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Old 08-20-2012, 10:01 AM
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motive gear. pro series

Has any body used the 7.5 gm 3.90 gear or know someone who has? I just don't want to do a 9 swap and drop 3k. If they will pull 1.40 short times without breaking then problem solved. Thanks for any help.

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Old 08-20-2012, 10:10 AM
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As you already know the 7.5 is just a weak rear end when compared to a 12 bolt or other larger rear ends. If you have a real light car and not putting a lot of torque through it then it might hold up. The gears are not the only weak part of that rear end. If you can you would be much better off upgrading to a larger rear end instead of putting money into that one.
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Old 08-20-2012, 10:23 AM
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I know its very weak! Someone has put axles and a detriot truetrac in it befor I got the car.just thought they might wrk with what's allready there.
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Old 08-20-2012, 10:36 AM
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The gear can pull a 1.4 60 foot, but the rear end can't. Or if it does, it won't for long.

The gear itself is a fantastic piece. I've ran motives in all of my cars. Inexpensive and I've never had a problem with them.

Your 7.5" will last for awhile, provided you don't put sticky tires on it. One good hit on slicks though and it'll be lights out from what I've seen. Good luck!
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Old 08-20-2012, 10:45 AM
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Well hek! I guess it go back to all motor and a new tune. Thanks guys.
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Old 08-20-2012, 11:05 AM
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Did they use the 28 or 26 spline axles? If they used 28 spline then it might hold up for a while. What is this in?
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Old 08-20-2012, 11:11 AM
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28 Spline.
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Old 08-20-2012, 02:34 PM
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Well that's better, but it's still not the best rear end for the job. What is this rear end in? Is it a S10 or a third gen Camaro?
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Old 08-20-2012, 08:48 PM
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There's people running those short times and even faster with the 7.5. You just need to be prepared to fix it when it breaks. And more than likely it will break sooner or later.

If your looking for a diff for reliability.... not the best choice.

I've built quite a few diff's for "class" cars running the 7.5 that leave with wheels up.. But they accept the risk and that they're on borrowed time.
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Old 08-21-2012, 07:04 AM
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Its in a 94FBird. It won't be at the track every weekend getting beat on! Just want a little more peace in the back of my mind whn I do hit the track! I understand and except the fact that its weak so maybe it won't give. up the ghost next go around.
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Old 08-21-2012, 07:06 PM
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Quote:
Originally Posted by onlyfnway View Post
Its in a 94FBird. It won't be at the track every weekend getting beat on! Just want a little more peace in the back of my mind whn I do hit the track! I understand and except the fact that its weak so maybe it won't give. up the ghost next go around.
Just build it with good parts. You might install a cover/girdle for a rear cover.

From there... cross your fingers
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Old 08-21-2012, 07:27 PM
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Yea it has a girdle for the cover! And the carrier caps is studded also.
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