I recently purchased a nice 98 6-spd Z28 that had some fairly loud gear whine when letting off the gas while in gear. The lower the gear, the louder the whine. I have found out on the Net that too much gear mesh (the pinion too deep into the ring gear) can cause gear whine during deceleration. So while under the car last weekend I found that the pinion shaft had about 0.020" of play up and down. That is not good. It should have very little to no play when the taper roller bearings are properly in their outer races. That much play also means that the pinion can be "scucked into" the ring gear during deceleration and that would explain the whine noise.

So this afternoon I marked the pinion shaft end and the nut with a black marker and put an Ingersoll impact gun with a 1.25" socket on it. After two 5-second bap-bap-bap sessions (hitting it with 400+ ft-lbs of impact torque) the nut moved a total of about 30 degrees. The shaft play dropped to just barely any (0.001"?). It still rotated OK by hand so I had not put anything in a bind. Took the car for a test drive and the gear whine was about 1/10th what it used to be. With the windows up, radio off, and trying to listen for it I could barely hear anything. MUCH BETTER!

The pinion nut tightening took me about an hour to do. I know it is not "to specification", and if you make the nut too tight, the bearings will die an early death. That is why I sneaked up on it. BTW, you need an impact with some serious grunt, since my little Campbell-Hunsfeld impact did nothing and a breaker bar with me yanking on it did nothing to move the pinion nut. You want to just take the slack out of the bearing play by pulling the bearings back into their outer races -- NOT crush the crush sleeve more. So be careful and frugal with the impact and keep wiggling the pinion shaft and checking your ink marks to monitor the amount it is being tightened.

The "official" amount required to torque the pinion nut is until it takes 15-18 inch-pounds (for used bearings) to make the pinion spin in its bearings by itself. On a new installation, it takes like 400 ft-lbs of impact hammering to get the crush sleev to crush, but then the final check is to just spin the pinion with a small, delicate inch-pound wrench. If the amount of effort required to turn the pinion in its bearings is 20-25 in-lbs, that is good. More than that and the bearings are smashed into their races too tight and will likely fail prematurely. This measurement is only really possible when the whole differential is taken apart and you are only working on the pinion. I did it the "half-arsed" way with everything still assembled and in the car, but am quite happy with the results so far. If the bearings die in the near future, then I will tear it down and end up doing it "the right way". If not, I am way ahead. Just thought I would share the experience.

Fred

 

what can you do if you dont have a 400 ft-lb impact gun. Also, how do you keep the pinion shaft from turning?

 

Sounds like you lucked up !!

 

If you don't have a 400 ft-lb impact gun, my best suggestion would be to borrow, rent or buy one in that order. Trying to snug the pinion nut with a 4+ foot cheater bar is tough to do, and nearly impossible with the car only 18" off the ground and the exhaust pipe and torque arm in the way. With the car on a lift you could try to do it. I would also recommend putting a big plumbers wrench on the pinion yoke and bracing it against something substantial if you try the "big lever arm" method, otherwise you will probably just turn the rear wheels even with the brake on. It will also help prevent gear teeth from being bent.

With the impact gun, I had the emergency brake on to keep the pinion from spinning. I also held the pinion yoke with my free hand so that the gear slop was taken up. No need to let the gear teeth bang together.

 

If you dont have a big gun the easiest thing to do is to get the sleeve started in a vice. Measure your old one and crush your new one half way. Getting it started is the hardest part. I have done a few for friends in their garages and I use a large pipe wrench to hold the yoke and then a breaker bar and pipe or my 3/4 drive rartchet and socket with a pipe(it can take the torque).

 

Well after several weeks of fun driving in a spirited manner (both with and without drag radials), the rear end started to whine on decel again. So today I got back under the car and tightened the pinion nut about 60 degrees with the big impact gun. There was no radial play in the yoke/pinion this time, but I decided to see what additional tightening might do. I was able to add about 45 degrees of nut turn without changing how hard it was to rotated the pinion by hand. The last 15 degrees I put in made the pinion harder to turn for sure, so I must have finally either taken up all the pinion gear slop or perhaps slightly crushed the crush sleeve a little more.

A test drive found all the whine GONE.

Now I can drive it around and see if this fix is permanent or not. It only took me about 30 minutes to do this time.

 

Never use an impact gun on a pinion nut.Get a piece on 1/8" steel about 2' long and 5" wide,plot out the 4 u-joint strap holes,drill them 3/8" and cut a hole in the middle with a torch for the socket to fit the pinion nut.Bolt up your new tool to the yolk,remove the nut and using red locktite reinstall it and torque it to 125 lb.ft. You''ll need a long breaker bar to squeeze the crush sleeve but a torque wrench will work for a retighten.

