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Speed sensor

1991 Buick,Skylark,3.3L,3spd auto. I am wondering how to remove the speed sensor from the trans. I have found a salvage part that seems good but won’t budge. Removed a nut & a bolt. I have many cuts & scrapes trying to find another of each,yet keeping in mind it’s 21 years old. Is there more hardware? Is it just a pain in the @#% ??? Please help . & don’t tell me it’s the tcc circuit. Please don’t tell me that. Speeds are way higher than they should be according to the dash. Tired of the chugging & it’s warm now so time to get to work -Karl

Are you saying that the speedometer reads too fast? If so, the problem is probably not with the vehicle speed sensor.

How far off? How fast is the car going when the speedometer shows 50 mph?

Yes,the speedometer reads to fast. When in 3rd gear the trans. starts to “chug” but it get’s smother as you increase speed. Until highway speed where the “chuging” stops but a moderate vibration takes place.

When I’m 50 it reads like 65-70mph, if not more. My lame ass Haynes manual says it could be the speed sensor or the tcc circuit. They offer no advice. Speed sens.,buy a different manual. Tcc, repair shop. It works fine other than some minor issues,like loping @ idle,but only after the engine has had a lode put on it. Never does it when you start it,warm or cold. In park,sometimes,@ it’s own choosing,off & on. The symptoms match the manual,(trans.), it will calm as you reach 50+, but still noticeable. It has sat a while I think,107,500+ miles,20years old.???-Karl

How much faster than actual? I think you might need to get hooked up to a scan tool and drive it while watching the VSS reading to figure out the right direction here. If this is the system I’m thinking of, it’s impossible for the VSS to generate a signal that indicates road speed that’s faster than actual. But I’ll check tomorrow to be sure.

OK, it’s the system I thought it was. The VSS sends speed signal directly and only to ECM. Then ECM sends signal to instrument cluster to operate speedo.

If you have the correct size tires on the car there is no way the VSS can report speed that is higher than actual. Problem is either ECM, instrument cluster, possibly wiring issue but I doubt it. Anyway, looks like you need a scan tool to monitor data while driving.

TCC has nothing to do with speedo operation.

OK that’s imformative,someone else said scan tool also. What can you tell me about the trans issue? It’s a 3 speed auto & when in 3rd gear it starts to sorta chug or surge. The reason why I thought possible vss is because my repair book says that it most likely the tcc circuit. It also says the vss works w/ the tcc by telling the tcc when to operate,which I guess would be the ecm. The book doesn’t provide much trany repair info,that’s a separate book I can’t seem to find. It only says to take to a shop. My brother is ass. manager @ Advanced auto & tells me they carry the tcc in stock so it should be possible for the backyard mechanic.My ecm has a tcc trouble code stored,as well as a quad driver module circuit. I was told on this sight the quad driver is in the ecm & should be replaced. I got one from the junk yard,tried to erase the codes the way the book says but it still has the same codes. Where is this tcc located? How much of a pain is it? Is that most likely the problem? Should I replace the ecm again or retry erasing codes? Thanks a lot for your time,hope to hear soon,pulling my hair out

Torque converter clutch has nothing to do with speedometer operation. ECM looks at a number of things, then decides when to engage the torque converter clutch. VSS input is one of these things, but so is throttle position, brake pedal, engine temp, etc.

Quad driver is the part in the ECM that actually turns the TCC solenoid on and off. If the ECM does not detect current flow when commanding TCC solenoid on it sets a code. Code can be caused by faulty TCC solenoid, open or shorted wiring, or faulty ECM. If you installed a used ECM and have the exact same issue it’s unlikely that the ECM is at fault.

TCC solenoid is inside the transmission. You’ll have to remove the valve body cover (side pan to access. Also check the wiring as it goes to the front of the transmission.

But I’m not sure what your chugging or surging is…hard to tell without driving the car!

Thanks a lot! That really makes more sense. I understand about not driving the car,the best I can explain is you will feel a pulsating in the pedal. It also causes a vibration in the wheel & the drivetrain shakes. It makes a deep rumble noise & it seems like the engine has to fight to get up to speed,not hard,but still. Again,this is only in 3rd. & the faster it goes the less it does this.Once you reach 45-50mph,it almost completely disappears. Thanks again-Karl