Hard Shift

[greyth]

My 00 extend cab Z71 4x4, 5.3L; lock diff; 3.73:1 rear; with 235x85x16s load range E: appprox 130K miles. after 120 plus miles of interstate driving; the next upshift from a stop first to second is sometimes extremely hard. Often times the second to third is also hard. This has only occurred after an extended dirve at constant speed such as interstate driving. Is this a sympton of a potential major tranny problem, or a problem with some external device that determins when and how to shift?? Fluid breakdown with temperature??

[hoorders]

My 00 extend cab Z71 4x4, 5.3L; lock diff; 3.73:1 rear; with 235x85x16s load range E: appprox 130K miles. after 120 plus miles of interstate driving; the next upshift from a stop first to second is sometimes extremely hard. Often times the second to third is also hard. This has only occurred after an extended dirve at constant speed such as interstate driving. Is this a sympton of a potential major tranny problem, or a problem with some external device that determins when and how to shift?? Fluid breakdown with temperature??

Mine does the exact same thing...........if I shut it off for a minute or 2 then restart.......it shifts fine.............dont know what the problem is though........

[greyth]

My 00 extend cab Z71 4x4, 5.3L; lock diff; 3.73:1 rear; with 235x85x16s load range E: appprox 130K miles. after 120 plus miles of interstate driving; the next upshift from a stop first to second is sometimes extremely hard. Often times the second to third is also hard. This has only occurred after an extended dirve at constant speed such as interstate driving. Is this a sympton of a potential major tranny problem, or a problem with some external device that determins when and how to shift?? Fluid breakdown with temperature??

Mine does the exact same thing...........if I shut it off for a minute or 2 then restart.......it shifts fine.............dont know what the problem is though........

 

I really appreciate the reply; at least now I know I'm not the only one. I'm going to the locals tomorrow and will pass along what I come up with. I may try a fluid change with a complete flush. Thanks again, great looking truck!

[-Devil-]

i know i aint much help ... but it sounds like something may be sticking from the extended treck with the temp and pressure building up in the tranny ...

 

i had an old tranny in my 69 camaro that did something similiar ... it went away after a full flush and a shift kit install ...

[Mlshelby]

Your torque converter is probably not achieving full lockup and is on the verge of setting a P1870 or P0894 code .The harsh shifts are from high line pressure because the PCM is commanding higher line pressure to correct the slip at highway speeds. This could be a faulty converter, valve body or solenoid. Could also be wear on the turbine shaft bushings.

[greyth]

i know i aint much help ... but it sounds like something may be sticking from the extended treck with the temp and pressure building up in the tranny ...

 

i had an old tranny in my 69 camaro that did something similiar ... it went away after a full flush and a shift kit install ...

Devil; Thanks for the reply. I'm going with a flush if I can find a dealer that can do for a start. I'm also going to check out the tranny cooler circuit of the radiator.

Best reagards and Merry Christmas. Let you know how it turns out.

[hoorders]

My 00 extend cab Z71 4x4, 5.3L; lock diff; 3.73:1 rear; with 235x85x16s load range E: appprox 130K miles. after 120 plus miles of interstate driving; the next upshift from a stop first to second is sometimes extremely hard. Often times the second to third is also hard. This has only occurred after an extended dirve at constant speed such as interstate driving. Is this a sympton of a potential major tranny problem, or a problem with some external device that determins when and how to shift?? Fluid breakdown with temperature??

Mine does the exact same thing...........if I shut it off for a minute or 2 then restart.......it shifts fine.............dont know what the problem is though........

 

I really appreciate the reply; at least now I know I'm not the only one. I'm going to the locals tomorrow and will pass along what I come up with. I may try a fluid change with a complete flush. Thanks again, great looking truck!

 

Thanks man!.........she has been a great truck.............just that crazy hard shifting every once in a while..........I'd like to change out my tranny fluid.....just cant get that dang plug out.. .........I might just take it in and let the shop deal with it the first time......let me know how you make out with the tranny..........

[buckshot]

Hey i got a 2500 non hd with a 6.0 and my transmission does the exact same thing. I have asked around and all i hear is well bring it in and we will see what we can do. Pretty sure all they want is my money. I am just an engineering student from Okla. State. but i do know when someone is trying to screw me (the stealership). If anybody hears of the solution or if I found it out please post it on here. Thanks. And Merry Christmas

[greyth]

To all responders this topic; I checked with a friend/fellow engineer who turned mechanic and he agrees with chevyjeep that the computer control is calling for higher pressure due to the slippage of the torque converter at highway speeds. I did finally get a P1870 code. As a test he advised to shut the engine off when you come off the highway before she has a chance to up shift. When the engine is shut off, the computer resets the command to the PCM back to normal pressure. That should take the "bang" out of the shift, but not fix the problem. Also you could use the tow/haul to keep the tranny out of lockup, but that takes more fuel. He said not to waste money on a flush. Since it is a "sometime" thing like when I haul my fourwheeler or pull a light trailer, I probably buy some time before going for a crate tranny swap. (looks like about $1800 plus installation!)

Many thanks to all of you for responding and all the best for a safe and happy Holiday season!

[Easter Bunny]

You're lucky. I paid good money to get mine to shift that way. lol

 

I now can catch a second without a problem. Not sure if I want to do that but it does it.

 

I had a shift kit installed and a transmission cooler while I had the tranny at the shop. I had some solinoid changed and decided to do the extra work while it was in the shop.