Hot Rods New guy needs help with 9" pattern

A friend to me to come here and post. I've got a 1968 f100 that I'm rebuilding the 9" in. Here is my pattern with 8 thou backlash. That with a 12 thou pinion shim. It's a 3.50 Richmond gear set if that matters. Also using a currie trac loc carrier and C7AE housing. All new bearings installed. Really have no clue what I'm doing lol. Hoping you guys can help.

Thanks.

 

Need to see coast side, but the drive side looks like it needs a little more shim, a tad high. How much preload did you get on the pinion? 25ish inch lbs (new bearings)? How tight are the carrier spanner nuts?, did you hammer them tight with a hammer on a spanner wrench? If the preloads aren't right the pattern will change under load. I also recall ford designed the 9" to start with .015 pinion shim, did the gear set spec the .012?

 

The carrier preload was set with a spanner. Not tight but the ring gear doesn't spin free. I used a sold pinion spacer. Richmond told me to use very little preload on the pinion. The shim that came out was 10 thou. You think going to 15 on the pinion is what it needs.

 

Definitely need to see the coast side. Coast side is where most noise comes from. The drive side you show is very close. You will need to use a thinner shim to increase the pinion depth, but only a couple thousandths.

 

Pattern looks pretty good in the middle of the tooth ,but I agree I would drive it a little deeper ,bringing it down just a bit,,but like race car says the coast is where they get whiney.

 

To get the coast reading I hold the pinion and push the ring gear correct?

 

.10 shim .8 backlash. Am I getting any better?

 

No, you're not. It's worse.

The contact area is all in the flank of the tooth. It should be up farther on the tooth, centered on the profile, slightly towards the toe (small end) of the tooth.

 

So it needs a thicker shim?

 

Yes, a thicker shim and reset your backlash. Your contact pattern is even lower in the flank of the tooth now, so you have to go the other way on shims, while maintaining backlash. Where you have the pattern now, concentrates the load in a small area and would lead to tooth failure, galling, etc.

The object is to spread the contact evenly over the surface of the tooth. You can't duplicate the load on the tooth by manually turning the gear set in the housing, so when you're setting it up, you want the pattern spread evenly on the tooth, but towards the toe end a bit. Under full load, the contact area will then spread towards the heel and cover the entire tooth.

 

Did the gear set come with shim specs? if not I'd go with .015 and that'll move the drive pattern. I've never used solid crush sleeve, I'd be setting preload at 15in lbs mininum. The spanners have to be hammer-tight to set the pattern. To assess proper the rear has to be exactly as you would drive it. You can't get a good pattern and then hammer everything down to tight, it will change.
When creating the pattern you push as hard as you can possible push against the gears, put as much a 'load' on them as you can. In thoery you should not be able to change anything by pushing, but theory is based on good mechanical practices and pushing, prodding and poking are a mainstay of an good mechanic.

 

I set preload to 15 in/lbs in pinion. Set preload on carrier bearings. Backlash at .7 .15 shim. Am I closer

 

I don't think I like the straight edge on the bottom of the pattern. Will that cause an issue.

 

Any thoughts.

 

I'd try another .003" thicker in the same direction.

 

Ok thanks. I'll give that a try

 

Doesn't the shim on a 9 inch Ford move the pinion out, not in?

 

Go with TagMan's suggestion of .003 thicker.

 

Pinion shined at .18 and backlash at .8 any better?

 

I think I would go back to the 15 shim and call it a day. The last two (.015/.018) should both run quiet.
You are just trying to equalize the marking compound above and below the pattern so the pattern will be centered top to bottom. I think you are very close.

 

What's going to be the stronger of the two? This isn't a daily driver and I love to drop the clutch. I don't mind a little noise if it will hold up better. She's no show truck by loves big smokey burnouts.

 

Looks good where you are. I'd prefer the drive side to be a little further towards the toe, but there's not much you can do to move it. Make sure the backlash is good in4 places (rotate the gear set to 4 different positions) and check the pattern all around the gear to make sure there's no run out.

 

Just want to thank all you guys that helped me out. Much appreciated.