My '94 Ext Cab, 4x4, 4.0L with auto trans is REALLY acting up! I reversed out of the driveway, placed it in O/D and tried to go forward. It moved forward in a very jerky manner and thumping/clunking sounds were coming from somewhere out back. Meantime, the engine seems to be bouncing between revving and stalling. The volt meter is swinging from 0 to 18 in sequence with the jerking and the clunking. I limped back to the driveway where it stalled before I was all the way in. It started right up but, when back in Drive, it would not go forward. (I did not want to mash the gas coz I was < 10' from my garage door) I saw a trip to the shop in its future so I decided to back out and park it along the street (to await towing). I had to try Drive again to get it parked straight on the street and it "worked" this time. There appears to be no problem going in reverse. I looked underneath and saw no leaking or smoking. There was some fluid stains surrounding the diff cover that appeared to be dry and old. Things are pretty rusty under there too. There are 109,xxx miles on it. I have only owned if for 5-6 months (or 1000 miles).

Could the problem be in the rear differential? (missing teeth maybe)
Could it have anything to do with the new Idle Air Control Motor the shop put on a month ago?
Am I really F**ked?

Thanks

 

Well the PCM(computer) runs everything, so first step would be to check that it is "sane".
Hook it up to a OBD 1 reader and see if it has any codes and can "talk" with the reader.

The noise you were hearing sounds more like the torque converter locking and unlocking, computer controls this.
Computer also controls RPM based on Park or In Gear.

 

OK. I will pass these thoughts on to the mechanic tomorrow. Is it wrong for me to think that I should have problems reversing too if it's a module/computer problem?

 

Differential issue would be same in reverse as well, not sure about the PCM and reverse, since there is no shifting required it may be just Reverse/lock no computer involved

 

MECHANIC SAYS TRANS IS SHOT !!! Will re-build it, plus torque converter, etc complete for $1,600-$1.800 with the higher amount being for busted-off bolts or other aggrevations. Will have 12 months/12,000 mile warranty.

NOT what I wanted to hear! I'm thinking it over. Will probably give him the OK. Meantime, if any of you reading this want to comment on options or the fairness of this price, please chime in. Thanks!!!

 

You should have the last year of the A4LD 4-speed trans in a '94 with 4.0l

Good read here on that trans: Ford Ranger A4LD Automatic Transmission

Price is reasonable, rebuilt A4LD runs around $1,500, with warranty, so only a $100-$300 to remove and re-install trans

From the above article:
"When having an A4LD rebuilt, there are a couple of things that you need to make sure of. First and foremost, do not let a shop do a soft parts fix only (clutches, servos, and bands). This will almost ensure that you will have another repair needed right after the 1-year warranty is out."

 

I printed the "Good read" and have instructed the shop not to simply follow the "soft parts fix".

 

So it's over 3 WEEKS LATER(!) and the shop STILL has my Ranger. The Story --> Got rebuilt tranny in and, before it could be test-driven much, it started running crappy. Eventually, it failed to start at all. Hours and hours of tests later it seemed that the fuel pump was acting up and it was replaced. Still problems. Now they have replaced the PCM. It is awaiting a tow to another shop so that the PCM can be "flashed". They say PCM's aren't known for failing - hence their confusion.

In response to my initial post, RonD replied that the PCM should be checked to see if it is "sane". Anyone out there feel that I have reason to be concerned that, maybe, the tranny rebuild was a knee-jerk reaction by the shop and that, maybe, it was unnecessary? To be fair, it is 20 y/o and was having some problems that were NOT fully cured by adding nearly 2 qts of fluid. But only has 109,XXX miles on it.

 

Being 2 quarts low can definitely have an effect. Number 1 being auto trans hate high temps so less fluid= less cooling. Number 2 low fluid can cause less lubrication and less pressure to actually shift the gears. So the trans being actually bad is not really a stretch no telling how well the PO took care of it. PCM's do rarely fail usually its either a defect in the original build such as bad resistors or poor solder quality or they can leak and cause it to short. Also OBD1 systems are very hard to diagnose as there wasn't much commonality with codes and such and it didn't monitor anywhere near as many parameters as OBD2 so it could have been an issue but if the mechanic wasn't very familiar with OBD1 fords he may not have been able to tell its condition. Most OBD1 stuff was manufacturer and sometimes model specific. So if he didn't have a decent manual or decent knowledge he may have missed the warning signs.

 

I have to conclude that it was low on fluid when I bot it 6 months ago. It did not show any signs of this though until about a month before it went south in a big way. No puddles of fluid in my driveway either. No whining noises. I hope you are not saying that my troubles might have been avoided if I had checked the fluid level right away! It mostly ran OK but it seemed to have more pep some days versus other days. I am hoping that the new PCM will get it to run well.

 

Yes, running with low fluid levels in an automatic(or engine) will cause higher heat levels and high heat kills automatics, just like it does engines, both need to run warm for best performance, but above the "normal" range is when metals expand too much and you get problems.
Who knows how long it ran with low fluid before you got the truck.
So trans rebuild was a good idea in any event.

Very confused with shops actions.
Faulty PCM is really a long shot, and 50% of diagnosed "bad" PCMs are a mistake, lol.
EEC-IV is the PCM used in your '94, and there is no question that they can fail, it is just an unlikely failure.
Simple first test is: does the CEL come on with the key and then go off after a few seconds?
That's the PCM start up self test coming out OK.
If CEL stays on then you read the codes, if codes are not readable then I would suspect PCM issue but still test the "test port" wiring.

Good read here on tests using the PCM: EEC-IV

PCMs failure to run tests would be a sign of internal or software issues, requiring its replacement.