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I just bought another Camaro! I have a 1994 Z28 and now I got a 1991 RS 305 TBI, beautiful car in awesome condition. I have one problem that I just can't figure for the life of me. The car initially was and automatic and has been turned into a 5 speed manual with a T5. The speedometer doesn't work and when i got it the guy said the car just needs a speed sensor. I looked under the car and tried to put in the VSS that I got from the GM but it won't fit. It seems to be a total different part. Do I need some kind of an adaptor or something?
Anyone? Thanx
I believe sometime around 1989 GM switched from cable-driven speedos with the VSS built into the back of the dash gague cluster (that then sent a speed reading to the ECM- but the speedo was still driven manually by the cable) over to a transmission-mounted VSS that was fully electronic from the sender to the ECM which, in turn, drove the speedometer electronically (no cables or physical connection between the tranny and the speedo).
Somebody please chime in on this.....
Regardless, in 1991 your car definitely used a tranny-mounted VSS, full electronic back to the ECM. No cable.
I believe sometime around 1989 GM switched from cable-driven speedos with the VSS built into the back of the dash gague cluster (that then sent a speed reading to the ECM- but the speedo was still driven manually by the cable) over to a transmission-mounted VSS that was fully electronic from the sender to the ECM which, in turn, drove the speedometer electronically (no cables or physical connection between the tranny and the speedo).
Somebody please chime in on this.....
Regardless, in 1991 your car definitely used a tranny-mounted VSS, full electronic back to the ECM. No cable.
That's exactly what I have to solve. How to convert the electronic speedo to the older transmission...
Is this a later or early T-5? Also there should be some adapters that fit there so you can connect it digitally. I am not sure what the name of the place is that sells stuff like that, but I did read on this board about it. So, I hope someone chimes in with the info. There is a place like that, I know.
I'm pretty sure you can just get a VSS for a 91 5 speed car and be in buisness. I know for a fact with the auto's the tranny isn't different, there is just an electronic sending unit that plugs in where the cable unit went.
I would think you'd still need to change something inside the tranny, even if you could physically bolt the VSS into where the old speedo cable went. The VSS uses a magnetic pickup that counts the "teeth" of a special gear attached to the output shaft inside the tranny as they pass by the sensor. That gear would almost certainly be different than the gear used to drive a speedo cable (in fact, I think the gears that drive the speedo cable are plastic or some kind of polymer, which would make a mag pickup totally useless). It might be as simple as changing to that VSS gear instead of a speedo cable gear inside the trans. Typically, when changing this internal gear to re-calibrate a speedo in a cable-type setup, for instance, it's a matter of removing the tranny tailshaft, changing the speedo drive gear and bolting it back together (my experience with this is entirely with automatic transmissions and rather limited at that).
Sorry, I'm out of personal experience and ideas on this one. I think you at least have a good grasp of the problem, however.
Lurking on this board somewhere is somebody who knows "THE" answer, I'll almost guarantee it. Maybe the tranny forum?
i just pulled my speedo gear today. i have a 91 305tbi t-5 5spd. the speedo gear is on the drivers side of the tranny-towards the back, next to where the driveshaft enters. theres an electrical plug on the top and then therese a 10mm bolt liek on the bottom right. when u look at it it appears circular. u take that bolt out and a lil fluid will follow then the gear is rite there on the eng od the shaft and u just pull it off....hoped that helped
Oh my gosh people I cant beleive the misinformation here. First, Damon it was 1990 when GM switched from cables to electronics in the Camaros. The Firebirds switched in 1986. Also, the drive gear on the tailshaft is the exact same plastic gear for both cable and electronic speedos. The metal gear you are talking about is the reluctor wheel GM used in 4th gens.
To get your speedo working right, you will need the electronic VSS unit, and the correct plastic speedo gear to match your rear end gears, and you probably need to change the plug for the VSS, too. You can find more info by searching the Tranny/Drivetrain forum, where I moderate.
I cannot find the correct part number for my VSS. I have a 1991 Camaro Z28 305 TPI with manual transmission. Initial searches said it was SC12. However, that thing is way to big for the opening on the side of the transmission. See attached pics to compare. The VSS out of my car has the cog on it. The SC12 is in the background.
Anybody know the correct part number? I'm leaning GM 10456087, but I can only find on eBay for $400+.
I cannot find the correct part number for my VSS. I have a 1991 Camaro Z28 305 TPI with manual transmission. Initial searches said it was SC12. However, that thing is way to big for the opening on the side of the transmission. See attached pics to compare. The VSS out of my car has the cog on it. The SC12 is in the background.
Anybody know the correct part number? I'm leaning GM 10456087, but I can only find on eBay for $400+.
The speed sensor for the T-5 has long been discontinued. Your options are either pay out the wahzoo for a NOS or used one, or get something to adapt a cable drive to electric and convert the signal into something you can use (if needed) with a dakota digital box or similar.
The speed sensor for the T-5 has long been discontinued. Your options are either pay out the wahzoo for a NOS or used one, or get something to adapt a cable drive to electric and convert the signal into something you can use (if needed) with a dakota digital box or similar.
WildCard600 - thank you for the response. I need to do the 'drill' method to see if the VSS is actually bad or if I have other issues. I through code 24 but the car drives fine. The speedometer will work on occasion but the odometer and trip do not work. I am sure the odometer and trip are separate issues. I have found some threads on here about those that I will try.
Outrageous that used VSS are going for $400 to $600 on eBay!
I've got one that came with a t5 I picked up. I'm looking for the electronic vss that was used before the big can design. I'd let it go for $150
Drgnbld - Thank you! I'll let you know after this weekend. I am going to test the VSS by attaching to a drill and voltmeter to see if it is actually bad or not. I'm kind of hoping it is bad wiring somewhere. Previous owner had cut the VSS wiring and the oil pressure sensor wiring at some point (over 20 years ago). I need to check those and make sure connections are still good.
Drgnbld - I tried the drill test on my VSS and it was reading voltage as the drill spun the VSS shaft. The faster the drill spun, the more volts I would get. I also back probed where the VSS hooks into the computer. I unhooked C1 from the computer and put pins in B9 and B10 and ran the VSS with the drill. I was getting voltage there as well. So, it appears I am getting voltage from the VSS to the computer.
My speedometer will work on occasion but the Code 24 comes on after a few minutes of driving and doesn’t go off. The code doesn’t persist after turning the car off and then back on.My odometer and trip do not work. I don't think that has anything to do with the VSS. I say that because when the speedometer does work, the odometer and trip still do not operate.
Ok, I am throwing code 24 and speedometer will work when it wants ('91 Z 305 TPI/manual).
I did the drill test and the VSS was showing increased voltage the faster the drill spun.
Decided to test ECM. Brian at Tuned Performance was nice enough to send me an ECM to borrow and test. Same problem.
Today, I decided to strip enough wire insulation to hook VM to purple and yellow wires at the ECM with alligator clips and see what VM said while driving. VM increased smoothly as I accelerated and never dropped. Speedometer never worked on this trip but I still threw a code after about 7-10 minutes of driving. Car doesn't seem to drive any differently with the code.
Any ideas on what the heck is causing me to throw the code?
04-19-2006, 04:05 PM
