Finally decided on a tire size, now to pick gear ratio for 700r4 and t56

[Rob68c10]

I have decided that I will be running a 295/40/20 on the rear. I have not yet decided on a transmission, but it will either be a 7004r or a t56 6 speed.


I plan on making this truck something I can cruise down the coast or on the power tour and not break the bank. I realize this thing won't be the most fuel efficient vehicle out there, but I want the best I can get.

I plan on running my stock 307 until I get the funding to put my 327 together. Neither of these will be high horsepower engines, with the 327 probably going to be around 350.

I am thinking like a 4.11 would probably suit me best?

[buckskins4ever]

honestly go with the 700r4 and 3.73 posi rear. Have the trans build to auto lockup without the need of vac lines or electric. you will be much happier and easy on the bank. 4.11 is a bit much for liking when it comes to cruising.

[hugger6933]

If your wanting the best in the compromise as far as power and econmy go 3:42

[Already Gone]

if you go T56 I think the 3:73's will do what you need them to. If you go with the 700R4 the the 3:42's will give you about 22/2300 RPM's at 70MPH.
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[Rob68c10]

Just checked an online calculator. It says with a 700r4, 3.73 and a 295/40 tire my rpm at 70 would be 2097. That sounds like it's right about where I want it

[Already Gone]

Running the tire size you want to that sounds about right.
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[Custom 68]

Here is what I know since I have ran both transmissions...
I would go with 3.73 with the 700 and 4.11 with the T56. I just swapped to the 4.11 and have gotten several miles but no big trips as I continue to work out the bugs but here is what I found.
The obvious thing is the overdrive in the 700 vs T56 you have the double overdrive I am using the newer tranny from the ls (gen 3 ) motors and the 5th is very close to the final drive in the 700 then I dropped to .5 for 6th. This was usable on the highway but still I thought needed to change from my original 3.73. The other think I had the issues with was first gear. In my case it was taller than my 700 because the gearing is much closer 1 to 2 and 2 to 3 ... The 4.11 helped that quite a bit I didnt feel like I was in and out the clutch all the time. I get the best of both worlds with the .5 dinal drive.
That said your T56 will probably have slightly different gearing and your tires are taller than mine a little. That said depending on your tranny but I dont think I would go any higher gear (lower numerically) than 3.73.
Included is an excel file save thsi out and remove the .doc extension for it to work I could not upload a .xls file. See if this helps
good luck
Dave

[Custom 68]

ok so the xls file I wanted to attach is too large, it is a pretty cool program if interested pm me with an email and I will send it to you.