Ok I am building this 12 bolt rear and putting a used 3.08 : 1 gear in it. I have all new bearings and have been reading everywhere that 25 in. lbs. should be the pinoin bearing preload. Well I have mine at 4 in. lbs. and I dont understand why it should be so tight on the bearings cause its sort of hard to turn as it is. I arrived at 4 in. lbs. by just tightening a little bit at a time and checking for play in the pinion each time.

(.035 shim on the pinion)

Just need to make sure I am doing this right before I go to far.

 

your method for checking preload is pretty meaningless. you check preload by using a dial type inch pound torque wrench and spinning the pinion and look at the reading on the dial as it spins. there is a slight differance in the break away torque and the spinning torque. on a 12 bolt or similar rear i use a 3' long 3/4" drive handle with a cheater on it. it takes a lot to get the preload on a 12 bolt. on a 7.5 ten bolt i usually go too far and have to start over ,i use to buy cruch sleeves by the bag. next 7.5 i do will have a solid spacer in it.

 

EDE, I am using a 0 - 60 in. lb. torque wrench (dial type). It breaks loose at about 6 and drops down to 4 while spinning I was just wondering why in the hell it has to be so tight on the bearings after the play is out of the pinion, I tend to do better at something if I understand why I am doing it. If you can tighten the pinion nut on a 12 bolt with only a 3' cheater bar I wish I had your arms because I have trouble with a 6' cheater bar, LOL. I hope the way i am doing it is not meaningless because its the only way I know to do it.

 

If it breaks loose a 6 and turns at 4 it is not tight, it is too loose for new bearings. By the words "tight" do you mean the turning force required to spin the pinion or the amount of force required on the bar to tighten the nut? You said you were better if you understood what was going on. When you have lots of pressure on your 6 ft bar you are not actually putting all that force on the bearing and it will stay that way, you are crushing the sleeve and that is what takes a big bar. The sleeve is designed so that when you crush it and the turning reading is say 20 in lbs, the bearing now has the correct pre-load which is not the several hundred pounds it took to crush the sleeve. Hope this helps

 

Yea that helps alot. Damn time to get the cheater bars back out.

Thanks.

 

...and that F'er needs like 300FP to crush...
I gave up and used a solid spacer & shims. Turns out that's another pain to set up, but you can dial it in to an absolute Inch pound & they're reusable. So they do have there pros.

Yea 'ede' I got the Raytech (sp?), and once I found the correct shims to get me close, I would run the spacer itself across some sand paper so I dial it in perfect

Ron