I was setting up my new Motive 3.73's and I called the manufacturer to find out about where to start on the pinion depth. They told me for Motives start at .035 pinion depth and shoot for about .010 of backlash with aout 15 inch pounds of preload. I started at .030 because there was only .025 in there with the old set of gears. Long story short .030 left the patern running too deep on the teeth. I did .025 and then stopped at .020 with the pattern that looked the best. Is there a wide range for pinon depths? Some of you that have set up gears, what were yours?

 

Well, were they talking about starting with a .035 pinion shim? There is not a wide range of pinion depth settings, motive calls for it to be within .002" of whats marked on the head of the pinion.

If you've got a pattern that looks good, you can set your backlash and pray. Or you could measure the actual pinion depth with a tool and know for sure the pinion depth is correct. I just did mine and tried 10 different pinion shims until I was happy with the pattern. I also tried the ratech pinion depth tool with limited success.

My diff is pretty quiet though, so I either am a badass or very lucky. We'll see if she'll hold some hard launches tomorrow at the track.

 

That exactly what I did. After about 5 tries and a lot of research. I did the best I could without any expensive tools. The preload I right on and the backlash is really close to .010. Mine has very slight wine from 55-70 but not real bad. I am ashamed to say I have had it apart 5 times already and am still not 100% satisfied. If i did get a hold of one of those depth setting tools are they really hard to use?

 

Don't be ashamed, I am doing my first gear swap. I put it back together and had a minor whine at 60-70 mph too. I am using an AAM 3.73:1 gear and fooled myself into thinking that I needed the pinion deeper than stock (from the stock .028" shim I used .035") I failed to realize that the pattern was too deep and cut off abruptly at the base of the tooth but otherwise looked quite good. I have now just finished pulling it all apart again and put in the stock shim under the pinion. My backlash right at .005" and the AAM gear instructions say to set it at .004". I find this odd since the service manual says .005-.009. Since the gear is new and the two numbers conflict I am hoping this is a good compromise. I have the car back together but have to test drive it now that it is back together.

 

AAM are two cut gears and the set up is different. They are great gears, follow the instructions, use the stock shim (mine was .032) get you backlash at 4 or 5 and you'll have quiet gears. Remember the pattern for two cuts is different so you only care about the depth.

 

.010 is too much and for performance cars and new bearings you want closer if anything. Don't bother with pattern until you have the backlash right and use the numbers on the motive gears for your pinion depth.

 

What's your guy's opinion on putting shims behind the pinion bearing race? Am i hurting anything? It is a pain having the shop pull the bearing every time when I need a change. Is this fine and essentially doing the same thing as puting them on the pinion?

 

If you do it that way, you may need to remove and install the race several times to find the pattern when you set up the pinion depth. To me, it's just a PITA. And you risk damaging the shims and the race each time you try to remove them too. But if you do it the normal way, you can hone inside a used bearing so it slips on and off easily until you get the right pattern then you change to the actual bearing. I think it's safer and and easier to do it the normal way.

 

The $20 ratech pinion tool is kind of gimmicky. There is a plastic button on the end of it that is supposed to center the tool on the pinion head. Problem is, on my motive gears the hole in the center of the pinion was taperd and would not allow the tool to sit flush against the pinion. I had to file the plastic button down and then re-measure the tool so I knew the overall depth. The $600 OTC tool is the shiznit and will get your pinion depth right on the first try.

I've recently heard something about 2 cut and 5 cut gears. Can anybody elaborate on this as in, which manufacturers use which method, and how the pattern changes between the 2?

I abused my new setup at the track last night and it held up, so must have done something right with mine. I was pulling 1.9 60's with street tires and stock convertor. Best run of the night was a 13.013 @105. That was next to a C6 A4 vette that got smoked with his 13.5

Oh, did I mention that trutrac diff is BADASS!!

 

The 2-cut is mainly used by the OE's(AAM). I am pretty sure the aftermarket stuff is all still 5 cut.
With the AAM's you should set up for proper depth and then adjust backlash until you get the proper pattern, which will look nothing like a typical 5 cut pattern. You are still trying to basically get it in the meat of the tooth, but they are on an angle rather than being an oval that is basically centered on the tooth.
If you are setting up a gear and dont have a depth tool a good starting point is to measure the heads of both pinion gears, the add or subtract the difference from the original shim (If the new pinion is larger- subtract, if the new pinion is smaller- add).
As far as the backlash on aftermarket gears, most reccomend between .008-.012", I prefer to stay at or under .010". Other people go by the .001" per 1" of ring gear for 5 cut gears.

 

so my motives were probably 5 cut then?

 

ive built many rearends.the best way to do this is to pull the bearing off the old pinion and reuse the stock shim.it has never faled me yet.if you dont want any gear whine id shoot for 0.007
10 will make a little noise.be sure to get a good preload on those crrier bearings as well.15 in lbs is about right on the pinion.

 

this is very true .i like to stay as close to 10 as possible when doing my own ,but if im doing one for somebody i do 7 or 8.anything over 4 is ok.but you will get a little whine at 10 or above

 

Is it weird that the pinion shim that gave me the best looking depth and pattern is .007" more than my stock shim? Stock was .025" suggested for the manufacturer was .035" and the one I ended up with was .032". I have a feeling my backlash is too wide cause it feels sloppy but it moved the pattern from the toe to the center of the tooth. I am doing this by feel. Is it possible to measure pinion depth with just a digital caliper? Any thoughts?