would sustaining 3000-3300 RPM on the highway hurt the 300-6 in anyway?

225/70R15 tire
3.50:1 rear end
c-6 trans

Gear Ratio Calc

is showing 3005 RPM @ 70MPH, which is the posted speed limit around here.
there should be some slip in the torque converter, thats why i gave the 3000-3300 RPM range.

i currently have a 2.75:1 gear, and i'm going this weekend to try and find a 3.25:1, but i have a feeling its either going to be 2.50 or 3.50:1.

Thanks, Rob

 

That's pretty high on an engine that doesn't like to run much past 3400 or so. Maybe yours is different, and runs ok up there, but mine sounded pretty strained over 3k.

The 2.75s will have just under 2400 rpm at 70, might be the deal if you can stand that tall of a gear in first.

3.25s are going to run a little high at 2830 or so at 70.

3.0s might be a better compromise. 2613 at 70. Much better than what you have, still plenty of snap off the line...

You going to keep those smallish tires? If you are considering different rubber, check the rpm/mph with your projected size.

Good luck.

 

I don't think it'd hurt the 300, but it's certainly going to make it wear out faster, and you'll probably be uncomfortable doing it for lengths of time. It's also going to be pretty noisy as well. I know those old F-650s and stuff that had the 300s in the 70s would rev them that high all day long.
Peak HP is at 3000 RPMs in a carb'd model, and 3400 in EFI, so they definitely are designed to be up there.

2.75s would be your best bet for highway, but are going to make you dog pretty badly in first.
As 85e150 stated, your best bet may be 3.00s. 2600 at 70 isn't too bad.

 

the "end game plan" is to swap out the c-6 for an AOD, most (80%) of my driving is around town or nothing above 55-60MPH...there are occasions that i have to run 70MPH to stay on the highway for an hour or 2 at a time.

as far as tire size goes...i want to find a set of mustang bullit wheels, the 5 spoke w/grey center, torq thrust looking wheels and probably a 235/65R17 (i think it'll fit)

 

this be a touch long but here it is .of allthe stuff my family and i keep around my favorite is my 1990 e;350 300 6 C4 3SPD TRANS with a get this a dana 60 open 4,10 rear. its an ex ryder moving van .i take alot of razzin about because its still yellow. i dont care, that truck has been my right arm for work. helpin the neighbors and such. she sported 81,thou when i brought her home. i now have over 161,000 on her and she still gets up. it just wont quit. gettin around to your ?. i have run that truck around the beltway, back and forth from west va and so forth for years. run these #S. you wont believe it. i know i worried about it for years but that crazy mule six seems to love it. i try to keep it at 55. but it really runs good just under 65. gets mileage that i still dont believe myself and i own the thing. near 15 years now. does it hurt it. i was always taught it would(that kind of rpm) but so far she aint said a word. unbelievable but true. the downside. its like the fellas said. lotta noise and that 6 is screamin. ive been waiting for a rod to come sideways outta the case but so far all is good. i need to get somebody to help me post pics soon. id like you guys to see this ole gal. i love that truck. been one of the most economical RELIABLE vehicles i have ever owned period. later paul md. ps i got the 8 lug 16 wheels.dont remember the tire dia and honstly i am done for this nite dont feel like lookin outsideeeeeeeeeee boss.(grin)

 

mr grey f100, read garb3z2s post about the mileage he was getting with a 3.73 rear. his truck is close to what mine does. i did not put it out there before because honestly i did not expect most folks to believe it.i still do not fully understand why or how these motors get better mileage the faster you turn them up. its usually the opposite. anyway, 13 in town and around 19 or twenty many times sreaming down the open road. i cant figure it out but i aint complaing paul md.

 

Your E350 probably has 30 inch tires, so at 65 you should be running 2985 rpm or so.... a bit high imo. Will it blow up? Probably not. But the engine will pull a higher gear without fuss.

 

I do 70 @ 2500 rpm in mine. Itll cruise at it all day long, but i still feel bad raggin on i tthat much. Part of me says "its your baby, be nice to it" and the rest of me says "its a 300, who cares?" Rev it out!

 

i just want a bit more pep around town, it's very sluggish from take off with the 2.75 + C6 combo, but i dont want to blow it up on the highway. I have to go at this in steps, so right now is regearing then hopefully this winter or early spring i can do the trans swap.

 

If you're going to be doing the trans swap anyway, definitely plan that in with your gearing. The overdrive is going to drop your highway RPM at 70mph by quite a bit and will put you at around 2400 even with your current setup. That's quite an improvement.

If you regear now and put in a 2.75 to bring your higher speed RPM down, and then put in an overdrive transmission, you're going to be ******* around town, and then be at 1800 RPMs at 70.

So be sure to keep both mods in mind when doing your planning.

 

currently i have the c6 + 2.75 that is waht it came with from the factory, i want to put a numerically higher gear ratio in and an AOD but right now all i can do is the regear. I think i'm going to try and find a 3.25 but i have a feeling all i'm going to find is 3.50 at the JY.

 

Oh, gotcha. I had it backwards. I thought from your initial post that you had a 3.5 in it now.
Yeah, with the AOD installed, a 3.00 or a 3.50 would do pretty well. I've never heard of a 3.25, but it may be because the 4x4 setups had less gearing options and it's all I'm familiar with.

 

i appreciate you running those no,s. dont have a tach and did NOT know the efi peaks at 3400. i knew she was up there but never new how far. the tires are 235/85 16. is that a 30.i never took the time to learn how to read the new stuff. guess i should. but i am gettin on now dont know if it even matters.(grin). anyway thanks ffellas its good info to know for me. they way i read what you all say. if i get an od trans i will have the best of both worlds. that 4.10 is zippy in town i like it. paul md.

 

Metric To Inches Tire Size Conversion

31.7" tall

with that tire and no OD

Engine RPM: 3040.5300537067
Vehicle Speed: 70
Read End Gear: 4.1

AB the 3.25 was popular in the cars, i guess because of the smaller tires...