I’ve looked through a bunch of searches and I couldn’t come up with the answer I was looking for.

I had a 91 RS TBI 110 mph gauge cluster.

I got a 92 Z28 TPI 145 mph gauge cluster.

from best I can tell it’s reading the same as my old 110 speedo did. And the 110 and 145 are almost in the same location. So when I’m doing a 110 the z28 cluster reads 140. I did find one thread that mention a speed buffer on TBI cars. If anyone knows any information that would make it read correctly I’d appreciate it.

 

The buffer box on TBI cars is under the passenger side of the dash near the ECU. It is a little yellow box with two screws holding it in place. I used a Dakota Digital box to adjust mine. How did you correct the Speedometer after your T56 swap? I am still running the 110 mph gauge cluster.

 

My buffer box was bypassed when we did the LS swap. I didn’t realize he had bypassed it.

Scaled the signal back by 78.6% so the speedo would read right. But that also scaled the odometer back so now it reads wrong.

 

So is there any difference in the buffer box with the 110 and 145 but both TPI? I changed because I wanted a real cluster instead of a cluster better suited for a v6. Car is a 91 Z28, and I have never driven the car, I got it as a non runner and have been waiting to install the 355 and T5.

 

Sounds like you're dealing with with minor incompatibility issues. There may be hacks to properly adjust for this, but I'd always recommend using the proper modules for your VIN. Anyway, I've been really impressed with the expertise at this shop when it comes to compatibility issues. They focus on cluster work exclusively, I'd say give 'em a call and I'm sure they'll help you out. https://www.instrumentclusterstore.c...t_clusters.htm