Why break in new gears?
Teching In
Joined: Jul 2008
Posts: 38
Likes: 0
I have had several gear changes performed in the past with bad experiences......here's my thoughts...........from the factory the gears are probably setup close to perfect and there isn't a real need for break in. You buy the car and drive the **** out of it, right? Well after you get that car you decide to take it to a local shop for a gear swap....they have Billy Bob working for them for $9 an hour and he's got a total of 3 gear swaps under his belt. He is turned loose on installing your gears........you get your car back and all seems fine but is it? I would recommend breaking in gear installs just because 1/2 the time they are installed wrong. Break them in, not because of the gears needing to wear in but because of improper installation.
I had an 04 cobra that I added some gears to, went to the track after 500 miles of easy driving, launched 1 time and they broke a tooth on the ring gear. Next installer said there was zero backlash on them........nice! So, break them in just to see if the installer has them installed correctly.....if not, you might be paying for a little more the next time! (carrier, axles, spider gears etc....)
I had an 04 cobra that I added some gears to, went to the track after 500 miles of easy driving, launched 1 time and they broke a tooth on the ring gear. Next installer said there was zero backlash on them........nice! So, break them in just to see if the installer has them installed correctly.....if not, you might be paying for a little more the next time! (carrier, axles, spider gears etc....)
Teching In
Joined: Jul 2008
Posts: 38
Likes: 0
This is an easy one! Think about it......new metal parts = new metal shavings floating around in the rearend. You have bearings back there and they don't like metal shavings! Change the fluid and get rid of the metal shavings after break in. This will extend the life of your new rear!
this deals with an on going issue with my car.
i went easy on a new set of gears ( second time mind you they whined before)
and still whines with the gas on good, Improper setup? or Break in
i went easy on a new set of gears ( second time mind you they whined before)
and still whines with the gas on good, Improper setup? or Break in
Whine is probably due to set up. Ive gotten noisey diffs from a couple people and had to crack it open and re-do the set up because whoever did it before me got lazy.
And why change the fluid/do a break in? Because anyone that's ever installed gears, and did the break in, then drained the fluid will tell you that there is a LARGE amount of break in debris in the oil. Yes a lot of diff covers have magnets. But, once you get a good coating of metal on there, the magnet doesnt work as well as it should. The fluid comes out looking like glitter glue that your little sister uses to make posters with.
Do you really want that stuff churning around in there while you beat on it for 1000s of miles? Not saying it WILL cause problems...but its just not worth it.
I read another analogy about a guy building a "$75,000" motor, then doing 9k dyno pulls. Yeah...but that same guy probably had dyno time on the motor before those pulls. The motor gets broken in and pre-run on the dyno before it gets stretched out like that. No where near the same as a rear...but just saying.
Ive re-geared probably two dozen axles by now. Mostly Dana 30's, dana 44s, and Ford 8.8s. Did a couple of 12-bolts including my Strange. I always make my customers/friends come back for a fluid change/inspection after 500 miles. I get all that nasty metal filed fluid out, clean it out real good, and re-fill. While its clean and empty I inspect the gears, and usually run a quick pattern just to make sure nothing happened to my initial set up. Never had a problem with any of the ones ive done. No whining, no slop, no problems.
If you want to pull a car off the lot with 00000.3 miles on it and beat it...have at it. If you want to install gears and take it right to the track and do 5000rpm dumps...have at it. Ill always be on the side for breaking parts in however.
J.
And why change the fluid/do a break in? Because anyone that's ever installed gears, and did the break in, then drained the fluid will tell you that there is a LARGE amount of break in debris in the oil. Yes a lot of diff covers have magnets. But, once you get a good coating of metal on there, the magnet doesnt work as well as it should. The fluid comes out looking like glitter glue that your little sister uses to make posters with.
Do you really want that stuff churning around in there while you beat on it for 1000s of miles? Not saying it WILL cause problems...but its just not worth it.
I read another analogy about a guy building a "$75,000" motor, then doing 9k dyno pulls. Yeah...but that same guy probably had dyno time on the motor before those pulls. The motor gets broken in and pre-run on the dyno before it gets stretched out like that. No where near the same as a rear...but just saying.
Ive re-geared probably two dozen axles by now. Mostly Dana 30's, dana 44s, and Ford 8.8s. Did a couple of 12-bolts including my Strange. I always make my customers/friends come back for a fluid change/inspection after 500 miles. I get all that nasty metal filed fluid out, clean it out real good, and re-fill. While its clean and empty I inspect the gears, and usually run a quick pattern just to make sure nothing happened to my initial set up. Never had a problem with any of the ones ive done. No whining, no slop, no problems.
If you want to pull a car off the lot with 00000.3 miles on it and beat it...have at it. If you want to install gears and take it right to the track and do 5000rpm dumps...have at it. Ill always be on the side for breaking parts in however.
J.
