First of all, sorry to make this a new post as I'm sure that I could find what I need if the search was working. OK, so I had Motive 4.10 gears installed last summer and have always hasa a small audible whine on decel and when my mechanic checked everything was well within spec. Preload, backlash, pinion depth etc. all were right on as well as the wear pattern was good. I have just accepted the fact that because I bought cheap that I will live with some whine (I also hear that Motives are good for some whine). Now normally I have the radio on and the exhaust note is pretty loud so I never noticed before but the other day I noticed that when I hit 55 mph I get a steady whistle/whine from the rear of the car. I dont know if it stops at a higher speed as traffic kept me around 55-60. At 1st I was thinking maybe a bearing but seeing as it starts at 55 mph and is goes away as soon as I go below 55 I am thinking its more gear whine. Anyone else ever have this and have any input? I am planning on a set of FRPP gears in the future but I dont have the time or funds to just replace the ones I have. If it is whine from the gear am I ok driving on it till next summer? Thanks for any input and sorry for the long post.

 

hmm i installed my gears last night, my neighbor helped he owns a shop and didnt have his dial indicator and he could "feel" it and said it feels like the correct backlash, well i said F it and put it all back together and i dont hear any noise idk

 

it could still be th bearings i had 1 that would only make noise when i let out of it doing over 45 and it was the pinion bearing

 

+1 did u get the bearing kit with the gearsor did u just throw gears in?

 

As I have said in other posts, our cars are basically 1/2 ton pickup trucks with flashy bodies and somewhat improved suspension.So they start out with clunky and noisy drivelines.[/align][/align]What youmay be hearing is increased NVH (Noise/Vibration/Harshness) from the driveshaft's now turning quite a bit faster than it did with the stock 3.27 gears. With the stock gears at 60, in 5th (an overdrive 0.62:1 ratio), the engine is turning around 1650 rpm, and the driveshaft is turning 2250 or so. [/align][/align]With 4.10s the engine is turning 2050 rpm or so, and the driveshaft is turning 3300 rpm. That's a pretty big speed increase, and also pretty fast to be spinning a 4" diameter by 4' long steel tube.[/align][/align]As for the gears, there's nothing wrong with Motive. They are in fact an OEM manufacturer for many automakers including Ford and have been making gears for FRPP (if the part number ends in M they are Motive) for at least a couple years.[/align][/align]There are at least three kinds of noises a differential can produce that can be described as whine. One is the "dreaded" whine of improperly setup gears, another can be a bearing whine from too much preload, and yet another can just be the normal whine of a normal ring and pinion gearset.[/align][/align]Motive makes an AX series 8.8" gearset that is lightened by grooving the rear outer edge of the ring gear:[/align][/align][/align][/align]Obviously this reduces rotating mass quite a bit, however I have read that it also changes the harmonic response of the gear to the extent that previously inaudible normal operating noises were shifted into the audible spectrum. I.e. they are noisier. [/align][/align]Car makers spend a lot of time on reducing NVH because that's what the majority of buyers are interested in. This is often done at the expense ofultimate performance, something the majority of buyers are more than willing to sacrifice for creature comfort.[/align][/align]Normal gear noise is normal. Ever hear the drivetrain on a 10-wheeler, pro-stocker, or top fueler? There's nothing wrong, it's just that transferring power via gears can be noisy...[/align] [/align]