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ZR-1 rear gear change

 
Old 01-24-2019, 03:11 AM
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ls7plus
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Default ZR-1 rear gear change

Has anyone here changed over to a 4 series rear end from the stock 3.45:1? If so, how did you like it? I'm contemplating a switch to a 4.11 in my '93 this spring to at least give it a little help keeping up with my '72 540 CID big block. With a torque peak at 5200 RPM, I always felt the '93 needed more gear.

Best wishes,

Larry

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Old 01-24-2019, 10:01 AM
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Evan70
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Had 4.11s in my previous 91 with just ported intake and long tubes. Made the car very responsive, and what I felt like it should have had from the factory. For my current 91 with 391 cubic inch, fully ported and long tubes, I kept the stock gears, which was the right decision as I have a hard enough time putting the power down in 1st as is, 4.11s would have made 1st useless.
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Old 01-24-2019, 12:19 PM
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ZR1Bob
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Did the 4.10 gears in both my '93 and '95. Best mod you can do for the money. Marc and Bob Haibeck have done many of these and Marc has considerable info on his website. Here is a link to his comments on the gears: http://www.zr1specialist.com/HAT%20W...ucts/gears.htm. Depends on what you hope to gain from the change. It significantly improves around town driving and sixth gear becomes much more useful. On the drag strip, while you can get to the end of the quarter mile in third gear with stock 3.45 gears, you have to shift to fourth with the 4.10s. But I drove my cars daily in the summer and only drag raced once or twice,so I was a happy camper. I also did a couple other simple mods that really improved the feel of the cars, including a Hurst short throw shifter with a stock looking gear lever and Hawk brake pads. After that, well, there is always Marc's 510 HP package that I did on the '95. That perked it up a bit....Bob

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Old 01-24-2019, 05:09 PM
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USAZR1
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I went with 4.30 cogs, in my 90 Z. My 91 Callaway Z had the older 4.09 gearset, while my 94 Z had 4.10's.
My favorite gear was the 4.30.
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Old 01-24-2019, 05:15 PM
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ls7plus
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Thanks to both Evan70 and ZR1Bob! I know quite well that even the 4.10's won't be anywhere enough to let the former "King of the Hill" keep up with my '72 with the 540, but have felt for quite awhile that the old "King" deserves a better chance to keep up with current "traffic."

Thanks so much, guys,

Larry
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Old 01-25-2019, 07:44 PM
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ZWILDZR1
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I loved the 4.10's in my first 91. But it also had headers, no cats, and the early 3" B&B exhaust along with a custom chip. The extra gear helped it a lot. I'm thinking about having my current car which has more hp changed to the 4.10's. One thing is for sure. It wouldn't hurt if you made the change. Just your wallet.
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Old 01-25-2019, 10:07 PM
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Thanks to all that responded. So very nice to have all this experience at one's fingertips! Some of the other mods mentioned will be given full consideration as well--great forum!

Sincerely,

Larry
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Old 01-30-2019, 12:50 PM
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Dominic Sorresso
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Larry,

One more vote for 4.10s. I could probably use 4.30s due to the taller 19 Z06 wheel/tire combo I have. My 4.10s give me a similar rpm band as 3.45s do w stock wheels.
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Old 01-30-2019, 04:00 PM
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Nacho_ZR1
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4.30 gears for sure! That's what I had on my Z and I believe I was one of the only members to pop a "baby wheelie" at the race track. I even had the stock heavy wheels on the front! The only other mods were headers and Corey Henderson tune. She made 432 rwhp. Take a look:

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Old 01-30-2019, 06:00 PM
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Evan70
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Yeah, but didn't you break a half-shaft doing that?
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Old 01-30-2019, 07:12 PM
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Nacho_ZR1
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Originally Posted by Evan70 View Post
Yeah, but didn't you break a half-shaft doing that?
LOL! I snapped the halfshafts on the last run of the evening. My 4000 rpm launch was too aggressive. But the shafts should hold up fine on normal drives or even launches in the 2K range. If I remember correctly, i took her to the 1/4 mile track one and she ran a 12.20 @ 115 mph. Not bad for a mostly stock Z!
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Old 01-31-2019, 01:21 AM
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Thanks to both Dominic and Nacho ZR1--more to consider! By the way, my '72 with the 540 makes about 640 (gross) hp, dead-hooks with 16 psi in the Mickey Thompson 275R 60/15 drag radials, and I haven't broken anything yet. I did have to have the tires pinned to the wheels recently, though, as it was turning the tires on the wheels and losing air pressure with every such launch, so we'll see what happens when that slippage is no longer there to absorb the torque!

Highest regards,

Larry
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