View Full Version : Top speed question

05-07-2001, 04:08 PM
The other night I had my car going about 5300 rpms on over drive. Now i am not for sure about my final drive ratio but at 60 in 5th I am pulling about 1900 rpms. I still have the factory size 225/60r15. Does any body have a clue as to how fast I was going and what my axle ratio is?

[This message has been edited by Nick (edited 05-07-2001).]

mike g
05-07-2001, 07:08 PM
you have 3.73 gears

and you were going around 160mph

05-07-2001, 11:17 PM
Originally posted by mike g:
you have 3.73 gears

and you were going around 160mph

Hmmmmm, 160 MPH with 373's? Personally, I don't know if a car with 373's could get up to 160 MPH if it was dropped off a cliff.

'88 GT, T-5, Flowmasters, MAC Cold Air/ K&N, More to come when I get some money.

mike g
05-07-2001, 11:24 PM
5300rpm in overdrive(.667 is the overdrive gearing) is 160mph

edit: i just noticed something he said 5th gear, but then he said being in overdrive and i did his gearing for an aod. so it will be alittle off if he has a t-5 since fifth gear is .675

[This message has been edited by mike g (edited 05-07-2001).]

05-08-2001, 01:59 AM
Thats scary because i have H speed rated tires. I have a theory though, couldn't higher gears raise top speed because it allows to use more of 5th gear. Oh yeah, it was a really long stright road to.

[This message has been edited by Nick (edited 05-08-2001).]

05-08-2001, 11:20 PM
Yes, higher gears do allow a higher top speed because 5th becomes usefull. Especially if the mustang is making more power than stock. But 160 is pretty scary in a near stock stang, now I don't know what suspention work you have done or anything.

92 Mustang GT
Mods: World Products Windsor Sr. Heads, B303 cam, GT-40 intake, 70mm throttle body, 75mm mass air, MAC fenderwall induction, long tube headers, high flow cats, MAC catback, tremec 3550, 3.73 gears, auborn locker.Mac upper and lower rear control arms, lowering springs, 12 degrees timing. 250 HP, 294 Ft/lbs at rear wheels
Best time: 13.7 @ 103.1 MPH

05-11-2001, 01:29 AM
I have Cobra Calipers and Kyb Shock and struts. The car was shuddering pretty bad.

mike g
05-11-2001, 03:35 AM
what are h rated tires rated to like 95 or something like that?

05-11-2001, 02:22 PM
132 mph

Dan the Man
05-11-2001, 02:56 PM
I don't know how fast you were going, but to figure out your gears do the following:

1)Jack up the car so the wheel are off the ground.

2)Get under the car and using a chalk mark the driveshaft and a point of reference on the differential.

3)Now still under the car mark the tire and a reference point inside fender.

4)Spin the tire one full rotation as you count how the number of driveshaft rotations. Almost 3 is 2:73, 3 and a bit, 3:08, 3 and a half 3:55, you get the idea.

Oh, don't forget to disengage the e brake and put it in neutral

Take care!

05-28-2001, 06:59 AM
Tire speed ratings are determined for a four hour test. So driving "H" rated tires up to 160mph is not exceding the speed rating, as long as you don't do it for longer than four hours.

05-30-2001, 01:23 AM
If im not mistaken my old 2.73s ran about the numbers you posted. I do remember 2000rpm @ 80mph, check it and see.

05-30-2001, 08:29 PM

Check this out, looks like you might have 327's

88 GT Cobra Hatch

05-30-2001, 09:21 PM
Snake, that page doesn't take into account wheel/tire combos. Are those calculations with stock 225/60HR15s or 225/55HR16s?

Glen Meades, Jr.
1989 Ford Mustang Cobra Conversion
Born on June 2, 1989

05-30-2001, 11:22 PM
stock 225/60 /15"s I believe I saw in there somewhere.
I'm running 225/60/15's and 308's and the gear charts are right on for me.

[This message has been edited by Snake (edited 05-30-2001).]

06-01-2001, 02:33 AM
I'd say you were doing 130 max.

160? Come on guys... I thought you people knew something about cars here...

mike g
06-01-2001, 07:42 PM
here is the site i got my calculations off of


i tested this with my own car with 2.73 gears and it was very accurate. go ahead and do try it yourself and you will see he was in the 155mph range

[This message has been edited by mike g (edited 06-01-2001).]

