3 speed automatic late shift problems on 1992 Festiva

[1992 Ford Festiva]

1992 Festiva 1.3 L engine. Automatic transmission 3 speed. I just changed my brake booster & master cylinder. Did not touch anything else. Once the repairs were made, the transmission will only change from the 1st gear to the 2nd around 25 mph then from the 2nd to 3rd at 55 mph. It worked fine prior to the brake repairs. Brought it to transmission experts, who found nothing wrong with my repairs that would have affected the transmission. The vacuum from the booster to intake manifold is at 20 lbs, in a normal range for this tran. I tried to adjust the pin from the booster to the master by 1/4 turn clockwise, no change. It is exactly the same length as the previous one was, as is the depth of the master cylinder space for the new vs the old. It makes no sense to open the transmission when it was working fine just prior to the brake repairs. The transmission experts have not being able to diagnose the problem at this time. There ultimate solution is to attempt a rebuild at considerable cost. Reinstalling the old booster seems illogical. Any thoughts from anyone with similar problem. Thanks 1992

[ryanprins13]

Hi. I dont know much about automatic transmissions. Wish i could help you more. My first thought is that your new brake booster leaks vaccum.
This is likely a terrible idea, but if it happened to me (since there are plenty of long, straight, deserted roads around) i would disconnect the vaccum hose at the new brake booster and either plug it into the old one or just plug the end of the hose and go for a drive to see what happened. If the new brake booster is the issue that should fix it. Just so you know you wont have power brakes when you do that test. Youll still have brakes, youll just have to push hard on the pedal to not stop very fast.

I can send you this stuff. Theres tons on diagnosing the issue. I would start with vaccum problems since thats what you replaced- a vaccum related component. If you want more info just ask and ill take photos.

First stuff to check always of course:


Sorry its sideways. I think were going with 'shift points incorrect" right?


I would start here


This would be the next test if thats all fine.



Heres another one. Theres lots more, im busy at work now, but if you want anything else let me know


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[jbibb1]

I've owned four different Aspire automatics and they all hit 2nd gear really hard

[lessersivad]

Sounds like a vacuum problem to me. I would follow Ryan's advice and find a deserted stretch of road and disconnect the 'new' booster and connect the old one. see how it shifts and go from there.

THAT would be the quickest and easiest thing to try.

Just because you have 20" of vacuum going TO the booster doesn't mean it's not leaking, thus dropping the vacuum, which in turn will cause late shift points.

[bhazard]

Have you confirmed that the vacuum line running to the modulator on the transmission is okay?

[lessersivad]

Have you confirmed that the vacuum line running to the modulator on the transmission is okay?

Well there's THAT too.....