Automatic Transmission weird shifting

Automatic Transmission weird shifting
1990 Ford Ranger 4X2 Super Cab V 4.0L A4LD Transmission
My vacuum modulator failed, automatic transmission fluid was being sucked
into the intake. The part has been bad for a good while about a year. I discovered it as my fluid level has been slowly dropping over the last year. The truck ran fine.
I purchase the part, Niehoff # TM115 fits 1987 - 1990 Ranger, when I ordered the part, there were two to choose from; Niehoff also had a TM332 which was for 1983- 1996 Ranger. Not sure what the differences are, altitude?
When I went to replace it things were tight with the cat so I took it to a transmission shop gave them the part and they installed it. The also changed the few inches of vacuum hose at each end of the hard-line as they were full of transmission fluid.
As I drove away from the shop I noticed that at 15 mph it would shift into 2nd (which is normal), then at about 22mph the rpms would go up a good bit, was it shifting back to 1st? Then after 1-2 seconds it would shift back into 2nd. Then as I would pick up speed it would go into third. This was Sat and the shop closed as I left, so I couldn't go back.
It repeats this pattern every time, I drove around all day and it would do it every time. If I took off and kept my foot into the throttle a bit it would not happen. It happens if just drive easy.
The truck never did this before. At first I thought that I was getting use to normal shifting since the vacuum modulator was replaced, but the more I drove it I know that this rpm increase, slipping sensation was not normal.
So what could be wrong? Did I put in the wrong part? Is the new part bad? Is there an adjustment involved?
And I did check to see that my transmission fluid is at the correct level.
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You shouldn't be buying the parts if you can't install them.
Hopefully you still have the original modulator. If so, replace the aftermarket with it, then go to the Ford dealer and have them replace the modulator. Otherwise, what I would suggest is you go to a wrecking yard, find your model truck with an original Ford modulator, get that, have your tranny shop replace it, then see if it works. If the wrecking yard modulator is also leaking, but the shifting goes back to normal, then you can take it to the Ford dealer and tell them the truck works fine, and your losing fluid, and you called a tranny shop who said the modulator is probably leaking and to take it to a Ford dealer to replace since they can't get that particular modulator. Naturally don't mention you already tried aftermarket or that it's a wrecking yard modulator otherwise your giving them something to blame you on if they put in a Ford modulator that doesen't work.
What probably is going on is that Niehoff when they made the aftermarket substitution, they made a mistake with your model and year. As a result, I would guess most if not all aftermarket modulators are going to be wrong for your truck. This is kind of a lost cause because it's possible that Ford themselves made an error in their documentation.
If you go to a dealer and the truck is shifting fine, the dealer then puts in a genuine Ford replacement and the shifting goes cockeyed, then it is their problem, and they will have to make the phone calls to Dearborne to get an engineer on the line to correct the documentation and tell them what modulator to use. For sure your not going to be able to do that, nor will any aftermarket tranny shop. And for sure Niehoff will likely not be able to assist either - although a phone call to them, while a very long shot, might work.
Your experience is one that goes along with the territory of buying aftermarket parts. Aftermarket manufacturers will often come across the situation where the auto manufacturer makes an unexplained change in a part - maybe only for 1 year - and it's not cost-effective for the aftermarket manufacturer to manufacture a special part for only that year. So they will take a similar part and make a substitution. Sometimes that works, sometimes not. The aftermarket manufacturer will simply look at the returns and if they see a high number of returns on a substitution, they might then pull it from their docs. Or they might not.
Ted
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thanks for the reply
I found out late yesterday that the parts store sold me the wrong part. They sold me a Niehoff TM115 instead of a TM332. I called Niehoff and spoke to a parts specialist and he confirmed.
I went to Ford and bought the correct part the Motorcraft TM74 and brought it to the Transmission shop. The owner who has been in business for 27 years, drove the truck with me. He noticed the transmission is slipping from 2nd to 3rd.
He is putting the new modulator in as we speak.
I do still have the original modulator.
I read you response after the above.
The plan was for me to do this but when I got under the truck it was a little more involved then I wanted. The Transmission shop spent more time then they thought too. The owner told me they had to take the cross member out.
Thanks

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