whining rear

-
roadrunnerh

roadrunnerh

Well-Known Member
Joined
Jul 11, 2011
Messages
3,240
Reaction score
540
Location
Pittsburgh, PA
So for my 8.75 in my '75 Scamp, I purchased a used 741 open case with 3.55's. I replaced the pinion seal, the gears looked good, I measured the backlash and came up with .010" (not bad for used gears).

After installation, the rear whines. :banghead:
Not a howl and no grinding sounds, just a high pitch whine.
At highway speeds it stops when coasting and when I apply the gas pedal it starts. This is behind a 225/904 currently, with plans for a 383/727 in the near future.

Someone suggested that this was a pinion bearing noise. Any other thoughts? Is this carrier going to scatter? I was going to drive this to Carlisle this summer 180 miles from Pittsburgh. Now I'm not so sure.

Any input is appreciated.
 
What do you mean? I didn't take it apart. Just removed the yoke and replaced the pinion seal.
New axles installed with green bearings from dr. Diff.
 
Try 140 weight gear oil to soften things up chances are those old gears made the wine before whatever they were in.
 
How you troque the nut on the yoke can change the preload on the pinion bearings and the tooth mesh pattern. That's what caused a whine in my first 7.25 rear.
At about 40 mph ( 276:1 ) it sounded like I was blowing a horn.
A seal doesn't support any weight and really shouldn't begin to leak for no reason.
You can almost bet bearing wear caused the leak. Sorry
 
RedFish said:
How you troque the nut on the yoke can change the preload on the pinion bearings and the tooth mesh pattern...
A seal doesn't support any weight and really shouldn't begin to leak for no reason.
You can almost bet bearing wear caused the leak. Sorry
Click to expand...

x2. I dont think if it comes and goes that it's dangerous or enough to destroy the rear. But, by unbolting the pinion nut you did "take it apart" and happened to hit the crutial fastener. On some rears removing the pinion and yoke do little. On others, it might as well come all apart. What did you torque the pinion nut to? did you run a pattern before you installed it? Backlash is important, but I'd rather see a pattern.
 
I didn't install a new the pinion seal because there was a leak. I changed it just to be prudent and it's easier to do it with the carrier out.

I torqued the pinion nut to factory specs - 250ft lbs.

Now I'm confused. Usually, the pinion seal would of been replaced with the carrier in the housing. How would you run a pattern then?
 
You said you bought a center section, and checked the backlash. You can run a pattern as long as you can see the gear teeth... The seal can be replaced with the carrier in or out. I find it easier with it in. It sounds like you may have overtorqued the pinion nut. 741 is not a crush sleeve rear and I torque them lower. Usually around 180. But the only way to know is to pull the centerestion, run the pattern, and verify it still has .010 backlash.
 
The FSM listed the torque as minimum 250ft lbs on the pinion nut.
180ft lbs does not sound tight enough.
 
...............did u rotate the pinion by hand b4 and after seal installation,was it harder to turn after...could have a bad pinion bearing, but usually they make a whirling noise, more than likely the gears whined b4 u got them as they usually have .020 bl or more when i find the used.....when u set up the lash tighter they whine like crazy.........this finding is from more than 30 used sets over the years....whomever sold them 2 u likely set them tighter.....kim.......
 
From the little bit I think i understand.

If it's a used third member, meaning it just came out of a car before you got it, the torque reading should be 0-1 inch lb..
If you messed with it and it's more, Your bearings may be fried if you used it much


By using a inch lb. bar torque wrench, ( not a clicker ) on the pinion nut, when it's turned and in a vise,
you take this reading.

It's hard to explain, because you're dealing with two torque figures.


With a crush sleeve, final torque seems to be 250 ft. lbs. and higher, depending on who's doing it.


This procedure is without a crush sleeve, using a solid spacer on a 489. Specified torque is 125 foot lbs.

You tighten the nut, you take a reading, over and over till you get to the specified torque without going over your preload.

If the torque isn't reached or is too much, you remove or add shims. And start over.

I don't know what specified torque you can get away with.

Use a chevy nut, it won't back off.
 
70 DUSTER CRATE said:
From the little bit I think i undrestand, when you torque the nut, in steps, you are constantly taking a resistance reading on the pinion.

By using a inch lb. bar torque wrench, ( not a clicker ) on the pinion nut, when it's turned and in a vise.

If it's a used third member, meaning it just came out of a car before you got it, the torque reading should be 0-1 inch lb.
If it's more, it's too tight and Your bearings may be fried if you used it much

You tighten the nut, you take a reading, over and over till you get to the specified torque.

If the torque isn't reached and your resistance goes up, you remove shims. And start over.

I don't know what specified torque you can get away with.

Use a chevy nut, it won't back off. There's alot of work to this.
Click to expand...

I never heard of that procedure. That's not what my '68 service manual says.....
 
Call it what you want. Can use it either way.

I should not have even brought the 489 stuff up. Sorry about that.

Go by your manual.
 
Neither does my 489.

Moper - I didn't say it was.

I misunderstood Supershafts, he's right !
 
last time i had a whine in my rear turned out to be an axel bearing
 
By your description & personal experience unfortunately pinion bearing is going. You need to replace/have replaced ASAP but if you can handle noise & rear is not spewing fluid everywhere trip to Carlisle should be OK. Drove my Dakota R/T over 10,000 miles and my 65 valiant 4,000 miles with noisy on the way out bearings before money/time allowed repair.
 
Maybe a bad set of gears. Could be why they were pulled by the guy sold them.
 
I have a 742 case 3.23's out of a car I drove and they were quiet. I might throw that in before Carlisle. My plan was to buy a carrier for the 8.75 swap in my Scamp and run them until I pulled the 3.91's from my Road Runner and installed a SG in the 742 3.23's to put back in the Road Runner.

Unfortunatley, these 741 3.55's are whining......:banghead:

More work.......lol
 
kimmer is correct. I have had 8.25 whine when the pinion is too deep in the ring gear. I always check the pattern 2 or three times. IFS 8, 7.25 and 8.25 are a pain so you want them right. 741s should be easier. Like everybody is saying here, worn gears, tight pinion nut whining gears.

Craig
 
You must log in or register to reply here.
-

Back
Top