what does the 4.9L redline at? (i don't have a tach.) and if I'm running 70 mph with a manual transmission and 3.55 rear end (open rear end, if that makes a difference, although i'm thinking of changing it to a traclock), what rmps are I running?

 

I have an 89' F-150, 4.9 w/ 4spd manual and 3.55 (If I read the axle code correctly) gearing and the stock size tires... at 70 it looks like I'm at almost exactly 3K on the Tach...

 

70 is just plain mean to the engine with that setup (which is also my setup)

65Mph with 3:55 rear end, no OD, c6 auto trans is 4000 rpm !! 70 is over 4000 rpm. mean mean mean'

don't do that to your engine. 55mph = 3000 rpm

change your rear end to a 2.73 if you drive highway

 

Umm... are we sure about those numbers?? The reason I ask is that I have a c6 tranny with a 4.9 motor in my 84 van.. I cruise at 70-75mph (I checked.. my speedo is accurate) on the freeway here (the speed limit is 75).. The Van does great until I get to around 80-85.. then it starts to overheat (I know I'm spinning the motor WAY too fast then)... I have a 3.5:1 rear end (so the tag says)... Am I really spinning that motor around 4000 rmps??? I didn't even think the motor would do that??? What is the actual red line supposed to be?? I have a holley 350 2 barrel on it with a Offy Intake manifold.. (no more computer).. If I'm really spinning it that fast I think I'm going to need to put an AOD tranny in there since The van won't like a 2.73 rear end (especially when I go off-road)

Mark
mark@legendz.com
<a href="http://mark.legendz.com">http://mark.legendz.com</a>
Off-Road and Motorcycle Information, Pictures, and Movies




>70 is just plain mean to the
>engine with that setup (which is
>also my setup)
>65Mph with 3:55 rear end, no OD,
>c6 auto trans is 4000 rpm
>!! 70 is over 4000
>rpm. mean mean mean'
>
>don't do that to your engine.
> 55mph = 3000 rpm
>change your rear end to a 2.73
>if you drive highway

 

Here is a formula I surfed across.
Engine RPM X Tire Diameter divided by
Differential Ratio X Transmission Ratio X 336= MPH

Accordingly you should be running approx. 2400 RPM at 70 with a manual overdrive transmission.


A gear specialist told me that a 3.55 with a E4OD in overdrive would be turning approx. 2100 at 60 MPH.

 

I'm still looking for what a 4.9 is supposed to redline at but here is a page that might help figure what rpm your motor is spinning.

A friend of mine has a speedo shop and we have been working on a web page for them (small shop).. The Javascript app that will show you what size gears to use in your tranny to fix your gear ratio will also tell you your driveline rpm.. To get your engine RPM you just need to figure in your tranny gear ratio... If I remember correctly my c6 has a 1:1 ratio.. which means at 60mph.. and a 3.5 rear end.. with 29.5" tall tires (30x9.50's) I have an engine rpm of 2392....

The web page is <a href="http://mark.legendz.com/brads/technical/gear.html">http://mark.legendz.com/brads/technical/gear.html</a>

Hope this helps someone... and if you know the normal redlin of a 4.9.. please let us know..

Mark
mark@legendz.com
<a href="http://mark.legendz.com">http://mark.legendz.com</a>
Off-Road and Motorcycle Information, Pictures and Movies

 

Clifford Performance says that the redline of a stock 4.9L is approximately 5,000 RPM. This is also dependent upon condition of engine, how it is built, etc... A modified engine can be turned to 9,000 RPM.