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Author
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Topic: Should I go with 3.55 or 3.80 gears?
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BaLleRz68
Journeyman Posts: 98
From: Bay Area, CA
Registered: Aug 2002
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posted 07-04-2003 04:44 AM
   
I can't decide if I should get 3.55 or 3.80 gears for my 8 inch rear end on my 67. Here are the plans for the engine (no particular order). I have a C4 tranny BTW.268H or 270H cam
Edelbrock performer RPM heads
600 cfm carb What would be the best gears to use for my setup? Where is the best place to purchase gears from? I've been looking online and found a few places Plan A:
www.gearsrus.com
Motive 3.55 or 3.80 gears $169
Auburn Posi $379
Installation kit $100+
plus installation Plan B:
I found a website that sells a whole 3rd member with a choice of motive 3.55 or 3.80 with a rebuilt T-lok unit. http://www.andale.com/stores/sf_home.jsp?mode=1&sfUrl=maeracing Do you think this is worth buying? How hard is it to swap out a 3rd member? How much will a shop charge? Any thoughts are appreciated. Thanks.
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Ryan Wilke
Gearhead Posts: 1501
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 07-04-2003 08:44 AM
Assuming this is also your everyday wheels, I'd suggest you go with the 3.55 gear ratio....When you say "3rd member", I'll assume you are referring to only the gear case/carrier not the entire rear housing. Unless you've got the necessary equipment and talent to setup the gears properly, I'd recommend you just swap out your carrier. By doing so, you'd be fairly certain that all your bearings & seals would be new, that your ring & pinion have the proper backlash, and that the traction-lok was fresh. Whether you buy a completed carrier or have yours rebuilt would depend on difference in costs. If you are looking at a finished carrier, ask about any core charge or not. If they don't want your core, then you can sell your carrier core to offset some of your cost. Most folks with minimal tools & skill can switch out the carrier. Basically, pull the rear brakes, pull the axles, drop the driveshaft, loosen the carrier & drain the fluid, once drained complete the removal of the carrier bolts and slide the complete (heavy) unit out of the rear housing. Reverse to install. If you have any doubts in the procedure, refer to your handy Haynes manual........ Good Luck!
Ryan  P.S.
If you have any future plans to be making 350-400HP, you may want to consider swapping out the entire 8" rear housing for a stronger 9" housing.
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jsracingbbf
Gearhead Posts: 1677
From: Batesville,MS. , U.S.A.
Registered: Mar 2002
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posted 07-04-2003 11:39 AM
Generally when a person refers to the "3rd member" he/she is refering to the entire "chunk" or "pumpkin" that sits in the housing. the other two members being the motor and trans. The case or carrier being the biggest part of this is what the differential or spool rides inside. If it's a street driven car, I'd go with the 3.55's but if it sees alot of track duty I might stick the 3.80's in it. Your not talking alot of difference in the two.
JS
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N266fords
Gearhead Posts: 557
From: Spokane ,WA USA
Registered: Apr 2003
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posted 07-04-2003 01:28 PM
thats alot of money to sink into an 8 inch rear why not take this time and invest in a 9 inch they also have bigger brakes..but hey i run 3.55 in an 8 with a mini spool on the street.I love it but you better know how to handle a car or it will come around on you quick just ask my wife.lol. P.S. i am now building a nine inch to handle my 393w..If you are running 14 inch tires i would run 3.55 if you are going to a taller tire i say 3.80 Bruce
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goldenbob
Journeyman Posts: 49
From: medford, or., United States
Registered: Jun 2002
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posted 07-04-2003 01:31 PM
I would go with the 3.80 if you are gonna take it to the track (drag strip). I went with 4.11 and gained .49 secs off my quarter mile. Since you have a 67 you have a wide choice of wheels and tires, you can always change your "effective" ratio by changing to 15", 16" or 17" wheels. I just put some 275 45x17's on my 67 (rear) and made it much more "streetable" for my low gear ratio.[This message has been edited by goldenbob (edited 07-04-2003).]
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steve'66
Gearhead Posts: 6522
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 07-05-2003 01:58 AM
3.55'sSteveW
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Fastymz
Moderator Posts: 11429
From: Reno Nv USA MEM#1240
Registered: Apr 2001
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posted 07-05-2003 04:57 PM
3.80 ------------------
SCOOP 2.26 60'S
14.9 @ 90.86MPH 65 coupe,351w,C4,Big Boss 429 hood scoop,8" 3.40 TracLoc. https://mustangsandmore.com/ubb/Fastymz.html
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