I have a 97 chevy silverado that once you drive about 20 miles and the transmission warms up it starts to shift hard from first to second gear and the rest are smooth shifts. this just started and everyone in my area says it must be rebuilt to solve this problem is this true?

start off by checking the transmission fluid when its hot and in park for the proper level,
check the color of the fluid compared to new fluid,
volvos probably use dealer specific transmission fluids and there is a possibility normal shelf trans fluid was used and that can cause all sorts of transmission problems.
hard shifts can also be related to transmission and or engine mounts. visually inspect those for wear and or breakage.
dark fluid or particles of metals on the dipstick can be a sign of major transmission problems
clean the dipstick off with a clean white rag to check that.
if its low make sure to use what the dealer recommends even if its high dollar, but if the fluid is already burnt smelling and or contains metal materials it getting time for a rebuild or replacement,
. at that price the previous owner might of known the transmission was going south.
good luck and hope you get more miles out of it.

i take it is a automatic check gearbox transmission fluid or the torque converter may be at fault

my 2004 chevy impala shifts hard when it warms up

Check fluid level at operating temp.may need a flush and filter change.

For gear shift issues and gear stuck issues,the help links are provided below. Click the link below to go through troubleshooting procedure:---- ---- Car will not move when in gear?

http://repairhelpcenter.blogspot.in/2012/02/car-will-not-move-when-in-gear.html ---- transmission sticks in first gear? http://technoanswers.blogspot.com/2012/01/mercedes-benz-transmission-sticks-in.html ----- Transmission not engaging in first gear? http://technoanswers.blogspot.com/2012/01/mercedes-benz-not-engaging-in-first.html ----- Vehicle only goes in First gear?

http://howtobyme.blogspot.com/2011/11/chrysler-pt-cruiser-only-goes-in-first.html

----

Car is stuck in park and the shift will not move?

http://howtobyme.blogspot.com/2011/08/car-is-stuck-in-park-and-shift-will-not.html

---- Engine will not go out of park mode? http://technoanswers.blogspot.in/2012/02/2002-nissan-sentra-will-not-go-out-of.html ---- Car stuck in park? http://technoanswers.blogspot.in/2012/02/nissan-sentra-stuck-in-park.html ----- Car will not come out of Park?

http://howtobyme.blogspot.com/2011/11/car-will-not-come-out-of-park.html

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Automatic transmission will not go into high gear?

http://howtobyme.blogspot.com/2011/11/automatic-transmission-will-not-go-into.html
--- Car wont downshift sometimes?

http://schematicsdiagram.blogspot.com/2011/12/car-wont-downshift-sometimes.html
---- Transmission will shift into drive?

http://schematicsdiagram.blogspot.com/2011/12/buick-park-avenuetransmission-will.html
----- Auto wont shift from park? http://schematicsdiagram.blogspot.com/2011/12/ford-taurus-wont-shift-from-park.html ---- Car Transmission will not go into Park mode?

http://schematicsdiagram.blogspot.com/2011/12/car-transmission-will-no-go-into-park.html
----- Shift indicator directly goes to 2nd when key is turned ON?

http://schematicsdiagram.blogspot.com/2011/12/shift-indicator-directly-goes-to-2nd.html
---- Third gear missing and engine losing power?

http://schematicsdiagram.blogspot.com/2012/01/third-gear-missing-and-engine-losing.html
------- Vehicle has whining sound in gear?

http://technoanswers.blogspot.com/2012/01/chevrolet-silverado-has-whining-sound.html
----- Hard to shift gears on Manual transmission?

http://technoanswers.blogspot.com/2012/01/hard-to-shift-gears-on-manual.html
------ Car hard shift at slow speeds?

http://technoanswers.blogspot.com/2012/01/car-hard-shift-at-slow-speeds.html
--- Automatic transmission shift lever hard to move on cold mornings?

http://technoanswers.blogspot.com/2012/01/automatic-transmission-shift-lever-hard.html
------ Gear shifts hard?

http://schematicsdiagram.blogspot.in/2012/02/2000-nissan-maxima-shifts-hard.html
------- Vehicle noticed sluggish delayed shifts while driving?

http://schematicsdiagram.blogspot.in/2012/03/vehicle-noticed-sluggish-delayed-shifts.html

-------

This will help.

Thanks.

it may be a bad tps ( throttle position sensor ). it causes transmission shift issues, bucking,jerking, idle surging, engine cut off, surge while crusing down highway. if this does not solve problem, it may be a sticking valve body in transmission. have a good day !! for an automatic tranny.

FYI
I have a 1995 GMC 1500 with 5.7 truck that the ABS Light comes on and then the tranny starts jumping gears and speedo goes crazy- Changed ignition switch and that did not help.
You said that you had changed the speed sensor on the tranny and that did not help ?? If so that was my next step. Let me know if you find and answer and I will do likewise.

You are your own best judge on that, i got a 95 silverado with 160,000 mi. and would not think twice about driving and pulling anything across the country, but one thing i would recamend (if it dosent have one already) is an external trans. cooler.

check the fluid level after vech warms up also make sure that the detent cable is adjusted correctly

get code check for any trans codes...sounds like front pump though...internal issue mechanical..need at least partial rebuild to remedy