of .0100" to .0105". I did have one section that was .0950" but I think that was a bad reading but still way within specs. Everything that I have read says the specs for this ring and pinion backlash is .008-.012" So my ten thou is right in the center.

https://static1.pt-content.com/images/pt/2011/02/backlash-1.jpg

Next was to check the mesh pattern with some goop. I was ready to go the the artists supply store and get some yellow oil based artist paint and add a couple of drops of lube to it cause I dont have a GM parts supply local. But what do you know. Napa had one tube left of the GM compound.

So I painted the ring gear and put some tension on the pinion, had to go in my closet to get a belt, worked perfectly. Then rotated the ring gear around four times one way then four or so times the other.

And this I what I got...

Drive side mesh....

https://static1.pt-content.com/images/pt/2011/02/drivepattern-1.jpg

Coast side mesh...

https://static1.pt-content.com/images/pt/2011/02/coastpattern-1.jpg


To me it looks like the drive side is spot on, dont know that it could get any better.

The coast side looks a lil out on the heel (outside of the tooth) and maybe a lil high on face (top of the tooth).

But.... Im thinking the pinion depth is correct. I wont mess with that. I like the drive pattern. And it being a new gear set thats prolly more important than the coast side right now.

I might be able to pull the coast pattern in a lil with some reduction in backlash. And to be honest, I think thats where my idling through the parking lot "clunk" is coming from. And it doesnt help that my rear end is held in with metal heim joints. Prolly exaggerates the sound through the body that doesnt have any interior yet.

But the "clunk still bothers me mainly because it was not there for 175 miles. I dont think the backlash has changed. Its right in the center of the specs. So I think they dialed it in for that backlash.

So... Im gonna pull some backlash out, Ill set it for .008" and see if it helps.

Other than that the bearings "look" brand new. Im not gonna tear the diff and pinion out of the case just to look at them and say they are good to go. I dont think its a bearing noise, the whine I hear. For all I know the whine is common and Im just hearing it more cause I have a metal on metal four link and no intirior to muffle the sound.

Im ok with the whine noise now that I have got to check it out. I like the gear mesh on the load side and Im not worried about chewing gears. That was a good thing to see.

The coast mesh is a lil off but maybe a backlash adjustment will help. Hopefully help with the irritating knock while rumbling through the parking lot :)




Ok, I wanted to remove a lil backlash today. And I did take what 74novabum said into account and realize Im going in the opposite direction, it could come around to bite me in the butt, if so Ill just end up doing it all over again and go the other direction. What 74novabum said makes complete sense and Im prolly stupid for not moving the pinion like he said I should. Why dont I? Well, same reason I dont do what I should most of the time, laziness, oh, and money. To reset the pinion would mean buying some shims. I dont have any on hand.

Id like to be able to get the rear end set up with some adjustments. And really, if it doesn't work out I will remove the center AGAIN and go for the pinion adjustment. Ill see what happens. Sucks to be lazy and poor, guess they go hand in hand though sometimes huh?

Ok, so I loosened up the bearing caps and snugged them down to a light 10lbs. Loosened up the bearing adjuster opposite the ring gear all the way. Physically pushed the carrier over towards the pinion to seat it into the pinion, hand tightened the gear side adjuster till it was hand tight. Rotated the gears to mesh, reseated the carrier over by hand, rechecked the adjuster for that side to see if there was anymore clearance (hand tight), there was a lil more turn, hand tightening the adjuster. Now I had the ring seated to the pinion in full contact (no back lash) but not over tightened.

Then it was time to "spread the case". Everything I have read over the past few days says the "case spread" should be .008"-.010". And they never say where that measurement should be taken from. I saw so many variations it was like there was no set method. I'm sure Ford has one written up but I couldn't find it.

I saw some guys using an indicator mounted to the top of one cap and indicating the top of the other cap. Problem is there is no really good way to mount the indicator to the top of the cap. Saw one guy clamp the base of the indicator to the top of the cap with vice grips. Problem with that is the further away from the cap you mount the base of the indicator is it will give a false reading. Because when you load the caps up the top moves out more the further away from the center of bore you go. So if the base of the indicator is further away from the bore it will show more movement. I didn't like that setup.

Another setup was to just put the base on the case and indicate one side. When it moves half of your desired number it should be good to go. I liked that one the best, but didn't use it.

But I opted to do something else. I have large bearing caps, and there is a great flat on the outside of them where the adjuster lock goes. So I decided to use a caliper (EDIT: Micrometer, not caliper) and measure it (the case spread directly). I like to get a real number when measuring and I can get a consistent repeatable measurement using mics. Its a lil slow, but with consistent use of the micrometer, feel and attention, I can get consistent results.

So I measured the caps during slack, no load and slowly turned the adjuster opposite the ring gear in. I crepped (not a word LOL) up on my goal (.010") till it was there. And I was surprised. The amount of preload on the bearings was pretty high. I made an adjuster turning tool, basically a two foot bar with two studs. And I had to get on the bar. And stupid me!! Thats one measurement I forgot to take before I slacked it all up, case spread.

