9'' gear swap from 4.33 to 3.50 or 3.25 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-14-2011, 11:41 AM
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9'' gear swap from 4.33 to 3.50 or 3.25

Gear guru's---

I built the 9'' in my mach 1 a year ago and I had a free set of brand new 4.33 gears from my brother-- knowing they were very low being im running a 532 BBF with a C6 i installed them anyway (they were free so what the heck)

Well after driving for a year and absolutely loving the accelleration side of things but hating the big block spinning 3500 rpm at 50mph. This is a street car and I need it a little more tame. Well after looking at different gear ratios I have decided to go with either a 3.50 or a 3.25

I have a detroit tru-track locker which will swap over but heres my question:
to swap my gears do i need anything other than a new crush sleeve???
obviously ill change oil while im in there but since all the bearings are new, I should be good just swap the gears and recheck my clearances/set up pattern. When I put the 4.33s in was my first time building a rear axle but has held up for just over a year with 600+HP in front of it so I must have done something right Thanks!

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Old 11-15-2011, 09:31 AM
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I'd upgrade from the crush sleeve to a solid spacer and shims...

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Old 11-15-2011, 10:39 AM
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Pinion seal: 7044NA

Inner pinion Brg. M88048. For Daytona support:HM89443
Inner race: M88010. For Daytona support: HM89410
Crush sleeve: 3104
Solid Spacer: 4105

If it were me.. I'd change the inner p/brg, pinion seal and crush sleeve or spacer.
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Old 11-20-2011, 06:55 PM
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I'd also use the spacer instead of the crush sleeve.

You probably won't be able to get the rear pinion bearing off the pinion so plan on a new one with the race.

Assuming your pattern was good you should be able to compare the setting numbers on the pinions and adjust the big shims behind the pinion support for the first test.
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Old 11-21-2011, 05:19 AM
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The other guys have the right parts.

Now - ratio. The 3.25's might not be much 'fun' if you have fairly tall tires. I made that mistake when I went to 3.25's from 3.70's, changed from a 26" diameter tire on a 15" wheel to an almost 30" on a 17" wheel in one big change. While my gas mileage is great, it is kind of a dog to about 30mph - and ~2000 at 60mph. I need to get anther long 1310 yoke to go back to the 3.70's and hope to over the winter, but is at the bottom of the update list right now.

Dave W
Irelands child
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