Break In Period

carguy1985 · 10-28-2005

Hello, so i have heard from a few people that there is a break in period and some say gears really dont need a break in period. I want to know because Tuseday ill be taking my car to get the 3.73s installed and i wanna know how long till i can get on it and feel the change.

I mean i know why you should break in clutches and Engines duh.. but gears really arent that complex.

Let me know if there really should be a break in period an how many miles.... i know ishould take it easy for first test drive listen for noise from the rear (should be easy with my O/R Xpipe and flowmasters) and see if everything is working properly.

Let me know
thanks

mbhmustang1998 · 10-28-2005

I have heard both ways too but id break them in if i were you. That way even if it isnt really neccessary you didnt lose anything by doing so and if it is neccessary you did it the proper way. You will have plenty of time to waste gas enjoying them!

Monkey Boy · 10-28-2005

Gears are more complex than you think. Let them break in for at least 100 miles, though I'd recommend 500. Why risk throwing away such a large investment?

carguy1985 · 10-28-2005

Ok well how should i drive, i mean basically no power shifting right ? i can go fast and shift pretty fast just not .. drag racing

BlueStreak03 · 10-28-2005

I wouldn't go slamming around with new gears. Let them heat cycle a few times to work harden the teeth. After 5 cycles or so then start getting on it a little more and more. More stress on a work hardened gear will make it a little stronger still. Don't take this to mean that you should be driving it like a Nextel Cup car after 5 cycles. Progressively put more and more torque through them.

engineer76 · 10-31-2005

Quote:

Originally Posted by Monkey Boy

Gears are more complex than you think. Let them break in for at least 100 miles, though I'd recommend 500. Why risk throwing away such a large investment?

I agree with Monkey Boy:
Break in is important. Te surface of your new gear set is already smooth, but it is definitely not polised yet, and it does not form a perfect thread pattern yet.
Give it 500 miles of easy to moderate driving before you really go for it.

Langod · 10-31-2005

I took it very easy on mine for a couple of days and took it for a long highway trip (about 250 miles or so) which should have really heated them up. After that I progressively got more aggressive with it until I was driving pretty normally after two weeks. After three weeks I did see if I could get the tires to squeal going into 3rd.... And that would be a big 10-4!

IMHO, 500 miles worth of break-in might be overcautious. 200-300 is probably more than enough.
I think it depends more on the number of times you drive your car as opposed to how far you drive. (like someone said above, heat cycles are more important than miles driven.)

engineer76 · 10-31-2005

Quote:

Originally Posted by Langod

I took it very easy on mine for a couple of days and took it for a long highway trip (about 250 miles or so) which should have really heated them up. After that I progressively got more aggressive with it until I was driving pretty normally after two weeks. After three weeks I did see if I could get the tires to squeal going into 3rd.... And that would be a big 10-4!

IMHO, 500 miles worth of break-in might be overcautious. 200-300 is probably more than enough.
I think it depends more on the number of times you drive your car as opposed to how far you drive. (like someone said above, heat cycles are more important than miles driven.)

Sweet... I tried that too squealing definitely works in 3rd gear.
I always knew that there are some other kids around with the same ideas what should work and what not. (4th doesnt...)

Regarding heat cycles and so;
it is right that the 500 miles might be a little overcatious - but hey it does not hurt.
Most gears are machined stress relieved and then nitrided. This is a process where steel gets an extreme surface hardness. This process is usually done @ around 1000°F - heat cycles of 200°F at the rear end might have a slight influence on a break in, but they do not have the same impact as regular wear since it is way below the stress releaving and nitriding processes temperature.
More important is the surface of the gears. Even the smoothest polished surface gets rough again after nitriding. Thats because nitridig actualy makes a part to expand and therefore creates a lot of tension in the surface. This nitrided layer is only about .010 - .020 inches deep but extremely hard.
This is the surface that has to be "driven" smooth again, and almost the only way to do that is to drive around and moderately stress the rear end.

Jiggy_One · 10-31-2005

Im just gonna spill the beans and tell you that I ripped on my 4.10s the minute I got the car back. I have been beating on them for the last 3K miles and all is well and quiet. I got the motives and you should be ok with a few breakin heat cycles. Dont baby it for 300 miles though. Also, get the 4.10's if you already havent got the 3.73's. Trust me, the 4.10's are just fine for commuting and are way fun!!!!!!!! You gas milage will depend on your ability to not hammer the throttle everytime out.

BlueStreak03 · 10-31-2005

The heat of a heat cycle isn't what really makes a huge difference. It's the stress that the gears are put under while hot. It causes a shift of the molecules which realigns them ever so slightly, on the scale of .0001 inch or so.

engineer76 · 11-01-2005

Quote:

Originally Posted by BlueStreak03

The heat of a heat cycle isn't what really makes a huge difference. It's the stress that the gears are put under while hot. It causes a shift of the molecules which realigns them ever so slightly, on the scale of .0001 inch or so.

I could not have said it more precise.

Thanks BlueStreak03

carguy1985 · 11-01-2005

I just dropped off my car today at the mechanic, i should have it back thursday, hes doing it on side for me =) 150bucks so ill wait the extra day.
Anyhow i already did the 373s, i was gong to get 390s but i talked to quite a few people who said that 390s are cool i fyou arent using you car as a daily. and i have a daily driver, and i need my car to be alright i cant afford, to rebuld anything right now =)
Ill post on results when i get car back
later

BlueStreak03 · 11-01-2005

No problem Eng. That's one of the few things I remember from my 2.5 million dollar Navy Nuclear education.

Mana4Real · 11-02-2005

I heat cycled mine twice and then drove it like a mad man. I never had any problems on mine and I had over 30k on mine. No bad sounds of any sort.