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Old 12-23-2008, 04:56 PM
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Ford 9 inch w/ 3.50 gears

I need an opinion on which way to go. A buddy just gave me a 3rd member for a 9 inch with 3.50 gearing in it. I currently have 2.75's in my truck with a 9 inch. Should I put the 3.5's in? The 2.75's are nice on the highway and cruising, but the truck is a dog off the line and around town. I'm also running a 650 DP, which bogs out with the 2.75's. I'm running a 289 with C4 tranny and 28" tires on the rear. I'm figuring about 2800 rpm @ 60 mph, with the new gears. I'm running 2100 @60 right now. Looking for suggestions here from people who have gone this route before I go through all the labor of changing them out. Thanks. BTW- Merry Christmas/ Happy Holidays to you all.
Ed

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Old 12-23-2008, 05:14 PM
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Put the 3.50s in. You will be glad you did! It'll make you truck better, all around, stop and go driving and on the highway. 28" tires are way to big for a 302 with a 2.75 gear.
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Old 12-23-2008, 05:16 PM
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I'm showing 2588 @ 60.

http://www.ringpinion.com/Calc_RPM.aspx

I think that would be a good choice.
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Old 12-23-2008, 06:05 PM
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Do it ... and after you do ... if you think the 3.50 gear is a little too much ... it is easy to go to a 29 or a 30 inch tire and cut the gear down a little. Remember to change the gears in your speedometer drive
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Old 12-26-2008, 04:36 PM
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UPDATE: Ok, I took your guys advise and changed out the 3rd member with the 3.5 gears on Christmas eve. I drove it around town today to make sure there wasn't any leaks or problems. I definitely notice a difference. Third gear is like cruising in 2nd now. LOL.. I stabbed it in the parking lot (not full throttle) and it broke traction pretty easy which I could barely do with the 2.75 gearing. I also noticed the Holley double pumper isn't pausing anymore and comes on quick. Haven't driven it on the highway yet, but suspect I'll be keeping it at 55 or 60 instead of the 70 mph. I also changed out the axle seals on the differential tubes because they were starting to leak on the inside of my rims. Can you say "Pain in the ..." I bought an axle seal puller tool at Sears, which was worthless (the one with a hook and handle on it). I also tried a hammer like it mentioned on the internet. No way! I ended up using vise grips and working them out. I know there is an easier way, but that worked without destroying the rearend. I'm leaving these gears in. Thanks for the all the advice and I'm glad you guys convenience me to do this..
Ed
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Old 12-29-2008, 06:40 PM
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I moved the carburetor discussion posts to the engine section.

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Old 12-30-2008, 10:45 AM
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kleen,
just food for thought:
(because there are no motor details given)

lower gears means alot less load on the motor while accelerating so you likely can run a more aggressive timing curve (all in at 2800 maybe with no ping???)

that will usually give better acceleration (due to higher Hg for better cylinder fill) with alot less gas pedal driving normal to help mpg...

easy to test to tell if a re-curve is worth the effort,,,NO WOT ALLOWED,,,just bump up the base in 2* increments so there is more timing per rpms and go for a normal drive....
very often just 2* added makes a world of performance difference...

if you pull a boat or trailer better to leave the timing alone likely....
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