so im trying to decide to either go with the regular c4 for a 302 swap and regear to 3.00, or go with an overdrive trans. what options are out there for a simple install, but as good as the c4? im trying to hit 2000rpms at 70mph. current gear is 3.55 also someone mentioned the c4 for the 200 6cyl i currently have is different than that of the 302 version of the c4. whats the difference?
Gear Vendor https://www.gearvendors.com/hrford3s.html If you turn too low of rpm you're running off the idle circuit which runs richer and mpg falls on its face. Most 302's get better mileage at 3000-3300 rpm
wouldnt that high of rpm (3k) kill a 302 after a few years? maybe im just to cautious, but ive always stayed out of anything over 3000rpms for any length of time. if this is ok to run all the time then my 3.55 will be what i stay with. lord knows id love the sound of headers and open dual exhaust at that rpm, but i dont want to hurt the engine in the long run. your opinion please.
It's a case that you'll need small duration cam(stockish) to maintain a good vacuum so you can run efficiently around 2000 RPM... Too much cam and it'll be running with power valve open due to low vacuum... The first 5.0 Mustangs with T5 five were carbed... Those used a 3.08 gear along with the .68 O/D for a 2.09 final ratio and gave in the lower 20s for MPG... With 225/60/15 tires that combo ran somewhere around 1800 RPMs at 60 mph... Soooo with a non lock torque converter you'd need approx a 2.30 - 2.50 final to run 2000 RPM at 60 MPH... With a AOD, your 3.55s would be equal to a 2.41... Since AOD is lockup, something like 3.80 would probably be a better choice... BTW not same but way back I had a '76 Mustang II 4cyl MPG model that came factory with a 8" 2.69 gear... Couldn't get it into 4th till around 35 MPH(had no O/D), but would make 32 MPG highway running 60 MPH(this was back when 55 was national speed limit) ... In that light should be a piece of cake for a 5.0 to pull a similar gear...
3k ain't high in my book with a V8...2500 with a six. A 3.55 is great around town red light to red light and maybe going to the next exit on the interstate. If you're talking a lot of interstate driving at 70+ mph then a 3.25 or 3.00 will be better. With a V8 I think you will be happy with 3.55 with an AOD. A 3.55 is a lot of gear at 70 mph without overdrive. I have a 250 six cyl w/t5 and 3.40 gear and it will be screaming its guts out in 4th gear (1 to 1 ratio) at 70+ mph on the interstate but it can hang all day around 50-55 mph.
You want screaming on the interstate you should have been with me on a Portland trip. Drove down 3 or more hours in my GTO with 4.10s at 65-70, squeaked out 5 mpg! Edit....TH400, no OD.
I know the feeling. Use to have 4.57 with 24" tires on my Falcon. Didn't use 1st or 2nd gear much. Could wind out the 1st 3 gears crossing a 4-lane intersection from a dead stop
I currently run my 302 with a 3.80 gear and C4 trans. By calculation at 3000 rpm and my 28" tires I cruise at 66 mph. I've been operating with this setup for a number of years with both a 351 and a 302. The short stroke 302 handles it better than the long stroke 351. A 26" tire will give me 61.45 mph @ 3000 rpm. My Comet came stock with a 2.79 gear. It was like over-drive on the highway. I would go through the 1/4 mile traps at 96+mph in second gear! BTW I will be driving my Comet 3 hours to Washington, PA for the National meet.
One thing that I found with a 302 is to get the best mileage on the high way it likes 2200 rpm, any lower and there is no throttle response! Run higher and the gas mileage suffers. Some type of over drive is a nice fit I use a T-5 with 2.95 low and 3.89 gears! With the over drive my final ratio is higher than it was with the stock 2.78 gears and the direct C4
in my comet gt I have a 302 c4 with a 3.55 posi and the gas mileage SUCKS I love the sound of the headers with the dual exhaust on the freeway or around town BUT your wallet and your cooling system better be ready I really like the 3.55 but I think its a bit much if you plan to use it for alot of freeway traveling and want to get decent mpg my sons 71 maverick grabber with a 84 5.0 stockish build stock cam quick fuel carb electric fuel pump with regulator and not running the vacuum advance hes knocking on 30mpg with a factory 3.00 rear end and a t5 trans. it has tons of power on the street and plenty of mpgs for the freeway oh and he has hooker headers with pypes mufflers just turning out the side off the headers
Yes a 3.55 gear with a C-4 will spin the engine a little higher at free way speed than is good for fuel economy, what would be a nice setup would be the 3.55 with over drive!
after much consideration between a rebuilt stock c4 vs ford aod, i am going to just go stock c4 with gear vendors overdrive. itll be a bit more money but you just cant beat the stuff itll do vs an aod. i just dont see how it can be beat. the gear combos are unlimited and you can still gear very stout and keep all the bottom end you want and still come out with a nice cruise gear at the end. this is what ill do.
I ran 3.73 9"inch EqaLok with a Tremec 5 Speed OD tranny in my 75 Comet witha 347 Stroker,Headers,Flowmasters Mandrel Bends Exhaust and got excellent on the road mileage and Kicked Booty too on the low end. I'm sold on OD Trannys . Both cars have them now . Cometized (Chip)
