I have a 1989 Ranger 2.9 automatic that has a problem going into 4th gear. At 55 mph the rpms are around 3400. At times you can feel and see(tack) going in and oout of 4th gear. When in fourth gear I get the normal 2200 rpm at about 55 mph.

transmission fluid appears clean and does not smell burnt.

Could throttle position sensor cause this problem.
Could speed sensor cause this problem.

If so is there a way to test these parts or just swap them out for new ones.


Thanks,

 

The 3-4 shift is controled by the ECU. Check for codes, vacuum leaks and a bad modulator. A TSP problem should show up in the codes, the 1989 didn't use the VSS for shifts. If you don't get more information you could try posting in our tranny forum.

 

Are you sure its the tranny shifting gears.. and not the torque converter locking and unlocking ?

 

Suggest u take it to a good reliable tranny guy. It will cost a lot more if u don't. Good luck on the tranny guy tho here in the Dallas Tx area we haven't found an honest one yet.

 

Solution can be found about half way down, but here is the story



Recently I purchased a 1988 bronco II XLT with the 2.9 engine and the A4LD automatic transmission. It was not maintained the best mechanically when I bought it. It would not start unless the accelerator was to the floor and would only run in short bursts. I replaced the throttle position sensor, manifold absolute pressure sensor, idle air control sensor, oxygen sensor, ignition control module, and went through all the grounds. None of these seemed to offer a complete fix, but did make it progressively run better until it hit a drivable state. We took it out on the road and it seemed to have a very hard time shifting between the drive gears. Upon inspection, the fluid was a very metallic color and seemed to have water in it. I dropped the pan to the transmission and found parts lying in the bottom of the pan. From here I took out the transmission completely and had it rebuilt 100%. When I got it back, it had all new guts and fluid. I took it back out on the road and found that it had a very hard time shifting into overdrive. All the gears 1-3 shifted perfect, but overdrive would only occasionally kick in. (Maybe 1 in every 30 shifts or the first time going into OD for the day) after going through the vehicle speed sensor, rear differential sensor, and the brake on off switch (BOO switch) (we had heard that if it knows it has the brake on that it will not shift into OD). Again we were left puzzled as none of these provided a complete fix or not even provide any help at all. The 1988 had an electric shift solenoid that provided the 3-4 shift. So we busted back into the transmission and replaced it. Got it back on the road and still no change. The linkage between the shifter and the transmission seems to be engaging well. From here all we had left to try to work on was the computer. The computer supplies a ground to the 3-4 shift solenoid to make it shift. We bought a computer from a local junk yard and slapped it in, and honestly it ran worse with the new to us computer. So we put the old one back in.

Solution

Here, we noticed that there was a ground strap that is just for the computer. It seemed like it had been painted over and did not have a good contact. Polished it down to bare metal and took it for a drive again. So far I have driven it only about 500 miles on the highway and it has shifted flawlessly ever single time. So before you scrap a vehicle over it, polish the ground to the computer. Keep in mind that the 87 and older 2.9s had a vacuum actuated 3-4 shift so this may not be your fix. But this sure did seem to help my issue in mine. If you have any problems that persist that I may be able to assist you with feel free to shoot me an email to: tottenelim@gmail.com as I may not be checking the forum for a while. I will try to get back with you ASAP and try to assist you. Thank you for everything y’all have done to help me get this project off the ground.

 

Good trouble shooting find, fix & feedback on this 18 year old thread. We're seeing more vintage vehicle resurrections of late, so this finding may come to help others on a like quest, sooner than we might think.

 

WOOOPS: I forgot something Important, Welcome to FTE !!!