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

 

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.

 

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?

 

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.

 

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.

 

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.

 

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