2000 5.3L tranny shifts hard

I have a 2000 Silverado 4X4 with the 5.3L. On warmer days or while pulling a trailer, the transmission shifts very hard from 1-2 and 2-3. I have 88k on the fluid. Only seems to do it when the outside temp is 70 or higher and after I have been driving for 30+ miles. Seems to be related to heat but there is no smell or noise and the fluid looks good. Any suggestions?

do u push the tow haul button?

My 2003 Silverado was in the shop 3 times for the transmission. The 3rd time they replaced the entire valve body. It never did fix the problem. They say it is normal. Ya, sure, normal. Seems it is an ongoing thing with them. Same engine as yours. It started slamming into 2nd then 3rd. Then it started making a "klunking" noise. I had 4,000 miles on the truck. It was one of the reasons I got rid of it and went and got a real truck.
Ford F-250 Super Duty Crew cab, 8 ft. bed. 6.0L Power stroke. Bail while you can. I'm working overtime, but i'm not wondering what the next thing to go wrong with my truck will be.

It is probably a sign that you should get a Sonnax, superior transmission, or someone elses valve body kit to correct for a worn valve body around the TCC apply valve. It would help is you had a scan tool that would show TCC slip, trans temp, and pending codes. If the PCM detects more than 130rpm of slip in the transmission while in OD with the TCC engaged it will set a pending P1870 code and command max trans fluid pressure resulting in harsh shifts, if the PCM detects the conditions for 3 consecutive tcc cycles it will light up the SES

It is not in the tow/haul mode although it does shift hard as if in that mode. I took it to a tranny shop and they did get a 1870 code and reset it. He said it did detect some slippage and went to the default mode to shift hard. He also did say something about the valve body being bad. Anybody have any info on a replacement/part number? P.S........I would love to have a "real truck" but unfortunatly I dont have the 40k to buy one right now so I must make do with this one.

ya the tow/haul does firm up the shifts a friend at aamco trans. he rigged his to stay on all the time he told me that the trans temp dropd like 20 degrees

dmiller

You shouldn't need a new valve body($400), just have the tranny shop put the Sonnax or Superior trans kit in it.

Mine shifted hard as well I have 81k on my truck and just recently changed my fluid and gasket, I replaced both shift seloniods on the bottom of the valve body and my truck Shifts 10times better than When I bought it. Its somthing easy to try and will cost you about $20 each. With my tow haul on my truck still shifts hard but I'm assuming thats normal.
-Jimmy