Along with our mild engine makeover, we're looking at improving the rear end on our '74 Comet. We have the standard 8 inch rear with the 3.0 gear and we're looking to go with a 3.80 (...or possibly a 4.11) with posi. Our Comet spends 99 percent of it's time doing city driving and is basically a weekend car, not a daily driver. Would this be a direct fit? http://www.ebay.com/itm/FORD-8-INCH-POSI-TRACK-DIFFERENTIAL-W-NEW-GEARS-MUSTANG-MAVERICK-COUGAR-FALCON/302369745458?_trksid=p2047675.c100011.m1850&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=45043&meid=347ff5ad5b6f492fbe6b3b3bafaab233&pid=100011&rk=3&rkt=3&sd=221129750629
Yes it will bolt in just fine...If you don't do much highway driving it will be lots of fun W/3.80s' But you may find your wanting an AOD trans after a while. 3.55 would be a mellower /better choice for a street cruiser with a 3 speed.
A 3.80 is a great choice for performance, but a bit much on the highway... With a AOD or T-5 it becomes a 2.58, or a great highway gear, meaning you can have your cake and eat it too...
Thanks for the response! We actually live in the city and do most of our driving from stop light to stop light. My son calculated our RPM's at around 3300 at 60mph with the 4:11. The 3:80 would probably be the best overall choice, but we're trying to get some "giddy up and go" type of fun with this car without breaking the bank. We talked about the AOD trans. That might be an option down the line.
With a O/D trans and a 4.11 gear, final ratio is 2.79 or what was in many Mav/Comet from factory... Having run 3.73 in my T-Bird for over ten years with O/D, I consider something in the 3.70/3.80 range the perfect all round gear set... BTW that also includes having a lock up converter in the 2400-2800 stall range... Most will probably try to sell a non-lockup but having lockup means it will run a couple hundred less RPM at highway speeds...
The 8" carrier shown on e-bay is a direct fit. It has the fill hole in the case. Earlier weaker 8" models did not; their fill hole was in the housing. I run a 3:80 gear and at 3,000 RPM my Comet with its tire height is moving at 62 mph. Highway cruising is no problem, and yes it will get up and go.
If I remember correctly your car is a 6 cyl and you are wanting to keep it that way. I think you will find those gear ratios will DRINK gas. The short amount of fun one will have will be short lived while the time standing at the gas pumps will be numerous. I suggest getting the car running, driving, and stopping good and enjoy it for what it is.
Gas cost is not an issue. This car is strictly a weekend driver, not a daily driver. After reading all the responses based on experience, it looks like the 3:80 is the way to go!
