1999 Hyundai Elantra transmission issue

My 1999 Hyundai Elantra 2.0 auto shifts through first and second and when it shifts again it seams to be down shifting and I lose speed drastically. This only happens when going uphill. downhill and flat
runs great. I start out doing 60 and by the time I get to the top of the hill (about a quarter of a mile) I'm doing a steady 30 mph. This happens on any grade of hill from small to large. From a standstill I can hear it shift from first to second and then to third but it seams to downshift and revs very high and i steadily lose speed until I'm doing 30 mph when it should be third gear and a steady acceleration.
I have already checked a few things so here they are. Transmission fluid and filter change (no plastic or metal pieces or even metal dust in pan) just a small amount of sludge. Fuel filter, pump, pressure, and sending unit fine. Air filter and throttle body fine. PCV valve fine. Timing belt was loose but tightened and fine. Spark plugs, wires and coil packs fine.
I have a small exhaust leak but can't seem to find it and a small oil leak which I can't seam to find either. It has 140,000 miles on it but the MPG is great so I really love this car and really want to fix it. Any help will be greatly appreciated. Thanks
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On Mar 25, 6:07 pm, snipped-for-privacy@yahoo.com wrote:

You're going to need to sort out whether this is an engine performance issue or a transmission concern. As an example, if the exhaust is restricted, the vehicle may lose power going up hill and stay in a lower gear trying to get to the rpms high enough to upshift.
If you're unable to feel this for yourself, you should take the car to a qualified mechanic.
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Oh i can feel it alright. and I don't think it's an engine problem. now with the exhaust I do have a small exhaust leak that I can't seem to find but the rest of the exhaust looks good I was thinking that it may be the catalytic converter but I'm not sure how to go about checking it. A friend of mine said to run it at night until its hot and see if it's turning red. He says this means it's blocked and over heating due to the restriction but I havn't noticed and redness or glowing when I look at it in the dark. Is there any other way of checking it?
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On Mar 29, 2:03 pm, " snipped-for-privacy@yahoo.com"

Not really, beyond taking it off and looking at it. On a 1999, you won't want to do that. You'll probably break a bolt and multiply your problems. If your exhaust leak is small enough you cannot find it, it won't be an issue.
In most cases, with a description of a slipping transmission, I'll say the prognosis isn't good. In your case, the description doesn't give me enough detail for me to be convinced the issue isn't with the engine or and engine or transmission sensor.
We're talking about a potentially very expensive repair here. Better to take the car to a competent and qualified mechanic for a diagnosis than to start taking guesses at this point. I will advise to stay away from the transmission shops. They have a tendency to want to solve all problems with a transmission replacement. If in doubt as to where to go, take your car to the local dealer. Each dealer should have at least one technician who has passed Hyundai's transmission diagnostic class.
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Well I found the exhaust leak. My damn manifold is cracked in 2 places. Looks like I'm heading to the junk yard. $225.oo for a new one is just too much lol.
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Check with your local dealer for recalls on your car. You should be able to do this by calling the dealer with your vin#. If you'd rather not do that, you can post the VIN here and I'll check for you.
If my memory is correct, there's a recall to inspect the manifold and replace if cracked. If it hasn't yet been done, you may get a free manifold.
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Well the car goes to the closest dealer on tuesday for a free manifold and front catalytic converter change. Damn i love free lol. he said that alot of the replacements that he has done have had the same symptoms and that it corrected them so i hope this works for me also. FREE!!! lol
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