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Hello all... Im new to this forum and not a big mechanical buff...

I have a 1965 ford mustang w/ a 302 @ C4 tranny. The stang drives great on the street but on the freeway, I feel like I am forcing it at about 60-70 mph.

I would like to be able to take the car to far distances that would require taking the freeway and not top off at 60 mph.

I was told I would need a differential w/ smaller gears but that my take off would be slower??

Can some please point me in the direction I need to go? Should I swap out the tranny for something else? I want to keep it an automatic though.

thanks in advance...
 

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people who drive cars made from about 1974 up have become accustom to the low rpm of over drive transmissions. before that all transmissions with the exception of a few 3 speed manuals were 1:1 drive. cars and trucks usually had anywhere from a 2.8 to 3.89 rear gear and the common speed limit was 70. my parents 66 ford wagon had a 352,cast iron cruise-o-matic and 3.00 rear. it made a heep of engine noise at 80 mph. all my mustangs came with 3.00 rear gears , 4 speed toploaders and short 25" tires and the engines wound pretty high. the 65-67 hipo 289 mustang came with a 3.5 or 3.89 rear and my dads 69 boss 302 came with a 3.5 rear. all these engines including chebby,mopar,amc,pontiac,olds, etc usually ran in the 3000+ rpm range on the highway at 70 mph. the ONLY reason for the o.d. trans was to spread the gears further apart and make 1st gear around 3 with a rear gear set around 2.5 so the whimpy 4 cylinder engine could get a car moving and you could shift into o.d. to get the rpm down to get better gas mileage. its never ben a problem for a 1960's engine to run in the 3000-4000 rpm range on the highway for long trips. my grandfather and a couple of friends including my dad had 1/2 ton to 1 ton 6 & 8 cyl gas engine pickups with 3 speed autos, 3 on the tree manuals , 3 speed with a granny transmissions with up to 4.10 rear gears and run at 70 mph. up till a few years ago a friend had a 1974 dodge 1/2 ton pickup with a 360 an auto and 4.10 rear gears and it would turn just under 4000 rpm at 70 on the highway. he drove it from arkansas to mojave ca quite often. it now has a 472 caddy engine with a turbo 400 trans and the same 4.10. like i said most people of today are used to 1500 rpm at 70 in cars of today. a 2.80 for an 8" came in most all 65-up 289 2v mustangs. the 3.00 was the standard for a 225 hp 289 4v engine. if you have a 2.80 or 3.00 you dont need to change it. putting an o.d. transmission in will not necessarily give you better gas mileage. in fact running a 1960's type engine at say 1200 rpm on the freeway could burn more fuel. these old engines were designed to run in the 3000 rpm range. todays engines have a long stroke around 4" as compared to the 2.87" stroke of a 289. that 4" stroke produces torque at a much lower rpm than the 2.87" stroke and the engine can run at a lower rpm without lugging it. lugging is also bad on the main and rod bearings and can lead to detonation. btw i was driving across texas in my 2006 f350 pickup truck and the speed limit in places was 85. i ran 85 for a bit but slowed back down after i saw the fuel going form full to empty real fast. my truck was turning about 3500 rpm and its a diesel. i would have kept it at 85 but i didnt have the extra $500 or so i would need for the extra fuel burned. 85 mph ! now i like that !
 

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+1. And, a better description of what is going on. Will it not go past 60 or 70 mph? Or does it seem to need a lot of throttle to do 60, but will go over 100 mph? Please be specific. You may have a problem with making normal power at higher rpms on the highway caused by improper fueling, ignition, or a damaged torque converter, etc. - and nothing to do with the tranny itself or gearing. More info and symptoms would help.

David
 

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I agree with the previous responses as we need to know your rear gear ratio to determine any kind of fix. On my Mach1 with a 351C/FMX auto and a 3.00:1 rearend ratio I changed to 3.50:1 in the rearend and added a AOD trans to compensate for highway cruising. The 3.50 gears gave me a quicker off line response while the AOD let me cruise on the highway at 70mph while maintaining 2200rpm, I haven't checked gas mileage yet but I think I'm still getting around 20mpg overall....Jim
 

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I have the same problem. My car has 4.62 gears and an 8 inch converter(4500 stall). I won't be running on any freeway's. The only good solution I have is a Gear Vendors overdrive but I have not yet convinced myself it is worth the bucks. Right now my bucks have other priorities. They do make a very impressive unit but it should be gold plated for the price.

Inevitably at some point this becomes the dilemma for street car's that see the strip or vice versa. It is particularly true with small block engine car's that need the high rev's at the track. My engine would shell out a regular T5 and spit chunks on the road so thats not an option. Moving to a Tremec would be similarly priced to the overdrive unit so I'd rather just put in the overdrive.

A seriously built AOD might work but they remove the lock up in these so you are still loosing rpm's in cruise mode. My C4 is rated for 700+ horsepower and in great health so there's no point in ditching it for something else.

I'm just using my set up as an example for you to consider your options.

afterthought: if its just gearing it will feel a bit like you are forcing it due to the higher rpm's on the freeway but this is where your real power band should just be picking up. If it really does feel like you are forcing it you may be in a gap with your carb tuning or total timing. My car, as an example, rev's freely to 8 grand and tops out at 125 or so(115 in the quarter). I want to be able to run it on up to 150 and go run the Texas mile which is my dream goal for my car.
 
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