Very Slow 5.0 help

MyHoFoSho · Oct 6, 2009

ok so went to have a set of 3.73 gears put in my car today because the car drives like it has a stock gear in it. Well the guy went to do it and said that it already has 3.73's in it. But the car feels very very slow. one of my friends said it drove like his car with 2.73's then he got the 3.73 and the car was really fast. When i drive down the e-way at 65 in fith the rpms are at about 1600. First gear is forever long and my buddy with the other fox with mostly the same mods walks all over me. I have edelbrock performer 2 intake, bigger mass air, cai, underdrive pulleys, and flowmasters. I mean the car is slow this is my first mustang so i am not relly sure what to think. Could the gears in the trans have been changed or what i am at a loss.

nick6690 · Oct 6, 2009

google gear calculator and it will tell you what gears you have.

MyHoFoSho · Oct 6, 2009

i did and with the rpms where they are and the speed i am at it says that they should be 2.73 but what if my stock gauge is off. but a idle it sits at 650 rpms and at idle the gauge was almost right on i set idle with the snap on brick connected to it and is was only off by about 50 rpms. so i am at a total loss for why this car is so slow if any one on here is in the toledo, oh area and has mostly a stock car with 3.73's in it and wants to drive my car let me know.

WHT306 · Oct 6, 2009

I would pull the diff cover and look for my self, it has the gear ratio on the ring gear around the out side.

The guy may have thought it said 3.73 but looked at it wrong.

Mustang5L5 · Oct 6, 2009

Drive by a radar sign...is your speedometer accurate?

Celeb · Oct 6, 2009

Jack up the back of the car. Put a piece of tape on the tire and one on the drive shaft. Count how many revolutions of the drive shaft for one full tire rotation.

Ex: My car has 3.55 in it. For every one complete tire rotation my drive shaft rotates 3 1/2 times. (3.5)

MyHoFoSho · Oct 6, 2009

i have driven by a radar that is how i know my speed. i will go out and check with the tape now and will let you guys know. any other suggestions

Mustang5L5 · Oct 6, 2009

Run the engine codes.

Maybe go to track and make a pass.

MyHoFoSho · Oct 6, 2009

i did the tape test and according to that i have 3.73's. But at 65 my rpms are at 1600. But why would my tach be off that bad. At idle it is almost perfect and the car doesnt even seem like it revving high my friend with the 3.73 is at 21-2200 at 65 and you can hear that in his car. Also i did pull the codes and had and egr and evap code can that put the car in limp mode and make in run like ass. I am not sure HELP i am tired of driving a slow fox.

Mustang5L5 · Oct 6, 2009

What speedo gear do you have? White 23-tooth?

MyHoFoSho · Oct 6, 2009

not sure my speedo is off the only reason i know my speed is that i drove by a speed radar on a e-way over pass that is accurate that is the only reason i know my speed i guess the rest of the time lucky i have not gotten a ticket yet lol.

MyHoFoSho · Oct 6, 2009

o and i have gone to the track before and it was slow lol. My first pass was my first time going down the track ever and was nervous. but went 17 almost flat and about a 3 sec 60 foot spun through 3rd but dont really remember was a long time ago. On the next pass went 15.7 and dont remember the 60 foot but spun just through 2 and a little into third all on street tires and a lowerd suspension and stock rear control arms.

HISSIN50 · Oct 6, 2009

302 LX Coupe said:
Jack up the back of the car. Put a piece of tape on the tire and one on the drive shaft. Count how many revolutions of the drive shaft for one full tire rotation.

Ex: My car has 3.55 in it. For every one complete tire rotation my drive shaft rotates 3 1/2 times. (3.5)

Spend five minutes doing this and then you will know.

MyHoFoSho · Oct 6, 2009

i did do the the tape test and counted out the revs from drive shaft to tire and for one tire rotation the drive shaft went around 3 3/4 times almost so i should have 3.73's but the car does not drive like it has them in it

HISSIN50 · Oct 6, 2009

Your speed vs RPM's are off for some reason.

Check codes. Post up the info on the MAF housing and sensor, and other pertinent mods that affect performance. You could even have something silly going-on like retarded ignition timing.

devilmachine · Oct 7, 2009

Mustang5L5 said:
Drive by a radar sign...is your speedometer accurate?

I'm wondering the same thing. I just had a state trooper tell me yesterday via a speeding ticket that my speedometer is off! Now that I know this, I hope to be able to correct the problem.

My '91 GT's speedometer says that I'm traveling 75MPH at 1900RPMs, well according to the "calculate MPH" calculator on allfordmustangs.com, my actual speed is 82.7. This would explain why not only I got stopped, but also my wife a couple of weeks ago traveling at what we thought--the speed limit. Of course, she didn't get a ticket!

Just like most of us, we buy these cars used and may not always get the truth from the person we bought it from as to what has been done to the car. One of the reasons for this is that they themselves may not even know what has been done because they've bought it from someone else too.

Anyway, MyHoFoSho, I feel my stang is sluggish too and it should run a lot better than it seems. I don't know what rearend gears it has either, but from some of the gear calculators, they are 2.73s. I've had several of these cars over the years but this is my first AOD car, so I'm still trying to feel this thing out. I still have to check the timing to see if that is where it should be. Good luck!

Everette

RsStanG1987 · Oct 7, 2009

May sound stupid but how is your clutch?

MyHoFoSho · Oct 7, 2009

i have a pro m mass air sensor for 19 lbs injectors will stock injectors. It is 75mm the only other mods are underdrive pulleys intake and cai along with the exhaust. The distributor is stock and probally the OE one. The clutch has about 7,000 miles on it i put it in when i got the car. So i would hope it is ok but has been slow since i bought it 3 years ago. How would i get the codes out out of the system any one know if you can but jumping the terminals or do i just have to scan it. As far as my speedo it has always been wrong the only reason i know my speed is by radar. Any one think some one could have changed the gears in my trans with some thing.

tannerc91gt · Oct 7, 2009

Different trans gear ratios? But still, my car has 2.73s for now and it accelerates pretty damn well. There are so many factors

RsStanG1987 · Oct 8, 2009

why dont you do a compression test?

Very Slow 5.0 help

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