Hugger

iTrader: (21)

SCROLL TO MY LAST POST FOR NEW PATTERN PICS. I have attached two pictures of my pattern. The gears are AAM 3.73's. The instruction says to "aim for .004" backlash. That seemed too tight so these are at .0055 - .006. I started out with a 31 thousandths pinion shim but the pattern seemed to be too deep in the tooth. The pictures below were taken with a 29 thousandths pinion shim and the backlash measurement from above. The drive side looks pretty good to me but I am concerned about the coast side running off the toe of the gear. What would you rear end gurus do with this. This is about the 8th try setting up this rear. I want to make sure it's right. Any advice appreciated.

cam

iTrader: (9)

Cant really see bupkiss in that pattern. You need to have tensiuon on the gear and spin five rotations in each direction to get a good pattern to look at.

All said and done though patterns dont mean much. If you pinion depth is acurate and your backlash is within spec your good to go. If your guessing on pinion dpeth ( no tool ) then check pattern I said above. Lots of resistance is key. If the rear is still in the car put the ebrake on a bit so its hard to turn. If not hold tight with aglove or sumthin on the ring gear while you rotate the pinion

chicane

It looks short. The hard line at the root of the tooth shows that...

IMO... I would throw the 0.031" back into it and open lash up to around .008-.010". I dont care what the inctructions say... the instructions dont take into account... housing irregularties, carrier run-out and such.

Hugger

iTrader: (21)

Thanks for the advice. When I had the 31 thousandths shim in it the pattern also had that hard line in the root of the tooth. I am not sure how to get rid of that??? I had hoped that changing pinion shims would make it better. It helped a little but pattern still looks a little off. Anyone else have any opinions?

Josh

mzoomora

iTrader: (36)

What shim was in the rear? How far from that are you? I know the .004" seems tight, but the newer gears are cut different and that is actually fine. AAM used to say to measure for pinion depth and then adjust backlash until you got a decent pattern- which will look different than a normal old school pattern. If I remember correct they said you could take them to .003, but I could be wrong on that. Their new instructions are different though.

What did it look like when it was at .031"?

Hugger

iTrader: (21)

When I had the .031 shim in it looked about the same as it does now. .031 was what came out of the original rear so I started with that. I can say that I think the pattern looks better with the .029 shim in it. It looked like the pinion was shimmed to far out with the .031 judging by the depth of the pattern in the tooth. Is that correct? Do I need to keep messing with pinion depth or just mess with backlash now to get it right. Can you look at the pattern and tell if the pinion depth is close? I am going outside now to mess with it some more. I am slowly running out of marking compound!!!

Hugger

iTrader: (21)

Ok guys and gals. Check this pattern out. This seems to be the best so far. This is with a .023 pinion shim and .006 backlash. Let me know what you think. Would you go ahead with a pattern that looked like this or keep messing with it. I really need some smaller shims to adjust it any finer than it is now. Opinions

chicane

Its still a tad short. I am sure that opening up the lash did the most for you at this point. I would go for 0.025-0.026" at this point... as you are closer than before, but you really need to center drive up... or even go a little toe with drive and center up the coast side.

Hugger

iTrader: (21)

When you say "short" what exactly do you mean? How do I get to where you are talking about on the drive and coast. Everytime I put in a larger pinion shim than what I have the pattern gets too deep in the root of the tooth. I really can't get any more fine adjustment out of it at this point. I have a huge shim set but the smallest they go is .005. When I +/- that from each side it throws the backlash too far out. I really wish I had some .002-.003 shims and I could fine tune the pattern some more. If I was to increase the backlash to .008-.009 do you think that would get a little more toe on the drive and center the coast. How noisy do you think this pattern would be? Thanks for all the help.

Josh

chicane

Well... actually, it still "crossed up". By that I mean that drive and coast are not equal and centered on the tooth... both toe/heel and root/tip.

The first picture is "short" with the good lash.
The second picture is "deep" with good lash.
The third picture is "Text book" with good lash.
The fourth picture is "Short Lash".
The fifth picture is "Deep Lash.

Now... with a pattern being "crossed up" it may only take a small depth change to get 'drive' where it needs to be without effecting coast too much. To really fine tune a set-up... you need the ability to adjust by 0.001"... and even 0.0001" if you have the measuring equipment to do so, but at that point your really splitting hairs more than anything else. I myself, like to split hairs... that is why everyone here has heard me state that near all gear sets can be totally quiet... if you pay attention to the set-up. If you cant make 0.001" adjustments... I suggest that you allow yourself to get into a position to where you can. Master shim kits are cheap...

If you increase lash, 'drive' will go heel and wipe higher on the tooth. So no, it wont help drive... but it will definately make coast look a little better. In the end... you'll want to pay attention to both drive and coast. But if your efforts dont yield both... set for drive and deal with it. There have been plenty of times where I couldnt get coast to look worth a ****... but drive was plastered... and luckly, the diff was silent.

