1992 Chevy Suburban c2500 454 w/ the HD automatic transmission. When I drive over 60 mph or up hill at 60+ my rpms jump 200 or 300 rpms. I know the truck has a brake solenoid on the transmission but want to know what you might think it is. The problem use to be at higher speeds but has gotten to 60+ mph. It isn't getting any worse. around 2000 rpms jump to 2200-2300 just to tell the rpms. Thank you all
When the transmission jumps the extra RPM by 200 or 300 RPM. That's your Torque Converter Clutch lock up disengaging or it's slipping. Pull the transmission dip stick out and check the fluid level and condition of the fluid, look to see that it's not burning. If the fluid is not burning then it's the Torque converter clutch unlocking and the Throttle position Sensor may need to be readjusted, or if the transmission is still running off a TV cable. The TV cable may need to be adjusted and or the transmission filter may be dirty and needs to be changed. Take it to a transmission shop and explain to them what the transmission is doing. I'm not sure if your transmission is an 4L80 or a 4L80E. If it's the 4L80E the PCM and ECM control the lock up to your converter. If the PCM detects a problem with the transmission, it drops the transmission fluid pressure to the converter clutch. If it's a 4L80, it's controlled by the TV cable and vacuum lines to the transmission modulator. Regardless they can look in to this when they change the transmission fluid and filter. Recap: Have the Suburban's ECM scanned for any transmission DTC codes. Service the transmission if the fluid is dark in colour and burnt. Adjust any linkage to the transmission that is an issue to it's performance. Good luck and keep me posted, be glad to help.
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