truck starting to shifting at diff. rpms

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deerhunter

New member
i own a 2005 chevy half ton 4x4. i noticed the other week it has been shifting at a higher rpm than usual. it does it most from 1-2 2-3 geart then its fine in over drive. it shifts about 400 rpms higher than normal and its gettin evewn worse gas mileage than its gets any other winter time. i took it to dealer and they scanned and test drove it and said its perfectly normal. ive never had a vechile that did this even if it was cold. they claimed that its cold and its doing it for quicker warm up. but it does it all the time after its been driving for a while. just seeing if anyone else that has the same truck do this as well and if its "normal".
also in the works of this problem happening i had a tranny cooler line start leaking after it was fixed it still does it. but they claim it has nothing to do with it. so does anyones else with the same truck do this while its cold out? i dont need a lechure on how things work. i use to work at a auto repair shop.

thanks for everyones elses input
mike
 
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ezra

Well-known member
just traded in my pos 05 z71 with 60k on it was on its 2nd tyranny and going to need to be tore down real soon if I did not trade it in.it was slipping between 2nd and 3rd.
 
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deerhunter

New member
thats where mine was doing it the most between 2-3. the rpms drop 200 rpms when it shifts to third. dont sound right.
 
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zr500rider

New member
Had same truck awhile back doing similar thing u describe......turned out to be intake gasket leaking.....really sucky mpg and shifting all the time....even after warmed up.....got gasket fixed and ran fine after that. Might check that out.
 
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G

Guest
Deerhunter - Mine does the exact same thing and I was told the exact same thing as you by a shop. I don't like the sounds of it and the thing has already eaten one transmission. I absolutely don't trust it and am just kind of planning some funding for another transmission.
 
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fredster

New member
The only GM trans that shifts later when it's cold is the allison trans. It does this to help the diesel engine warm up faster.

I have had three trucks with 4L60's and they did not shift later when cold. The torque converter will not lockup until the trans gets to 100 degrees, which can give the impression that the RPM's are higher, but that does not affect the actual RPM shift points -

If your shifts are late, there is a valve sticking or other problem in the trans -
 
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apex1

New member
half ton transmissions DO! hold the truck in gear longer when cold to help get it warmed up, I have had three 1500's from a 01' to a 04 and now a 07' all have done the same thing when its cold out(usually in teens or lower it will hold the truck in gears 1 and 2 longer to help warm the truck up, I have had nor problems with transmissions on any of mine, first two made 150,000 before I traded and I do use my trucks-pulling sleds car trailers work ect... sounds to me3 like your transmission is working properly, but thats just my opinion....
 
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tyeeman

New member
I'll second apex1. I had a 99, have 01 Sub both 1500's with the 4L60E and they both have delayed shifting when it's cold. My 02 1500HD with a 6.0 and 4L80E also has delayed shifting when cold but is a little different than the regular 1500's. If you do have a sticking valve, you may notice that some shifts are abnormally hard or really hard. That is computer upping the line pressure to ensure the shift is made. If you do have really hard shifts get to the dealer ASAP you might be able to save the tranny.
One problem some GM trucks did have is there is a proportioning valve that controls line pressure, it's a steel ball valve that bottoms on the aluminum case. The aluminum eventually can get peened up and valve does not seal properly. I cought it early enough, my dealer took out the valve body, had a tranny shop install a hardened valve seat, $400.00 end of story. The thing that turned me on to this was that at normal highway speed towing or not, the tachometer would all of sudden jump about 100 rpm then slowly come back down to where it was.
Went to the dealer and requested that the tech go for a ride with me with a "co-pilot" an electronic scan tool. He picked up on it right away. Had I waited longer I would have been putting in a tranny.
Dumb question but, , you don't have your tow/haul button engaged when your not towing do you? Just had to ask.
Good luck!
 
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G

Guest
No, the tow/haul button is not on. That is kind of what it feels like though. In my case the shifts are the opposite of hard. When it finally does shift it just kind of eases into the next gear. Sometimes when I am driving about 30 it feels like it is stuck between gears and the revs build - almost like it is in neutral but it isn't. This only happens when it is cold. At night my pickup lives in a heated garage. The first trip of the day is fine but when I go out to drive it after it has been sitting outside it starts doing this stuff. I don't trust it. The pickup needs tires anyway. If the tranny goes again maybe I will just throw it away and get a new one.
 
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deerhunter

New member
i do have a universal gm warrenty(at least thats how the dealer explained) up to 100,000 miles. im at 79,000 now. but if you come in with complaints and they cant find nothing wrong then i have to pay for computer hook ups, etc. im going to take it to another dealer that my wife works at. im want to be safe than sorry.

cant be intake leakihng... it dont use any collant.
 
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eao

Active member
From the owners manual

When temperatures are very cold, the Hydra-Matic®
Automatic Transmission’s gear shifting may be delayed
providing more stable shifts until the engine warms
up. Shifts may be more noticeable with a cold
transmission. This difference in shifting is normal.
Click to expand...
 
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