shift flare aka runaway shift
Hello all it's been a while. this is not a problem anymore but I feel so happy about fixing something that I took the time to help anyone experiencing shift flare, especially with the 31th transmission. If your caravan or neon has the 3 speed 31th transmission like my 98 caravan (why they would use the same tranny in such different vehicles is beyond me), there is a common simple solution to shift flare. I got a salvage transmission for my caravan that only had 17k miles on it. salvage yard owner showed me his salvage title when he bought it in 2000, really nice guy at bullseye salvage in new hampshire. He told me it was sitting on his shelf all these years, so I was a bit hesitant but for the price I took a gamble. Had a mechanic friend install it and then I replaced the filter and added 4 quarts of new atf+4. While it was still up on jackstands I turned it on. I then proceeded to check the fluid level and added 3 more quarts before it became a stedy level of fluid. I then ran it in reverse for a minute or so, then drive and took it through all the gears for several minutes to get all the bone-dry internal parts nice and soaked, all while on the jackstands. I didn't want it's first run to be dry and under load. I then took it on the road and was dismayed at a light throttle 2-3 shift flare and somewhat early shifting into second and third. shifted fine under moderate or heavy throttle, but light throttle reapeatedly made a 2-3 flare. took it home and found that it needed another quart and a half, so total of 8.5 new quarts it took, meaning it was indeed bone dry within. another road test yielded the same 2-3 flare and somewhat early shifting. that's when I looked online and in the full service manual and got excited. fluid level/quality is an obvious first step, but next should be adjusting the throttle linkage cable that goes to the transmission. this is very important as it regulates transmission fluid pressure according to the gas pedal. it is used for kickdowns and for shift timing/quality and if it is not in the proper position you will get early or late shifts or shift flares which may not be evident if you are always heavy on the gas pedal. The factory service manual says to check and adjust this cable BEFORE doing any kind of pressure tests or band adjustments, since the transmission fluid pressure is directly affected by the position of the cable. So any pressure tests and band adjustments will be wrong if your throttle cable linkage is incorrect. Now, right above the shift lever shaft at the transmission is the throttle linkage shaft and lever. You can follow the cable from your throttle body at the intake if you have trouble finding it. alternatively, you can open the throttle valve at the intake by hand and watch what moves at the transmission. Now, look at what some MIT graduate was paid a million dollars to design. If I didn't have the cut end throttle cable from the salvage transmission I never would've figured out how to adjust it. the service manual had no pictures and was not nearly adequate in explaining. Anyway, I noticed that my inner cable at my throttle body was hanging out of it's place, I can pull and push the cable about a quarter inch before it started pulling on the lever at the transmission. now look at the cone-shaped spring contraption which is attached to the bracket at the transmission which holds the throttle cable. at the top part of the plastic thing right after that cone spring is a fat u-shaped clip that covers the top of it. Use a flat head screwdriver in the slot there and pull that cap up. it doesn't come off, just goes up about a half inch. Now Pull the throttle lever at the transmission as far as it will go towards the ENGINE and hold it there with your right hand. with your left hand, you should be able to play with the outer cable before the bracket (the part of the cable between the bracket at the tranny and throttle body at the intake that is), back and forth towards the bracket. Now you can see how the cone-shaped spring works. it's only purpose is for this adjustment. you're supposed to let the spring take up the slack of the cable and then press down the clip. My spring didn't have enough tension to take up the slack in my cable. Perhaps a routing issue, but I kept playing with it and pulled it a bit harder manually till it took up the slack. Push the clip down to lock it in place. Now let go of the transmission lever and it will pull the cable. My slack was gone at the throttle body and my 2-3 flare was gone as well, verified about 10 times this morning. I hope this will help someone coming across this with this particular transmission anyway. If your transmission has a throttle cable, and you're experiencing shift problems, check your fluid, then check this cable. I'm happier than a pig in "you know what" right now.
Last edited by mirageman; Oct 10, 2012 at 10:53 AM. Reason: added info


