nurmikko22

iTrader: (1)

I just installed a set a motive 3.90's into my 10 bolt and everything was fine through the 500 mile break in period. The gears never made any noise during the break in and the first two pictures are the patterns before the break in.

After the 500 miles was up, I did some hard pulls on the street and noticed a slight whine from 40-50 while accelerating. The next, day while driving the gears went from a slight whine at 40-50, to much louder and they made noise almost any speed when I was on the gas. I took the cover off and the 3rd and 4th pictures are the gear patterns after the break in. I also noticed that the pinion preload was only about 5 in-lbs, so I can only guess that one of the pinion bearings wasn't fully seated???

As you can see from the pictures, the drive side is just hitting the toe of the tooth, but the coast side still looks good. I've tried increasing the pin shims by .008" and have increase the backlash slightly, but I still haven't been able to move the drive side pattern. Any thoughts on which way I need to go? Right now the pinion shim is .040" and the backlash is .007".

guppymech

iTrader: (7)

For your 'after' pics #3&4 I bet you don't have the carrier and its bearings seated fully in the rear end housing. It's crooked thats how you ended up with that crazy pattern on the drive side. I found to get accurate paint marks on the gear mesh I had to treat each trial assembly as a final install, to include installing the carrier bearing caps and torquing the cap screws. IMO try a thinner pinion shim and for the final install shim the carrier bearings as tight as you can without deforming the shim when you drive the last one in. A tight assembly will stay aligned better under power.

LS1-IROC

iTrader: (4)

You should be okay if you can get the pattern back to your before pics if you haven't put too many miles on it after the pinion moved.

nurmikko22

iTrader: (1)

So I was able to work on the car again tonight, but didn't have much luck. I went from a .040 pinion shim to the stock, .032 shim and wasn't able to get the drive pattern to move. I tried going from 0 backlash to .010", and I could notice the coast pattern moving slightly, but couldn't get the drive pattern to change. I then dropped down to a .024" pinion shim, .010" backlash and it produced the patterns in the pictures below. As you can see the pattern is way to high, but I finally got the drive pattern to show contact on more than just the tip of the toe. I'm not sure why I can get the coast pattern to look good and is responding to the changes, but the drive side isn't. Anybody have any thoughts? I also tapped on the pinion races to ensure they were seated properly, but it didn't seem to help.

nurmikko22

iTrader: (1)

Anyone have any thoughts???? Have you seen this before? Could the crush sleeve have compressed during driving? I have a solid pinion spacer on order, so we'll see if that helps at all.

nurmikko22

iTrader: (1)

I was hoping this issue might be related to my crush sleeve, so I ordered a solid pinion spacer. I put the setup bearing on the pinion and torqued the pinion nut, with pinion spacer installed, to 125 in-lbs. The rotating torque of the pinion was 10 in-lbs, so I then put the carrier and its shims in. I torqued the bearing caps to 65 ft-lbs and the backlash was at .009". With the carrier in place, the rotating torque of the pinion was 25 in-lbs, so it seems the carrier preload is correct. When I checked the pattern, I still got the same thing....good coast pattern, but the drive is just hitting the tip of the toe as shown in the posts above. At this point I'm out of ideas and don't know what to try next.

I did notice that the center portion of the pinion tooth is polished silver, while the tips still have the black finish that it came with. If the center or "meat" of the pinion tooth has been broken in already, would this explain why only the tip of the pinion tooth is showing up on the gear pattern? Please give me some ideas on this.