So I'm building a new third member with all new parts including case, except I bought some used OEM Ford gears. I have about .001" of runout on the backside of the ring gear but my backlash varies about .006" and doesn't change back and forth on opposite sides of the ring gear like it would if it was because of ring gear wobble. I can check the backlash at one tooth, it'll be .011, then two teeth over it is .008 or something. The backlash varies randomly. I've got the backlash varying between .008 and .014 right now. Everything is tight and squared up with all new bearings/races. I've got 24 inch lbs of pinion bearing preload, and cranked the side adjusters pretty tight for carrier preload. I found some people mentioning that some OEM Ford gears are "timed" as indicated by some yellow paint marks on each gear. Apparently they were lapped with a certain timed mesh from the factory. I have the timing marks lined up. So my first question is what could be causing this rapid change in backlash by only moving a tooth or two over on the ring gear? I've also noticed when I rotate the pinion yoke in the forward direction, the gears make kind of a scraping sound that you can also feel in the yoke while turning. Spinning it in reverse it is perfectly smooth. I currently have a .018" shim behind the pinion support. I found that if I space out the pinion support to .036" the scraping noise is almost gone but the pattern is way off. If anyone has an input that'd be great. The first two pics are the coast side, third is drive side. This is with .018 shim and backlash .008 to .014.

 

That's close to an acceptable pattern. You might want to move the pinion in just a little more which will take the drive and coast a little more off the toe. Remove .005" shim at a time from behind the bearing retainer.

If you're not already doing it, when you rotate the pinion to get a wear pattern, force something under the ring gear to add drag.

Can't help with any other answers

 

Right now the drive side is favoring the root of the tooth and the coast side is favoring the face. So the drive side says that the pinion is too deep and the coast side says it's not deep enough. Setting up used gears is difficult because the pattern is hard to read. You might not get an ideal pattern with used gears, so don't expect it to look like you think it should.

If this was mine I would start by adding .005 to the pinion shim and see what the drive side does. This might be going in the wrong direction, but with used gears it's a toss up and you have to experiment. If the coast side goes way off then go the other direction and see what happens. Usually with used gears you want to set them up by what the coast side tells you because it has much less wear on it and the pattern will be more true.

 

Thanks for the replies. I was wondering why they say to look at the coast side when setting up used gears. Now I know. The pic of the drive side is at an angle where you can't quite see the bottom of the teeth, it may not be as deep as it appears, but you guys probably know more at what you are looking at than I do. I added about .004 more to the pinion shim and it looked like the pattern on the coast side was touching the top of the teeth and a little further to the toe side. I'll try a little less shim and see what happens. That roughness/noise I have when turning in forward still has me puzzled. But I guess I'll get to that later. There are no burrs or damage to the gears that I can see that would cause what I am experiencing, but who knows.

 

Look at the pattern on the teeth. Notice that there is a wedge shape to it and that the wedge favors the root on the drive side and the face on the coast side. It doesn't matter how far down the tooth it goes. What you want is a pattern that doesn't favor the root or the face, with flat ends or maybe oval shaped ends and the root and face being nearly equal in length.

 

Ok I get what you mean. I was looking more at the location of the marks on the teeth instead of the shape, although I'm sure both matter. I think I found what was making it rough when turning it forward. I noticed little nicks in the leading edge on the pinion gear. I very lightly used a dremel and buzzed the nicks away so that no metal was protruding out from the smooth surface of the teeth where the gears mesh. That seemed to have smoothed out the roughness, but a little still remains. Do you think this will cause a lot of noise? Will it "wear in" these little nicks or stay rough forever? I definitely don't want to put this together with a high chance of there being a lot of noise, I've lived with some whine in the past and it sucks. By fixing the nicks in the pinion my backlash consistency is much better. I read the specs for OEM Ford gears are .010 -.016 backlash so I've got it at .013 - .015. I brought the pinion in a little deeper with a .015" shim and here's what it looks like. First two are coast, third is drive. I'm thinking I need to go a little further out with the pinion. Sound right? Thanks for the assistance guys.

 

Yea, coast looks too deep. Take it back out a little. Use a flat stone to remove the high spots on the pinion teeth.

 

As far as your variation in backlash, take the ring gear off the carrier and run a flat file across the back side of it. You might be surprised at the pattern that will appear with all the high and low spots. Once you get the backside filed as flat as you reasonably can, be sure to torque it evenly in a few steps to the carrier.

 

This may help.
http://static.speedwaymotors.com/pdf/910-82720.pdf

 

I've been preoccupied with other projects lately but I spent a little time on the gear setup tonight. I switched from a .015 pinion shim to a .018 shim and I think I've got the pattern about as good as it gets. Backlash is .012-.013 with decent carrier bearing preload. I'm thinking this is a good pattern but I figured running it through you guys once more couldn't hurt. Looking back at my first post I'm using the same shim with a little more, but now consistent backlash. The drive side doesn't look perfect but these are used gears. Think I'm good?

 

Yea, with used gears I'd say it's pretty good. I think you are right, it probably isn't going to get any better than this.