I currently have 3.70 posi gears with a th350 tranny. I want to get my rpm's down at highway speeds. My question is, have any of you guys ever run 2.75 gears with a 350 3 spd tranny and if so, what was your low end power like?
Going to that high of a gear, you are going to lose on the take of quite a bit. Not real sure how bad your rpms are without knowing your tire size, but if you need a major change, something in the 3.20's would be better, if you only need to bring them down a little, 3.50's work well. I have not had them behind a 350, but my car does pretty well with 3.50's behind a C-4
Olskoolrodder here's a link that has a calculator on it that can can help you choose the proper gear ratio. http://www.summitracing.com/expertadviceandnews/calcsandtools/gear-ratio-calculator Sent via Illinois Bell Telephone Company's Car Radiotelephone
My Son is running 2.78's in his T bucket with a 306 Ford. Thing launches like gangbusters, but his car is light and he is running a 3,000 stall convertor. I was going to buy him some deeper gears for Christmas a few years ago but he loves the ratio that is in it, and when he leaves a light I have to push mine hard to keep up (and I'm running 4.30's.) I've driven his car a few times and it plants you in the seat when you give it a little extra gas. I would say try it and if you feel you need more gear it is easy to change them in an 8 or 9 incher. You might be surprised. Don
thanks guys... a little more info... 29.5 tall tires weight prob close to 2200lbs torq convert 2200-2800 i took my first trip this weekend and at 65mph I was at 27-2800 rpm I ran the calculations on an online calc. I wanted to be close to 2000rpm at 70mph. The calc says 2.7# will get me there but was curious mainly if I would need a push vehicle to take off. exaggeration of course but you know what I mean... hind sight I should of gone with an overdrive tranny.
thanks Don... will try and see what happens... also my rear end whined so loud my ears rang for hours. bearings going bad maybe??
My 429 and C6 + 2.75 rear-gears combo still smokes the tyres on take-off in my 3,800lb '55 F100 - if I want it to So in a lighter can the 3.75s won't be a problem.
A zillion stock Fords of various weights, all well above yours, used 2.75/2.79 gears behind 3 speed non/OD automatics and were just fine. Your lower weight will add substantially to your performance potential, even with the taller gears, and as you have surmised, the rpm at cruise will drop a bunch.
I say go with the 2.75 and don't look back, your turbo 350 has a 2.58 first gear, and with that lite of a car it should still haul ass, down the road treat you self to a cheap 5 speed swap and you'll really dig it !!
My deuce roadster has a chevy 350 with a TH350 trans. I built my car to cruse long distances so I am using 2.79 gears in the Ford rear. The car is about 2400 lbs. so I don't have any problems off the line but I didn't build it to race with. I cruse along at 70 mph and my tach is only showing about 2300 rpm and get over 19 mpg. One of my friends has a car with 4.56 gears and is dying to go to the Nationals in Louisville but wont even try with those gears but refuses to change them. Sure an overdrive is the best of both worlds but changing the gear set is the easiest.
I had a not to well thought out combo of a 2.8, x303 cam, 29" tire and 2800 + stall TC. All this behind a 302HO and a C4 in a 2350LB car. Problem was the TC never stalled and the tranny always over heated. I installed a 2000 stall TC and a 3.55 and run 21 to 25K at 55 to 70mph and the tranny runs cool. The nice folks at BM Hydro recommened that the TC be stalled at highway speeds for a street driven car and max r's of 21 to 28k. Am considering a 3.0 and a less radical cam. Lou39
The good thing about nine inch Ford rear ends is that complete ready to put in 2.7 something third members are fairly easy to find and not very expensive compare to the 3.5, 3.7 and 4.11 gears (at least around this area) That lets you keep the 3.7 third member intact just in case you want to swap third members and go to the drags and still have 2.7 road gears.
^^^^ That's the way I would do it, I have 2.73 in my 55 Pontiac not terrible but my tires are 26 inches tall. I am about to put 3.73's in and will probably got with a 700 r4 if I find it to annoying.Going to Lake George it was great,but around town I feel it needs a little more.The only reason I am doing 3.73's is I have them.
...I ran 2.79 gears with a 1500 stall behind a 327/350 combo in my coupe before swapping it out for 3.25 gears...and really like the difference it made in low end power after the swap. On the other hand...with the 2.79, I could still get passing gear while doing 80 mph...
great info guys, thank you... if I can locate a complete third member with the 2.75 or close and keep my existing one for drags, I think that is what I will do. thanks again!!
I have a 2.75 rear gear too. I took it out of a Torino. I figured if it could push a Torino then what trouble would it have on my f1.
I had a 2.73 posi behind a TH400 bolted to a Pontiac 421 tri power in a '62 Studebaker pick up. It would spin the tires in first, what more do you need? That and the top end was higher than a reasonable person would want to go.
My 62 Impala wagon at 4000# with a Vortec 350 and a 350 th with a Nine inch Ford rear with a highway gear would run right at 2000 rpm at 60-65 MPH. Not sure what ratio the rear end was but high for sure. No where's near a race car but a great highway cruiser.
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