I'm just past 154,000 miles. Changed the fluid about every 20K. I normally use the t-tech service that changes ALL the fluid including the converter-about 20 quarts). Last changed the fluid at 147k(Mercon III). 1997 4.2 V-6 4x4 but rarely use the 4WD(only in snow/ice). Not sure which trans I have(don't care) but it is a 4 speed automatic. Stock transmission-No Mods of any kind.

At about 60 MPH in O/D(highway) starting to feel transmission jerking(the tach never jumps in rpm so I know it nevers completes any downshift) At lower speeds(in the city) everything is ok. A few weeks ago I thought I only noticed this 1-2 times on a cold engine. Today it was happening after warmup on the highway. Anyone ever hear of this? I'm thinking of having the freebie transmission checkout at a local transmission shop.

 

I don't think you should go there unless you want it rebuilt.

Change to Mercon V fluid. Your transmission (it's a 4R70W) came filled with regular Mercon from the factory, but Ford released Mercon V in 1998 to deal with torque converter shudder in this transmisison. It sounds like this is what's happening here. The TC is locking and unlocking a few times a second. It causes a shuddering or shaking feeling.

Mercon V fluid.

 

Hope you have been changing the T'case fluid as well??? It spins just as much as the tranny does, even if you don't use 4x4......

I don't think this would make any difference on your shudder problem, but just thought I'd ask.......

Also, don't know why you'd use Mercon III, unless the truck was specific to that.... Mine is a '97 and is supposed to use just "Mercon", but it's got the 5.4 and e40d tranny. I thought that Mark K. said that you should NOT use the Mercon V in a tranny spec'd for Mercon only?? Maybe I'm wrong on that one, but just thought I'd toss that out too.....

Good Luck!

 

I suggested Mercon V because the only A/T with the 4.2L is the 4R70W.

The E4OD/4R100 cannot use Mercon V, only Mercon.

He has pretty much the same truck I do. His dipstick will say just Mercon. Mine came with regular Mercon from the factory too, but I'm now using Mercon V and it's quite happy.

4R70W=Mercon V (even if it came with Mercon)
4R100=Mercon

 

Cool......

Nice to know that about the 4r70 that were originally spec'd for Mercon. I guess the other just stood out because it did affect me.

Didn't mean to confuse the issue more then it already is!

 

Talked to my local Ford service advisor today. Admittedly they usually don't help much.

The important difference here is whether you have a jerk or a shudder. The jerking motion is more like a lunge front and back. That's what I have. A shudder is more like a vibration.

Per the service advisor they have heard of the jerking problem I descibed. The source of the problem is the vehicle speed sensors(VSS) located in the rear of the vehicle. When malfunctioning they confuse the electronics in the transmission. The transmission doesn't know what gear to be in.

Thanks for all the help.