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Discussion Starter · #1 ·
I have a 69 Mustang that is running well but i have noticed 2 things recently
1.) I have noticed that it seems to hit high rpm's before switching gears. Sometimes I can alleviate the issue by releasing the accelerator then repressing it

2.) When I release the accelerator I notice that there seems to be a a quick deceleration instead of coasting

I have a stock 302 with a 2 barrel carburetor.

I was wondering if anyone has run into these issues before or if these arent issues and they are normal?

Any feedback would be great!
 

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What are you considering "high rpms"? Typical part throttle shift points are 1~2 in the 10-15 mph range, 2~3 in the 18~25mph. Take a look in your Ford shop manual, it'll have the ranges in there.
 

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Is the parking brake on?

Is your transmission fluid low?

Gotta start with the basics before you start tearing things apart.
 

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The de-acceleration is likely due to the fact the trans is still in a low gear.

Your vacuum modulator may be going bad. Pull the vacuum line for your modulator at the vacuum source. Inspect the hose and look for any sign of transmission fluid. If there's any trans fluid at all, the vacuum modulator is shot and must be replaced.

If there's no sign of trans fluid:

- When did the shifting problem start? Or, has is always shifted at high RPMs since you've had the car?

- If' it's always shifted at a higher RPM than you prefer, you can adjust the vacuum modulator. Remove the vacuum line at the modulator. Insert a very small screwdriver into the vacuum port. There's a slotted screw inside. Turn the screwdriver one turn clockwise, then test drive. If it shifts at an even higher RPM, go back and turn the screw counterclockwise two turns and try again. Keep adjusting the modulator until the trans shifts how you like it.
 

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Discussion Starter · #5 ·
thank you everyone for your responses.
Fluid is good, no break and I didn't see any fluid in the hose connected to the modulator. I'm still going to go ahead and replace that since it's a cheap fix. Worse comes to worse it's the transmission but I want to try everything I can before going that route.
 

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Discussion Starter · #6 ·
wanted to update everyone. I had a number of issues going on from coil needing to be replaced to the timing being off to the carburetor needing adjusting to the fuel filter being replaced to the gas tank needing to be replaced after siting for so many years. Once all of that was taken care of i am no longer seeing the issue.

sorry for my late response but its been a work in progress. Now onto the interior and i am sure ill have plenty of questions.

Thanks to everyone for your suggestions and responses!
 

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Low vacuum is a likely culprit for your shifting issues. "letting off" on the gas would help it catch the next gear, by allowing vacuum to build inside the manifold.


Having a poor running engine with timing problems and/or vacuum leaks would sure cause this!
 
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