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Old 09-25-2013, 08:06 PM   #1
TexasAxMan
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Default Which gears?

I have a '66 with a mild 302. It's about 10:1 compression with a pretty thumpy cam, not sure of specs. Also a T-5. Stock 8" with 2.79 open diff.

Looking at an eBay diff completely built with gears (TJ's), but unsure of what gears will best suit my needs. Mostly city driving with limited road excursions (45 minutes to the beach, 2 1/2 hours to Austin).

Would you recommend 3.55:1 or 3.80:1 gears? And why?
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Old 09-25-2013, 08:32 PM   #2
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Also, what speedo cable gear would I need?
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Old 09-25-2013, 08:35 PM   #3
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Depends on the engine build and what you're using the car for.
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Old 09-25-2013, 08:58 PM   #4
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I think I covered that ...
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Old 09-25-2013, 09:46 PM   #5
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Is the rear diff that your getting a trac loc? If not even with the 3.55 gears your gonna break one side or the other loose all the time.

If you can afford it get a trac loc and go with the 3.80 gears those gears will really wake that 302 up .

I went from stock 3.08 to 3.73 and the difference is outstanding.
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Old 09-25-2013, 09:48 PM   #6
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I have a 3.80 with a 26" tall tire.First gear is pretty short and 5th gear i can only use above 70ish. Not sure if that helps you.
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Old 09-26-2013, 02:55 AM   #7
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Where does the engine make power, and what type of city driving? Driving Miss Daisy? Driving away from a bank robbery?
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Old 09-26-2013, 10:03 AM   #8
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The trac-loc is a given.

More like the bank robbery style of driving.

If it makes a difference my T-5 has a.68 5th gear. Rear tires are 245/45R17, so 25" tall. By my calculation, a 3.80 would put me at 2500 RPM @ 72 MPH, vs 77 with the 3.55
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Old 09-26-2013, 01:09 PM   #9
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I have 3.80s with a 25" tall tire a a mid performance 302 that puts down about 290 hp to the wheels. My T5 is a cobra spec with the .63 OD. I am happy with the 3.80s but sometimes I find myself asking if 4.11s would have been better BUT NEVER "geez I wish I had 3.55s right now" If you are running a cam thats above 1500rpm on the low end then 4.11s would be good with a .63 OD.

I have a 1500 to 5500 cam and in most cases the 3.80s work well but with the .63 OD I need to have speed above 62mph to be happy in 5th.

-Gun
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Old 09-26-2013, 03:28 PM   #10
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Depending on where you're engine makes power, sounds like a 3.80-4.11 is what would work for you.

I have 3.55 and sometimes wish i had 3.25's.....others I wish I had 4.11's....and sometimes I'm sad I bought my TKO600 before the T56 extreme was released.
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