changed gears in a 741 now have a whine

I recently did my first gear change in a 741 from 3.23 to 3.73 motive gears and now have a slight whine when foot on the pedal. I could not quite get the 2.77 dim. Motive put on the pinion from the pinion to the center of the carrier bearing. It did however have a good even pattern of the yellow paste I put on the gears and I did get the back lash to .006 as they required by adjusting the carrier bearings. Could my backlash be off, I did seem to notice a good bit of back and forth rocking of the wheels before i set in on the ground the first time after doing the change. Any thoughts, opinions?? thanks

You need to get back into that rear end.

when you were checking the pattern, did u wedge a peice of wood in there so it was under pressure (resistance to turning) as is is going down the road??

No I did not do that but now that you mention it it makes sense to assimulate actual turning pressure. Free turning could give false pattern. I'll have to pull it and check first chance I get. Thanks

Backlash will cause no whine. The pinion gear depth is incorrect.

StrokerScamp said:

Backlash will cause no whine. The pinion gear depth is incorrect.

Click to expand...

It can if there is an excessive amount. I pulled a 3rd member from a guys car to check it for gear whine and it had .038" backlash. Amazingly nothing was ate up from all the slop. I tightened it up and checked the pattern and it looked good so I put it in and it was quiet. That was a rare case of course but you just never know.

This is another ? in my thread. How much torque should I use on the pinion nut?

There are a few things to got right all at once to make it silent.
The pinion depth needs to be right. Not "close" but within a thou or so max. if you need the right shims to do this, get them.
The rotating torque figure needs to be right.
The backlash needs to be within spec. I thought they use .008-.010" but it's been a little while. There is enough resistance just by putting pressure on the carrier with a gloved hand while you turn the pinion to make the pattern look right.
Once those are right, you need to follow the proper break in procedure which is easy but you can't rush it.
step 1 - put car on jackstands with rear installed and oil level full. Start vehicle, and carefully bring it up to about 30mph in drive on the stands, and keep it there for 15 minutes. Then shut it off get it off the stands, and let it cool overnight.
Step 2 - Once fully cold, drive vehicle very lightly for about 5 miles. Do not beat on it at all. Just light driving, smooth light accel and decel. then park and let it cool fully again. Step 3- Once cool, take it out and wail on it and listen for noises.

You must give new gears a chance to seat to each other before they get really driven hard.

I found a pinion depth tool made by Ratech for 8-3/4's. It was cheap and easy to use.
I actually found it on ebay and I think it was only like $27.00 or something. It made pinion depth guessing a thing of the past.

Ratech p/n 10007, there is one on ebay right now for $26 free shipping.

Is this a Sure-Grip, or open? Could the spider gears be causing the problem? I don't see how they could since they are turning with the carrier, and the side gears, without any relative rotation themselves when going in a straight line. Just mentioning it because I have a diff that feels fine when both tires are rotated back and forth, but if one is held from turning, the other one can be rotated about 45° back and forth.