But I did have to loosen the adjusters with the same tool and it seemed to me the force I used to loosen it was not even as much as I used to load it up, but that doesn't mean anything. Just a perception really. I wish I would have measured the case spread before removing it. My bust!

Oh, on a side note. One of the papers I read, from a dealer of rear end components, talked about how difficult it was to measure the .008" case spread (yes, that's true) and said he torques them down to 150lbs. WHAT!! Yes, foot pounds. He went on to say he has never seen any problems with over tightening the carrier bearings.

So for a check I broke out the 200ft-lb torque wrench. My adjuster bar wont connect to the wrench. But I was able to lock the square drive down and dial the wrench up to 100 ft-lbs and get a feel for the force needed. Then gripped my bar at the same length for how long my torque wrench handle is and gave the bearings around the same amount of preload. And I picked 100ft-lbs to account for the guessing factor. WAY too much preload. I could actually feel the bearings as they topped off and fell over on the internal rollers when I rotated the carrier. Not something I would have rotated much more much less driven on. I don't get the 150lbs preload. Not for me anyway.

Ok, where the hell was I? Oh yeah, case spreading. So I got to my goal, .010" of case spread. So the case was all in tension. Oh, make sure you tension it from the adjuster opposite the ring, otherwise you are running the ring into the pinion, not good.

So I got the case loaded up, time to set backlash. It was still prolly at zero, maybe a lil off due to the case spreading, but not much.

Then its time to move the carrier over, off the pinion by .008"-.012", standard backlash for the 9" with new gears, and they would still be considered new gears with only 200 miles on them and not any dramatic wear issues.

Reading how one hole in the adjuster is usually good for .005" I took the ring gear adjuster out by one hole and turned the opposite adjuster in by one hole to see what that gave me. It was pretty close to .005". Took it to the next hole, both sides and it pushed the ring out by 12 thou total. And I rotated the gears in between measuring to take the slack out. So with two small turns and after rotating it the final backlash was 7 to 7.5 thou. A lil tight yes. But I was gonna go with that.

I buttoned up the bearing caps and checked the backlash again, it didn't move.

So I painted the ring for a pattern check. And this is what I got (below). The pictures are a lil deceiving. Its hard to take pictures of what I see to come out in a pic.

The pictures dont show the minor contact patches. The heavy, obvious scraping of the marker shows up. But the actual points of contact are more apparent in real life. I can see the thin coating of the marker better (with some good lighting) than what the camera picks up. The camera picks up the contrasts that are very apparent. My eye sees the light marks that are real.

But for me, in person the contact areas look pretty good. They are centered top to bottom, side to side. Drive is more centered. Coast is better than before. Its more towards the root and not as high.

BUT!! I do think my backlash is too tight. And saying that Im still gonna button her up and see.

I am prepared to remove it again if all is not well. I think I have a handle on the remove and replace by now, not that I like it.

I don't know. I just hate the idea of a massive backlash in a gear set. And I may be a lil new and missing the fact that they do really heat up during driving. I'm prolly setting this drop out to live up to its name, Drop Out. I'll let you know if i have to drop it out again.. Umm, what a "book" of a post huh? JR


Drive pattern....

https://static1.pt-content.com/images/pt/2011/02/2nddrive-1.jpg


And the coast pattern...

https://static1.pt-content.com/images/pt/2011/02/2ndcoast-1.jpg

CamaroAJ
02-19-2011, 08:39 AM
it looks to me based off the amount of contact pattern that you don't have any load on the ring gear when you are turning the pinion gear. i like to use a pry bar between the ring gear side and the case housing to load it with some pressure then turn the pinion gear. it will show you a different pattern if there is no load vs. a loaded ring.

according to this web site http://www.differentials.com/specsi.html your backlash for aftermarket gears should be .007-.010 so you are a little loose to start with.

my question to you is what kind of play do you have in the spider gears? how about the spider gear pin? i have seen those worn out and causing a noise like what you are talking about.

JRouche
02-19-2011, 11:14 AM
it looks to me based off the amount of contact pattern that you don't have any load on the ring gear when you are turning the pinion gear. i like to use a pry bar between the ring gear side and the case housing to load it with some pressure then turn the pinion gear. it will show you a different pattern if there is no load vs. a loaded ring.

according to this web site http://www.differentials.com/specsi.html your backlash for aftermarket gears should be .007-.010 so you are a little loose to start with.

my question to you is what kind of play do you have in the spider gears? how about the spider gear pin? i have seen those worn out and causing a noise like what you are talking about.


I load up the pinion with a tight belt and turn the ring gear (as stated). Its pretty tight. I have to use a special bar to turn the ring gear.

I have 7-7.5 thou for back lash (as stated) so its on the tight side of the specs.

No play in the diff. Its brand new..

Thanks for your input. JR

big gear head
02-19-2011, 02:31 PM
First, you don't need to paint every tooth on the ring gear. The pinion needs some clean teeth so it can clean it's self. Only paint about 3 teeth in a row in 2 or 3 places on the ring gear. This will give you a more clear pattern.

