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2000 Blazer transmission shift problem

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Old 09-11-2012, 11:26 PM
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Default 2000 Blazer transmission shift problem

a year ago i had my transmission 'serviced' at a local garage. the car had approx 100K mi on it, after this service the following problem arose.
In the mornings, especially cold mornings, the tranny shifts from 1st to 2nd OK but doesn't make it into 3rd, instead the engine will rev high and i
have to get off the gas pedal until it engages back into 2nd. This 'slipping' occurs until the engine and tranny run for a while,heating up,and then it will work properly. again this problem seems to be temp related since it is much worse in cold weather. any ideas ???
 
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Old 09-12-2012, 05:41 PM
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mine also did that in the cold then i dropped the tranny pan and my trans was toast i would have it serviced again to see if there is any metal in the pan or it thats what i did my pan was loaded with metal.
 
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Old 09-12-2012, 06:00 PM
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Use the search feature here. Lots of posts about things like that but unfortunately most of them end up in a rebuild or 'new to you' trans.
 
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Old 09-12-2012, 09:03 PM
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reading thru some other postings i found one claiming the tranny uses the wheel speed sensor data. well it happens that i have problems with my ABS as well. Does anyone have info on the relationship between the ABS wheel speed sensors and tranny shifting ?? This still doesn't explain the fact that the shifting problem happens when engine is cold and disappears when things heat up (i don't think , anyways)
 
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Old 09-13-2012, 03:25 PM
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All the wheel speed sensors go to the ABS module - the PCM (main computer) controls the transmission, its 'speed' input being the VSS on the transfercase

The ABS module and PCM do 'talk' but its mostly limited to stuff like
ABS: "My sources say this vehicle is in a low traction situation - now pulsing brakes"
PCM: "OK! turning on the idiot light to distract the driver!!"
or
PCM: "HITHERE! I've just been REALLY turned on and am getting ready for some good 'ol CRANKING! - ABS module? are you ready for this?!!"
ABS: "no. I'm feeling very depressed. somethings not working right and I don't know what I'm supposed to do anymore. turn on the idiot light to tell the driver to throw money at me till I feel better...."
PCM: "...typical woman..."

I'll leave further psychoanalysis of the relationship to either your imagination or the professionals - whichever amuses you more

I'd be very surprised if they are related problems - The behavior you're describing sounds very much like something internal to the transmission, as opposed to and electrical/computer related. Lucky money would be having the trouble somewhere in the valve body, then the transmission doesn't have to come out to fix it.
 
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Old 09-13-2012, 10:00 PM
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Default thanks roypai

enjoyed your analysis. you should have your own column in a newspaper ala click 'n clack. is a valve body rebuild/replacement within the capability
of a DIYer with self-esteem issues ?
 
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Old 09-14-2012, 11:26 AM
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lol! I enjoyed that interpretation of how the ABS and PCM communicate. I'm sure it is probably something along those lines. To the OP, try looking at the shift solenoids, My 1st and 2nd gear shift really rough (almost jumping into gear) and i am thinking along the lines of a new 1-2 shift solenoid.
 
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Old 09-14-2012, 08:08 PM
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I got my transmission out, apart into (almost) every piece disassembled on a work bench and it was honestly the most terrifying thing I've ever done to a vehicle. But now that I've got it back together, installed and 15,000 km on it running smooth as silk, I wouldn't hesitate to do another one - swore up and down during it that I'd never do it again tho.

I used a rebuild kit that came with virtually no instructions but was saved by the fact that I bought one of THESE manuals when i got the kit 'just in case' - about half way through the job i was starting to loose my nerve and getting really stressed. I took the torque converter into a local transmission shop to get it flushed and was lamenting about all the parts I had in the kit and how i had no idea where they went - the guy was a godsend - said bring in the parts and I'll tell you - no charge. In the end he basically told me - yup you're doing fine, you're right those are the right places for those parts, you've got a really good manual here, etc etc - gave a couple pointers on what NOT to touch(all stuff inside the transmission - valve body is pretty straight forward)

So from a DIY'er who was feeling pretty low in self esteem during his project - yes it's definitely within the capability but it could be stressful.

Get another daily driver at least on standby so you don't have to feel rushed (I took almost 2 months doing the drop, rebuild and re-install)
Get a good manual - the one I linked (apparently) is a good one - there's also an 'updated' one available that includes the 4l65 data - not sure which is better
Find a local TRANSMISSION shop and see if they'll sell you the parts and maybe a little encouragement - failing that you could take in the parts to an auto parts store and drive them nuts with 'I need one of THESE and it goes HERE'
The other thing I did before I started is scoured youtube for how-to videos - some are good some are crap, but they at least give you an idea of what to expect

The job seems really complicated and scary till you've done it. Now that I've written all that, if your problem really is in the valve body - It 'should' be a (comparatively) cheap repair at a tranny shop - most of the money in a transmission job comes from the hours needed to take the sucker out and put it back in. The valve body really is right there after the pan comes off. - go youtubing and see what you think!
 
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Old 09-15-2012, 09:24 PM
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Thanks all for the advice and encouragement but before I dive in could someone try and explain why the valve body would not function properly when cold but once things warm up after 5-10 minutes of driving everything runs perfectly ? and why would the shifting problem occur as tranny attempts to go from 2nd to 3rd ?
 
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Old 09-15-2012, 10:06 PM
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When the oil is cold it has a higher viscosity meaning it's thicker. So if the valve body has any buildup like from a deteriorated clutch pack it would be harder to flow the oil until it warmed up enough to lower the viscosity. There's usually a diagram showing what's in use so you could see if there's a pattern I.e clutch pack holding sun gear driving internal, pinions are neutral. You could then see if you had any other problems associated with that part, or it could be a broken servo spring or buildup on the 2nd-3rd shift valve. Just my opinion though GL!
 


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