I have a 440 mopar and a 727 3spd tranny. What gear ratio would be good for driving on the highway? And what rearend would be good to look for? I want the rearend to have disc brakes, so anything mid 80's and early might be out of the question. I have done some research and found out that mustangs and ford exlporers have 8 8 and 9 inch rearend that range from 2:73, 3:27, 3:55 and 3:73. I think the lower gear ratio the better it would be for a 3spd. Any help would be great. B-dub...
Depends on tire size, how the engine is built (torque curve), and how you drive....usually ratios around 3.0 to 3.5 are commonly used. I run a 3.25 ford 9" (with drum brakes) in my 55, with 27-28" tall tires, but I usually don't drive over about 70 or so. Taller tires, you can run more gear. High rpm engine (big cam), you want more gear. Hi speed driving (over 75) you want less gear. Personally I don't see much need for rear disks on a hot rod, and it would be neat to run a Mopar 8-3/4 rearend, then you could get a few pumpkins with different ratios and swap them out. I've run 4 different ratios in my car over the years.
Squirrel, the tires I'm running are 31" and the front end has a disc brake kit. I'm really wanting to make the truck as safe as possible. I did the calculations on the website that 53sled provided and it is calculating 3:55 gears. Plus the truck is only going to way maybe 1500 lbs, so I think I'll have plenty of power to get going. Your ideas are good and I appreciate the advice. B-dub...
With such a light truck and such a big engine, you'd probably be better off with a lower number gear ratio, closer to 3.0. You won't need much gear to get it moving, and highway cruising will be more pleasant at lower rpm. With such a light truck, I especially don't see any need for rear discs, you'll just lock up the rear wheels if it has good brakes back there. Unless the tires are really, really wide
Even a bone stock 440 will pull a land yacht with a 2.45 out back. Any 8¾ will be more than adequate as would the 8.8 Ford. With so little weight you will never have enough tire to really hook up... As mentioned, a third-member style axle has big advantages for gear changes. .
We're running an 8 3/4 with 4.56 gears and a 29" tire behind ours. Turns around 3,700 rpm at 70 mph on the freeway. Probably not practical, but it sure is fun coming off the line.
Thanks guys. I will start looking around and see what I can find. Again, I appreciate all the help and advice.
I had good results with that in a '69 Charger. Like was said 2.75-3.25 should do. Rear axles 9", 8 3/4, 12 bolt shouls all work.
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