It's having pretty much the same problems it was having before I had it rebuilt. It slams into reverse when you first pull the gear shifter down .Hanging up in gear way too long and then slamming into the rest of the gears. The transmission shop doing the work has put a new core ,new valves, new solenoid pack, and new pump in it ,trying to fix the problem. I've put a new shifting lever on it with overdrive lockout button and wires. I plan on replacing the alternator whenever I get it back from the shop. The only other thing I've heard to possibly try is the throttle position sensor. The owner of the transmission shop said slamming into reverse right off the bat made him think it was a pressure problem. That's why he replaced the pump. The other guy that works there seems to think it's an electrical problem.

 

You didn't mention if there were any codes in the system.
With that problem there should have been and be a code(s).
There are several inputs that are supplied to the PCM and based on what they read can determine pressure and shift scheduling.
Do you know if any pressure checks were done? If so, what were they and the readings.

 

I'm not sure .But,t they are a reputable shop that's been in business over 20 years. I'm sure they've done pressure checks and checked for codes. Something I left out is it doesn't do this all the time. It may drive for a hundred miles fine or it may only make it 2, before it starts messing up.

 

Another thing I was told to possibly try is to change the computer. I just can't afford to go blindly replacing things without knowing that it'll solve the problem

 

Certain inputs from various sensors are sent to the computer. If any of them are missing or incorrect due to faulty parts or bad connections the wrong results are obtained.
What year, model,mileage of your vehicle?

 

It's a 94 Ford van E250 with a 5.8. It's got about three hundred forty thousand miles on it

 

A lot of times a person posting information regarding a problem provides only the info Which THEY think is important or sufficient. Many times it is not !
So if we ask additional questions it is because we may have come across a similar problem , but to help eliminate certain causes that may not apply.

Why was the trans "rebuilt"?
What was the original problem?
Unfortunately, a lot of good parts get replaced when there may be nothing wrong with them and an incomplete diagnosis might have been made.
Not wanting to attempt to make the servicing shop look bad , it does seem like that is what is taking place.
When a good, complete diagnosis cannot be made some shops will just replace the trans with a known good unit and if the problem is still present they have eliminated the trans itself as the problem and this gets expensive and entails a lot of work.
It is a tough decision on your part and possibly a second opinion from another facility is in order.
Until you can verify the alt is the problem,might be a good idea to get that second or even third opinion before replacing a possibly good alternator.

 

It's hard to say what the original problem was, I've been milking this transmission for years. It started out if you drove it hard it would slip. Right before being rebuilt it got to the point where it wouldn't shift out of second gear, even manually. The last week or so it was hanging up in all the gears too long. I'm with you on the second opinion before replacing any other parts

 

Well the transmission shop where it's at gave up today. Said they hooked it up to a shift box and a new computer and the transmission works fine. They think it's something electrical in the harness.

 

I find this very puzzling, when someone comes in with a trans problem, one of the first things done is a pressure check. If the pressures are low it could involve the electronic pressure control solenoid or the pump. The test will tell you quite a bit. To just assume it is the pump without verifying it is shooting from the hip and hoping to hit the problem.
From what you described the slipping was a result and not the problem. Something like a faulty throttle position sensor could be giving false info to the PCM which sends the signal based on faulty info ,to the EPC (electronic press control sol.) thereby affecting line pressure and shift points. I'm not saying this is the exact problem , but is worth checking out and making sure the inputs to the computer are legitimate and rational.
That other second opinion is in order.