Transmission slip. | Ford Explorer Forums - Serious Explorations

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Transmission slip.


Active Member
June 11, 2011
Reaction score
City, State
Seaman, Ohio
Year, Model & Trim Level
1992 Ford Ranger XLT
I believe my automatic a4ld transmission is slipping due to a vacuum leak. It slips in 2nd gear. It is a 1992 ranger 3.0 can anyone assist me? I recently replaced the vacuum modulator, could that have caused the problem?

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Adjust the bands? no it was not slipping before, it has been seven years since it was serviced.

I believe it may be adjustable, it had one extra valve on it, I did not understand that. Is that extra valve causing a vacuum leak in turn needing a cap to fix the slip?

So you're saying that the new modulator has 2 vacuum port connections instead of one? Either you purchased the wrong modulator or this modulator requires an additional vacuum cap. I'm sure that any open vacuum line will leak.

The older one never needed a vacuum cap. One end goes into the transmission case and there is that one valve that the vacuum hose connects to. now the new one at the very end pointing to the catalytic converter had a small valve that is threaded. so the threaded valve needs a vacuum cap? or needs to be sealed in some manner?

Do as Brooklyn Bay recommends.

1. Make sure you have the right modulator.
2. Change fluid and filter.
3. Did you catch and replace the small pin that should have fallen out when you changed the modulator?
4. Search this site for a4ld modulator. There are a number of posts with pictures that should help you identify whether you have the right one and other useful info.
5. Follow the vacuum line from the modulator to the intake to make sure the vacuum line is connected to where it should be.


I see only one vacuum line connection on this modulator on the right side of the picture.

That is the adjustable type modulator. What you believe to be another vacuum line is where you make the adjustment. understanding is that for most applications, an adjustment is rarely required.

That's an allen screw. If you look closely there will be (should be) a bit of Loctite or similar product on the threads. The non-adjustable will have what looks like a large button covering that area of the modulator. I'd still check for that pin and make sure the modulator is seated properly. Similar "neighbor" issue resolved when I found there was no pin. Found it on the garage floor.

Yes I understand that. I almost missed that pin that goes inside the modulator, how ever I found and placed it where need be. as I said before I installed it correctly. I'm thinking that threaded area needs a cap on it or needs to be sealed somehow.

I sealed the adaptable valve on the modulator but it is still slipping. I can hear a vacuum leak when the engine is running. where could it be?

My pin broke.

Two piece pins don't work so good.

Half came out with the mod.

Other half tweezers.

New pin... 1, bam 2, bam 3, Nice!

I know this sounds more like a vacuum leak to me to.... Just reminiscing! Good times....