Got a formula today! Need a little help.
Got a formula today! Need a little help. I got a 93 formula today and the speedometer is way off. My dad drove it and he seems to think it has 4.10's. How do I really tell what it has and how do I fix the speedometer. I searched but couldn't find what I was looking for, thanks for your help.
Dustin
Dustin
TECH Enthusiast
Joined: May 2004
Posts: 549
Likes: 0
From: St. Peters, MO
Okay go outside and have your dad help you. Roll the car forward in neutral just far enough that the driveshaft makes one full revolution. Some assembly chalk helps here. Count the number of times your wheels turn. Should get you close enough to guess. However what tranny do you have? Because the 6 speeds had different ratios back then and 4.10 would be way steep. 3.73's and 3.42s were the norm for the 6spds back then.
Here are the T56 gear ratios for 93-95. Apparently the 93 got two different T56s, what a strange year that was for f-bodies.
http://www.f-body.org/tech/tech.htm#T56
http://www.f-body.org/tech/tech.htm#T56
Thanks for the comments. It is a bright red 6 spd 
I want to get rid of this 110 mph gauge cluster and swap in the 150, I see many on ebay for cheap. Is that a hard thing to do? Why did they do the 110 rather than the 150? Also the ABS INOP light is on I imagine that is because of the gears. I figured an easier way to know my gear size is compare my speedo's reading to how fast I am really going and do some math knowing that stock gears are 2.73.
Dustin
I want to get rid of this 110 mph gauge cluster and swap in the 150, I see many on ebay for cheap. Is that a hard thing to do? Why did they do the 110 rather than the 150? Also the ABS INOP light is on I imagine that is because of the gears. I figured an easier way to know my gear size is compare my speedo's reading to how fast I am really going and do some math knowing that stock gears are 2.73.Dustin
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The only way to fix the speedo in a 93 M6 car is a SLP speedo calibration box which to my knowledge isnt produced anymore. Either that or throw some stock gears back in it. Im with Bizzzatch350 though, check out www.speeddensity.org for all the 93 info you can handle. 
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Originally Posted by Fire-formula 93
Thanks for the comments. It is a bright red 6 spd I want to get rid of this 110 mph gauge cluster and swap in the 150, I see many on ebay for cheap. Is that a hard thing to do? Why did they do the 110 rather than the 150? Also the ABS INOP light is on I imagine that is because of the gears. I figured an easier way to know my gear size is compare my speedo's reading to how fast I am really going and do some math knowing that stock gears are 2.73.
Dustin
I want to get rid of this 110 mph gauge cluster and swap in the 150, I see many on ebay for cheap. Is that a hard thing to do? Why did they do the 110 rather than the 150? Also the ABS INOP light is on I imagine that is because of the gears. I figured an easier way to know my gear size is compare my speedo's reading to how fast I am really going and do some math knowing that stock gears are 2.73.Dustin
At least that's the way I understand it.
Get some chalk and do like a poster above suggested, that will tell you alot. Or get a car to pace you and get your actual speed, then compare it to your tachometer.
In your one to one gear (4th in your case) bring your car to 70 MPH, pacing your friend. A cell phone is handy, have him tell you when you're doing 70. Now look at your tachometer, if your tach reads 4100 RPM approximately, then you have 4.10s.
, i have one of those arrest me red ones too 
Originally Posted by contraststriker
Here are the T56 gear ratios for 93-95. Apparently the 93 got two different T56s, what a strange year that was for f-bodies.
http://www.f-body.org/tech/tech.htm#T56
http://www.f-body.org/tech/tech.htm#T56
93 T-56s go by gearing, the 2.73s had a different geared six speed than a 3.23 car, I believe the RPO codes are M28 for the 2.73 six speed and M29 for the 3.23 six speed. Evidently 3.23 "wide ratio" T-56s are geared exactly like a Corvette Z06. I think Dakota digital makes a box for reprogramming the speedo
Hey thanks for the speeddensity link. I was wondering why I did not have a MAF sensor. I am glad to hear I made a smart purchase for once. $4300 with 113,000 miles, not too bad. It is in great condition for a 93. I have to do my emissions test this weekend, anybody have any trouble with that? I am probably going to change O2 sensor before I go and maybe get a high-flow cat.
