Automatic transmission rant

[sidsidsid]

Argh I hate automatic transmissions, or perhaps I hate automatic transmission repair. Ok yes i understand its a complex piece of equipment. But the standard answer to every lousy problem seems to be $2000 rebuild. I cant believe these things cant be made more servicable. Everyone says how complicated they are to diagnose. WHATS TO DIAGNOSE, when all they want to do is rebuild the entire thing. Whine about metal particles and dirt. If they are so sensitive to dirt and debris, why dont they have a serious filtration system and stop trying to scare me about stiring up the crud in the bottom of the pan.

Sigh... deep breath... ok, i feel better now.

99 Explorer XLT 2wd. (I have 3 explorers, not a new vehicle to me.) Transmission has been working fine, but i cant speak to its service history, 150K miles. On two recent errands, I have encountered the 2-3 shift flair. Found lots of good info here and elsewhere about the nature of the problem, repair recommendations, discussions about valve body updates over the years. The local shops all agree with my thinking, but just cant get past the notion that it has 150K miles and unless i rebuild this puppy the earth will stop spinning and the moon will crash into the ocean. And Im sure if I talk to enuf people that global warming will come up too.

soap box off. now, where did i put that check book.

 

[drdoom]

I am with you on this. Best wishes.

 

[sidsidsid]

I yield to the professionals

Ok, I must bow to the greater wisdom of the professional.
The 99 Explorer is in the transmission shop.

This noon I visited the shop. Arrived at a good time, my unit had been open for a couple hours, was spread out across the table. He explained that basically it was suffering from reasonably normal wear and tear for this unit, perhaps a little abuse from neglect and maybe a little towing. (There is a hitch on the explorer).
- he explained they had already found three sticky valves in the body (little spring loaded pistons in the passages).
- he explained that the thin nature of this valve body makes is susceptible to warping if you over heat it. Not an issue in my case,
- two of the clutches were showing signs of burn, and he scooped up some of the black soot in the pan and said that's where this comes from.
- and then he picked out three pieces of metal (and I could see other pieces in the pan), the largest about a quarter inch, and said this stuff is from your torque converter.
- showed me the rubber cups that go on the solenoids, and how they were pretty firm, not like the more supple replacements. he suggested this is probably where the 2-3 shift lag was coming from, the brittle cup leaks or drags excessively, or a solenoid issue.

Otherwise he said no problems, should come together just fine, and be done next day. They will be making all the technical updates that apply to the unit. Will also replace the rear engine seal while the transmission is out, showing signs of weeping.

So, not what I wanted to do, but probably better off in the long run. (I'll keep repeating that until it feels better.) I would be interested to understand just what aspect of a torque converter failure causes it to shed pieces of metal. Would that be from thrust bearings/washers? Surely not vane parts? The pump? I had no other symptoms that i was aware of, other than the 2-3 shift flair, which was actually sporatic, worked ok most days, but it would flash the OD light when it was acting up.

thanks, -sid.

 

[sidsidsid]

Rebuild complete.
Shifting smooth and sweet. It better, for $1800.

2 servos
Pump bushing
Speed sensor
Torque converter
Banner kit
Filter
EPC solenoid
Shift solenoid
Trans fluid
Lubeguard (plate additive)
Rear diff fluid (synthetic)

Transmission works very well, shift is smooth and positive. Mechanic claimed the failing torque converter was a weak point in this vintage explorer. Otherwise just generally dirty and worn. (Banner rebuild kit - friction plates and an overhaul gasket set with sealing rings and metal clad seals.)

 

[zot64]

Nicely done, good info and follow up, thanx.

 

[sidsidsid]

Some additional followup.
About a week after the repair I started getting sporadic bad behavior. 2-3 shift flare. Delayed 2-3 shift, and hard 2-3 after delay. Also O/D flashing. Returned to transmission shop, they extracted the following codes.

Code C1230 – Wheel Speed Sensor Rear Center Input Circuit Failure
C1230 is the commonly the rear speed sensor on the top of the differential or one of the front speed sensors.

P0733 FORD Description - Gear 3 incorrect ratio
This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B

A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined by TCM based on gear position

If the actual gear position is higher than the position sensed by TCM, the slip ratio will be more than normal. And if ratio exceeds a threshold, TCM judges this as a malfunction.

In any case, all issues were resolved with replacement of speed sensor located on top of rear differential. Its been about a year, 12K miles, and no further issues.

 

[imp]

Some additional followup.
About a week after the repair I started getting sporadic bad behavior. 2-3 shift flare. Delayed 2-3 shift, and hard 2-3 after delay. Also O/D flashing. Returned to transmission shop, they extracted the following codes.

Code C1230 – Wheel Speed Sensor Rear Center Input Circuit Failure
C1230 is the commonly the rear speed sensor on the top of the differential or one of the front speed sensors.

P0733 FORD Description - Gear 3 incorrect ratio
This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B

A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined by TCM based on gear position

If the actual gear position is higher than the position sensed by TCM,........ I would mention by way of clarifying: gear "position" is a misleading term, for me anyway. The gears in automatic transmissions do not "move about", as in manuals. Thus, TCM compares relative shaft speeds to one another and then uses that info to either accept shaft speed ratios as OK, or reject info in form of a warning light. The trouble codes stating "incorrect ratio" are not exactly accurate descriptions of what's going on. To keep the vehicle moving, should TCM detect incorrect shaft speeds in relation to one another, after a certain gear is selected, as say, 3rd. gear, it may revert the transmission BACK to 2nd. gear, throw a trouble code, flash a light, and keep the vehicle running in 2nd. gear. The operator, if technically minded, may sense by tachometer speed, sound, and performance, that something is amiss, aside from seeing the flashing light.


the slip ratio will be more than normal. And if ratio exceeds a threshold, TCM judges this as a malfunction.

In any case, all issues were resolved with replacement of speed sensor located on top of rear differential. Its been about a year, 12K miles, and no further issues.

The self-diagnosis ability of these units is undoubtedly a marvelous improvement over the old days' "guesswork" method, which required a high degree of experience with a given transmission, to make accurate calls. added to the fact that we novices can also read trouble codes, this puts us in a stronger position when dealing with the "rip-off" guys (usually!). imp

 

[sidsidsid]

roger on the "gear position" clarification and shaft speed ratios. i was quoting from the manual, but i felt the explanation was a little lacking. i get the jist of what it was trying to convey, but i couldn't improve on the description. and i presume the P0733 code was an artifact of the misbehaving speed sensor on the differential, resulting in the perception of a bad ratio. thanks, -sid.

 

[imp]

If the shaft to shaft speed comparisons are not within the accepted range for the given operating conditions, it could be said the "gear ratio" is incorrect.

Matter of semantics.

They often try to confuse us non-experts: makes 'em more dough! imp