9 Second Club
Joined: Jan 2006
Posts: 457
Likes: 1
From: Kinston, NC
When an engine builder builds a $75,000 engine you would have to think they would be very careful with that investment correct? How much break in do you think they give the engine before its straped to the dyno....?
NONE
Once its up to operating temprature you make 8,000 RPM pulls.
Parts will seat themselves, just change the oil after.
NONE
Once its up to operating temprature you make 8,000 RPM pulls.
Parts will seat themselves, just change the oil after.
gears on the other hand need to be took down the road in a low gear, accelerated and deaccelerated numerous times to wear a good pattern on the gear. then enjoy! thats all that is neccesary if your backlash, and pinion gear is pulled up correctly. thats how i have always done it with many sets of gears i have installed.
gear whine can come from gears, as well as bearings that are worn out. most of the time i install all new bearings in the rearend at the same time we install the gears. that way we dont have nothing to worry about
Launching!
Joined: Jan 2009
Posts: 241
Likes: 0
From: Mead, WA
On my setups/custom axles, I tell them this...
Fill it with fluid and drive it around two blocks, in a figure 8. Come home and check the fluid and top it off. Doing this will slosh oil to the wheel bearings and remove any air pockets. It will also give you a chance to check for excessive heat.
Now drive it on a busy road, with lots of lights and no more than 30-35 mph for about 15 minutes. Crawl under and feel the pinion snout and diff cover. If it's hot, let it cool for a few minutes and do it again. And keep doing that while gradually working your up to longer/faster speeds until you can eventually drive it on the freeway without it getting hot.
If you ever burn your hand or can't hold it there, then let it cool for 30 minutes and change the fluid immediately. Diff fluid can not handle high heat like engine oil can and will break down to the properties of water, and WILL burn the gears up. Dump the oil at 500 miles to remove suspended particles, phosphates, etc from the new gears/bearings.
Heat is needed to break in the gears. New gears and heavy preloaded bearings create a lot of heat when new. The human body can handle about 108-110* before it tells the brain it's extremely hot. Diff fluid can handle about 180-190* before it breaks down. If you're feeling 110* on the snout, you can bet the pinion bearings and fluid there are feeling more. The pinion is the most critical, as it is not submersed in fluid all the time like carrier bearings are.
So if you are already driving it on the freeway for extended periods, then either the damage is already done, or your ok to.
Fill it with fluid and drive it around two blocks, in a figure 8. Come home and check the fluid and top it off. Doing this will slosh oil to the wheel bearings and remove any air pockets. It will also give you a chance to check for excessive heat.
Now drive it on a busy road, with lots of lights and no more than 30-35 mph for about 15 minutes. Crawl under and feel the pinion snout and diff cover. If it's hot, let it cool for a few minutes and do it again. And keep doing that while gradually working your up to longer/faster speeds until you can eventually drive it on the freeway without it getting hot.
If you ever burn your hand or can't hold it there, then let it cool for 30 minutes and change the fluid immediately. Diff fluid can not handle high heat like engine oil can and will break down to the properties of water, and WILL burn the gears up. Dump the oil at 500 miles to remove suspended particles, phosphates, etc from the new gears/bearings.
Heat is needed to break in the gears. New gears and heavy preloaded bearings create a lot of heat when new. The human body can handle about 108-110* before it tells the brain it's extremely hot. Diff fluid can handle about 180-190* before it breaks down. If you're feeling 110* on the snout, you can bet the pinion bearings and fluid there are feeling more. The pinion is the most critical, as it is not submersed in fluid all the time like carrier bearings are.
So if you are already driving it on the freeway for extended periods, then either the damage is already done, or your ok to.
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it's laughable to think that "brand new" cars have never been beat on. When that car is driven onto the trailer and off of the trailer it is seeing the lead foot of a guy who drives a car hauler around. This guy does not care about engine temperatures or anything. Seen more than a few times in my life.
The break-in procedure i received with my Moser 9" was either: 3 min forward and reverse each, drive for 15 miles, let cool. <or> 3 min forward and reverse each, get on the tree.
So I've posted about the gear noise I'm having, you guys are saying this will never go away unless it gets fixed before the gears wear down a little, or that it will once the gears wear a little?
So I've posted about the gear noise I'm having, you guys are saying this will never go away unless it gets fixed before the gears wear down a little, or that it will once the gears wear a little?
The break-in procedure i received with my Moser 9" was either: 3 min forward and reverse each, drive for 15 miles, let cool. <or> 3 min forward and reverse each, get on the tree.
So I've posted about the gear noise I'm having, you guys are saying this will never go away unless it gets fixed before the gears wear down a little, or that it will once the gears wear a little?
So I've posted about the gear noise I'm having, you guys are saying this will never go away unless it gets fixed before the gears wear down a little, or that it will once the gears wear a little?
Mosers are known to be noisy and it is just a fact. Doesn't mean there is something wrong at all. You also have to consider a higher gear ratio will make more noise too...
