Need some help calculating engine rpm from vehicle speed

toph99

Diamond Member
Aug 25, 2000
5,505
0
0
my crown vic is shifting out of first(not sure of the first gear ratio on an AODE tranny) at a little less than 50mph. it has 205/70r15 wheels and a 3.27:1 rear end. It doesn't have a tach(was going to be getting one until i got laid off two days ago) and it feels like the tranny is slipping a bit trying to shift into 2nd, so i want to make sure i'm not over-reving it. Does anyone know what the redline on a 93 4.6L SOHC is?

also if someone could point me to a web based calculator for engine rpm from gear rations/tire speed i'd greatly appreciate it, i have quite a few calculations to do.
 

Mill

Lifer
Oct 10, 1999
28,558
3
81
Right here.

Actually damn it only has manual tranny options. You will need to google and find out which manual tranny they have listed most closely fits your first gear ration in the AODE.
 

toph99

Diamond Member
Aug 25, 2000
5,505
0
0
hm, where's Evadman when i need him, he has all sorts of gear ratios written somewhere... Do you know of any other calculators millenium? i know i've seen ones where you can enter whatever gear ratio you want, but i've long lost those bookmarks :(
 

Mill

Lifer
Oct 10, 1999
28,558
3
81
Originally posted by: toph99
hm, where's Evadman when i need him, he has all sorts of gear ratios written somewhere... Do you know of any other calculators millenium? i know i've seen ones where you can enter whatever gear ratio you want, but i've long lost those bookmarks :(
I pretty much promise you that you will find what you want in this google search right here

One of those search results will have what you are looking for. :)
 

toph99

Diamond Member
Aug 25, 2000
5,505
0
0
thanks millenium. iirc, the first gear ratio is 2.4, hopefully someone will know for sure. if that's the case then it's shifting at 5000rpm, when it should be capable of at least 6000. i definitly need to get a tach for it
 

toph99

Diamond Member
Aug 25, 2000
5,505
0
0
less than a thousand km's ago. It could just be the nature of the tranny, i'm not sure how fast/firm the shifts are supposed to be on a stock AODE at WOT
 

crab

Diamond Member
Jan 29, 2001
7,330
19
81
What exactally does a slipping transmission feel like?
 

toph99

Diamond Member
Aug 25, 2000
5,505
0
0
the engine will rev to where it shifts, sit there for a while, i can feel first diengage and sit neutral for a bit, and theni can feel first gradually engage. maybe slipping is the wrong word, but that's the first thing that came to mind.
 

earthman

Golden Member
Oct 16, 1999
1,653
0
71
I seriously doubt its supposed to shift at over 5000 WOT. The engine probably makes its peak power near that speed. If it was really slipping it would rev up at much lower throttle openings as the engine outran the transmission. Also if it was slipping it would cease to work at all within a few days, they self destruct very quickly under those conditions. The hesitation going into 2nd is not unusual, they are designed to be "smooth" rather than snappy, which would make for hard shifts that would scare out the old people that usually drive these boats. There may be a shift kit to improve this, or you could try some B&M Trick Shift to improve it.

Update Info:

- 4.6L OHC SEFI

- 239 Horsepower @ 4900 rpm

- 287 Torque @ 4100 rpm

- Redline 6000 rpm

These figures are for the current base model, the '93's are probably somewhat less.

 

ASK THE COMMUNITY