Gear Pattern.... yay or nay??

[Bullett801]

Much, much better. As per the 1978 Pontiac manual: tighten bearing caps to 55 ft lbs, expand brake shoes so that 40-50 ft lbs torque is required to turn the pinion nut, unloaded gears will not give a good pattern. Turn pinion one full revolution, then turn back the other way one revolution. Under this light load the contact pattern will extend only about halfway. Under heavy loads the pattern will spread out. Under very heavy loads the pattern will extend from near toe to near heel on the drive side and be broader between the tops and bottoms of the teeth. The most important thing is that the contact pattern is centrally located up and down the face of the gear teeth. So don't look for the whole face of the gear to be wiped clean under very little load. The recommended backlash is .006"- .008". .012" is a bit big and remember that it will only grow larger with use- never smaller. Great going- you are almost there.

Thanks Bonnewagon! Prob is I don't have the axles yet, but I researched some YouTube vids and think I can rotate it simulating a load without axles another way. That's today's mission. I'll also decrease the backlash as you advise and hopefully that will give me what I am looking for. Been a learning experience! If I were to do these on a reg basis would def spend the cash for the higher end tools to make the job easier! But I enjoy a challenge! Thanks again!!!

 

[Bullett801]

So here's where I am at. Pinion bearing Preload at 20 in. Lbs, pinion shim .020, carrier is set at .000 (.015 feeler gauge will not fit between bearing race and shim on either side anywhere) and backlash is just under .010. Checked that in multiple areas. This is the pattern under a load

 

[Bullett801]

Guess I will go with no news is good news approach on this post then. Thanks to all who helped and I will let you know the outcome when I get it on the road...

 

[pontiacgp]

Do not forget to tighten up the pin and use a 6 point 5/16" box wrench. Also while the rear end is out of the car it is easier to fill the rear end before you put the cover back on if the axles are installed.

 

[Bonnewagon]

It is still not ideal. A bit too much towards the heel. But like I said before, it is hard to get perfect contact with used parts.

 

[Bullett801]

It is still not ideal. A bit too much towards the heel. But like I said before, it is hard to get perfect contact with used parts.

Think I should keep on messing with it then, OK. I will keep playing around with it. Thanks guys!

 

[pontiacgp]

if you are going to play with it a bit for used gears I would set the backlash more than .008.

 

[Bullett801]

OK I will get it a little tighter and increase the pinion shim thickness by about .005 then post a new wear pattern if it looks good. TY so very much guys! I am getting close.....

 

[Bonnewagon]

Bill, just keep playing with it. Since it is your first one and in no rush you have the luxury of time to try different shims, different backlash, whatever you feel like. This is a learning experience and you have all our brains to pick. Lots of experience on this board. Don't be like me. I was a stubborn bonehead and didn't go by the tooth pattern pictures in the FSM. I got about 15 feet before my gears ate themselves.

 

[Bullett801]

if you are going to play with it a bit for used gears I would set the backlash more than .008.

I will shoot for .012 backlash gp. Thanks guys!!