when stopped my speedo is at zero so its correct but the faster i go the further off it gets. 35 on the speedo is actually 51, 50 on the speedo is actually 74. could the speedo gear in the tranny be bad or is there some way to re-calibrate it.

jptaylor

------------------
1989 formula
jasper 350 (punched to 397ci)
trick flow twisted wedge heads(2.02 intake and 1.72 exhaust)
1.6:1 roller rockers
jacobs omni magnum ignition
isky cam
flowtech jethot coated headers
mufflex 4" mandrel stainless exhaust
no cat
holley 670
open element
custom fixed headlights
97 formula interior
macewen white faced gauges
3.42 posi rear end
baer racing 4 piston calipers front and rear
underdrive pullies
hard wired cooling fans


IN EVERY RACE THERE IS A WINNER AND A VICTIM, YOU LOOK LIKE A VICTIM!!!

 

Smells to me like your car came with 2.77s and the 3.42s are a mod...

You need to get the right speedo gears for your new rear gear.

------------------
"So many Mustangs, so little time..."

 

Yeah, sounds like you need to go down to the dealership and order the right speedo gears for your rear end ratio. It should be accurate to within +/- 5 m.p.h. once you get the correct gears for it. They should have the gear combos in their computer at the dealership for each ratio.



------------------
89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

no, excuse me for not making myself completly clear. the speedo pickup or gear or whatever it is in the tranny was changed when i swapped the gears and it was correct until a few weeks ago. i did the rear swap about 4 years ago. so once again i pose my original question.

 

Sounds like a bad speedo head to me.

------------------
1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

 

If you have access to a scan tool, it will tell you the speedo reading in you ecm. If your ecm and speedo read the same, then either your VSS or the corresponding gears are bad. If the ecm is correct, then the speedo it self is bad.

 

My 85 was pretty bad, never realized it for years. Indicated 70 was actually closer to 85. No wonder i always got where i was going in a hurry considering i never had the cruise set for under 70. lol Strangest thing was my odometer would be pretty close to perfect using the mile markers on long highways, even for 60-100 mile stretches. I never investigated further, i just didn't care.
...ed

 

If the speedometer gears are right, the cable will turn the correct number of turns per mile, and the odometer will always read the correct value. There could be a defect with the speedo head, such as low return spring tension, which would cause the speedo to read high, or excess drag on the shaft, which would cause it to read low.

------------------
1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

 

ok, maybe im an idiot but i didnt think i had a speedo cable. my speedo plugs into the wiring harnass behind the dash.


------------------
1989 formula
jasper 350 (punched to 397ci)
trick flow twisted wedge heads(2.02 intake and 1.72 exhaust)
1.6:1 roller rockers
jacobs omni magnum ignition
isky cam
flowtech jethot coated headers
mufflex 4" mandrel stainless exhaust
no cat
holley 670
open element
custom fixed headlights
97 formula interior
macewen white faced gauges
3.42 posi rear end
baer racing 4 piston calipers front and rear
underdrive pullies
hard wired cooling fans
www.geocities.com/jptaylor2/FIREBIRD.html

IN EVERY RACE THERE IS A WINNER AND A VICTIM, YOU LOOK LIKE A VICTIM!!!

 

I have the same problem and still cant figure out what the hell is wrong with it. It's really beginning to annoy me.

Rob

------------------
1987 IROC-Z Auto (LB9)
Black/grey with the stance of a streetfighter

Mods
Custom exhaust. 4 Inch pipe from the headders all the way back to a single muffler at the rear. No Cat.

Future mods:
K&Ns
RAM Air
New Underdrive pulleys-either March performance pulleys or Auto Specialties Performance
Air foil

 

Ok then, forget about the cable, but the gears will still turn at the correct rate, making the VSS send the right number of pulses per mile to the ECM. But there could still be a problem with the speedo head.

I don't know what the odometer would do in your case, I was commenting more on Ed's problem with his 85. You might have to do as Glenn suggests, and see how fast the ECM thinks the car is going.

------------------
1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

[This message has been edited by Apeiron (edited December 19, 2000).]

 

ok, about two years ago i put a bypass on the vss. it didnt affect my speedo then. however about a year ago my whole dash went out, not too bad though as it was only one underhood wire that was bad. when the dash started to work again the speedo was off.

jptaylor

------------------
1989 formula
jasper 350 (punched to 397ci)
trick flow twisted wedge heads(2.02 intake and 1.72 exhaust)
1.6:1 roller rockers
jacobs omni magnum ignition
isky cam
flowtech jethot coated headers
mufflex 4" mandrel stainless exhaust
no cat
holley 670
open element
custom fixed headlights
97 formula interior
macewen white faced gauges
3.42 posi rear end
baer racing 4 piston calipers front and rear
underdrive pullies
hard wired cooling fans
www.geocities.com/jptaylor2/FIREBIRD.html

IN EVERY RACE THERE IS A WINNER AND A VICTIM, YOU LOOK LIKE A VICTIM!!!

 

I have this same problem. I removed my dash and guages to clean them, and now I can go from 0 to 80 in about 1 sec. (Gee I wish that were true.) Is it possible that the speedo needs to be reset?

-Mark.

------------------
86' Firebird
240,000 Mi.

 

Glenn91L98GTA is right, check with a scan tool to see if the computer is getting the right speed. If it is, the it probably will be the speedometer itself. I have seen this on at least a dozen F-bodys with a VSS and an electric speedometer.

 

Tires different than stock height?