I have a 1989 S15 4wd that I dropped a 3.4L crate motor, 4.3 TBI and injectors, headers, under drive pulleys. I replaced the 8062 ecm with the 4288 ecm and have $AO file. Using Tunercat and have the truck pretty much dialed in. After a recent manual tranny rebuild I now have a 4th to 3rd gear grind on the downshift at higher rpms. My theory is my rpms are dropping too fast while decelerating.

I know what you are thinking if it didn't do it before the rebuild. But before this rebuild I set it up the tranny too tight at 0.003 preload on new bearings and it ground on the upshift from 3 to 4. Now I'm exactly 0.002 preload on new bearings and that problem is solved but a new one is generated.

If you drive like a normal human being the tranny is fine. But I'm hard on this old truck and I despise lollygaggers, texters, and gawkers.

I'm slowly changing the Throttle Follower Coeff and IAC Decay Delay. I was hoping someone on this forum could steer me in the right direction to get the rpms to hang at the higher rpms longer.

Thanks