Shudder/slip in overdrive

My '97 has started recently slipping or shuddering when cruising at around 50-55 mph. It usually does it when going up a slight incline or when just barely excelerating. When I step on the gas harder the shudder goes away. I'm not sure if its a transmission issue or some sort of ignition issue. I've read a few reports of similar problems, but haven't seen any solutions or definite answers. I know if I put the tranny selector in "3" it will never do this. The problems seems to be with overdrive. I'm not getting any check engine lights either.

Thanks in advance,
David

How many miles does this van have on it? Good service record?

It has 88K on it and I've owned it since new. I have maintained it very well. I've changed the oil every 3K until a couple of years ago when I switched to synthetic. Now I change it more like every 5-7K, which is fine for synth. I changed the tranny fluid at 50K like it called for and again just a few weeks ago (AFTER I started having this problem--was hoping fresh fluid would help it. Oh well). I've changed belts, coolant, air filter, fuel filter, every maintenance item it would need.

I have never replaced the plugs (they are supposed to be good till 100K), so that *could* be the issue. I am taking it to the mechanic again tommorow to see if he can track it down. I will post when I know something.

It is frustrating when you take care of a vehicle and you don't get the payback. I've had the rack and pinion fail twice, the manifold gasket leak, rear brake cylinders go bad twice, some cruise control cable started sticking and almost caused my wife to wreck (stuck the pedal to the floor!), heater hose leak, radio broke, the power sliding door has recently quit working, and various other issues. I hate to bash American cars, but I have purchased a new vehicle from all of the big 3 and none have been able to touch my Toyota I bought 2 years ago. It was the first Japanese car I'd ever bought--and won't be the last.

I've heard that a failing MAF sensor can cause this type of behavior. Its a 100 dollar part, but is easy to replace yourself. Its located on the air inlet duct that comes off of your air cleaner. Have you gotten any check engine lights? If you take it to a dealer, they will tell you it needs a new tranny. Also faulty on the venture/montana/olds van is the valve body in the transmission. This can be replaced ($300 on ebay) and it should also fix the problem without being charged for a rebuild on the transmission.

We also are having the same problem with our 2000 Montana.
Ours gave us a code, I bought a code reader and retreived it.
The code mentioned that the EGR valve was stuck in the open position.
Maybe needs a good cleaning or replacement.
I haven't checked into it yet because our mehanic is on holidays.

What we are doing in the mean time, when going up hills we shift down manually. If we do that no problem.
Hope this helps
Davey Carpet

I have an appointment to take it to a reputable tranmission shop on Monday (8/9/04). I will be sure to post the fix once I get it back.

Well, the transmission shop got it to throw a code--and it wasn't the transmission. It was a cylinder mis-fire. I took it back to my mechanic and he replaced the plugs and wires. That took care of the problem! Whoo hoo!