Trans slipping???

Mike picked up that '91 Merc CP wagon from me yesterday here in OKC, and began his trip back to IN this morning. He texted me that he felt the trans was slipping a bit, after he crossed into Illinois. The fluid level was right and did not smell burnt or look discolored. I checked all the fluids before he took the car, and he checked them also while on the road. The PO before me had the trans serviced with a shop that uses BG products in their repairs, so it has a lifetime BG warranty. I drove the car on a 120-mile run last Saturday with no issues at all. The car has 97K miles and change on it.

Anyone have any ideas?

 

If the car had been sitting for a while it might just be fluid exchange between the torque converter and valve body might be a bit sluggish and eventually loosened up a bit. BG sells a product called trans conditioner that I have personally used for years on multiple cars without issue unless the car sits for a while then it seems to take some "warm up" time for things to get flowing again. If the car hasn't sat then I am kind of baffled by the "slipping" issue.

 

All of the slipping that I ever experienced was preceeded by a leak; detected or not.

 

It was my daily driver, of which I put 15-20 miles per day on the weekdays. He said the fluid level and color were fine.

 

I am baffled Patrick...did you ever notice it before?

 

Not at all. Only thing was that typical guess-a-gear that I've experienced with every Ford AOD I've ever had, that happens at about 40-42 mph at part-throttle, while in OD. But at all other speeds, and especially on the highway at 70+mph - smooth as silk!

 

Are we sure the parking brake is released?

 

I've only used the park brake once on the car, and it releases upon placing the car in gear. You'd be smelling brake lining, , too, if it were engaged.

 

I got the Oklahoma Queen safely to her new home bout 40 minutes ago. Earlier in the trip I had to manually shift from OD into D when cruise control began to loose speed on some of the steeper hills but otherwise things were going great. Right as I began going around St. Louis beltway (great timing huh?) it started slipping badly in OD but worked fine in D. In OD it was almost as if it wasn't connected at all, in fact I checked several times to make sure it wasn't in N.

When I could get off I check fluid and it didn't seem low or smell burnt so I let it cool and proceeded. Still would not work in OD but since it seemed OK in D I proceeded carefully. Did not notice any issues while in D except occasionally a little mild shudder somewhat like a u-joint if I started out with a little enthusiasm. I babied her home and she is snug in her new slip waiting for a checkup. Any thoughts would be appreciated. Hoping it is just an adjustment.

I love the car otherwise. I don't think any other car I have driven would leave me in as good of shape as I am after 17 hours of driving.

mike

 

Check the kick down cable. Make sure it is connected at both ends, and that it is not stretched.

I know what you mean about those seats. They are truly an all day seat with no discomfort. I've done almost 1,000 miles in a day, and still felt just fine.

 

mashaffer , WOW 17 hours in your new longroof and from what I see Loving it . my thoughts are with Mike a simple adjustment on kick down should solve this hiccup . its great to see you with a new to you ride

 

What is the car?

 

It is Pat's 1991 Colony Park... the Sooner Schooner.

mike

 

Glad to see you made it home fine. I didn't think about the cable, but it's possible all it needs to work is an adjustment, assuming it has not stretched. That is a great road car, comfy as can be.

 

I've been in the transmission field for 16+ years and run the largest transmission shop in Berkshire County, Mass.

Here is the fix: Avoid Illinois.















How did he sense the trans was slipping? Did he hear the engine rev, or if the car has a tach, see the tach needle rising up without increase in mph? It's possible he could be hearing a fan clutch that is locking up more than it should be. When checking the trans level, the car should be in park with the engine idling and at operating temperature. Best to check after a short drive. If the level is checked with the engine off, it will give a false reading of being overfull. If the false reading (when the engine is off) shows proper level, then the fluid would be too low when being checked properly---with the engine running.
As others have mentioned, the TV cable from the engine throttle arm to the trans could be at fault. The cable controls shift timing and pressure rise in the trans. There is a plastic bushing that eventually cracks and fall out causing a disconnection of the cable from the throttle arm. Luckily there is a preload spring in the trans to put it at mid-pressure to help save the trans incase of bushing failure. But, mid pressure is not enough in all circumstances.
Darn, I was re-reading the replies and saw that this was slipping in 4th pretty good. Chances are the overdrive band is compromised. The fluid may only contain a light burnt smell. There are other possibilities too, but we'd need more info to help sort it out.

Mark
Berkshire Transmissions
North Adams, Massachusetts