Questions and Answers

Deceleration Vibration

Q. My name is Linda. My sister has a 1987 Dodge 100 pick up, carb I think. 6 cyl. auto trans, 100,000 miles.

The problem is this:
On acceleration and deceleration it vibrates between 5-10 miles per hour. If you pop it into neutral it stops which leads me to believe it is not brake related, rather that it has to do with vacuum or something on these lines. All hoses seem to be tight and crack free. After dropping the trans pan and cleaning and replacing the fluid, it still does it on declaration but improved the acceleration vibration. I thought it was similar to another car that did the same thing and asked for a trans module. I was told this vehicle it is not required. Can you elaborate as to what my next step should be? The vehicle seems fine, only has trouble when stopping and starting. Idles good and no problem other than the down shifting and up shifting, around 5-10 mph. Well that is a lie. The battery dies out fast after 4-5 days sitting but that is from lack of use. I believe it only gets used every other month or so.

Thank you for your time,
Linda

A. Without getting into too much detail about something you can't do much about, the problem is in either the lockup torque converter or the first gear sprague clutch. If the lock up torque converter is not unlocking completely, you will get these symptoms. A transmission shop will be able to do a fluid pressure and electrical test for this.

The sprague clutch has a series of one way rollers that provide engine braking on deceleration. If it is the sprague clutch, the transmission will have to come out to check and replace it.