52 GMC half ton 350 high output crate motor with claimed 340 horse backed by a built 700r4 with a one wheel peel open drive rear maybe 3.10. I want to put a posi in so while its open, change gears, we do lots of long hauls and quite often pull our old camper maybe 3500*. Right now running 60mph around 2000 2200 rpm what gears would be ideal for snappy around town and hyway hauling. Snappy, never thought I'd ever say that, must be getting old. Thanks.......Snappy,, kinda growing on me.
My first choice would be 3.73. Second would be 3.42. 3.42 would be better on the freeway, 3.73 better around town and towing. Sent from my iPhone using The H.A.M.B. mobile app
They don t make gears that are great in town and great on the highway, you must make a choice in between and that compromises both town and highway. For me it would be around 3:50, that’s what I’m putting in my Galaxie! But I don’t have the overdrive transmission like you, so I would recommend around 3:70 or so, maybe a tad lower. Bones
I just bought a 3.5 limited slip 9 inch Ford for my 48. 292 straight six, mild cam lump ports 4 barrel intake with runners that are too big for common sense and cast headers backed up by an AX-15 5 speed. I may end up pulling a light weight camp trailer. This chart lets you put in a few knows and get the rpm at certain speeds http://businesspath.com/business_paths/auto/rpm-calc.html This one is for don't laugh electric car folks but it is so freaking simple to use. Plug in any 3 known variables and get the 4th. http://advanced-ev.com/Calculators/TireSize/ The only thing is that you end up multiplying the result rpm by the overdrive ratio to get your rpm with overdrive That doesn't take much though as mine at 70 with a 26.5 tall tire 3.5 gears came out to 3106 rpm X .79 od ratio = 2795 rpm at 70 in 5th gear.
I have 3.54:1 with a 5lt and 700R in my 35 Chebby. Cruises @ 2k rpm at 60mph with 28mpg and 235.75.15 tyres.
3:73 with your 700R4 OD trans is what you want. Plenty of Snappy and will pull your trailer. no problem.
Where your cam comes in is going to have a lot to say about what the right gear should be. r Sent from my iPhone using H.A.M.B.
Talk to the experts..! The folks that actually build the T-200-4R's and the T-700-R4's. They will tell you, the best overall rear gear is the 3.73. Even the Ford ADO's, same thing. Been their..! Mike
It's not always the perfect outcome but tire diameter juggling can play a big roll in gear ratio selection, some cars allow more flexibility than others though. A non fendered car may not look quite right with a shorter tire but it may accomplish a "happy medium" when the ideal gear ratio is not available or the timing is not right for an expensive ring and pinion change. On the other hand, full bodied cars have limited clearance to accomodate large diameter tires without major modifications.
700r4 od = .68 ? In o/d so 1 3.73 becomes 2.53 . 373 for take off and 253 for highway looks like win win to me
IIRC, the 700 has a pretty deep first gear to get you rolling. You might also want to talk to the rebuilder and see if it’s set up for a locking torque converter. What’s the cam like in the motor? My buddy has a 330hp GM crate (several years ago) with 3.5’s or so in a 56 Nomad. It locks up a little early in town. Lots of variables, but there’s a sweet spot somewhere.
This is exactly why the T-200-4R is a better all around trans. Lighter than the T-700 Smaller than the T-700 Much...better gear ratios than the T-700 Properly built, equal to a "little" stronger in the first three gears than the T-700-R4. Much closer rpm drop at all gear shifts than with the T-700-R4 so you don't need two redlines marked on your tach. Mike
Forgot to mention my DD (SUV) has 3.73:1 rear axle with OD auto and 235.75.15 tyres. My 35 Chevy is a lot lighter and can easily get away with 3.54:1. 3.73:1 would be better in a heavier PU. If you use a 200R or 700R and need to drive 1:1, e.g. Tow a heavy load, leave it in 3rd gear and don't use OD.
3.73. My OT truck, 5.0 AOD with 3.08 rear is made for the Hwy only. It’s a miserable towing vehicle. Getting moving is hard on the engine. Stopping even at low speed is hard on the brakes. You really really need that engine / gear braking capability. Just that little extra helps with grades. It’s not fun to be pushed through the yellow/red at 3 mph with a heavy trailer.
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