just got the gears...break in period??

I broke them in, in the parking lot..

my gears were used though, so they already had heat cycles. I dont think it is an absolute must, but it cant hurt to do 2 heat cycles just to be sure.

After i got my 4.10 gears installed on my 98GT i asked the same questiosn about "heat cycling" and changing the gear oil and a break in period, etc.

this is what the ford tech told me:

"do you change the gear oil, heat cycle the gears or have a break in period when u buy a new car??"

I said:

"good point"


bottomline: no you dont need to do any of the above, have fun!

I am still for a small break in period for other peoples car. just in case it helps i like to error on the side of caution than on the side that has me doing the job all over again.

BUT you can get away with a whole lot more than you think with a rear end. put it this way I got a free set of brand new 4.10's becaue of a small chip at the end of one of the pinions teeth. it is out of the contact area and the rear end has been fine for 10k+ now.

Now don't get me wrong you should set pinion depth and backlash. but the truth is many don't and for the most part you would never tell the difference.

Mine oh about two minutes....

What I did on mine.. I drive it around for 15 mile drives not getting on it the whole time and came home and let it cool down for 30 minutes and took it for another 15 mile drive. I did this once more. I think this is what I did.. if not it was something very close like 10 mile drive instead of 15, I dunno! But after i did that I got on it and it was fun!!

btw I changed my gear oil about 3k miles afterwards.. part of the reason why you wanna do this is because you can check the oil for any chunks of metal that shouldn't be there.. you may have small pieces, but anything big shows something is wrong and your gears may not be wearing correctly.

I say rip it up!!!!

"First time you drive the car, only drive it about 15 minutes or so; DON'T accelerate hard or drive exremely fast
Stop the car and let the gears cool off for about 2-3 hours, unless its very cold outside then matbe a little less
Then Drive again for about 30 minutes or so, no hard acceleration or fast driving speeds, and let the gears cool off again
Then the last time drive the car about 45 minutes or so, no hard acceleration or fast driving, you get the picture, then for the last time let the gears cool.

After that give the gears HELL. If you don't do this break your gears may decide to whine."

is what I read about a break in period.

i remember being told a 200 mile break in was needed FWIW....................

the 2 sides that i think of are these.

side 1: the racer-the guy with his car on a trailer that only runs at the track and has never seen what a stop sign looks ike except maybe on the stop on the return road to the pits. this guy swaps gears out all the time rebuilds a rear on the fly along with his whole engine and then makes another pass 90 mins later at 200+mph. does this guy warm/cool his rear 3 times before ripping off a 7 or 8 second pass? isnt he running the same frpp or strange gears we are?

side 2: the daily driver-this guy races just as hard but more that likely is still making payments on his car. he gets to the track and does his thing and then drives his beauty home and then to work in the morning.

so to me the big differences between these 2 guys is this. guy 1 has the finances and technical knowledge to gear swap any ole time he wants. be blows a rear, so what, his car is running again in 2 hrs or less. guy 2 has to depend on his car all day everyday. the big difference is the advice you hear is #1 who is giving it to you. is the guy a racer and knows the gears are fine the second the fluid level is topped off. or the guy that is thinking that this rear girdle may never be off this car again and will more than likely see 100k miles.

yes there are always going to find guys "i broke in my gears and i blew my rear after 2 passes" or "i never broke in my gears and i have 300k on my car with 500 passes on the strip".

the answer to the question is this. yes your gears are going to be ok to run hard the second they are installed(properly of course). BUT if you are going to drive your car day in and day out. just a little bit of precaution and breakin may not be such a bad thing.

yes, i have had my gears for almost 100k and almost 400 passes and i was one of the guys that broke in my gears for the 500 miles.

-jp