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Discussion Starter #1
Hi all,
I was curious as to what the best rear end ratio would be for my needs. The car is a 302 with some mods, but nothing real serious. Just edelbrock performer cam, intake and carb (600 cfm.) Also opened up the heads some. The block is originally a 289 the heads are the 289 heads, opened up as I said. Had to shave a bit off the block when it was decked and the heads, so I figure compression is around 10 to 1. Anyway, the trans is a C4. I am not looking for a stoplight derby machine here. This is my daily driver and will spend most of it's time on I-26 carrying me to school from Charleston to Columbia (after working on my wife's escort I decided to become an engineer after my navy time is up...I think I can do better). So I figure about 500+ miles of highway driving a week. Needless to say, fuel milage is important (but not important enough to put the stock 2v stuff back). I don't want to be winding it out cruising at 80 mph. After I graduate I may put a cog back there, but for now I want to get the best mileage I can. I guess I want it to cruise in top gear like a car with OD. Is this possible without it being a complete dog? What's my best ratio choice here?
 

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I susspect what your really wanting is some scratch not gas mileage since your stock rear is set up for best performance and gas milage. but i would say 3.55is your best bet for upping your performance and getting off the line nice. now if you install an aod you can bring that up even higher into 3.75 to 4.11 so you can get off the line performance and reasonable gas mileage. but the 3.55 will get you scratch and wont eat up your gas to bad. course just my 2 cents worth others may disagree. and unless your racing you really dont need a spool or possi everyday drivng is fine with what ford gave you.
 

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I have 3.55 (non posi) in my Fairlane with a 302 kinda rebuilt, C4 with shift kit, and 2000 stall convertor. It's awesome, I had 2.79 in before and it sucked, it's a 3600 pound car with a little motor. Gas milage is abit better, it chirps in second from just going so that's cool :D, and I get about 20 miles per gallon. The motor needs work still.
I wouldnt go any higher then 3.55. Between 3.25-3.55 is the best bet for a highway commuter. Have fun.

Rick
 

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Costs?

What's it cost for 3:55's? just parts...

and an AOD? what's the cost involved in that too?

Thanks,

Robert
 

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For a 3.55 gear set your are looking at about $180 for new ones. However, you can also get them for cheaper from Ebay or out of a junkyard. Installation can very for $150 to $300 if you take it to a shop.

AOD's were kind of weak in the beginning. Ford seemed to beef them up in the later years before switching to AODE's. Lentech has built ones for $1600 that can handle up to 500HP, but that doesn't seem like the goal that you are shooting for. I'm assuming you could probably find an AOD used for around the same price as a C4. However, you will probably need to build it up a bit.

Good luck.
 

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I have to agree with what Jim K says. I believe a 3.50 gear is too much for a highway cruiser. I went from a 2.75 to a 3.50 and i was turning 3300 rpms and everyone was still passing me. Plus, my mileage went from 15 with the 2.75 to 12 with the 3.50 gear running a mild 351c.
To have a shop install an AOD you're looking at around anywhere from 1400-2500 depending on location, what they do to it and how greedy they are.
An AOD usually is good for about 30% increase in highway mileage. I went from 15 to 20 with the mild 351c. I have an AOD behind a 460 in my 70 Cougar, I am getting 18.6 on the highway at 70 mph with a 3.50 gear and a bad alignment. It's a mild motor, but it has enough cubes to move the car at an o-k rate. I'm still tuning for better mileage with the 460, but the mismatched engine component situation is rather limiting.
 

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thanks,

I don't need a shop to install anything for me... just curious on the parts cost associated with the job.. :)

Robert
 

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Discussion Starter #9
AOD Question

The AOD is another possibility I am considering. I have a T5 I could sell to get the cash or trade for one. I have a concern however. The edelbrock web site (My carb is a performer 600cfm) says that aftermarket 4bbl carbs aren't compatible with the AOD. Is this just there carbs? Also, is the reason for this supposed incompatibility the TV linkage? I mean I would use the Lokar TV cable which seems pretty universal. Just want to know what the deal is here. I suppose if I really want gas mileage I am after I could slap the 2bbl carb on my intake...but that's no fun. So why won't the edelbrocks work with the AOD?
 

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I found a compromise...

I'll just win the 67 at the nationals for my daily car, then I'll put 9" and 4.11:1 in there... cam, headers, yada yada yada woohoo, sounds like a plan... now, i just have to win the other one..

drats!
 

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gears

Kirk,
Jim's right on here. For highway cruising at 80 mph do not go above 3.00 gears. I swapped out my 3.00 for a 3.70 and I have very little headroom on the highway. I can cruise at 60 all day, but 80 mph is only seen on the way up or the way down. Also, the AOD is definitely compatible with aftermarket carbs. The are a bunch of guys out there running AOD's with everything from Holley's to Demon's. YTou can find more info on the internet, and there are a few companies that specialize in the linkage and cables needed to make the swap. I'm sure there are guys on this forum who have done it.
Paul G.
 

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Edelbrock says they don't work with an AOD as a disclaimer for people who don't understand the importance of throttle valve actuation in relation to throttle movement, and also because Edelbrock doesn't make a retrofit cable or rod system.
Let me know if you have any AOD specific questions, I work in a tranny shop and have installed several AOD's into 69 and 70 Cougars--2 of mine and a few other people's.
 

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Just an alternative. Keep the 3.00 gears and the C4 and install a lower first (and second if you like) gear on the C4. That'll give you good OTL performance and decent highway gearing. Sets are available in a couple of different ratios.
Only downside is a wider ratio between gears.
 

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Discussion Starter #15
C4 Gears

Hey, where can I get these gears. It would be sort of like a 2 speed with overdrive if I went that route huh. And what sort of cost am I looking at for this vs an AOD conversion. This is intriguing. I could get c4 reliability with good mileage.
 

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Discussion Starter #16
AOD it is I think...

Okay, I really like the AOD idea, espically after seeing what I can get one for. Seems pretty straightforward. I'd go with the Lokar TV cable kit and the windsor-fox crossmember. I'd have to figure out which speedo gear to get, but that's no biggie. My biggest concern is actually the shifter. I'd like to keep it looking stock as possible. My car has the factory console. How difficult is it to adapt the c4 shifter. I have heard they are similar or identical, but I don't really know. Is it just a matter of modifying the indicator window, or is it a little more involved. Maybe CougarAOD has some insight here since he's done this. I was also considering the AODE, but it seems to be a little out of my price range considering the 400 bucks extra for a controller. Also, how about hooking up all the lines from the C4 to the AOD. How big of a deal is that?
 
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