Contact Pattern

[NovaPwr]

This is where I am at right now. I am a little confused trying to interperet these dang little pictures of correct and incorrect patterns. Chicane helped me out a good bit but is out of town and said to ask in here once I got to this point. Any opinions? I have the backlash at .009 , maybe just a tad over that. Am I correct that it's calling for more backlash? Appreciate any input.

[JEFFTATE]

I am no expert , but I've built a few rearends.
( I have to refer back to the book every time , but I've done it )

If you already have.009" backlash , then you DON'T need more backlash.
The contact on the drive side is too far in , so maybe the pinion depth is too deep ?
I would move the pinion gear out some.

And then reset the backlash and look at the pattern again.

Just my opinion.
Double Check my advice !

I don't really know rearends that well.

[big gear head]

The pinion is too deep, and don't use so much marking compound. Just mark 3 teeth in one spot and 3 more in another spot. Use a thinner pinion shim and see how it looks. Take about .005 out of the shim. It probably needs more, but start there. Keep the backlash between .009 and .007.

[NovaPwr]

The pinion is too deep, and don't use so much marking compound. Just mark 3 teeth in one spot and 3 more in another spot. Use a thinner pinion shim and see how it looks. Take about .005 out of the shim. It probably needs more, but start there. Keep the backlash between .009 and .007.

Thanks, after studying those pictures of patterns I did just that and put in a thinner shim on the pinion. Then it took awhile to get the backlash right but it finally came out to .009 Pattern looks to be centered on both sides now....or pretty close. I have had enough for one day! Thanks for looking it over for me.

Dave

[big gear head]

Post more pictures tomorrow. I'd like to see what you got.

[JEFFTATE]

You are welcome.

And thanks for the thread !
It helps me (us) learn when we see this stuff.
That's what this website is all about.

[NovaPwr]

Post more pictures tomorrow. I'd like to see what you got.

Here is where I am at right now. Still too much paint on there, I just resmeared all the old pattern out and ran the gears forward and reverse about 6 revolutions each. What do you think?








The backlash right now is at .009 and the pinion shim is back to the original .028 that was under the 3:31 pinion. It was at .036 on the first set of pattern pictures. From studying all these little pattern pictures through my dang bi focals best I could see was that this time things looked better......but I am not sure. Pattern seemed to be favoring toe but centered between root and crown......I think. Coast side seems to be centered although I saw some sites that wanted it centered root to crown but favoring toe. ??? My old 72 service manual for 10 bolts just shows they want pattern centered on both sides...??? I would appreciate your advice. Aside from a sliced knuckle, sore back from crawling under the car a zillion times, wife spewing explitives all evening about how the house smells like cat piss, garage is attatched, ( that danged fomoco posi additive) and what's her tupperware doing there full of posi lube and clutches soaking in it, this has been a real fun job! Thanks.

[JEFFTATE]

I know what you mean about the "Wife Factor".
Mine complains about smells and noise too.

The pattern looks good to me.
It's close to centered in all directions.
It's almost a little close to the crown on the coast side , but I think if you decrease the backlash to about .007" to .008" to get the pattern deeper , you may get a noisy diff...

BUT !!
Get another opinion because I'm not 100% sure.
I'm still learning this stuff !!

[big gear head]

It's hard to tell about the drive side because of the way the light is hitting it. Looks MUCH better than before. The coast side looks like the pinion might be out a little too far now. I'd like to see the drive side a little better.

What brand of gear is this? What was the recommended backlash?

[NovaPwr]

It's hard to tell about the drive side because of the way the light is hitting it. Looks MUCH better than before. The coast side looks like the pinion might be out a little too far now. I'd like to see the drive side a little better.

What brand of gear is this? What was the recommended backlash?

It's a US Gear 3:73 gearset. I
believe it said .008 to .010 will dbl check. My work light quit so I need to get some bulbs before I go further. I wiped the gear clean then put on a small amount of paint. Hopefully this will help to see everything better.







Thanks for lookin at em for me.

Dave

[big gear head]

If I was the one building this I would put about .002 back in the pinion shim. I think you are about .002 off right now. Otherwise it looks good.

[NovaPwr]

If I was the one building this I would put about .002 back in the pinion shim. I think you are about .002 off right now. Otherwise it looks good.

Thank you much, I am hoping this will be the last time pulling this apart! Appreciate the help.

[NovaPwr]

Just wanted to post up the results of my rebuild and say thank you to those who were able to offer me the well appreciated advice during my rebuild.

I would have posted some pics of the last contact pattern but broke my camera when the back of my arm hit the 500 watt halogen light while I was jockeying around under the car trying to get a good angle with the camera.

I will make sure to install the protective "cage" over the front of the light next time I change a burned out bulb! Smashed the front door right off of the camera, burned the back of my arm and reopened the gash in my finger all at the same time.

But on a positive note, the rear is very quiet, seems very smooth and I really like the 3:73's vs the old 3:31's. I really enjoy doing my own work and aside from the aforementioned incidents, I think it was actually pretty rewarding.

A big thanks to Chicane, big gear head and Jeff Tate for their help through this "adventure" as my 10 year old grandson called it. This is a great site and I have really learned a lot of good things in here. Thanks guys!

Dave

[JEFFTATE]

A big thanks to Chicane, big gear head and Jeff Tate for their help through this "adventure" as my 10 year old grandson called it. This is a great site and I have really learned a lot of good things in here. Thanks guys!

Dave

Dave , you are very welcome.
I'm not really an expert on rebuilding differentials , but I find them interesting and I enjoy talking and comparing information.
I'm still learning about this myself.
It helps me learn / re-affirm ideas.
Thank you for giving us an opportunity to learn.