Dustin
Dustin
I am probably not going to go that fast anyway but I just dont like seeing a 110 mph on a formula, it makes me mad and I dont know why. Anybody feel the same way or am I just crazy?
Nah I agree
Originally Posted by slowmofo
Wern't cars w/o the 150 speedo governed to 115? Might be wrong..
Probably because they wouldnt have Z-rated tires option which was QLC if they had the 115 speedo
On The Tree
Joined: Jun 2005
Posts: 147
Likes: 0
Speedo blues Cyberdyne offers a unit the will allow you to change the frequency the gets sent to he speedo. I got mine from Jegs. the PT# is 280-9901 and it cost 43.99. here is a link to the Jegs website for that part. they will not be available until the end of the month. they are on back order. the older version of this that I have will not work past 70 MPH though. you might be able to call Jegs 800-345-4545 and get a number for Cyberdyne to see if they have that fixed yet.
http://www.jegs.com//cgi-bin/ncommer...36&prmenbr=361
http://www.jegs.com//cgi-bin/ncommer...36&prmenbr=361
Launching!
Joined: Dec 2004
Posts: 284
Likes: 1
From: Hebron, Oh
Ive got a 93 with the m29. I put 3.42's in it first, and it was ok. It's like the newer 6 spds with a 3.73. I later put in 3.73's, like a 4.10 in later 6 spd when you calculate the ratios out. I have the slp speed cal box, but my cruise control never works with it hooked up. Unhook the box and my cruise works. I called them years ago to find out why. They said I was the first they had heard of that. Yeah right. It could be why they don't sell them anymore, but I don't know. The m29 has the same gearing as the zo6 1st thru 4th, but I think 5th and 6th are similar to the mm6 ratios. I love the 3.73's, but it will put you at about 2300 or so at 80 since 6th is .62 versus .5 for mm6 cars. To find out your current ratio. Have somone rotate your wheel while you count driveshaft rotations. If your driveshaft rotates almost 2.75 turns then you have 2.73, almost 3.75 = 3.73, you get the idea. My neighbor has 93 a4 with the 115 speedo and he has 2.73's and car shuts down around there, but you can bypasss that in the pcm.
The transmission difference in 93 for the six speed came about because when GM was ready for production, Borg Warner didn't have the F-Body spec transmissions ready, so GM went to Chrysler and bought a handfull of viper transmissions, hence the close ratio M29 six speed. That and a set of 4.10's at the track with the right height tire and traction would be KILLER.
Speedo correction options are limited. Other then the above mentioned SLP Speedo Recalibration Box (serach Ebay, they pop up from time to time) and the cyberdyne (never heard of that one) there's also the Dakota Digital SGI-5 box which should work too.
If you're planning on swapping a 150 MPH speedometer/cluster into the car, remember the following: If it's another 93 cluster you're putting in, simply put the cluster in. If it's a 94-97 cluster, you need to remove the Tachometer filter for the tach to work correctly, OR, put in an aftermarket ignition box which will send it's own signal to the tach. Tach Filter Location
Oh, and 93's are just plain faster than 94-97 LT1's.
Speedo correction options are limited. Other then the above mentioned SLP Speedo Recalibration Box (serach Ebay, they pop up from time to time) and the cyberdyne (never heard of that one) there's also the Dakota Digital SGI-5 box which should work too.
If you're planning on swapping a 150 MPH speedometer/cluster into the car, remember the following: If it's another 93 cluster you're putting in, simply put the cluster in. If it's a 94-97 cluster, you need to remove the Tachometer filter for the tach to work correctly, OR, put in an aftermarket ignition box which will send it's own signal to the tach. Tach Filter Location
Oh, and 93's are just plain faster than 94-97 LT1's.