I don't see any real problems with the pattern as it is. It's not easy to tell with all of that marking compound on there, but it doesn't look too bad. I thin you may be looking in the wrong place for this clunking noise. Do you have a manual or automatic transmission?

JRouche
02-19-2011, 07:41 PM
First, you don't need to paint every tooth on the ring gear. The pinion needs some clean teeth so it can clean it's self. Only paint about 3 teeth in a row in 2 or 3 places on the ring gear. This will give you a more clear pattern.

I don't see any real problems with the pattern as it is. It's not easy to tell with all of that marking compound on there, but it doesn't look too bad. I thin you may be looking in the wrong place for this clunking noise. Do you have a manual or automatic transmission?

Yeah, I started just painting five teeth and all the other teeth got real painted up anyway so I decided to paint all the teeth so I could do a good 20 revs on the drive side and 20 on the coast side. I did many more patterns and adjustments than what I posted. I only posted some of the better patterns after some adjustments. I tried to adjust the contrast in photoshop to show the pattern I see in person. Unfortunately it didnt happen. The flash of the camera really blends the gradient I see in person. They low grey colors where the teeth are actually meshing. What you are seeing is the heavy mesh pattern, you dont see the minor thinned out mesh.

But its good to hear from a pro that it doesnt look like a terrible pattern.

And really, the pics dont show the thin film mesh. In person you can really see where the gears are meshing.

And yeah, I dont think I have worked out the knock. I think it will still be there. But there is a bit of piece of mind knowing that I wont be wrecking the diff or any other parts of the rear. Thats why I opened her up. Just to confirm its within specs and Ill drive it till something breaks.

And I did open the backlash up today. Put it to .0075-.008". I thought .0065-.007" was a lil tight.

If I removed some gear whine Ill be happy. If I still have some knock on decell at 5mph I might live with it, not like it, but will live with it. But knowing how I am Ill still be looking for the cause.

But Im glad I pulled the center and checked the pattern. It doesn't look bad to me so even if I have the whine there Ill just chalk it up to a noisy gear pair and move on. To be honest the knock is more of a concern for me. I dont like hard metal on metal knocks. Something will give, usually at the wrong time.

Oh, its a new B&M prepped 700r4 auto trans.

Thanks for chiming in. I appreciate ALL the help I can get. JR

big gear head
02-19-2011, 08:15 PM
If it was a manual transmission I would say that it's probably some loosness in the controll arms and the backlash from the transmission, clutch disc and the rest of the drive train is causing it to knock. With an automatic you usually don't get that kind of backlash in the drive train.

JRouche
02-19-2011, 09:46 PM
If it was a manual transmission I would say that it's probably some loosness in the controll arms and the backlash from the transmission, clutch disc and the rest of the drive train is causing it to knock. With an automatic you usually don't get that kind of backlash in the drive train.

Its an auto.. Any other ideas? Thanks for the input... JR

chicane67
03-13-2011, 12:07 AM
0065 to 007 isnt too tight... if you are running standard 75-90 or a straight 90 wt.

TheBandit
03-16-2011, 08:03 AM
JRouche - I've setup a few diffs in the past with success, but I'm no expert either, so take my advise for what it's worth.

First, the pattern looks good to me. It's well centered on the tooth. You might be able to get a clearer pattern by applying more pinion load as you turn the ring gear, but I don't think it will change the results. You mentioned one place having a backlash of 0.095 and if that's really true, you have a problem! I think a chipped tooth on the pinion may cause that sort of backlash.

The wear pattern from actual use you showed in the very first picture may tell a story. The pattern going out toward the heel suggests to me that under load you're getting some movement that you can't produce on the bench. I've read that some people setup pinions deep so that under high loads, the tooth will ride more centered. At any rate, this can happen for a few different reasons. Bearings and bearing preload are the first things I would check. If you don't have a small inch-lb torque wrench, let me know and you can borrow mine (picture here (http://thebandit.xtremefabricator.com/SAS/frontgears26.jpg)). I don't know the specs on a 9" Ford, but for the 8" Toyota diffs I've setup in the past, you want to see something in the neighborhood of 10in-lb resistance on the pinion without seals or the ring gear in place. In the Toyota diff, bearing preload is a function of the crush sleeve or solid spacer bushings, but I don't know about the 9" so check into it. You also want to see good preload on the carrier bearings, which is harder to measure or produce. I made a large spanner wrench for Toyota diffs and I have cranked on it around 150ft-lb on the carrier retainers to get as much preload as possible. My application was rock crawling and I put my diff through some serious abuse with never a problem. Rereading your post, it looks like you've done this.

That all said, most of the problems with a bad pattern are going to show as gear whine and not "clunk" or "knock" as you've described. You said the diff was whining from the get-go and you've been driving it this way for a while before the knock sound kicked in. Have you been able to inspect the pinion? Are all the teeth intact? Do any of the bearings or gear surfaces show heat discoloration? Is the input yoke/flange tight?