I have an 8 1/4 A-body suregrip axle with 2.7x gears that I am going to put under my Barracuda but wanted some steeper gears. I purchased a set of 3.55's with and installation kit and decided I want to do this myself as much for a learning experience as to save a few bucks.

Anyway, my question is regarding the wear pattern I get with the gear compound that comes with the installation kit. Reading the compound is not as clear as the illustrations that are provided and I want a second opinion that I have the gears set up correctly before I button it up and install it.

The new pinion had a depth number from the centerline of the carrier bearing to the top of the pinion etched on it. I do not have the proper tool for measuring this but I feel confident that I am accurate to about .005" using a vernier to make the measurement.

Based on this measurement I installed the pinion with the original shims, new bearings and the yoke. I torqued the bearings until I got 20 in-lbs of torque to turn the pinion (I do not have the crush sleeve or seal installed yet).

I put the differential in and adjusted the carrier bearings to .008" of backlash (spec I have is .006-.010") between the ring and pinion.

The wear pattern I get on the drive side is a little wider than 1/4" wide starting at the outer diameter edge of the ring gear and goes across the face of the tooth and starts to taper off about 3/4 the way across the tooth to nothing at the inner diameter. The coast side does the same thing but starts from the inner diameter and tapers off at the outer diameter. The wear pattern is an even mark that is not quite centered between the top of the tooth and the root of the tooth with it being biased toward the top of the tooth.

The sheet of wear patterns I have from West Coast Differentials http://www.differentials.com/techi.html indicates that the pinion depth is set correctly (looks most like the middle one on the right column of acceptable patterns). Certainly looks nothing like the illustrations for deep or shallow. It's just not perfectly centered top to root of the tooth.

Do the people that have experience concur that I have the pinion depthe set correctly?

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Dave Clement
68 Barracuda (Hot-Rod \6)
http://mysite.verizon.net/vze4pgxf/

Did you measure the pinion depth from the main cap parting line to the face of the pinion? This may or may not give you an accurate measurement. The parting line may not be the true axle/carrier centerline. Measure the OD of the carrier bearing race, devide that by 1/2. Measure the carrier parting line to the lowest spot of the race seat on the carrier. Figure the difference between the two amounts and that will be the # that will have to be added or subtracted to the pinion depth marked on the pinion face. Of course the pattern still needs to be double checked.

Cecil

I measured the parting line to the bottom of the bearing bore and the measure the same on the cap to determine where the parting line was in relation to the center line of the bore. Then used a guage block across the parting line as a reference point to measure the pinion depth. I used a vernier to measure the depth, that is why I say I am only .005" accurate on the measurement.

What I have read that measurement is only to get you into the ball park and the pattern is what's critical. I am looking for some concurrance that my description of the pattern is infact representing a properly set pinion depth.

Thanks for the inputs!

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Dave Clement
68 Barracuda (Hot-Rod \6)
http://mysite.verizon.net/vze4pgxf/

Dave, seeing that you have not done your final assembly, I would try a thinner spacer under the pinion. This should help center the pattern.
When changing the pinion depth, the coast side pattern tends to move more / faster then the drive side.
Backlash adjustment changes the drive side pattern faster / more then the coast side.

I usually try a number of different pinion depth settings before I feel good about the pattern. Trying some different shim settings, this is a good way to learn gear mesh so have at it.
DD

Doug, Thanks!

I will give it a try!

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Dave Clement
68 Barracuda (Hot-Rod \6)
http://mysite.verizon.net/vze4pgxf/

Look to NOT have real sharp edges to the patterns. Also I prefer to have the pattern slightly favor the ID. Load and wear will move the pattern out toward the OD.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd