All,
I have a 1991 Ford Econoline 250 - Mark III Conversion Van.

I purchased the van from a family friend that let the vehicle set a considerable amount of time (6+ yrs). The price was right.

The fuel tanks, fuel rails, pumps (except high pressure front external pump), and ascending units were replaced with all new filters as the gas resembled more of a tar substance then gas not to mention the broken ascending unit and rail tubing that rusted out. A considerable amount of rust was also found in the bottom of the tanks as well. All brake lines were replaced as they rusted out as well. I live in the rust belt area of America. All gas was replaced in both tanks with all new.

The vehicle today has two main problems after the correction of the above problems. The 4 speed auto transmission - AOD will "neutral" out when it hits Overdrive, especially if it shifts into overdrive and if I let up on the gas (i.e. accomplished getting to cruising speed). I believe the Overdrive Band could be bad but the vehicle's fluid is clean and there is no sign of burnt smell I can detect. Would I be able to smell a burned out band? I think, from my experiences, there is also the possibility of bad servo or a valve body situation.

Then there is the engine, which only has a claimed 75K original miles. I have known the family for over 35yrs and the vehicle is clean inside and out....so it may be true The engine seems anemic and I know its not. It appears to miss, no backfires, just like timing is off or maybe not getting the full amount of fuel. At idle the motor is smooth and it starts every time. Fuel pressure at the rail is at around 35-40 lbs. There is no check engine light. I have been driving it about 30-40 miles a day to and from work (back roads < 55mph) for the past week. This seems to have made the transmission considerably better as it can reach 50 miles an hour for long stretches in Overdrive at cruising speed. I have been able to accelerate up to 70mph but do to the transmission issue was not able to maintain.

I think I need someone to say my next form of "attack" on this vehicle is a correct approach. I plan to replace the plugs, wireset, and distributor cap and rotor. At which point I will do a compression test on each cylinder and compare all cylinders. If all is good in compression I will check timing. If timing is good I will focus efforts at the fuel system again. I will also during the "ignition attack phase", described above, will replace a rusted out muffler. I figure I should correct any issues with the motor first because a)the transmission may never be right if the engine is not correctly running b) its the more expensive part of the two (engine vs transmission).

Then If I get the engine up to normal levels, I will then pull the valve body and transmission servos to clean, check, and if necessary correct. If no luck I will replace the transmission with a rebuild.

Please chime in if I am missing anything or maybe something to try before I go down the road I have laid out above.

Thanks everyone for your time,
Solomon_Man
1990 Ford F-150
1991 Ford E-250 Mark III

 

It sounds like a good plan to me. The ignition system is where I'd be looking for a misfire. As for the transmission, the AOD is notorious for sneezing the dinky 1 1/2" wide OD band and the symptoms are much as you describe. The later AOD-E and 4R70W are direct descendants of the AOD but were all upgraded to a larger 2" wide OD band and a bigger servo. Your transmission can be retrofitted with the 2" band, but it requires changing a few other internal parts and is not an inexpensive proposition. If the OD band is the only problem, a reputable transmission shop should be able to replace the band with another 1 1/2" piece for far less than the cost of a complete rebuild. It's one of the first parts that comes out during disassembly, so they don't have to tear the whole thing apart. They probably won't provide a warranty, but it can be done.

 

BlueOvalRage,
Thanks for the nod on my approach. The price on the vehicle was right but I am amazed at how many little things are bad on the vehicle as it sat for a while and I am afraid of not approaching the problems correctly.

I have rebuilt the AOD in a classroom setting a few years back. I do not remember it being a overly difficult transmission as I rebuilt 4 transmissions that semester.

I think I am going to try the valve body and servo first as I should be able to check them once the pan is dropped. If I have to remove the transmission from the vehicle I may just refresh everything with a rebuild kit as the kits are not that horrible.

I will try and get to the vehicle over my long 4 day weekend and see if I can reduce some of the problems considerably.

Thanks again,
Chris
Solomon_Man

1990 F150 Lariat
1991 E250 Mark III

 

Flush the cooling system, radiator, etc... check the condition of the hoses, do the same with the serpendine belt.

Just adding to what you have do/will do.

 

All,
Thanks for the advice.

I am amazed on how much a ignition tune up will change things.

The vehicle, I believe, had the original Motorcraft Spark plugs. The cap was severely pitted with white corrosion that was very apparent. The distributor rotor was a great deal rusty at the ends. Plugs look severely worn but very normal in color etc. It always started right up but the engine seemed to stumble at high speeds and did not have a great deal of torque. With the new ignition items its no longer anemic.

I also corrected the heater blower motor relay and replaced the muffler as the old muffler had pie size holes.

The only real problem with the vehicle is the overdrive band is not engaging or is having problems in some way. I will research this some more before tearing down the transmission as most items have been due to the lack of maintenance. So maybe I will get lucky and it will be a valve in the valve body or something to due with the servo/accumulator setup. For now I will drive it in D instead of Overdrive D.

Again thanks for the help,
Chris