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Discussion Starter #1
just this weekend i had griggs subframes and 4.10 gears installed on my 99 cobra convertible.
the shop went over a breakin procedure for the gears for the 1st 500 miles that i should follow.
the procedure basically is this:
-1st 100 miles drive 15-20miles then let gears cool down for at least 30min. limit speed to max 50mph
-next 400 miles limit speed to 60mph and be soft on the pedal.
this breakin procedure seems a bit excessive to me and almost is impossible to follow with this new found torque.

is this shop just being ultra conservative. those who argue and say breakins are myths can make the comparison to new stangs that essentially have new gears installed yet they dont require breakin periods from the factory. what about saleen that stocks some new saleens w/ aftermarket gears? i havent heard of any mention from saleen to breakin the rear gears?
whats your take on this? i want some peace of mind and put the pedal to the metal already...
:D
 

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the shop that did mine told me 200 mile break in, after I got mine done I drove it for a day or so, then I had to make a 230 mile drive home from las vegas to la, I havent had any problems, probably been about 10k miles by now
 

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after i got my 4.30s they told me to go 300 miles before power shifting or romping on it really hard.
 

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Discussion Starter #4
what about freeway driving? i wonder if constant high speed driving like around 70-80mph would be okay? so what about factory cars? there is no break-in period?
 

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After I had mine in, I took a 10 miles drive. All was OK, when I left the shop got me rubber 1st,2nd,3rd,and 4th.

No probs. yet.
The factory gears dont need a break in. Let her eat!
 

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Discussion Starter #6
yeah i figured there is no break in period for factory car so y isnt it the same w/ aftermarket gears..same concept but different procedure? thats why i think this break-in procedure is all propaganda..lol
so sounds like 1 to 1 for yay or nay.
 

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That sounds a bit too extreme. Driving about 30 miles taking it easy...not over 50 mph, then letting it cool down completely, then doing another 30 mile drive the same should be way enough break in.

Lisa :)
 

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Discussion Starter #8
yeah exactly. and to think this shop was 45min away from my house. i would've been home the next day if followed that procedure. i have been nursing the throttle a bit but will let it open up once i hit the century mark.
 

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Mash the pedal now!!! I had my gears put in about a month ago. The first day I heat cycled them twice and then got on it pretty good the next day, they are good except for the stupid whine that it has, but I have heard 4.30's whine more than other gears
 

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ALkYuLA said:
dont break the 4.10's in!!!! take them out and get some 4.56's now!!
I used to think that was too much, but installed 4.56 in mine from the 4.10.....WOW!!! Im in love. but I have always warmed them up and cooled them down 3 times before I really get on it, but I dont see where it is a necesity on a gear install done correctly.
 

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it's virgin metal, in a new confined space, traveling at a high rate of speed, install plays a key role in wether the tolerences are correct... i'd tend to belive contact pattern, pinion angle and the amount of shiming required would be relative to the gear whine people hear.. and wether or not a breakin time was given..
it's a crap shoot since everyone had gears installed by different shops and different techs and some of the parts are cast..
results will vary... personally i'd give it a lengthy breakin time..
heat cycling the whole 9 yards 10x longer than normal..
but thats just me..
~J
 

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stanger maniac said:
just this weekend i had griggs subframes and 4.10 gears installed on my 99 cobra convertible.
the shop went over a breakin procedure for the gears for the 1st 500 miles that i should follow.
the procedure basically is this:
-1st 100 miles drive 15-20miles then let gears cool down for at least 30min. limit speed to max 50mph
-next 400 miles limit speed to 60mph and be soft on the pedal.
this breakin procedure seems a bit excessive to me and almost is impossible to follow with this new found torque.

is this shop just being ultra conservative. those who argue and say breakins are myths can make the comparison to new stangs that essentially have new gears installed yet they dont require breakin periods from the factory. what about saleen that stocks some new saleens w/ aftermarket gears? i havent heard of any mention from saleen to breakin the rear gears?
whats your take on this? i want some peace of mind and put the pedal to the metal already.
:D
Why not take it easy at first and give it a few heat cycles to break in? As I recall, Jay at Lamotta Performance, ran my 98 on the lift for about 20 minutes to put a little easy break in time on the 4.10 rear gears before I drove off. Also I believe Ford advises about 1000 easy miles on new car. That means rear gears also.
 

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i did my own gears FYI...

i ran the car for five minutes off the ground right around idle, then let it cool. Then i took it down the highway for 5 minutes (all i have in fron of house) stopped let cool, repeated 3 times

next day drove for a half hour, let cool

and took it easy forfirst 200 miles(i wasted a tank of gas in one day :) )

mine dont make any more noise than anyone elses ive heard with UCA's and LCA's and Alluminum Driveshaft
 

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stanger maniac said:
the procedure basically is this:
-1st 100 miles drive 15-20miles then let gears cool down for at least 30min. limit speed to max 50mph
-next 400 miles limit speed to 60mph and be soft on the pedal.
Did ya get 'em done at Rearend Specialties in Santa Clara? That's the breakin they recommend. IMO it is excessive. The gears should get a chance to heat cycle a few times before you romp on it, so just take it easy for at least 100 miles and change the diff oil after 500 miles.

That's what I did and no problems.
 

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Discussion Starter #16
michael,
yes the gears were done at rear end. i find it lame that they dont warranty the labor when bringing in your own parts.
im still trying to get used to the gearing and i have been taking it easy so far w/ around 70miles since the gear install. ill keep it up for a few more miles..but anyhow, i wouldnt even consider my normal driving style as mashing the throttle....just want the peace of mind that i wont be causing problems for the rear end in the future if i dont follow this break-in religiously. they have a pretty good reputation on gear installs so im confident the install was done correctly. so far, i hear no whining except from my inner self saying..why do i have to break it in..jp..lol
 

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I have Strange Engineering 4.30s in my Cobra that are quiet and shift real smooth... I waited about 90 or so miles till I got on mine, and went to the track the next week after that... My shop told me to go easy until 100 miles...
 
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