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2002 Sierra 4.3 w/ 4L60e trans.

This is my first auto rebuild  

I had originally lost 2nd gear and then I lost 4th gear. I rode with 1st and 3rd for a few weeks before I got around to replacing the fluid/filter and shift solenoids only to still have the issue.

I ordered this rebuild kit. Since the research I did on the issue could have been several things (sun shell, sun gear, 2-4 band, servo, ect) I decided to replace everything I could when I was in there.

During the rebuild (and not being a knowlegdable transmission tech) I couldn't seem to see any sign of reason to why I lost 2-4 gears. Well, everything in there looked like it was in excellent shape. No metal in the pan, gears,clutches, seals all looked fairly new (for my first look inside an automatic). I went by the book on the rebuild as well as the installation of the shift kit.  Taking my time and double checking every step. (So I thought)

Upon reinstalling the transmission and dumping 10qts in proir to start up, when I did start the truck the motor had a strain on it like it didnt want to stay running. After a minute of running it started to act normal. Then I proceeded to check the fluid and the dip stick was almost full to the top of the tube. The pump was not circulating the fluid (I assumed). I let it run for about 5 minutes longer then I tried to test Reverse and nothing, Drive and nothing, 1st and nothing, ect. I then realized I had broke the rotor in the pump.  So I removed the transmission again and yes I broke the rotor:


And the pan after the first removal:


Since I had the transmission out I decided to pull everything back out and inspect it since I had ran it with no circulation of the fluid.  Everything seemed to look ok until I found this:


Which is 654c in the skematic in the input clutch housing


So moving along I reassembled everything and reinstalled the transmission for the second time now ain:   I started the truck up and it had a slight strain on the engine causing the headlights to dim due to lower RPM's.  Well that went away after a minute of running and I checked the fluid and well I got the TC right this time.   So backing out the garage I had reverse!!  So putting it in drive for the first time I took off real easy.  First gear then shifted to second gear (slightly harder shift then before the rebuild/shift kit).  Second gear rev'd up to 3K rpm and then it just broke, as in it dropped off like it was in neutral or slipping.  It never went to 3rd gear.   So once it slipped out of 2nd and it went back to first gear it never would shift back to 2nd gear.  Just stayed in first gear.   I brought the truck back home and called it a night.  

The next morning I went out for another test drive, shifted from 1-2 and then the same thing happened.  So I proceed to pull the plug on the harness to run the truck in default.  In DRIVE there was no 3rd gear, it was in first gear.  Manual shifting I could get 1st and 2nd gear and they function well.  At WOT it will still not shift from 1-2 with the harness plugged up.  

So I pull a code from the CEL and I get the DTC P0741 which is the TCC.  But from the research I have done even with the TCC being faulty (could be several reasons why it tripped the PCM) that should not effect me from shifting into 3rd gear/OD

Right now I have reverse and only when the truck is cold I have 1st and 2nd gear until it warms up then I only have 1st and reverse.

I am giving in and finally posting for some help! I am at a loss on what to do, what to check, and really not looking forward to pulling the transmission back off again  Maybe someone with more experience than me can chime in.  And help me out.  

This is my best guess. The 3-4 clutch pack is not working so when the trans shifts to third it neutralizes. After that it goes into limp mode. In limp mode when the shifter is in D or OD the trans is locked in 3rd gear. In manual 2 you get 2nd gear. So when you're in limp mode your trans is locked in 3rd except your 3-4 clutch pack isn't working so all thats applied is the forward clutch and the rear sprag which are the same components applied in 1st. When you shut the engine off the computer resets and it will shift from 1st to 2nd again but when it tries to shift to 3rd and 3rd isn't there it goes into limp mode again. Now why is there no third? You may have cut one of the teflon seals on the input shaft when you put in the pump. Did you have the tool to install and resize those seals? You could have assembled the main drum improperly. Is the 2-3 accumulator installed properly? Is the accumulator housing under the pan possibly loose?{3 bolts}. Did you use the wrong valve body gaskets? Are you sure the checkballs are in the right places? ....What you should do first is scan the computer again. If it is going into limp mode there should be other codes besides the PO741. Another thing you could do is drop the pan and check the accumulator housing. Next drop the valve body and check the 2-3 accumulator in the case and make sure you have the checkballs right and the valve body gaskets right. Next air check the 3-4 clutch pack.  Let us know what you find.  

Thanks for the very useful info and for the past few days I have been continuously working on the transmission.   And here is where I am at so far.

I pulled the transmission back off the truck and started to disassemble it again. I noticed the very bottom teflon oil seal on the input shaft was cut in half and missing a very tiny piece once I pulled the pump out. This could be due to be not having the correct tool to install those rings. Then i pulled the input housing out and then air checked it again and it functions but I did not check the clearances because I could not locate the required spacing. I disassembled the housing and did not notice anything else damaged. The stator tube was fine.

Ok, after putting the trans back together and using the input shaft seal tool, also verifying that the 3-4 clutch pack was installed correctly and checked the clearances. As well as air checking everything and recleaning of the transmission.  

