help: how do i break in my new 3.90 diff
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help: how do i break in my new 3.90 diff
i just had west coast corvetees install their heavy duty rear end w/ hardened output shaft and 3.90 gear set. they toold me to take it easy for 300 or so miles.
My question is, what is easy. can i really accelerate hard right now. can i take third gear up to 6000 rpm. what is the good way to break it in. what does take it easy mean. how long till i can really drive it like i stole it.
after break in should i replase the diff fluid. can i do that myself or will i have to take it in for thatt. any help or advise is greatly appreciated. thanks, Patrick.
My question is, what is easy. can i really accelerate hard right now. can i take third gear up to 6000 rpm. what is the good way to break it in. what does take it easy mean. how long till i can really drive it like i stole it.
after break in should i replase the diff fluid. can i do that myself or will i have to take it in for thatt. any help or advise is greatly appreciated. thanks, Patrick.
Instructor
Joined: Dec 2004
Posts: 175
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From: highbaugh kentucky
just dirve it around for a hour or so and youll be good. Theres no break in with gears, either there not going to run good or they are, it has nothing to do with the breakin. they just told you that as a saftey procedure.
Pro
Joined: Aug 2004
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From: Janesville WI
I don't think its the rpm's that matter so much as how fast you get to that rpm. You can drive at 6000 rpm all day long and it wont hurt the rear end at all. You'd be doing 50 mph in 1st. That certainly won't hurt the rear. Just don't accelerate to 6000 rpm quickly.
Collections Hold
Joined: Aug 2002
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From: Fort Wayne Indiana
Originally Posted by Vettegetsmwet99
just dirve it around for a hour or so and youll be good. Theres no break in with gears, either there not going to run good or they are, it has nothing to do with the breakin. they just told you that as a saftey procedure.
Team Owner
Joined: May 2005
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From: Flagstaff Az.
gears
When A&A installed my gears I was told to drive it easy for a few hundred miles. Since it was over 500 miles back to my home I didn't have to worry about it. I wouldn't romp on it or run it up to high speeds in the taller gears until you get the miles on it the installer recommended. It doesn't take long to put a few hundred miles on it. I think it is much better to be safe than sorry. 
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Joined: Mar 2001
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From: Whippany NJ
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St. Jude Donor '08-'09
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Originally Posted by tiojames
When A&A installed my gears I was told to drive it easy for a few hundred miles. Since it was over 500 miles back to my home I didn't have to worry about it. I wouldn't romp on it or run it up to high speeds in the taller gears until you get the miles on it the installer recommended. It doesn't take long to put a few hundred miles on it. I think it is much better to be safe than sorry.
Race Director
Joined: Dec 2004
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From: Haymarket VA
I was advised to take it easy for 500 miles. I kept it below 3k RPM and never got on it. At 508 miles I hammered it. I was told by a very knowledgable transmission builder that 1 in 20 rears go bad no matter what you do or who builds them. I wanted to be in the group of 19.
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Pro
Joined: Oct 2005
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From: Richmond VA
I just replaced gears in another vehicle last weekend. Everything I've read anywhere says to drive the car for about 15 - 20 minutes and let the gear oil cool down for 30-40 minutes (repeat 3x). Then take it easy for 300 - 500 miles (no hard pulls, just smooth, slow acceleration)The reason for this is because as you begin to run new gears, small imperfections in the surface of the ring and pinion are compressed into the gears causing heat build up (compression). This is referred to as work hardening. The gears will actually become stronger over time because of this. The opposite is also true, if you run the gears the first couple of times without a cool-down period, the gear oil may overheat and become degraded. This allows the gears to run without proper lubrication and become overheated themselves which will cause the gears to become softer and possibly cause premature failure.
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thanks for the feedback so far.
picked the car up and drove it t my office. approx 20-30 min. at night i drive it home approx same time. i have done several trips all 20-30 min total of 150 miles with about 8-10 hours setting or cooling between each trip. I have not gone over 5000 rpm normaly shifting between 3000-4000 rpm and never accelerating hard.
the weird noise.........
everytime i back out or pull out while turning sharp. i hear a weird noise like something clunking in my rear end or tranny. is it just because of the posi traction or is there something going on. it only does it right after it has set for a while. and ony when i am turning sharp like when i back out of my garage andthen pull out of my driveway. can any one tell me what this might be
picked the car up and drove it t my office. approx 20-30 min. at night i drive it home approx same time. i have done several trips all 20-30 min total of 150 miles with about 8-10 hours setting or cooling between each trip. I have not gone over 5000 rpm normaly shifting between 3000-4000 rpm and never accelerating hard.
the weird noise.........
everytime i back out or pull out while turning sharp. i hear a weird noise like something clunking in my rear end or tranny. is it just because of the posi traction or is there something going on. it only does it right after it has set for a while. and ony when i am turning sharp like when i back out of my garage andthen pull out of my driveway. can any one tell me what this might be
Pro
Joined: Oct 2005
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From: Richmond VA
With a clutch type differential, it is possible that the clutch plates were not soaked in friction modifier long enough before being installed. This can cause the condition you describe. It generally stops doing this after a short period of time. Hope this helps.
Drifting
Joined: Jan 2001
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From: Slidell La
Originally Posted by Uncle John
Then take it easy for 300 - 500 miles (no hard pulls, just smooth, slow acceleration)The reason for this is because as you begin to run new gears, small imperfections in the surface of the ring and pinion are compressed into the gears causing heat build up (compression). This is referred to as work hardening. The gears will actually become stronger over time because of this. The opposite is also true, if you run the gears the first couple of times without a cool-down period, the gear oil may overheat and become degraded. This allows the gears to run without proper lubrication and become overheated themselves which will cause the gears to become softer and possibly cause premature failure.
I hope you added the posi lube from GM in the differential. Now just drive easy for the 3 to 500 miles. I drove my new c5 under 50 for the first 500 miles. Not easy to do but you really want to run the gear set in and allow the wear surfaces to mate properly. Remember gears fail from Shock and heavy loads given proper lube. So don't shock and aw.. Ops Shock and Load. 99 Nassau Blue
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Joined: Jan 2005
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From: Eads, Tennessee
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St. Jude Donor '05 thru '24
Originally Posted by Bob Chapman
If I had paid West Coast Corvettes to install gears and I had questions about the install and break in who would I ask? How about West Coast Corvettes?
