Mustang Matt

Need some help and suggestion on a noise from my rear Differential area. I installed a set of Ford 4:10 gears and also installed new trak lok clutches. The gear install went well and gears are pretty quiet except I have a very light knocking noise that I can hear usually in 4th or 5th gear around 30-40mph under very light throttle or floating the throttle a little bit and not really accelerating or decelerating. I've rechecked my backlash setting and it is .009" Ring gear runout was within .001" The pattern on the gears came out excellent and like I said they aren't whining or anything. I got a shop to put it up on a lift and listen to it with a stethoscope and they couldn't duplicate the noise on the lift an said the gears and bearings all sounded good. They suggetsed it could be wheel bearings. Didn't notice any type of noise like this before the install though. Other mods are a 4inch aluminum driveshaft, Upper and lower control arms with poly ends. Car has almost 50,000 miles on it. I'm thinking maybe it's something to do with the spider gears or trak lock clutches or maybe a driveshaft u-joint. Any help or suggestions are appreciated.

brunobluto

I agree with your diagnosis. I dont think its the ring and pinion, sounds like you installed it right. A slight knocking noise when the driveline is under little to no load makes me think driveshaft or the new trac lok clutches. My first guess would be the clutches since the noise is only there after you i nstalled them.

157dB

The fluid level is how high?

6-Speed

What type of gear oil did you put back in and did you add any friction modifier?

Mustang Matt

Yes, I used friction modifer and first filled with 2 liters of mobil 1 75-140. I took it back apart to double check gear pattern and everything and used Lucas 85-140 this time also with friction modifer.

jeffdavis411

Did you ever figure this out? I have the same problem after installing the gears tonight.