When I test drove, the transmission was doing the same thing but this time throwing DTC P0757 (solenoid B stuck on).  I did some research and found this:

:
Some customers may comment on any of the following conditions:
• An illuminated MIL where DTC P0757 is found as a history code in the PCM or TCM;
• No third and fourth gear;
• The transmission does not shift correctly;
• The transmission feels like it shifts to Neutral or a loss of drive occurs; and/or
• The vehicle free wheels above 30 mph. High rpm needed to overcome the free wheeling.
This condition may be caused by any of the following:
• Chips or debris plugging the bleed orifice of the 2-3 shift solenoid (367). This will cause the transmission to stay in second gear when third gear is commanded and return to first gear when fourth gear is commanded.

• A 2-3 shift valve (368) or 2-3 shuttle valve (369) that is stuck, restricted and/or hung-up in its bore.
This condition may also be an indication of a damaged 2-4 band or 3-4 clutches. This clutch damage may generate debris causing the 2-3 shift valve line-up to stick in the valve body bore and set DTC P0757.
1. Inspect the condition of the transmission fluid for signs of overheat or a burnt odor. If either is noted, the transmission should be disassembled for further investigation and repaired as needed.

See Figure 1.
2. Inspect the inside of the oil pan for signs of clutch friction material. A small amount of friction material in the bottom of the pan is normal. If a large amount of clutch material is noted in the fluid or bottom pan, the transmission should be disassembled for further investigation and repaired as needed.
3. Inspect and clean the 2-3 shift valve (368), the 2-3 shuttle valve (369) and the valve bore of debris/ metal chips.
4. Inspect and clean the 2-3 shift solenoid (367B) opening of debris/metal chips. While inspecting the 2-3 shift solenoid (367B), look for a screen over the solenoid opening. If the solenoid does not have a screen, replace the solenoid. All current GMSPO stock shift solenoids have a screen over the solenoid opening.
5. If clutch debris is found, it is also important to inspect the pressure control (PC) solenoid valve fluid screens. Clean or replace the PC solenoid as necessary. It is also important to flush and flow-check the transmission oil cooler using J 45096.

Refer to SI “Automatic Transmission Oil Cooler Flushing and Flow Test” for the procedure.



Just for kicks, I went ahead and replaced the solenoid and pulled the 2-3 shuttle valve out and cleaned the bore.  Reinstalled the pan and test drove it only to have the same exact thing happen.  

I have gone through the valve body with a tooth pick, the gaskets are the correct gaskets, all 7 check balls are in the correct locations.  The forward accumulator is installed correctly.  

I dont see how I could have burnt up the clutches on 3-4 with less than 5 miles on them.   I also dont know what the hell is going on to stop it from shifting to third.  

Video of the test ride after I got it all back together (before the solenoid replacement)
http://www.youtube.com/watch?v=0yLup4_xqRA  

some of the resizing tools are shown about half way down this page..

they are available from several sources...

http://www.transmissioncenter.net/Tools.htm




#39X. 700R4 / 4L60E Teflon sealing ring installation tool. Makes Teflon seal installation and resizing easy and perfect every time. These are the four rings on the input shaft and they can't be installed without this tool. Cost $158.00. (Here's what happens if you install these rings by making an angled cut. (a) The rings get hot, expand and overlap. (b) The rings stick together at the angled cut. (c) Then when they cool off and contract they're too small. (d) The next time you drive the 3-4 clutch burns up. (e) Even if the rings don't stick they hold the pressure better if not cut.)


i don't build transmissions very often.. and even i have a set of these..   along with some of the other 700/4l60 tools  

First off, Wayne is correct, that is the tool that is used to put the rings on the input shaft.  However, most sizing tools wear out after time (I am assuming you borrowed it from someone).  

That being said, the best "sizer" for the rings on the input drum is the part that rides on it.....the pump.  I'll betcha ya cut the rings when installing the pump (again), I have done so many times when my sizer got worn out.  So here's a tip, that may help...set the pump on the drum for at least fifteen minutes....rotating it every few minutes....this will help to properly size the rings.

Then, when you go to install the drum and pump thereafter, be very careful to "draw" the pump down onto the case and also onto the drum "slowly".  By this I mean to tighten in a criss cross pattern...without tightening too much until the pump goes down evenly.  If it feels like it is getting too tight or something does not feel right.....pull the pump and double check the rings...lot of work I know but a hell of alot easier than pulling the tranny out again.

Hope this helps ya out brother, and keep us informed either way!!  

I hate to say it but i think you may have cut a teflon seal on the turbine shaft again.When you air checked the input drum did you do it through the pump or right from the input shaft? Did you air check it again after the pump was in the trans? Did you have any difficulty getting the pump all the way down? Did you have to hit it with anything or were you able to push it down by hand? Did you have the trans standing straight up when you put the pump in? That PO757 is one of the codes i expected you to find the first time. Its possible there is something wrong with the valve body but its not likely. Judging from the video the electronics and valve body are working but the 3-4 clutch hydraulic circuit is leaking. You should probably try to air check it through the case before you pull it out again though. Are you lubing up those seals real good before you put in he pump? Try using STP oil treatment that stuff is really slippery.  

hello did you get it figured and fixed, I from scrolling through the thread saw what looks like a broken pump rotor and the plastic piecs is the rotor guide