Tyes91Z

Hello all,

I jus recently bought a 91 Z28, 305 TPI. I have plans for the car later on, but for now I just want it run and drive correctly. My first issue is my speedometer doesn't work...at all. I went throught the fuse block and found 2 blown fuses and replaced them, but I'm pretty sure they were interior lighting and stuff like that. I have seen it mentioned in other threads that the speedometer is mechanical. If thats the case, then that means something somewhere is either broken or not hooked up. Where do I start with this?

My next issue is the transmission. The person i bought it from claims the engine and tranny were rebuilt 2 years ago and have around 24k on them. The transmission winds out first gear almost all the way before shifting, shifts into 2nd extremely hard, into 3rd normally, and will not shift into O/D at all. A few folks i have talked to have suggested that the valve body needs to be adjusted. Other than the shift points, the transmissions feels and sounds solid. We adjusted the "kickdown" cable on the throttle body and that didn't seem to have any affect. Is this any issue that can be adjusted or do I need to start hunting a transmission?

And the bigger question is, could these 2 problems be related?

Thanks in advance and I will try to keep the stupid/redundant questions to an absolute minimum.

luvofjah

iTrader: (2)

I'm not 100% sure, but someone can chime in, the speedo signal comes from the trans...
I have a working speedo gauge off a 91 Firebird, if they are the same ??

Rafael

camaronewbie

1991 car so your speedo is electrical. There's a small wire harness driver side on the tailshaft of the tranny - make sure it's plugged in good.

Tyes91Z

Ok, will do. Now this harness I assume hooks to a sensor in the housing, is there any way to check the sensor itself? I'm looking at the issue from 2 different directons. One being that jus the speedo is not hooked correctly or hooked to bad sensor. And the other direction being that whole cluster is bad. None of the other gauges are working correctly either, with the exception of the tach, and it reads high. I have read the sticky about the 90-92 tachs and how to fix them so I'm not too concerned with it at the moment.

Also, could there be any relation between the speedo/cluster issue and the transmission not shifting correctly?

Thanks for the input!!

camaronewbie

OK - oil pressure should be fed from a sender just above oil filter on the block, has 3 wires, two are larger and are red or orange, the smaller of the 3 is the gauge wire.

Coolant temp sender in driver head between #1 & #3 spark plug, has single dark green wire to it.

I have no idea on exactly how the speedo works - I know there's a Vehicle Speed Sensor in association with speedo, but exactly how that works I have no clue.

There is a 'sensor' on the tranny for the speedo, translates rotating gear from shaft inside tranny into electrical pulses for the gauge (and VSS I assume). But VSS shouldn't have anything to do with tranny shifting, I have no ECM at all now that I'm carbed, and my tranny shifts as it should - I assume no ECM = no real use out of the VSS as far as any tranny functions are concerned, except maybe torque converter lockup which is not a shifting per se.

Only thing that mechanically instructs tranny to change gears and when is the TV cable - make sure its adjusted properly.

Tyes91Z

We adjusted the cable some, and it didn't seem to have any affect on it. But my buddy who did it adjusted his sisters car and now her transmission shifting funny. I will adjust it again the correct way and see if that does anything.

I bought this car a week ago and I'm just trying to get basic drivability squared away before I start tinkering with it. Thanks for all the info.

dualdj1

Most of your problem stems from the fact that you're not reading vehicle speed. I'm pretty sure the computer won't allow O/D if it doesn't sense speed as it doesn't know if it can safely activate the lock up torque converter. If you have good connection, I'd guess your speed sensor is bad. Get a scanner on it first and drive and see if you're reading vehicle speed. Not much other way to test it, just have to replace it if it's not reading. It probably also has a speed sensor buffer unit. I don't think these really go bad, but it's also possible. If replacing the sensor doesn't work, I have a VSS buffer chip I could send you if you want to pay shipping, or you could probably get one at a local yard.

Start with the scan, see if you're reading speed, if not then check connections again, replace sensor, and keep moving down. I think that will fix your trans problems as well, as the trans will be computer controlled, at least partially.

Tyes91Z

Ok, very good info thanks. I was wondering how the VSS tied in, but i have had alot time to search and read up on it. And I also wasnt sure if the transmission received any input from the computer. It looks like my biggest obstacle right now is time. I'm working some serious overtime right now.

I like a good project and I like having something to tinker on. So far from what I've seen and read here, this car is gonna be much more enjoyable than my other project (a heavily modified 93 GMC Typhoon).

dualdj1

Yep, I'm not 100% positive on that for your specific model, but anything i've dealt with that has transmission control and speed sensor, they are related. At any rate you need your speedo working, and the sensor circuit does pass to the ecu as well, so remedy that problem and hopefully your trans issues will be fixed as well.

91bluez

i bought my 91z28 after it was sitting for a couple of years.....new dizzy she flashed right up.....the left side of my dash doesnot work(speed,oil)i checked the wires all was good...then i pulled the gauge cluster and the circut board(thin plastic panel) had lifted away from the contacts on the back...check that and see if its done the same.