Canadian Hummer Club Forums

ok threw the years once in a blue moon i thought i felt slip here and there, and then all was fine so dismissed it... (after ckecking fluid and smelling it)

all was perfect... but yesterday it seemed to rev more going up a slight incline... so agian i check fluid blah blah and was all good... but today was driving around 70km and felt the motor rev so put foot into it more and there was a definate rev... like it was in neutral..... i pulled over and let idol while i looked for any leaks on road... and looked good, so i put in gear and worked... for about 4 mins and had to pull over due to no gear, and this time i move shifter to drive, to see if anything helped, but nada... so sat there for minute and put in reverse and heard usual clunck and then back to drive and heart cluck and started again and this time made a 1/2 hr. drive home... is this a warning sign for its last dance? im in the country so would suck to be stranded in the middle of no where...

anything i could look for? or break down and get a trany? looks like a doit yourselver project... but heavy... was hoping someone might know if this is it for that tranny? or tork? not sure how to test

Could be 100 different things. To narrow it down we need to know what shifts are lost. Seems you have a reverse and forward which could be good news. Do a shift test from a stop with one third throttle and check for a 1,2,3,OD shifts and converter lock up.
If you cant move forward or reverse the trans is likely gone.
If you just out a gear or 2 it may be just wiring, a solenoid or other electrical part in the valve body.
Eventually a code may pop up like P0753 or P0756 or a code starting with P07xx and will light the MIL lamp but sometimes it takes a while for the codes to pop.
 More info needed!!

You can pull the speed control fuse which will disable shift adapts and trans will resort to default shifts. Very hard shifts so dont be alarmed and you will feel if all shifts are there or not.`If you get all the shifts with the fuse out and dont get them with the fuse in its likely the wiring between the trans and controller or PCM.

Ok, I basically when stopped I then did 3/4 throttle driving straight and Seems all shifts are at 2100- 2200 rpm....then I stop and put brake to floor AND gas for few a seconds and it stays at 1500 rpm steady.... (Shouldn't be higher?)

I started here cold and drove few blocks and seemed all perfect,I turned around to head home and going around 50-60km (felt like slips out of gear to neutral ) I was able to rev to 3000 rpm and no change in speed, (I shifts to 2nd gear and no change in slippage )

Then when I slowed to 30kish I felt a klunch to gear again and I drove home fine those few blocks.

When all good there's no telling tranny slips, then all of sudden feels like goes into neutral but it's not,.

I'm defiantly no good at diagnosis, so hopefully this info helps..

Grrenmeanie your correct I defiantly have drive and reverse, and seems normal for about 5 mins then "feels" like it pops to neutral . I slow down/stop basically and can feel it "kick"into gear again and then fine for driving, this is why I'm confused I figured if blown wouldn't move.

Best to get the pan removed and checked out at a reliable trany shop.This will give peace of mind if all is well inside.

Sounds like an intermittent electrical or solenoid problem or even the TCC failing.
If you take it to a shop they will likely tell you to rebuild or replace the transmission. In my opinion i dont think that is a good idea yet as it will be thousands of dollars to do this.
I suggest you do a fluid and filter change on the transmission and replace the electrical items in the valve body. The parts are not expensive. The electrical part numbers are listed below except filter and fluid.
5714925                                     1-2 sol
5714926                                     2-3 sol
5744098                                     Presure switch
5714373                                      Presure control
5744093                                     TCC sol
5715037                                      wiring harness
You should be able to do this yourself in a couple hours if you have some basic tools.
You want to. 
-Support T case on jack
-Remove Transmission crossmember
-Drain transmission- drain through a rag over a bucket so you can inspect any debris.
-Drop the pan- Keep track of the bolts as they are not all the same. Inpect the bottom of the pan for junk. Fine silver silt is fine.
-Pull out the filter and the bushing. Sometimes it can stay in if in good shape.
-Undo the wiring connection to all the electrical items. This idiot proof and only connect up one way. 6 bolts hold the pressure switch in place.
-Remove all electrical items- You will need some torx drivers for this. Canadian tire etc.
While you have electrical items out clean out the bores behind and give them a push with a long wood dowel to make sure they are all moving back and forth. They have spring behind that will push the valve back. If any are stuck and not moving try flushing with some brake cleaner and try again until they move freely.
-Replace all parts and reconnect wire and put new filter in.
-Install pan it up and refill with new dexron 3.
-Put the crossmember back in and remove jack. Cross fingers.
If this wont solve the problem, ringing out the wiring would be the next step or you can ring out the wiring as a first step which is also the cheapest step but involves removing the doghouse to access the PCM. At the end of all this you will only be out 150 bucks for all the parts and there is a good chance your issue may be solved as a result. If none of it works you can  then entertain the more unsavory options.
For some step by step instruction the video below will help you get it apart.
You are not doing a trango install but the video shows the breakdown steps you need.
Once you get to the pressure switch part of the video you wont need to go further. I doesnt show solenoid removal until the valve body is on the bench. In your case you would be replacing these with the valve body still in the truck.
http://transgo.com/4L80E_HD2Video.html

I think I'm almost obsessed with this job, lol,,..... Already ahead of ya...today I jacked tcase, and dropped tranny pan,

I'm gonna try out a valve solenoid kit with a harness, (basically all the parts you mentioned) I'll call my parts place tomorrow, see if in stock or if they can get,.

Thanks for the step by step. !! Lol crossing fingers, so far fluid smell great and fresh and the pan had zero junk in bottom, the magnetic bolt had some shavings but that's all.

At least the dirty part of job is done, rest hopefully will go smooth,.

We'll I NEED a high five!!!

This camper just fixed his tranny, lol I still have a grin ear to ear, greenmeanie thanks for that step by step.

I didn't do my wire loom as looked mint, but the rest all went in to be safe,, and changed filter while in there.

This job was mega easy imo anyone can do this job, my biggest fear was to strip the solenoid bolts, but those came off easy.

Took me 1.5 hrs to remove cross member and take pan etc. all apart, ( this included cleaning things and inspection best I could) , then 1 hour to screw the new items in and filter service, and button all up,

Now I have a permanent grin! Thanks club members, I'm sure I was saved for bending over and getting a rebuild ;-)

I love it when a plan comes together!!