What is causing occasional slipping and or hard shifting in Transmission?

Asked by May 26, 2014 at 09:50 PM about the 1994 Ford Mustang Convertible

Question type: Maintenance & Repair

Occasional slipping and hard shifts with Transmission. Fluid levels are good and fluid is
clean. I had the fluid and filter changed about 8 months ago. I have not put any
additives in the Tranny. No leaks. Find that it does it more when tranny is warm or hot.
What is causing this and what can I do to resolve it and/or fix it? It may go for a while
and not do it or it may happen often. Never know when it will happen. Want to remedy
because I love my car.

8 Answers


What makes a transmission slip usually is pump is bad not cerculating fluid to the bands or filter stopped up.Remedy,and additive would not hurt at this point i think i would try a bottle of lucas in it,it will help clear lines and filter,may help ,,

3 people found this helpful.

Pump indeed. It's an old car. Additives like Lucas - or Brake Fluid - will cause the Nitrite seals to soften and swell - for a while. Then it will turn the seals to mush - not right away - but it will. See about taking it to a Transmission shop and having it properly diagnosed. Expect to pay 1 hour labor for a proper diagnosis. The seals within the Transmission get old and hard over time. Honestly - there is no reason to change a Transmission filter - if there's debris in it - it's destroyed anyway. A complete fluid change between 60,000 and 100,000 miles - yes (14 to 16 quarts). One consideration is a remanufactured Transmission. Ford (and I'm sure some competitors too) have reman transmission for right around $1800 with a terrific parts and labor warranty. Sounds like a lot of money? It's only about 5 car payments of a new car.

1 people found this helpful.

Take the pan off again and look to see if there's a lot of metal shavings if so the tranny is on its way out if not try researching the shift solenoids or the tcc shift solenoid its called a torque converter clutch solenoid

1 people found this helpful.

Wad up three $100 bills and shove them down the filler tube - same effect.

Right. For all the parts I had to replace, I could have bought another car. I guess next time I buy a BMW or a Porsche.


I have the same car with the same exact problem! Did you ever find out what was wrong? I'd be curious to know because I've had a few mechanics look at mine and they can't seem to figure out what's causing it.

2 people found this helpful.

I guess I will try the Liqui Molly automatic transmission repair fluid when I get hold of it. Let's see what it does.

I agree with Tracy, I have a 2002 GT 4.6 and it has had some mods, I noticed that it had some weird stuff going on when I drove it normally, (so I never noticed anything for the first 3 years I owned it) but what happened was a strange shuttering feeling as it would shift into 2nd under normal operation, sometimes when it downshifted as well. I did a partial fluid change as recommended by the Ford maintenance online program I have that's made for Ford certified repair shops. It goes into detail showing possible reasons and remedies that are available as the problems arise and the info is uploaded to a cloud where it's shared with the network of other shops running the software. This is most likely cured by a simple partial fluid change. They state that only changing part of the fluid is necessary unless it's burnt really bad. Also it states to NOT use any synthetic fluids. Only vehicles Ford used synthetic were a few oddball Vans. I did this at 70k and my trsnny was like new, super smooth and quiet but will slam second so hard on upshift or downshift I need to be careful cuz it will break the tires loose an fishtail like crazy if your not ready for it. I used about 7 or 8 quartz, by just drropping the pan and cleaned off the magnet which had minimum shavings on it. I left the fluid in the torque converter and refilled through the filler, no need for new pan gasket if you didn't ruin the existing. The dealership will use a machine that connects between the radiator and the line in. They will run the car and they fluid is caught in a pan while the infeed tube is sucking in fresh fluid. They run it till the cycle is complete. This also leaves some old mixed in with the new. It is the closest you can get to new fluid without taking a chance of airpockets or lines not filling up completely. If you drain it dry you will risk these problems, they recommend not draining it ever unless you do a partial by dropping the pan and allowing it to drip for a while, I waited 20 minutes but it still had drops every so often. I'm do for another change right now at 130k. That's why I came hear, to hear what fluids others have used. My buddy rebuilt a tranny and used synthetic even though I warned him not too since the manual was very strongly recommending to not do it. His tranny was junk in 1 year. It was a Ford F150 truck that had the Natural Gas conversation that used either fuel. I figured this might help others that are having automatic trans problems. Total cost for a diy change is about $60. Can't remember if I used Mercon 5 or 6. That's what I'm checking next.my guess is 5.

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