Just got my 4:10's installed and wow... what a difference. Only thing is when decelerating there is a whine when doing more than 30ish MPH. The mechanic told me about it and he has done many 4:10's but said he never had this issue. He said it's installed correctly. Would friction modifier help me at all?

 

what brand 4.10's did you get? i hear the motiv gears will whine.

 

FRPP. I have done some reading and some posts say the backlash would cause it. I might have to take it back. Can anything else cause it?

 

First off if your installer has installed many 4:10 gears in Fords he should know that fiction modifier is an absolute must. If not fire him! If he didn't put it in he's a "loser" in my book. Second...gears whine because of poor install. It's all in the proper shiming of the ring and pinion that gets the clearances correct that makes the difference. Ford installs thousands of 4:10 gears in truck rear ends everyday and they don't whine. I own 2 vehicles with 4:10's from the factory and they don't whine. Sorry.

 

ok so I am going back Monday then. I asked about friction modifier and he said use whatever the manual says so I did.

Thanks!

 

Just so I have a bit more info when I go back. Is it a specific adjustment that's out of whack that causes this?

 

I had a good and trusted friend install my 4.10 gear set, and he had them in and out, set and reset 4 times, so I know he did everything he could possibly do to ensure they were right and they still whine on deceleration. They are Motives and I expected it to a degree and told my friend that. I guess it's luck of the draw sometimes. The only issue is accepting the fact that they will whine ... so relax and enjoy the new found rush of acceleration !

 

And this is where I am confused. I get conflicting info. Some people say whine is an install issue and others say there sometimes is nothing you can do. I went back to the garage and he said it is set up perfectly and that there is nothing he can do. And now it either is not as bad as it was or I am just getting use to it. I just don;t want to make the mechanic redo it if there really is nothing that can be done...

 

A proper install will not whine or howl.. Pretty much no matter what gears you use.

 

Here is how this works. There is specific pinion to ring gear endplay, backlash and gear contact pattern specifications for power side and decel side of the gears that Ford puts out that is used for all 8.8 gear installs. Do a search to get them I do not have them but know they are a must. They must be adhered to or you can have the issues you have. This is why they make shim sets directly from Ford to make these adjustments. A earlier poster said his installer had to pull the differenial 4 times and they still whine. I still say when Ford does 4:10's they don't whine. All you need is these values and a dial indicator to verify they correct. There is plenty of info on the web about how to set up a 8.8 rear end. Do a little searching and take that info back to your installer and question him and see if he can show you it is set up "perfectly". I can put your rear gears in and make it run down the road...but to do it without making it whine is a different story. You have to do it right!!

 

Well after alot of reading I think it has to do with the pinion gear "preload" There is no whine on acceleration or when maintaining speed. Only when I take my foot off the gas and only above 30 or so MPH. If it is the preload what is the fix? DOes the whole diff have to come back apart?

 

Well if and I say "if" it is a preload issue with the pinion gear then here is the issue. Did you have your installer change the pinion bearings and crush collar? If he did not change the pinion bearing and crush collar that was set at the factory than "NO" that is not your issue. This is the very first thing that is done when changing all the bearings out. He would change the bearings on the pinion gear and install a new crush collar and torque to the proper specs which set up the pinion preload. There are a few steps to get the pinion depth set correctly first but if he didn't change out the bearings it is a none issue. To me it sounds like there is too much backlash between the ring and pinion gear. It should be set between .004 and .008 I believe.

 

I bought this. http://www.americanmuscle.com/rearendrebuild.html I think it has all new bearings etc.

 

Hey Tim....You bought the complete rebuild kit which is a good thing. See all the shims in that kit?? They are to adjust all of the parameters I have been talking about. I can't say that your rear gear is out of whack. All I am saying is there is only one correct way of doing it. I don't know how to help you otherwise. But I know what I am telling you is correct. For the record they can pull the rear cover off which will cost you some new rear end fluids plus the Ford friction modifier and all of the items I have said can be checked with a dial indicator can be checked in less than 1 hour. I say...make your installer prove it's a perfect install.

 

I might just go to ford and ask them to check it. But if the gears are set up right as the mechanic states and it is the "preload" what's involved in fixing that?

 

Now here is were I am running out of suggestions. I believe most on this site will agree with me that if they are set up correctly they will not whine. Yes... Motive gears seem to whine but you bought the Ford Racing gears and most would say they don't have the same issues. My best advise is to get a second opinion by someone that knows all the specs. That is my best suggestion.

 

I understand what you are saying but from what I have seen on a few different sites now is that because it is only whining on deceleration it is more than likely a bad pinion bearing or preload. SInce the bearing is new I was thinking preload. In your opinion is it possible to be the pinion issue? Like I said I have zero whine any time except when I take my foot off the gas above 30mph. I will probably have the dealership take a listen and see what they say.

 

Ford dealer did my gears after somebody did the first time, Neither the dealer nor a Old school race car hobbiest could get them quiet. For a third time Im taking the car to CRT performance in Ohio, Its a 4hr ride for me , but from what Ive heard he gets them done right !

 

It could be a pinion preload issue. Only having it checked by someone that knows what they are doing will tell the truth. Putting gears in is like having sex...you ain't going to get it right on the first try. It takes practice...practice ...practice!

 

Turns out it is what I suspected. The pinion bearing is not set up right. Hopefully the guy who installed it will make it right. Otherwise I have to pay pretty much the same price as the install since the whole thing has to come apart again.