 

There is no torque spec for a pinion nut. Also, it takes much more than 125 ft/lbs to crush a crush sleeve. You can use a impact to tighten a crush sleeve, you just have to take your time and not over do it. Tighten unitil you feel the slack almost gone, then just hit it a little at a time until you get your 15 or 25 in/lbs tightness. Also, rather than make the tool you are speaking of, you can just use a larger pipe wrench with a cheater pipe to hold the pinion yoke. Also, you never retighten a pinion nut. They are crimped nuts and are only intended to be used once. Just spend the $2 on a new nut.

 

Sorry,but anyone who sets up a set of gears and uses an air gun on a pinion nut is a hack IMO.I wouldn't be caught dead throwing a pipe wrench on a customers $125.00 billet yolk much less my own.I've reused pinion nuts for 25 years and never had a problem.I know people mean well throwing advice on there but give good advice.
BTW 125 lbs/ft is not a "spec",its a learned limit that will keep the pinion nut tight and not crush the sleeve making the bearings to tight from doing tons of pinion seals.

 

Any large gear shop will be using an Impact- and a big one. And I can guarantee few if any would use a 2' homemade pinion yoke holder, especially when building a rear on a bench. IMO anybody who would reuse a $2 pinion nut is a "hack", why not just reuse the crush sleeve also at that point? Also we are not talking about a billet yoke here, we are talking about a guys 7.6 with a stock yolk being reset in his garage. He may not even have a torch or welder, let alone ever need this tool you want him to make ever again. I have been to many large diff shops, worked in a couple, and supplied and installed a lot of parts. Not all advice is universal. Not everybody needs or has the money for an all out race rear, just like not everybody is using a billet yoke. For a guy working on a stock rear at his house my advice was fine. For a race diff I wouldnt even be talking about a crush sleeve.
Dont come around throwing words like "hack" when you havent completely read through the thread.

 

So my described tool won't work on a bench but a pipe wrench will? So now I know why moser 12 bolts whine,they must crank down those pinions with big ole air guns.Sorry you got pissed at the hack comment but blipping an air gun a few times is not good advice and that ain't got **** to do with money,how expensive the parts are or building a "race" rear.

 

Gotta like that

 

Gee Glennster, tell us how you really feel!

I had an OBVIOUS problem with the lack of pinion tightness left over from the last pinion seal replacement (previous owner). The pinion moved a BUNCH when wiggled up and down and the gears howled loudly on decel. I found by tightening it the howl went away. The easiest way to tighten it was with an impact gun. You can sneak up on the tightness in small increments this way. What is so terrible about that advice? I did not say to setup your new gears with this method.

I am also the kind of guy who just tightens the bolts down on a leaking header gasket. You must be the type of guy who replaces the header gasket without even checking to see if any of the bolts just need snugging up. Takes all types... I tighten a valve cover or oil pan before just ripping it off, cleaning surfaces, and replacing the gaskets (and RTV where required). Maybe you pull the engine if an oil leak shows up...?

While we are discussing being all **** and such, I tighten my wheel lug nuts in 5 steps -- 20ft-lb. increments in a star pattern up to 100 ft-lbs with a double going-over at 100 ft-lbs. Do you do this?

 

Easy dosent equal right and my **** don't leak from loose bolts because I use a torque wrench not an air gun.When you get ready to do some performance mods to your car see how far that air gun goes zipping down those new heads or hammering those rocker arms down when they come loose.
I'm not trying to be an dick but you stated you did it "half-arsed" and now you want to jump my **** and call me **** for explaining the right way?

 

The right way or just "your way". I am not knocking your method, it is just that like mzoomora said, I do several a week with a air wrench and never had a problem in the last 15 years.

 

I explained the "right" way -- WHEN SETTING UP NEW GEARS AND CRUSHING A NEW CRUSH SLEEVE -- in the last paragraph of my first post. That is what I found in published documents at least. I was not going to remove the rear axle assembly and tear the rear end apart to use that method without trying to just tighten a very loose pinion nut first.

I have a beam-type and click-type torque wrenches that are used often. The impact is used for breaking stuff loose on occasion, and for tightening my pinion nut (twice). I am impressed that your "stuff" never leaks. Most of the stuff I put a wrench to does not leak either, but it sometimes starts to leak over time if I have not touched it before, and I remember having trouble with a SBC valve cover that required more than one attempt on my part to fix a leak -- and the rear intake seal on an old 7500 rpm SBC kicked my butt a few times too. Turbo Regals seem to leak no matter what you do. Maybe yours doesn't?

Is your 125 ft-lb amount what you always do after replacing a pinion seal?

 

Anyone want to comment on why my r/p howls on cruise (holding speed with slight gas)

It's the only time it does it, but it's LOUD!!

 

A cruising howl can be bad pinion bearing preload, improper pinion depth, or maybe a damaged gear set. Go in and check you backlash in a few places, it may come up different from place to place.

 

Holy crap thats more torque than a Honda makes

 

Thanks for the input, I will check into it.