Preload, backlash and reading a pattern

Jody Treadway

Jody Treadway

Croc wearing fool
Moderator
Joined
Mar 20, 2005
Location
Hendersonville, NC
Part deux, people
Working on @farmboy's 14 Bolt rear lately. The most recent work was installing the ARB and ring and pinion. I won't bore you want the bolting the ring gear to the carrier. Just use Loctite and torque it to spec.
Started by bolting the pinion support to the housing and adding 5 thousanths depth shim. It's been my experience 14 Bolts with aftermarket gears require 0-10 thou.
Then I dropped in the ARB and ring gear. Granted diffs that use threaded adjusters are easier to setup, but still require some skills. Here ya go
Dropped in the carrier and moved the ring gear towards the pinion with the adjusters. When I was close, I tightened the other adjuster a bit to better seat that bearing. Once seated and smooth, I continued adjusting the ring gear side until zero backlash was attained. I could spin it, but there was 0 BL. This is where you smack the ring with a dead blow to take out any free play, sure enough there was still a little wiggle. Another few turns seated it with no BL.
Now you are ready to add backlash and also preload the carrier. I do so by using a spanner wrench and tightening the non-ring gear (NRG) adjuster. I put all my weight into it and then hit it with a dead blow. Sure enough, 0.008" BL was achieved. Tightening the NRG adjuster will push the ring gear away (backlash) from the pinion. At the same time, it preloads the two carrier bearings by pushing them into the races and housing.
Preload will help keep the carrier from deflecting under load and also achieve proper bearing wear and life. Don't be a hack and use a screwdriver and a hammer. Invest a few bucks in a decent spanner of some kind. It won't look as skoady this way.
Here some pics to look at while I post about the pattern.
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So, I added a 5 thou pinion depth (PD) shim and have 8 thou BL. Ran the pattern and it was shallow. How could I tell? The paint was rubbed out at the top of the tooth on the drive side of the ring gear tooth. The coast side was great. Centered and a gradual pattern. Problem is a shallow pattern will break RG teeth as so much of the power is transmitted through a small area where the tooth is weakest. Moving the pinion closer to the centerline of the diff is needed to correct this.
Another point is you can always look at the pinion tooth pattern too. It will just be opposite the RG pattern. You can see the pinion pattern shows deep (distinct flat line at base of tooth). If you're ever unsure if it's deep or shallow, look at the comet of the pinion for comparison.
See pics
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It needs to be deeper as stated previously.
Being a 14 Bolt, I removed the 5 thou PD shim and assembled it with zero shim. This is pretty common on aftermarket gear setups on these. Don't worry.
I ran the pattern and it was too deep by about 3 thou. I even tried opening up the BL a hair to move the pattern out, but that didn't help.
In the end, I left this pattern and setup as the final one. Here's why:
#1 is nobody makes a 0.003" shim for a 14 Bolt. It was either slightly shallow at 5 or slightly deep at 0.
A reasonably deep pattern will be stronger in an off road application. You will be carrying the load on a stronger portion of the teeth. Yes it will generate more heat on break in, but that can be dealt with. In Sam's case, I want him to have zero worries about woopow, so this is the final product.
This will give him a trouble free life on the trail no doubt. Sometimes, you have to sacrifice drive for coast, noise for strength, etc. In this case it is by no means too deep or anything. Just moreso than absolutely ideal.
Here's some pics with the final assembled pic at the end.
Ask away with any questions. Next up is a HP Toy third that should be enlightening for you Toy guys out there.
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How do like to apply pressure to the assembly to get a good marking? The right amount of drag seem paramount for a good show of contact.

Do you like to make two sets 180 degrees apart to check carrier run out as well?
 
WARRIORWELDING said:
How do like to apply pressure to the assembly to get a good marking? The right amount of drag seem paramount for a good show of contact.

Do you like to make two sets 180 degrees apart to check carrier run out as well?
Click to expand...

I paint 4-5 teeth and rotate back and forth using a wrench on a ring gear bolt. Once the paint makes its way to the pinion, I rock it back and forth rapidly.
I do check backlash at 12,3,6 and 9 o'clock.
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Ive always felt like having a slightly deeper pinion and tighter backlash than "standard" helped with the shockloading we put our gears through. But it might not be ideal for a rig that sees alot of street time (heat generation).

Any thoughts, since I am sure you have seen a number of broken gear setups?

Also, I know you have made comments on here in the past, but any changes or suggestions when re-setting up used gears vs new?
 
paradisePWoffrd said:
Ive always felt like having a slightly deeper pinion and tighter backlash than "standard" helped with the shockloading we put our gears through. But it might not be ideal for a rig that sees alot of street time (heat generation).

Any thoughts, since I am sure you have seen a number of broken gear setups?

Also, I know you have made comments on here in the past, but any changes or suggestions when re-setting up used gears vs new?
Click to expand...

For a trail rig, especially a LP front, I set them up a hair deep. Just to where you can see a faint flat line at the base of the drive side tooth. As long as the break in is proper, heat won't be a continuing issue or anything.
Regarding setting up used gears, you'll never get an accurate reading off the drive side due to wear. SO I set them up off the coast side pattern.
 
That’s how I learned to get a pattern. I’ve never had to thin out marking compound using this method. Frankly I’ve never tried another method, and chuckle when I see people using blocks of wood trying to load the ring and pinion. Mainly because they struggle so hard attempting to do what they are doing. Common sense is key, you don’t use the whole thing of marking compound on 4 teeth to check the pattern.

But no clue about comp setup of gears or anything. I’ve always done them back to factory spec. I gotta do the 14 bolt and HP60 for my JK soon. Might attempt that for it.
 
iwaxmyjimmy said:
That’s how I learned to get a pattern. I’ve never had to thin out marking compound using this method. Frankly I’ve never tried another method, and chuckle when I see people using blocks of wood trying to load the ring and pinion. Mainly because they struggle so hard attempting to do what they are doing. Common sense is key, you don’t use the whole thing of marking compound on 4 teeth to check the pattern.

But no clue about comp setup of gears or anything. I’ve always done them back to factory spec. I gotta do the 14 bolt and HP60 for my JK soon. Might attempt that for it.
Click to expand...

Always go for a centered pattern heel to toe, root to crown if possible. With aftermarket ratios and lower machining QC compared to OEM, you can't always get it.
For a HP front, you wouldn't want a slightly deep pattern as it will not deflect under forward load, but it will marginally go deep. Shoot for centered.
I setup front LP60s a bit deeper than ideal as they generally shell the teeth off the ring gear due to deflection. For them I go a hair deep and maybe like 6 thou on BL. Biggest thing is to really preload the carrier so it won't deflect much under load. Once I get my ideal pattern and clearances, I add 7 thou to each side of the carrier for added prelaod.
Does it work?
Ask @McCracken, @farmboy, @GONOVRIT, @jeconn, @Kap10merica, @PQR, Bryan Webb, Tony Woody, Josh Beck. It's a solid recipe.
 
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