Out getting firewood with a trailer. In Low range backing a trailer up a wash, so frequent shifts from R to D, and when I finished that, the transmission began shifting very hard and I had a P0102 code which is unregulated air in the intake. ie. a vacuum leak. What would cause both things to happen at the same time. My first thought was vacuum modulator, but the 5 speed OD doesn't have one. Shifts are computer modulated? It shifts on time. Don't have to over-rev, but it bang shifts. I've been running around in "2" so it doesn't beat itself to death on the 1 - 2 shift especially. But sure would like to know what caused both problems at the same time. I've used up a can of carb spray around intake and vacuum ports, also underneath trying to find where the intake air is coming in at, and nothing found so far. All wiring looks fine. It's fairly clean underneath. 158000 mile vehicle. Reasonably well cared for, but I use it like a truck.

 

Welcome to the forum

When you get an engine code the computer may change transmission shifting to "Safe mode", which will mean harsh shifting, a direct shift is better/safer for the transmission than a slow smooth shift, just FYI

So the two are related but I don't think you have a transmission problem

Clean MAF sensor to start with

P0102 Mass or Volume Air Flow Circuit Low Input

The computer knows it is running a 4 LITER engine, so it knows exactly how much air should be flowing past the MAF sensor at any given RPM and Throttle position
The MAF sensors main purpose is to fine tune the WEIGHT of that air depending on elevation, temp and humidity.
If MAF sensor is showing lower than expected flow then could be it is dirty or could be there is an air leak so not all the air the engine is getting is coming thru the MAF sensor


Simple quick test for vacuum leak
Engine needs to be warmed up, operating temp, and idling
Unplug the 2 wires on the IAC(idle air control) Valve
IAC Valve will close all the way and engine RPMs should drop to 500, engine may even stall, either is GOOD, it means no vacuum leak
If idle doesn't drop then you have a vacuum leak

 

Thanks! I'll give those a try. Replaced the MAF sensor last year when I put in all 3 new 02 sensors, but of course, that doesn't mean anything.