I have a '90 firebird and have just finished installing a ZZ4 with '89 TPI and wiring harness. The factory dash is electronic and the '89 harness and computer don't appear to have the ability to run the speedometer. Is there a way around this without going to a mechanical speedo? Before answering, it gets a little more complicated. I have also replaced the factory 700R4 with a '97 T56. The T56 was installed back in the spring and was hooked up to the '90 wiring harness with no problems running the speedo and cruise controll. I want to get this straightened out asap. Any help would be greatly appreciated. Thanks, Rob.

 

The 87-89 Firebirds had electronic speedos and used the same 7165 computer that the camaros with cable speedos did. You'll probably need a wiring diagram from an 89 Firebird then.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
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Since '89 Camaros have a cable driven speedo, they must use an external speed buffer module in the cluster. Sounds like you will need a VSS for the new manual transmission (assuming that the original stock VSS will not fit in the new trans), and a speed buffer module ('92 305 TBI setups came with an external speed buffer module that will work). The speed buffer module has a VSS input, a 4000 pulse per mile output for the cluster and ECM, a 2000 pulse per mile output for the cruise control, and will need ignition power and ground.

Tim

 

Forgot to mention - if your '90 setup was originally TBI, you should already have the external speed buffer module.

Tim

 

Tim, the car was a 305TBI. I used the cyberdyne calibrator box to make it work before the engine/harness swap. Where would the buffer box be, and how would I connect the tranny to it? I would guess it just gets straight wired from the tranny sensor but I'm not as good at wiring problems. I found the original factory sensor wires from the bulkhead connector under the drivers' side dash but didn't see where they attatched to anything other than into the bundle of wires. Tanks for the help, this one's been harder to solve than some of the other bugs, Rob.

 

Your wires are purple and yellow, and the buffer should be in the general area of where the ECM was. If you need one, I have one for sale on ebay or if you just want to see what it looks like. Do a search for VSS Buffer.

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