Possible issue with tranny

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trix13440

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Hey all, new question. 02 Montana, I've noticed my mileage sucks, badly.
Been keeping an eye on my tach as I drive, and here's what I've noticed.
30 mph, and the tach is almost 2k rpm.
40 mph, tach is 1.5k rpm
55 mph, tach is around 1.8k rpm.
Is this working as intended? Because I have to say, I don't think so. Every car I've driven, with a tach, the rpms are quite a bit lower than this.
If those are the right numbers, what are some other possibilities for crappy mileage? Getting new plugs and air filter in a few days, just because. But it runs like a damn top, so it's hard to think its just plugs.
Thank you again for any help :)
 
I would start with checking the basics, Air pressure, 4 wheel alignment, Wheel bearings, type of tires, are they matching? check all the brakes making sure they do not drag excessively.

check the factory service bulletins, check to see if you find any TSB related to fuel mileage.

You may a have a bunch of little things adding up to a large drop in mileage.
 
Don't believe tires are matched, but I can check the pressure, brakes and bearings tomorrow
 
Rear tires were severely under inflated, 20, and 22 psi. I prefer 35.
Also, for the 2nd time in 2 weeks, I found the hose clamp, for the filler neck to tank hose, was loosened. I can't of any way it would happen accidentally, so if I keep checking that hose, and it stays tight, my mpg problem may be fixed.
I'll update later this week
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Do keep us posted. The RPM will have variables to it. Keep an eye on fluid. Just as a matter of maintenance, when was last your filter and fluid changed? You can easily do that yourself and at a relatively low cost.
 
Air filter? Not since I've owned it, but that's only a month and a half.
What I usually do when I get a new car, is to do plugs, oil, oil filter and air filter just as a matter of course. But due to my current financial situation, it's not an option at the moment.
I can tell you the oil is clean, with no residue indicating a head gasket issue. Radiator fluid, too. Everything I can check, is showing good signs.
I do have one question though, how do you tell if your tranny fluid is low on these? The dipstick just has a bulb looking thing on it, not the holes with cold and hot next to em, like I'm used to
 
I thing they made the tip of the transmission dipstick round so it would slide around the bends in the dipstick tube without getting stuck . There should be markings on it showing the level.
 
@trix13440 Sorry for the confusion, I was referring to the transmission's filter. You'd want to drop the pan and you would be staring right at it. Replace with another filter, check the pan gasket, bolt it back up and replace with ATF. One thing I've done in the past is pulled the return line for the trans oil and started the car for a brief moment to squirt out some more of the old fluid.

Just something to think about later on with doing your own maintenance.

BTW what kind of mileage are you getting? 3400s can get good mileage, but I wouldn't expect WOW mileage on that minivan.
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Not sure of the exact mpg, but I just used a little over a quarter of a tank, to drive roughly 70 miles. Same tank size as my jeep, which used a little under a 1/4 to make the same trip. Highway, isn't too far off what it should be, but city driving my mpg is toast.
Unfortunately, I don't have the space to drain tranny and change filter
 
when I experience bad mileage, (Liters/100Km where I live), I found a dragging rear brake. The parking brake portion had seized. If you smell burning brake odour, there's your mileage problem...
 
Great tip Midnight.
BTW did you ever calculate the mileage?
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