4.10s break in period advice

[gtkid]

Good day all, just picked up my car yesterday after having all my mods put in. I have a question about my new 4.10s in my manual trans 2005. The mechanic that put them in told me "just take it easy for 500 miles". FWIW hes a chevy fanatic.(I used ford racing brand) Its been about 40 miles and i haven't noticed any gear whines. Should i do some spirited runs and see if anything breaks? Ive read so many mixed opinions. This break in period is killing me, i want to see what all my mods have done!!!

 

[JEWC_Motorsports]

Beat the shit out of it, if its going to whine its going to whine from the beginning.

 

[BruceH]

I like to do heat cycles. The gears will lap in pretty quickly but until they do they will run hot. About 3 complete heat up and cool down cycles is what I shoot for, usually 15-20 miles each.

 

[weather man]

Agree with Bruce, heat cycle a few time and then have your way with them.

 

[TexasBlownV8]

I do (and recommend) what Bruce says, too. Run through a few good heat cycles before putting extreme stress on the gears. ..breaking in a set of 355's myself right now

 

[gtkid]

Thank you guys so much for the replies, is it a good idea to get that gear oil replaced after a few hundred miles or not necessary???

 

[Townson]

Got mine installed, cruised for about 30 miles at varying speeds. Took it home. Let it sit overnight. The next day I started beating the Hell out of it.

About 3,000 miles and 20 passes later, all is well.

Thank you guys so much for the replies, is it a good idea to get that gear oil replaced after a few hundred miles or not necessary???

I wouldn't worry about it honestly. I mean, new gears are installed in the factory, gear oil added.

Car is shipped, sold, gears aren't even broken in properly unless someone is super picky. The old oil that was in there was more than likely what came in it when it was new. Did it cause a major catastrophe? Nope.

 

[gtkid]

I wouldn't worry about it honestly. I mean, new gears are installed in the factory, gear oil added.

Car is shipped, sold, gears aren't even broken in properly unless someone is super picky. The old oil that was in there was more than likely what came in it when it was new. Did it cause a major catastrophe? Nope.

This is exactly what crossed my mind at work today...thank you for the reassurance

 

[Norm Peterson]

I like to do heat cycles. The gears will lap in pretty quickly but until they do they will run hot. About 3 complete heat up and cool down cycles is what I shoot for, usually 15-20 miles each.

This ↑↑↑ . . . one cycle might be sufficient in some cases, but it can't possibly hurt to do a couple more just to be sure. Worst case, impatience can be expensive.

Immediately after running the first heat cycle or two, touch the diff cover at your own risk.


Norm

 

[skaarlaj]

I've done 4 gear swaps and after verifying they're not running too hot, or making excess noise, "to the floor she goes", with no problems

 

[BruceH]

Got mine installed, cruised for about 30 miles at varying speeds. Took it home. Let it sit overnight. The next day I started beating the Hell out of it.

About 3,000 miles and 20 passes later, all is well.



I wouldn't worry about it honestly. I mean, new gears are installed in the factory, gear oil added.

Car is shipped, sold, gears aren't even broken in properly unless someone is super picky. The old oil that was in there was more than likely what came in it when it was new. Did it cause a major catastrophe? Nope.

Factory gears and aftermarket gears are not the same. I'm not saying something bad will definitely happen by not changing the gear oil out but an aftermarket set of gears is going to get the fluid pretty hot when the gears are lapping themselves in. How that affects the fluid I don't know.

 

[Grimlock]

After my 4.10 install, I heat cycled 5 times and didn't really get above 50 mph during that period (not sure if that mattered). After that, all was well.

 

[Norm Peterson]

After my 4.10 install, I heat cycled 5 times and didn't really get above 50 mph during that period (not sure if that mattered).

It does at least to some extent. Heavier tooth "contact" pressures and faster "sliding" velocities will generate more heat.


Norm

 

[Grimlock]

It does at least to some extent. Heavier tooth "contact" pressures and faster "sliding" velocities will generate more heat.


Norm

Good to know. That was my installer's recommendation as I walked out the door. Even then, I waited quite a while before any WOT shenanigans took place.

 

[ArtQ]

From the other end of the spectrum. Installed Ford racing gears, went straight to the track, launched at 7000 rpm, repeat 100 plus times. no issues. More than one car, and trying different ratios of gears. Lots of track only cars don't break in gears. If they are set up right you will not have an issue. Do you change your rear end fluid on a brand new car after a few heat cycles?

 

[Marble]

I like to do heat cycles. The gears will lap in pretty quickly but until they do they will run hot. About 3 complete heat up and cool down cycles is what I shoot for, usually 15-20 miles each.

The guy who does my gears does the heat cycling before I even get the car back. He does an initial cycle, then drives it about 30 miles, let's it cool, then drives it again. His gears installs are silent.

I have broken shit though...he just laughs and shrugs his shoulders. He knows what I'm doing with the car...

 

[Coosawjack]

What about new cars......never any break-in procedure for gears??

 

[Norm Peterson]

What about new cars......never any break-in procedure for gears??

Not specifically . . . but it gets covered by the general recommendations in the Owner's Manual.

Page 205 in the 2013 O.M.

BREAKING-IN​

You need to break in new tires for approximately 300 mi (480 km).
During this time, your vehicle may exhibit some unique driving
characteristics. Avoid driving too fast during the first 1000 mi (1600 km).
Vary your speed frequently and change up through the gears early. Do​

not labor the engine. Do not tow during the first 1000 miles (1600 km).

Norm

 

[Thereaper]

The car in my avatar was doing 150 MPH when it rolled 100 miles, that's my break in.

 

[Cammed 05]

I set mine up. Drove 3 miles to the 4 lane and made a hit on the way to get some food. Beat the shit out of it
Since. 115k later it's getting some whine but I'm ok with that.


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