pcopp

Harvested a T56 AND Rear from a 1995 Firebird Fornula for our 1986 Z28 5 Speed.

Rebuilt and re-geared the rear end. Works good.

Got the trans installed and got the pressure plate rubbing issue solved. Trans works well. Clutch is good.

Last problem we are having is with the VSS. We installed from Hanlon Motorsports the VSS/OSS lockout switch. It uses the VSS signal to trigger the reverse lockout solenoid. Key on, not moving, it engages the reverse lockout to let you put it in reverse. When the car is moving the VSS is supposed to generate a voltage that overides the device so that the reverse gear is protected on the 4th to 5th gear shift.

Our problem is that the VSS is not generating a voltage when rolling so the reverse lockout solenoid is always energized and reverse is not protected.

We tested the VSS that was in the trans when harvested and it generates a voltage when pulsed near a piece of steel. We installed a Dorman replacement and a Standard Products replacement, both are the correct part number for the trans according to RockAuto. All test fine pulsing near a piece of steel, none generate voltage in car while driving. We look in the VSS port on the trans and we see the reluctor wheel. We checked continuity on the wiring. Everything checks.

Anyone have any ideas?

stew'86MCSS396

How are you checking the output of the VSS while the vehicle is moving? IIRC it's supposed to output AC but tbh I don't know what kind of output you should expect probably varies with rpms.

Idk if the Hanlon Motorsports is typical of others on the market...have you verified the ground is good, +12v is good, have you determined which VSS wire is the signal and which one is the reference connected them respectively? Last 2 wires goes to the solenoid on the lockout which my understanding polarity don't matter.

pcopp

Good Morning,

Thanks for the reply. I will provide more background.

We spoke to the manufacturer of the VSS/OSS who sells through Hanlon. They were very informative and helpful.

We were advised that the T56 VSS should be output voltage on AC scale when car is moving. They advise that the VSS can be tested as follows: on AC scale, measure anywhere from 0.3 to 0.5 V when pulsing the VSS near a piece of steel. We checked the original VSS and the two replacements and all three check per this test.

As far as the device, it is a micro relay. It receives 12V switched power and chassis ground. It then has two leads that connect to the Reverse Lock Out Solenoid (RLOS) and two wires that connect to the VSS.

With car stopped and key on, the device sends 12V to the RLOS and engages it so that you can easly put the car in reverse (vs. having to force the shifter into reverse). When you place the car in gear, the rotation of the reluctor is supposed to generate a voltage through the VSS which goes to the device and cuts power to the RLOS, releasing the RLOS and locking out reverse to prevent a misshift.

The device has a test lead and when we power with a 9 volt battery as suggested by the manufacturer, it releases the solenoid. So, if we could get the VSS to generate a voltage, we would be good.

As far as testing operation of the VSS in the car, we ran the leads of the VSS into the passenger compartment through the shifter port of the trans tunnel. With the car driving at various speeds, we never get a voltage on the AC scale of our multimeter connecting direct to the VSS leads and we flipped positive and negative to confirm polarity was not the issue (which we did not think was since the VSS is a simple coil reluctor).

We look into the trans port for the VSS and we can see the reluctor is in place.

So, we have no reason why one of the VSS's that we have will not generate voltage signal. We have the original GM VSS harvested with the trans, a Dorman A/M P# 917-644 and an A/M SMP P# SC144. Both Aftermarket part numbers confirmed through Rockauto catalogue for the 1995 firebird with 5.7L T56.

pcopp

I guess I forgot to mention, the VSS on the 1995 T56 is a two wire VSS, not a three wire so there is no reference signal. This VSS is supposed to generate a voltage when car is moving and any voltage signal is supposed to release the RLOS. In the ECM of the Firebird, I assume as the voltage varies with RPM, the ECM generates a signal to the cluster speedo for the speed of the car.