No reverse and forward doesn't move till 2300 rpm

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#1
Make
Chevy
Model
Trailblazer
Year
2006
Miles
176000
Engine
4.2
I bought my trailblazer from my brother in-laws only a week and a half ago and drove it 380 mules back to where I live. I was driving to town and the Rpm's started getting higher. I pulled over checked the fuild and it was where it was where it should be. Cycled through the gears and reverse was gone. Turned around and went home but i had to bring the rims up before it would even move, check engine light came on as soon as I started moving. Got home and parked it. Got a ride to the parts store, changed the fluid and filter and there was no metal in the pan, fluid was dark but didn't smell burnt. No rattling around the transmission when run through the gears while sitting still. I figured it was screwed and I was going to have to rebuild it but I ran across a couple of forums that discussed the boost valve failure. I'm trying a Hail Mary and ordered a boost valve from Sonnax hoping for the best. I'm currently stuck waiting on UPS to get here was just curious if I even have a chance in hell with this or if I should start shopping for a rebuild kit.
 
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grcauto

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#2
Once out of first gear does it shift fine through the rest of the gears? I believe 1st and reverse use the same drum/clutch pack. Reverse is obtained by applying the band which holds the drum.
What codes did you get?
 
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#3
I'm currently living in the middle of nowhere and have no way to get to a shop or parts store to get the codes read and nobody I work with has one either. I could still feel a drag on the transmission when I was driving it home but it was going through all the gears. I can feel it go into reverse but not enough for it to move, it felt like I had my foot on the brake and put it in gear but the rpm's just rise with no movemet. I've been afraid to try anything with the truck cause I don't want to cause anymore internal damage if I have to rebuild it, which will end up being my first one I have done.
 

billr

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#4
Tearing into an auto trans is not a trivial or inexpensive project. I suggest you invest in a scanner that will read codes and live-data for all codes; be sure trans is included. Or, how about and ELM327 type connection to a laptop/phone? Those take more fiddling, but can be much less expensive.
 

grcauto

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#5
I was thinking you may have a bad seal for the piston of the 1st/reverse clutch but that wouldn't account for the drag in the upper gears. Codes may help but pressure gauge and readings are a big help also. I'm not sure but I think you have the 4L60E. ATSG is a good resource manual for doing work on these.
Keep us informed.
 

billr

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#6
Agreed, pressure readings are probably going to be needed. First, though, confirm it is the 4L60E. That is the only type auto-trans that I have interest in anymore, so I will eagerly research and learn along with the OP. To tell what type the trans is, look for a P/N tag on it (usually near tail-shaft?). Or, maybe it will be coded into the VIN. Photos may help, too; especially looking at the pan shape and bolt pattern.
 
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#7
It is a 4l60e, there's 16 bolts in the pan and it shallow. I ordered a Bluetooth obd2 reader and it should be here Monday morning. I work nights which limits my ability to get rides anwhere, because everyone else is working while I'm off. I have access to go get whatever I need to help diagnose it Saturday so I'll hopefully be updating that night. Thank you
 
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bp042665

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#8
we are here to help this is what i do for a living i build transmissions i have seen this but it is most likely going to have to come out to fix the first set of clutches at the bottom of the case is low and reverse but reverse also has a drum and what i have seen is the 3/4 clutches will weld to the steels and stay applied and it is locking up the movement in reverse and drag in high gear when going forward giving high rpm going forward
 
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#9
OK update. Over the weekend I ohmed every fuse and only found the one marked Rain blown, changed it to no big surprise nothing no drive line affected. Also noticed that the shifter wouldn't go all the way to 1st. Adjusted the cable and it worked as advertised, indicator went to all gear selection. Now when I went for my test drive and put it in d the hesitation in first was actually starting in 3rd and shifted to 4th like its supposed to. Manually dropped it in first and it was like I was dragging g a house behind me, it got up to 3500 before it moves, second gear was the same and still no reverse. Got my code reader last night before I came to work and to my surprise the only two codes I had were p506 and p0128 WTF. How can my transmission be this screwed up and not throw one code that is helpful. I await any help please I'm more than confused at this point
 

billr

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#10
I gotta ask... are you sure that code reader will display trans codes? As a sanity-check, disconnect a trans fuse or electrical cable and verify that a reasonable code is set and read. Is the CEL never set, does it come on properly at key-on? Like you, I'm surprised if no code is really being set. My 4L60E sets "P1870" (internal slip) periodically, even though no bad operation is noticeable. I would think you would, at least, be getting that catch-all P1870.
 

grcauto

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#11
The generic codes should be available with any code reader since it's a "P" code. That being said I would expect some kind of code with the symptoms he describes.
 

billr

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#12
I don't think all P codes are generic, only up to P1000 are generic and supported by all readers.
 

grcauto

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#13
Shouldn't this thing set a P07xx generic code with symptoms like this? I admit I never used a generic code reader and can't say for sure but for slippage in this degree I can hardly think a generic code would not be available.
 
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#14
The code reader is a kiwi3 and I currently running torque. I'm still trying to figure this thing out and or trying to if a different program will work. I am just a carburator adjustment, swap parts type of person. Cars now adays are computer on wheels and I don't speak the language very well
 

billr

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#15
Okay, but confirm that the CEL (check engine light) comes on at key-on, then goes off after the engine has started. Let's get past that primitive test.