Trans. mechanic said 700r4 is ok in his book

[dmnall]

Well I have 3.73 in both my trucks and my 94 GMC has 4l60E (700r4 electornic controlled) and if you check out <a href="http://www.ring-pinion.com">Randys Ring and Pinion</a> and click on Calculator and calculate your Tire Size and Gear Ratio to 60 MPH and on that site it says 1800 - 2800 RpM is recommended for Small Blocks.

So with 3.73 Gear Ratio, and 275/60-15 Tires with following Tranny Combos and RPMs:

TH350/400: 2767 RPM
OD Auto: 1887 RPM
4 Speed: 2695 rpm
5 Speed: 2156 RPM

3.42
TH350/400: 2537
Auto OD: 1730
4 speed: 2471
5 spd: 1977

3.07
TH350/400: 2278
Auto OD: 1553
4 spd: 2218
5 spd: 1775

well as you can see these are basically Trannys that are set up with 3.73 Gear Ratio out of most newer trucks but with 700R4 you can have them built to run up too 3.08 gear Ratio but I would recommend leave 3.73 and just get the 700r4 and run it that way because if you are running Carb then ya don't want to lug the engine!! If you are running fuel injection then run 3.42 or higher since the computer will change Timing, Fuel and engine rpm to keep it from lugging with OD on @ 60 MPH !!

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Truck #1 68 Chev LWB Fleet w/ Wood Floor (Sucks Gas and Hauls Ass!) and in process of Body Work...

Truck #2 1994 GMC Sierra SL w/ 4.3L Vortec V6, 4L60E Auto!!