Gents, would like to ask for your input.. 1960 F100 468 Big Block Chevy (Yes, Chevy!) Very mild engine, RV cam, Performer intake with Edelbrock 750cfm, 1976 Engine (not square port heads) Dual Exhaust with 2 1/2 Block hugger headers. non overdrive trans (2.52/1.52/1.0) Stock TC. 27.10 Tire Height I do some Highway driving and the 3.89 Gears that came in the OG Rear End are driving me bananas! (2900RPM's or so at 58mph) Anyone running a similar combo with either 2.75's or the 3.00's?? What is your preference from experience? I'm not looking to drag race the truck and will not be doing any HD Towing. Looking to get a decent MPG but don't want that trans overworking all the time. Will the torque of the BBC overcome these freeway gears ? I thank you in advance.
Stock 289 2 barrel C4 Fords and such had 2.89 gears. Big block Fords had the 2.75s routinely. Given your intended use, your torque monster BBC should do fine with the 2.75s, even with the tire size you are using. Ray
2.75 is nice, although if you plan to tow with it 3.0 would be better. 2.47 if you want to really cruise. I've run all of them at one time or another. I started with 3.00 in my 57 suburban, then put the 2.75s in it after my first trip to California. When I stole the 9" to put in my Chevy II, I went with a 3.08 ten bolt. Then I won a GV overdrive, and the 3.08s work pretty slick with the .78 OD.
Keep the 3:89 gears and swap in an OD transmission. You'll love it. @ 65mph In OD you'll be at 2200 and you get to amplify a really low first gear and monster hole shots. With the 3.00 gear @ 65 you'll be at 2400 And you'll give up a bunch of torque off the light. Roughly 25% of the 468 BBC torque is dropped thru gear multiplication. How's that better? How much effort & $ went into building UP the power of the engine? The 275 @ 65 will be at 2275 and giving up even more torque off a light. ( 30%!) The rpms are close to the OD but the fun gone and the engine is castrated. Will 2.75 or 3.00 gears get you down the road , sure. It works for every grandma quite well and I see no reason it won't do just as well or a little better in your truck too.
I ran 3.08s in a couple small block trucks over the years, did a lot of towing, and never had much problem except trying to pull 7,000 pounds over Donner Summit in the 305 powered truck once. I also had a set of 3.08's in an 82 gmc 4x4 with 33 inch tires and an all stock 454. made 4 low range kinda useless, but ran up and down the road great. still pulled better than my small block truck with 3.42's. The 2.75s seem a bit steep to me, but with the little tires your running, should run just fine, better than my 3.08s with 33's.Lotta years ago, so I don't remember rpms or mileage anymore. Sorry.
Get the tallest gears you can....compare that monster motor to a smog era mid 70s Trans Am that had a wheezy motor and are nearly as heavy in weight.....they had 2.41 gears regularly...your bbc's torque will easily pull any gears in your scenario..
A good friend of mine still has his first car, (bought in '71) an OT '68 Impala SS 427 (425 hp), M-22, 3.08 12-bolt posi. That thing accelerates way quicker than I would ever have imagined, pulls smoothly and strong from 15 mph in 4th gear, and seems to loaf down the highway at 70
Between the two 2.75s without a doubt. The first time you take a highway trip with 3.00s you'll be kicking yourself for not putting in the 2.75s. Had a stock 455 Pontiac with a TH400 and 2.56 gears for my daily, it was a dream on the highway and still ran high-13s in the 1/4 mile. Your 468 should kick ass with the 2.75s.
the modern trucks with 323's cid (5.3L) the final drive ratio was 2.79 and my BBc has a final drive of 3.08 (4:10 rear gear .75 OD ) , but my buddys 454 1 ton ( carbed TBI motor ) has 3:08s and it lights the tires for a block plus pulls down milage as long its on the free way , and tows great , in the city stop and go its like everything else no milage ..
My 40 Pontiac coupe has 3.00 gears and a super duty Pontiac 389 with 28" rear tires and is happy in 4th gear in the 4speed at 15mph and way fun over that. Gary
I had a 68 Firebird 400 that someone stuck a 2.56 rear in it....and it drove great! Engine was just purring at highway speeds..
Sorry took me so long to update you, Truck was finished a few months ago (Thank you Industrial Chassis!) and been having a blast! Ended up with 2.75's, this thing cruises down the highway at comfortable RPM's ! Eventually as time and money permits I will end up with 3:55's with a Gear Vendors overdrive . Thank you all for your input!
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