06-02-2001, 01:40 AM
Acoording to your website, with his tires and RPM's at 60, he should have 2.42 gears in the rear end. And at 5300 RPM's in OD, he should be going about 170...

There ain't no way in **** he was doing 170mph in that car.

If he doesn't even know what rear end ratio is in the car, do you think he'd know enough to build a 170 MPH Mustang? Cause I can gaurantee it didn't come from the factory going that fast.

06-02-2001, 04:43 AM
Something else to consider here is tach accuracy. I know that stock ones can be off. I think that these can be checked by a computerised engine diagnostic.
I heard a story a few months ago about some cops that did a radar check on two of their SSP's. One clocked in at 145 mph & the other came in at 140. I'm not sure exactly what year this took place but it was back in the mid 80's somewhere. The story was told to me by a guy whose brother-in-law was a hiway patrol officer in central Texas.
Just something I found to be interesting I thought I'd pass on.

06-02-2001, 10:24 AM
F.Y.I. I think the magazines were getting like around 140MPH out of the stock 5.0's during the late 1980's road tests.
Once the lower acceleration gears are installed the top speed should drop some.

06-02-2001, 04:30 PM
i have ofter heard top speed being around 135 - 145 and it is my understanding top speed is limited by drag not the rpm limiter i have also heard rumors that you can actually get a 5.0 going faster in 4th beacause of the increased torque fighting the drag but then they blow up easier oh well ive had my speedo reading 125 and that was fast enough for me

mike g
06-03-2001, 01:33 AM
read what it says sawbones with 1:1 ratio not overdrive...just have to mix and match the rpm to mph. i dont feel like arguing so just stop responding.

GT Dave
06-04-2001, 12:22 AM
You have 3.55 gears.

You were in 4th gear at 114 mph.
If you were in 5th, then you'd be at 170 mph.
Unless you have 400 HP, you didn't go 170, sorry.

[This message has been edited by GT Dave (edited 06-18-2001).]

06-04-2001, 01:08 AM
There ain't no way in **** he was doing 170mph in that car.

If he doesn't even know what rear end ratio is in the car, do you think he'd know enough to build a 170 MPH Mustang? Cause I can gaurantee it didn't come from the factory going that fast. [/B][/QUOTE]

So are you saying I am just another stupid kid with a fast car? The only reason I didn't know the final drive ratio is because the person I bought the car from changed the gears and he didn't tell me about it when I bought it. Besides that is what this site is for.

06-04-2001, 04:15 AM
Please, let's keep our topics civil!

1983 Mustang GT (http://www.mustanggt.org/photo/83tuttle.htm) 306/T-5(project in progress)
1994 Ranger Splash (http://www.geocities.com/mt83rd/index.html?986572015220) 4.0L/A4LD(daily driver)

06-16-2001, 07:55 PM
It seems to me that the reason no one can come up with the correct answer here is due to the fact there may not be enough information to calculate the answer that Nick is looking for.
All the calculations I have seen need a rear end ratio to calculate MPH,or a MPH value to calculate rear end ratio. Since we don't have either figure, all the formulas are useless.

'85GT Hatchback
White w/ GT Hood Decal
K&N Air Filter, '91 H-Pipe, 2 1/2 Hooker exhaust w/ Aerochambers, Energy Suspension Poly bushings in rack,shock tower & sway bar
Many new parts in Suspension,Drivetrain & EEC IV
Paint job & complete exterior restoration to OE, Maximum Motorsports Chassis Brace Kit, AOD Performance Rebuild W/ High Speed Stall Converter,Shift Kit,Wide Ratio/Upgrade Kit & Tranny Cooler, FRPP 8.8 3.55 diff, 2 1/2 SS X-pipe, JBA Egual-length Shorties, Front & Rear Disc Brake Upgrade.

Justin 93LX
06-19-2001, 12:11 AM
I think it's possible

In a very long straight away i was able to get well past 140 on the speedometer with 3.55 and overdrive.

Just kept getting faster... I didn't look at the rpms i wish i had. I figure i was doing 160.

My car is stock besides 3.55 and flowmasters

93Boy tang
06-23-2001, 09:10 AM
SO about how fast would you go with 3 27 gears. Top end.

07-14-2001, 04:37 PM
Was out the other day and took note of the RPM's in 5th at 50 MPH with stock 225/60/15's
and 308's = 1400 rpm's
Oh ya that was the 5.0 HO


[This message has been edited by Snake (edited 07-14-2001).]