loud gear whine after install on decel

[type911]

Purchased 3.73's and FMS-M4204F288 dif. After install around around 3k rpm's on decel there is a real loud vibrating sound. almost like bearings are destroyed although brand new. pinion marks are right where they should be in the center of the teath on the ring gear. Anythoughts? thanks guys.

 

[mo_dingo]

Did you use a dial indicator to measure backlash & runout?

List everything that came with the dif. Were there gears already installed? Need more info on that.

The wear pattern could have been right in the center (i.e. pinion depth is correct), but if the backlash is wrong, the pinion teeth will be to close/far from the ring gear teeth, and cause whining.
Scott

 

[Quick5pnt0]

First off, who installed them? The first thing i would do is bring it back and rant and rave......

Did you/them put the additive for the posi?

 

[type911]

I had razors edge a local shop in S. FLa do the install. I first purchased a used set of gears that after 10 hrs of install time they found that the ring gear was slightly warped. purchased new Precision gearset and still a real bad whine and chatter. Said screw it and decided to put in a new Dif while we were in there since the old one had 160k on it and was real loose. after 8 more hours of adjusting it still is real loud on decel. at around 3k. I watched them prestty close and I dont think they used anyhing but trial and error with the shims to get the teeth lined up. at this point I am considering takeing it elsewhere because I am over a grand in parts and labor and still no satisfacion although they said to bring it back to see if they can correct it. On them of course. real nice people who do some wicked engine work. You can catch them in the next issue of race magazine. I just want a rearend that makes no or very little noise. I dont think they used any friction modifier.

is there anything I should tell them to make sure to do on their next attempt to make it work?

 

[Quick5pnt0]

YES, use friction modifier....LOL
I'm almost certain the posi will whine like a bit%h without it.

 

[type911]

one final question. Is there anything I should ask to make sure they do no what they are doing?

 

[HISSIN50]

it sounds like backlash issues.

as far as i know, friction modifier is for the LSD (clutches) - it has nothing to do with rear end gear sounds.

 

[Joes95GT]

The friction modifier serves just as it's name implies. It modifies the friction through reduction.

Have you ever smelled that stuff? If I were friction, I wouldn't want to be around that either.

Excessive backlash (excessive = greater than .013") leads to banging and slamming in the rear housing. Backlash too tight (tight = less than .008") leads to busted teeth off the ring gear.

A toed in or out gear pattern produces a whining noise.

Now, it can appear that your gears were set-up "just right," and they may have been, but the actual casting in the pinion or ring gear could be flawed, which is producing the sound.

With that said, if my lawnmower had a ring and pinion gear, I wouldn't put a Precision gear set in it.

I'd be willing to bet that if these people are as honest and good as you say they are, your problem is the actual gear set. FMS is the only way to go.

Joe

 

[89MustangGX]

OMG, 10 hours with one gearset and 8 hours with another?

If you didn't have so much money into them already, I'd tell you to find another shop and QUICK! There's NO reason to spend that much time -- they should have identified the problem with the gears very quickly and the second set shouldn't have taken nearly that long.

 

[type911]

friction modifier was used. baclash was .011. a perfect rectangle in marking paste. all in spec. I am leaning toward a bad set of gears as well. It will be in the shop tomarow for what i am sure will be another 8-10 hours. Could the crush sleave be a possible solution? It wasnt loud at all and then one down shift and wheeerrrrrrrr!!!!! I say this because the sound wasn't pressant at first but showed up later from one down shift.

 

[89MustangGX]

This won't all apply to you, but this was a thread I posted for help on my own problems -- good info and a good picture of what the gear pattern should look like. You don't have to pay attention to all my questions, etc -- but the replies have good info in them. These guys were right on -- everything they said was right.

http://bbs.hardcore50.com/vbulletin/showthread.php?t=18084

Also a good board for technical questions -- these guys don't fool around, they are 100% hardcore. You can post there as well and probably get good responses.

Whatever you do, don't put too much wear/tear on the rear, you are only hurting it if it's not setup right.

 

[type911]

:worship: You are my hero! that sight is great!! cant wait until tomarow to see how they look once opened. I realy appreciate all the help from all of you. thanks again. and again.

 

[mo_dingo]

I can't believe the shop didn't use a dial indicator. That is plain stupid.

If [size=+1]ME AND A FRIEND[/size] could install my gears in 3 & 1/2 hours (first time), then that shop is trying to clean out your colon. Tell them to close their shop and try putting bouquets of flowers together instead. Find another shop immediately.
Scott

 

[type911]

I do believe they did use one after talking with them they told me backlash was at .011.

 

[mo_dingo]

I do believe they did use one after talking with them they told me backlash was at .011.

That is somewhat reassuring. But you still need to find another shop. They are reaming you.
Scott

 

[type911]

UPDATE!!!

All is well. quiet as quiet can be. 2 words. Crush Sleave! Wasn't seated all the way. so that one down shift did it. These guys are good guys. It is partialy my fault for buying used gears off e-bay buy cheap buy twice. it took them a while to shim it before they came to the conclusion it was warped. Awewell another e-bay lesson learned. thanks for all the help.