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Old 02-18-2011, 10:25 AM
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96lt4c4 96lt4c4 is offline
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Yukon 3.75 gears for Ford 9 inch....noise

Make a long story short, I built my own housing to put a Ford 9 in a 1999 Camaro SS. The car is a stick and the stock rear was making noise, so after two gear changes in the stock 7.5 and all them making noise I decided to build a 9. Everything turned out real nice except now the 9 is making noise. I started with Richmond Excels, which I know the reputation Richmonds have for making noise. Of course they made noise as low 10 mph. So, I bought a set of Yukons. I have a set in the 8.5 10 bolt in my truck and they are silent. Anyway they are 1000 times better than the Richmonds but I still have a small whine on acel and decel. I started out with the same .019 pinion shim I had with the Richmonds and the pattern was too deep. So I started to bring the pinion out. I went to .021 all I had was a .010 and a .011 to add together, back lash at .006. It still looked too deep to me but I was out of shims and the next jump I could make would be .025 and it was to far out. I loaded up the center section and took it to a local machine shop. Jimmy Mattingly’s Machine Shop. He builds pulling tractor engines and is a major Ford guy. Anyway Jimmy told me to open the backlash up and that my pinion shim looks OK. He gave me a couple more shims a .012 and a .014. This time I opened the lash up to about .008 and put the .010 and the .012 in to give me .022. It looked pretty good to me but it seemed like the drive side was staying too deep and the coast was coming out more than the drive. So I went on and tried .011 and .012 to give me .023 and it looked like the coast was too far out and the drive was good. I put it together with .022 and about .008 back lash and it has a small whine. I am thinking about just unbolting the pinion and replacing the .010 with the .011 put it back .023. I figure the lash will open up a little more but should still be in spec. looking for some opinions on where to go. I am about done with rear ends.... I only put about 5 miles on the car for a test drive. I want to fix the noise so I don’t mess the gears up.

If you would like to see the 9 I built here is a link to it on LS1 tech
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