95 Windstar Transmission - Lock-up In and Out

Hi,
Anybody see this happen in a Ford auto tranny? The '95 Windstar will go in and out of lock-up, over and over, on level ground at highway speeds. In other words, the lock-up torque convertor will engage and then disengage repeatedly when either my foot or the cruise control tries to maintain a steady speed on level ground. Ordinarily, a car will disengage the lock-up overdrive when you stomp on the pedal to pass or go up a hill, but the Windstar is extremely sensitive to any slightest movement on the pedal, causing an oscillation (visible on tachometer), showing the RPMs dropping when entering lock-up and then rising when disengaging from lock-up. Lock-up just simply disengages too easily. This is probably a common problem, so maybe somebody has had the same problem and can share the solution.
------Thanks!

The Computer will commant the T/C to unlock if the fluid gets too hot (or thinks it is), or if the programmed slip in the T/C cannot be maintained (to prevent damage). Also, it is *possible* that it's related to the A/C compressor cycling. Isthe HVAC system in Defrost, or A/C when this happens?

A/C and defroster not on.

However, you make an interesting point. I thought I noticed the other day that it didn't oscillate when the tranny fluid was cool. Seems to only happen when the tranny fluid is warm, but its not really getting too hot, based on the low-stress driving I'm doing.

Maybe it does have something to do with an internal worn part along with something the electronic controls are doing. I'm trying to figure out if I should take it in to get it fixed. Maybe I know enough about it now to explain it properly to a tranny technician/mechanic.

Thanks for the post.

...Seems to only happen when the tranny fluid is warm, but its not really getting too hot, based on the low-stress driving I'm doing....

I'm not positive if this applies to a '95, but most OBDII compliant vehicles wont lock the TC until normal engine operating temps have been reached per the engine coolant temp sensor.
G/luck
Joel

Joel, you are correct.

It could be something as simple as the computer *thinking* the trans fluid is too hot.

It will go into lock, so the computer is not preventing that. The problem appears to be that it won't stay in lock if just the slightest throttle movement occurs. Very slight throttle movement. All 4-speed automatic overdrives will lose lock-up if you stomp on the pedal and/or go up a steep hill, but very small, slight throttle adjustments shouldn't do it. I would call it kind of a "throttle sensitivity" problem.

Frankly, I've had better luck with GM automatics, having had GM units in my former 2001 BMW 525i (yes, they bought them from GM!!!), and my present Pontiac minivan with the fine Buick 3.8L V6 and GM 4-speed auto.

I got a feeling I'm going to learn a lot when this is all over. There's nothing better for us car nuts!

By the way, Joel (rodeo_02), the only stronger chick magnet than a 2001 Windstar is a 1995 Windstar with extra chip marks on the paint..... I caught one licking my bumper, but, hey, she's only human......

By the way, Joel (rodeo_02), the only stronger chick magnet than a 2001 Windstar is a 1995 Windstar with extra chip marks on the paint.....

I know whatcha mean. But we have to give the other fella's a fighting chance with the ladies, right? :banghead:
As far as your '95 easily coming out of TC lock, my '02 isuzu does this. Oddly enough, it's got a GM 4L30E which IIRC is in some BMW 3 series. The SLIGHTEST throttle changes cause that one to go out/in. Really annoying. On the other hand, my 2001 windstar with the supposed "new & improved" AX4N needs a MAJOR throttle change to come out of lockup. It holds tight. Are you new to this windstar or did it just start doing this?

Joel

I bought it used about a year ago. I ignored all the warnings about head gasket failure on the 3.8L V6 and bought it anyway (for cheap). I like it because its quiet, smoothe riding, hauls lots of stuff, and crash tests well (both at www.nhtsa.gov and www.iihs.org ). I haven't had any major problems yet except for this transmission annoyance which it has been doing since I got it.

About the GM tranny doing it, I admit I did find a mention of this same problem on some old post on the web somewhere of a '91 GM Chevy Cavalier automatic, so I know GM trannys can do this, too. I found the one reference using some keywords in www.google.com . Ford trannys have a worse reputation for sure, though. Also, I think BMW started using ZF (German) auto trannys lately, as I guess they were embarassed to be using GM's units. BMW is supposed to be elite and I'm sure it bothered them that they couldn't make one better for a long time.

I was thinking about spending the money and buying an AllData CD which has all the Ford Technical Service Bulletins (TSB's), of which there are many.

You know, what I would want, is for a tranny to stay in lock-up as you reach 55 mph, and stay in lockup until you go down to 46 mph, as a hard rule. Just speculating here.............

...You know, what I would want, is for a tranny to stay in lock-up as you reach 55 mph, and stay in lockup until you go down to 46 mph, as a hard rule. Just speculating here.............

There might be a software upgrade out there to improve this. Other than that, keep your ATF clean, cooling system clean & tip-top and enjoy your low cost ride!
G/luck
Joel