silver05gt1

I just had a set of Motive 4:10 Gears installed on my car today and the whine is awful, so loud it almost drowns out the radio (but only when I take my foot off the gas). The guys who did my gears have done 3 other cars with no problems and no whine. Now this time they said that when the better matched up the shim was not where it should be. They said the shim required for the gears was .30 but when the gears matched the shim was at .23. So they were unable to stop them whining. 3 Different guys looked at the car and all had the same result. Has anyone else had this problem? I went ahead and ordered a set of FRPP 4:10 gears this time, but the company I ordered the gears from swears up and down it is a setup problem not a gear problem. What do you guys think? Gears or install?

BlackPhantomGT

There's a lot of posts on here about Motive gear whine. I had read somewhere that it was related to the machining process. Don't know for sure. I have FRPP 4:10's and there's is no whine at all.

silver05gt1

Thanks for the response Phantom. I am looking forward to getting a good set of gears in the car. I am obviously mad about getting the crappy ones, but I guess you live and learn.

Steven6095

As far as I have found out and this has been thrown around for awhile here and my dealer actually proved this to me with their OEM gears.
Motive makes some of the Ford Racing Gears (especially the 3.73s)
There are two different versions I do beleive of the 4.10s

silver05gt1

Well, I don't know if Motive makes the gears for Ford or not but I know this, I had the FRPP 4:10 gears installed in it today and the whine is gone. The rear-end does not make a sound now. So I would have to say it was the gears.

Stooge

Is this a new rear end?? Why so many noise issues with the stockers and the aftermarket. Looks like the same rear that was in my 81 F150??!!

silver05gt1

No it is pretty much the same solid axle 8.8 that has always been in the Stangs as far as I can tell. I have a new issue though for anybody, believe it or not.....The rear-end has about 600 miles on it now so the break-in period is pretty much over and today the rear-end started to clunk, when I engage and disengage the clutch. Basically if I allow slack in the driveline I hear a clunk when I reapply a load I get a clunk. It didn't do this when I got the car back so I assume something has happened. Anybody else had this problem?? I am about to get rid of the 75w-90 they put in for the break-in period and put the 75w-140 the dealer calls for back in the car, do you think that will fix it?? I got the back wheels off the ground and check for any major slack in the pinion and with the clutch in you can barely move the thing so I would have to say the backlash is set right. Anybody got any ideas???

Stewart

Hmm I had motives installed and zero whine, couldn't be happier. It sounds a lot more like it has to do with the installer mixed in with the rear end being more picky.

spyder7724

after 3 sets of gears and being apart 5 times mine is finally silent...most of the time. first motive 3.73's terrible whine, then precision 3.73's not as bad but still very annoying at cruising speeds...now i have the motive cnc xp series 4.30's. i had to increase the backlash to .020"!!! to eliminate the cruising speed whine.
here is the problem i've found with this particular version of fords 8.8" differential:
the carrier seems to be machined either oblong or off center. this causes the ring gear to rotate untrue and backlash varies as much as .007 while turning the ring gear. no doubt this is where the noise is coming from. these rears make noise from the factory in some cars other don't. some start later after thousands of miles. ford has had this same problem with the rangers and explorers which use the same carrier(31spline posi). i talked to a rep at FRPP and word is that ford has a redesigned 3.73 gear just because of the 05-upmustang and explorer/ranger problems. it has the backcut ring gear and a different part #. evidently from what he said the 3.73 is the worst for noise due to tooth pitch and count/harmonic frequency bla blah blah.....and yes motive does make gears for ford but now it's only the 4.30 ratio. all new FRPP gears will eventually have the backcut ring gear and special lapping process to help eliminate noise but it still doesn't fix the root of the problem....the carrier(posi unit). i would advise anyone who is seriously upgrading differential parts to spend the extra $350-400 and get an eaton posi unit. for one it's stronger and clutches won't fry as quickly when doing burnouts/hard launches and you'll save some headaches and tension trying to get that stock POS to stay quiet.
hope this helps guys!!

mustangman02232

cause the guy who installed yours installed them correctly