9 Inch Whine

jayem · #1 (**permalink**) 08-04-2003, 01:03 PM

The new gears in my 9 inch rear end whine in 4th & 5 gear.
I've had the gears re-adjusted but thet still whine. What do you
recommend. Thanks for the help. Jay

CowtownCobra · #2 (**permalink**) 08-04-2003, 01:10 PM

Get louder mufflers

jayem · #3 (**permalink**) 08-04-2003, 01:26 PM

Very funny!

blykins · #4 (**permalink**) 08-04-2003, 02:08 PM

Jay, you sure it's the rearend and not the tranny? The tranny sits so far back, it could be it that you're hearing.

Let's ask some more questions:

1. Does it make the sound in 4th and 5th only?
2. Does it do it under full acceleration, and likewise when you let off the gas (coast)?
3. Do you know what your backlash and pinion depth are supposed to be? And what did it compare at when you had them readjusted?
4. Is your tranny old?
5. Are the bearings in your rearend new?

I'm thinking it's not the rearend...it's the tranny. Especially if you have a short-throw shifter like a Pro 5.0 or a Hurst. Those are extremely noisy and you can hear the tranny more profoundly.

If you were having problems with your rearend, you would get some other noises under acceleration and under coasting...probably along with some roaring sounds. I think the only thing that would whine would be bearings about to seize. If so, you could check this out when you pull the center section off the housing. The gears would be blued....or your rearend grease would smell burnt.

Hope this helps...

BTW, what tranny are you using?

jayem · #5 (**permalink**) 08-04-2003, 02:27 PM

The transmission is a brand new super-duty T5. It does have a short throw shifter. The rear end was rebuilt using new bearings.
The whine is in 4 & 5 gears only, but only under load. When you let off the gas the whine stops. Jay

blykins · #6 (**permalink**) 08-04-2003, 03:16 PM

Jay, you may get some input from a few of the more experienced members, but I think it's a combo of your tranny and the shifter. My 2002 Mustang GT with a 3650 Tremec and a Pro 5.0 shifter will make some tranny noise if you listen closely.

However, you may wanna jerk the center section out and check the backlash. You should be close to .008". I'm a little perplexed now, because if your backlash would be off, it would probably be off on the coast side also...causing a little noise when letting off the gas.

If you're rearend looks fine under inspection and backlash checking, I'd suspect it's the tranny. Like I said earlier, it may just be tranny noise...especially with an aftermarket shifter.

Does anyone else have any input for Jay?

Rick Parker · #7 (**permalink**) 08-04-2003, 10:55 PM

If the rear end gears were improprely adjusted you would hear it in the other transmission gears also, certainly prior to 30-40 mph.

Try this: Slowly AND without traffic around (find a smooth quiet road) slowly run up to 40 in 3rd let off on the throttle and listen for any unusual noises or rumbling, accelerate slowly in 3rd and do the same listening procedure (Be sure there is not traffic around you.) Then try it in 4th and then 5th allowing for a little higher speed but not to drowned it out by the exhaust. Sometimes if the rear gears are not adjusted you can actually feel them meshing improperly.

Good luck.........Be Safe

Rick

Rick

trularin · #8 (**permalink**) 08-05-2003, 03:53 AM

Got to go with the trans on this one, the rear would make noise through most of the speeds.

Unless you have a burr on a gear in the rear. It might whine at a specific speed.

Try loading the engine down by going the same speed in say third gear and see if the whine is still there.

Just a thought.

zipzip · #9 (**permalink**) 08-05-2003, 05:51 AM

It may not be gearing at all. Bearings can whine also, or cause gearing to whine. I would doublecheck your end play settings. Too much end play or too much preload - I'd suspect that they're too tight. What might explain the on and off situation is that the speed must be high enough to make the whine. We get that on our gearboxes at work - they won't develop any noise until the higher speeds (you should hear the whine at 30,000 rpm!)

Pinions should be set in preload (set by rolling torque - 8 in-lb max), gears (diff) are also preloaded, but set through a combination of case deflection and preload.

Check this out: http://www.fnc.ch/Technik/9-Inch_rebuild.htm

jayscobras · #10 (**permalink**) 08-05-2003, 09:11 AM

IF YOU HAVEN'T ALREADY ONE THIS AND BEFORE YOU GO TEARING INTO THE ASSEMBLIES, GO TO YOUR LOCAL AUTO PARTS STORE AND BUY TWO CONTAINERS OF GEAR CLOIMBING OIL. ADD ONE TO EACH, THE TRANNY AND THE REAR. THEN SEE IF THE NOISE CONTINUES. IT WORKED IN A FRIENDS COBRA AND IS SO MUCH EASIER.

JAY