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I am trying to get my wheels and drive train matched up. What rpm should I be looking to run at 60 mph. I will be using a 350 with th400 trans 3.73 diff and 15 inch tires in my 46 on s10 frame. I will be using the speed calculator on line to determine the tire diameter that I need. Dave

Most of my vehicles without OD run a little under 3K going down the freeway (closer to 70 though). If I were me, I'd look for 23-2600. Lower might give you a bit better gas mileage but may not have the power you want to accelerate a bit without downshifting.

My 59 Suburban has a 350, 3.40 gears and 31x10.5-15 tires and cruises nicely at 60, 70, or faster if needed. You will probably want taller tires than that with your 3.73 rear gears.

23-2600 with a 3.73 and a 3-speed isn't really realistic.

Depends what the engine you're using is set up for. What RPM does the cam want to run at? How about the intake? There are a lot of variables here.

My truck runs at about 2800 at ~70 MPH. I've got 31 inch tall tires and a 3.42 though.

doing the math (unless I did something wrong) if your engine spins 2800 rpm @ 70 mph with 3.42 gears, changing the gears to 3.73 would mean 3053 rpm @ 70mph. Dave asked about 60 mph, 3053 rpm @ 70mph equates to 2617 rpm @ 60 mph.

And I have the same 31x10.5R15 Tires you do. With the look homer52 is wanting, I don't think he'll have room for a 31 inch tall tire or one would fit. He's told me a bunch of info on his truck, I didn't mention all the information in my post.

I wrote my post assuming his tires wouldn't be any taller than 28". I could be wrong though.

Right you are, 28 is my max. Dave

sell that sucker to me and let me figure it out..

my 52 that I had with the 235, s-10 five speed with
2:73 gear could run 90 less then 3,000 ... took awhile to get there..lol

well, if 28 is your max, and you already have your drivetrain, I would run 28" tall tires and see what it does. You may need to change gears in the rear end if it spins too fast going down the freeway.

3.73 rear and 28" tall tires then 60mph is 2700rpm with a 1:1 trans (non-overdrive).

My question is, is that a good rpm to be at? Should I be higher or lower? Do I need to build the engine to perform at that rpm. I want to do this right the first time.

Where I live there are NO freeways, I would have to drive for 2 1/2 hours to get to an area that has a 65 mph speed zone. I don't drive much over 60, I hate those flashing lights in the rear view mirror.

what you said in your post with what you had should work just fine.. around here you would get stopped for driving to slow

Don't over-think it... Get it together as you're planning. You can always change the gears later, but 2700 is just fine.

WOW, did I screw up. I looked at a video of how to check gear ratios, I had done this before and I don't know how I came up with 3.73. This time doing it I followed directions and counted rotations of the pinion as I rotated the wheel 10. 17 on the pinion 10 on the wheel, so 17 plus change x2, divided by 10 brings me to what I think is 3.42. That brings my rpm at 60mph to 2622 with 27 inch diameter wheels. I think I worried a lot about nothing. What a Dummy.

with your engine/tranny combo, you will like that a lot better than 3.73!