As it is now... your coast doesnt look all that bad, but it is wiping a little hard on the root and drive is heel. At a bare minimum... drive needs to be at the center... or better yet, a little toe to combat tooth flex. As you can see in the "Text Book" picture... drive is a little toe just for this reason... and coast is centered.

Hugger

iTrader: (21)

Thanks Chicane... So do you think if I INCREASE backlash slightly on my most recent pattern I can get the pattern more centered on the coast? I think I can make the small adjustments needed by swapping some shims around. The backlash on the pattern right now is a very tight .006, maybe more like .0055. All my patterns have seemed crossed up for some reason. I just don't want to get backlash too high. What is the maximum backlash I should shoot for?

Hugger

iTrader: (21)

Well I got the pattern looking great with my test bearings in... I very carefully catalogged everything and cleaned the housing thoroughly. I even zip tied the shims together to make sure none fell out or got lost. When I go to put everything back together the pattern looked completely different. This is with new pinion bearings and a new crush sleeve. In fact when I reinstalled everything the pattern looked awful and the backlash was zero. I could hardly turn the pinion. Am I losing my mind? How could this have happened. Now I am back to shifting shims side to side and I am at .009" backlash right now and the pattern still doesn't look very good. It really feels like the pinion is too far out of the hole now since the pattern is pretty deep in the root of the tooth. The drive side is to the heel and the coast side is all over the toe. What have I done? The only possibility I can think of is that I didn't use a press to install the large pinion bearing. Instead I put the pinion in the freezer for a couple of days and then baked the bearing in the oven and it slid right on. I used a piece of pipe and a hammer to seat it some more. Is it possible that I have too much space between the head of the pinion and the bearing. Would any slack not be taken up when tightening the pinion nut to crush the sleeve? The carrier bearings are the same ones I used during the test. Could the new bearings and crush sleeve throw me out of whack this much? Right now I have the pinion set at about 24 in/lbs of drag. Please help.

cam

iTrader: (9)

Verify pinion depth first. Then set backlash within spec. These are the two most important things to worry about. You can chase patterns around forever and get no where. What I said above is pretty solid aside from the typos.

Ever put marking compound on a gear set thats run a couple of seasons? Heck do a hot and cold pattern test and watch how much the pattern changes. I do check pattern but I dont set up for pattern I set up for pinion depth and backlash and use pattern to fine tune and verify that its good. I've yet to have one bad if the pinion depth is accurate.

Every rear i have set up this way is whisper quiet. And ya I recomend a press for the pinion bearing you want to be sure its seated properly. A local shop would probably do it for 20 bucks if your nice to them and ask properly

Hugger

iTrader: (21)

I wish I knew that the pinion depth was accurate. My last set of gears had the depth printed on them but the AAM's I am trying to install now don't have a target pinion depth written on them. I don't have the stock pinion to measure against either. How do I know if the depth is correct?

Sharpe

iTrader: (7)

Gah, this must be driving you mad, but you'll be one smart cat after this is all said and done. Good luck.

Hugger

iTrader: (21)

One more question. Do you think it is possible that my large pinion bearing is not pressed all the way on since I didn't use a press? If so that could explain why my pinion is acting like it is too far in the mesh.

BJM

iTrader: (1)

That is certainly a possibility, I really crammed mine on using a press just to be sure nothing could move later.

By the way I used AAM gears and they had nothing written on them either, not very useful unless they only mark the pinions that are off of the nominal tolerance.

cam

iTrader: (9)

First off i agree get the bearing pressed on this should be considered manditory as far as I'm concerned.

Its not that big of a deal with the right tools. Apologies MODS for non sponsor link but its only a tool. Get one of these bro

http://store.summitracing.com/partde...5&autoview=sku


***edit*** I just noticed the part where you said you dont have markings on the gears. There must be some way to find out call the vendor or go for factory spec and hope for the best.

chicane

The two most prominent things that will screw up depth will be the pinion bearing not being pressed on all the way or not having the inner pinion bearing race not seated fully into the housing. Ill bet that one if not both of those conditions exisist right now. Especially, if after you stated that it set up correctly, with the 'test fit' bearings.

The inner pinion race land (in the housing) is normally subject to burr's from the removal of the inner pinion race itself. You have to make sure that the land is flat and free of any burr's for the new race to seat correctly. I myself, normally use a straight die grinder with a 2.00" diameter, 3M 60 to 80 grit disc. Clean the housing out with brake clean (non-chlorinated) and re-install the race and make sure it is fully seated.

Then move on to the pinion bearing itself. Just make sure it is fully seated.

In other thoughts... pinion "setting devices" are useless... unless you are having problems with a "problem housing". As they can not account for housing irregularities and machining tolerances. The paint will tell you worlds of exactly whats going on. Its the only way to "see" what is going on mechanically.

If it set up nicely with the set-up bearings... it will set-up without them. As long as everything is done the same way. Dont sweat it man... you are closer than you think to being done.