New diff instead
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
New diff instead
So after installing a Pfadt transmission mount and having all noises including my gear whine get amplified by 100% I decided to send back the hardened C6 output shafts and clutch springs I ordered from RPM and ordered a stage 2 diff instead. I was going to order a new ring and pinion to go with the diff build because of the noise, but with the ring and pinion along with the shafts, springs, seals etc. It work out better to just get a completely new diff and just slap it in when the converter goes in.
Now when its done I just send the core in for the exchange.
I now have my mind on the break in procedure, and know to be very easy on the new diff and converter. I do plan to follow the break in steps closely, but I was wondering.. If brand new vehicles gets driven off the lot without a break in and are fine most all of the time, why is it so needed for a new diff that is even better than factory? The micro polished gears are supposed to help avoid noise too am I right?
Just looking for thoughts and opinions on break in procedures.
Now when its done I just send the core in for the exchange.
I now have my mind on the break in procedure, and know to be very easy on the new diff and converter. I do plan to follow the break in steps closely, but I was wondering.. If brand new vehicles gets driven off the lot without a break in and are fine most all of the time, why is it so needed for a new diff that is even better than factory? The micro polished gears are supposed to help avoid noise too am I right?
Just looking for thoughts and opinions on break in procedures.
Tech Contributor
Joined: Jan 2007
Posts: 19,398
Likes: 1,138
From: Dyer, IN
To answer your question about factory break in. Many powertrain components are delivered to the vehicle manufactuer after enduring a break in cycle, which checks for leaks, noise, sensor output, etc.
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
FWIW: Rick Kim just installed 3.90's in my rear. I already had his Stage 4 setup which used my older but fine Z06 3.42's. This time he asked that I carefully break in and heat cycle the new gears keeping it under 50MPH for the first 500 miles. I've still got about 300 miles to go. 
I will tell you 577/530 and 420Ft/lbs of torque at 2k RPM with 3.90's is going to be
I will tell you 577/530 and 420Ft/lbs of torque at 2k RPM with 3.90's is going to be
Last edited by WKMCD; Oct 11, 2012 at 08:21 PM.
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
Good to know. I have heard that an auto is very easy on the drive train compared to a manual, so I don't think the irs will be in too much danger. I am pretty much attempting to set up a bullet proof drive train for when I get into heavy engine mods. The car will see some drag strip, but remain a daily driver.
I have also heard of the figure 8 thing for new diff gears. But it depending on what RPM sends as instructions and I'll go from there.
I have also heard of the figure 8 thing for new diff gears. But it depending on what RPM sends as instructions and I'll go from there.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Its HIGHLY RECOMMENDED to use the builders break in recommendations!!
GM recommends that you limit top speed and RPM for the first 800 miles.. We were very careful to do that on my brand new 98 Coupe, 02 Z and my 11 GS Vert. So far ZERO ISSUES for the drive trains!!!!!!!!!!!
GM recommends that you limit top speed and RPM for the first 800 miles.. We were very careful to do that on my brand new 98 Coupe, 02 Z and my 11 GS Vert. So far ZERO ISSUES for the drive trains!!!!!!!!!!!
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
Yes, I will follow the recommendations as closely as possible. I will be breaking in a new 3200 stall converter and a rebuilt torque tube as well as the new diff. Everything but the transmission itself will be new from the flex-plate back. I'm pretty excited about this build. I will probably be overkill on the break in to make sure it is perfect and lasts a long time.
