i discussed my tranny problems with the shop ( 91 ext 4.0 liter.A4LD tranny 157 thou mi. rebuilt last year.)it seems to let go in 4th gear at 50 or 60 mph just for a sec. causing a thump or clunk. they said it may be the torque converter letting go momentarily, possibly electrical. is their anything i can check on this without returning to the shop, warrenty is over. also, anyone know the cost of swapping out the torque converter? rick

 

ricks 91 aero van tranny clunk update. i dropped the van off at the tranny guys place. after driving it around he thinks its an engine miss, not the torque converter unlocking that is causing the problem..? i will go get it fri late or sat afternoon. guess my next bet is plug wires, (originals i think)other than that it could be the ignition module i guess...any ideas? seems to clunk at 50 to60 mph under slow acceleration, or going up hills on expressway at 50 or 60 mph............... rick

 

This is a guess. If your plug wires really are originals they are most definitely in need of replacement. A poor set of wires will cause the engine to ping and knock. This increases anytime the engine is under load. When you state the OD seems to come off going up a grade, my guess is the engine is pinging/knocking and the anti-knock sensor is releasing the OD to compensate (i.e. to reduce engine load). If replacing the wires solves the problem, this was likely the reason.

 

i replaced my plug wires on my 91 aerostar van this weekend with a bosch premium wire set. i left the spark plugs alone, they are only 1 yr old "champion truck plugs" that came with a three yr unlimited mile warrenty. i have put about 60 miles on it today with no klunk happening at all.!! the test will be this week on the expressway to and from work. so far so good. it already runs and idles sooo much smoother. i just attributed the rough idle etc to other things,..not plug wires.....guess there is more to them than what meets the eye. . go figure. the wires i took off were motocraft. so i believe they were original. i replaced plugs last yr and they were motocraft ..originals also i think. thanks again aero. rick

 

addendum: its official, no more problems with the tranny. no clunks no thunks, no errors. after replacing sparkplug wires. !!!!!!!rick

 

Congratulations and happy motoring!

 

 

spark plug wires create a malady of problems. I have run the gamut of them.

 

new here...first post...this is a great place !

i have an '89 xl...235k mile...i've owned it for about 4 years now...original tranny as far as i know...i'm a little surprised to here some of the comments about this being a fussy tranny...obvously i'm in the minority when i say i haven't had any problems up to now...and i'm not easy on it at all...i haven't ever changed the oil (for shame)...i need to...but now i'm scared to mess with it, lol....now if you'll excuse me, i'm going to find some wood to knock on.

 

All years of A4LD's require the engine to be operateing properly or the throttle pressure will vary and cause all types of eratic shifts!! early A4LD's more so than 4.0 . Most types, have ports for pressure test on the passenger side of trans if i rember correctly and pressure generally about 1400psi. See service manuel to check for proper readings and port. Also the pressure is adjusted by the {kickdown linkage} hope this helps

 

I recently serviced my transmission and replaced the vacuum modulator, in the process lost the rod between the modulator and valve body, (fyi I got a new modulator rod from the Ford dealer) I dropped the valve body down and hung it from the connecting rod "z' Link. and apparently the connecting rod bent because now when the transmission is hot it won't engage into reverse. (works fine when cold) I just had to repalce the u-joints and at the same time I dropped the pan and valve body again to see if I could notice anything and now it goes into reverse properly but doesn't go forward properly in fact if I put it in low manually it just seems to be bypassing fluid in the valve body. Do you know where I can find the measurements of this "Z" link? or where I can locate one?
Thanks, Tim (tsthumpr@yahoo.com)

 

Plug wires on this engine are very important due to the ignition system used. Inferior wires will fail prematurely (may last 5 years instead of 10+). . Probably the clunk was your drive shaft backlash during the misfire. BTW you would have been better off with MC plugs or Autolites, they have been found to be the best for this vehicle.

 

Accurate speed sensor is required for correct AT operation, I think this is an easy exchange, it's located on the rear of the transmission housing near the output shaft. Did they test the vehicle under load & with the wheels rotating to check the sensor...... or another method ? Either way the PCU needs to know how fast the output shaft is moving for accurate gear change.

 

As I found out recently, the speed sensor in the rear end is only on 92 and later vehicles. What year are we taking about here?

 

I own a 1991 explorer 4.0 Auto, and i believe it has the A4LD tranny, well the modulator has been going out on it for some time, but the damn thing is snugged by the cat converters and i couldnt change it out, cant even touch the modulator valve with my fingers, so i let it go for now, figured a few quarts of tranny fluid would hurt until i got it changed, was driving it on a trip and was in OD, cruising at 65 mph, running good too, then we noticed smoke. . . . . then noticed alot of smoke . . . then the speed slowed down, and then it stopped going forward, acted like it was low on tranny oil, it would run and pressurize move a little then nuetral out , run, nuetral etc... got it up a hill and off the road, there was tranny fluid everywhere!!! i had a quart on me and poured it in the tranny, and as i poured it in, it ran out between the engine and trans . . . had to pour more in it the next day to get er to drive on a trailer to tow it home!

So my questions are these:

could the pump have gone out in the Torque converter?
could the front seal have gone out?
how hard is it to change the front seal?
what is the easiest way to swap teh mod valve?

ty in advance for any help!


Mkrewson, Missouri