4L60E lost first and overdrive

94 Chevy S-10 Blazer 4X4 4 door w/4.3 Vortec CPI , 135,000 miles. Situation goes as such, vehicle drove normal on way to work, but on return trip home i noticed as soon as i put in in OD (as i ussually do) what i thought was first gear was slipping.i drove aprx. 2 miles to nearest gas station to check fluid level in transmission. it was barely touching the stick ..so i added 1 quart to bring it to top of full hot line. Noticed no change in 1st gear slippage. I got on highway for my 22 mile trip home and noticed only one shift to get up to 65mph then realized it was starting in 2nd gear and only shifting to 3rd without ever going into overdrive. i Stopped, put the shifter into 1st and tryed shitfing manually,but still no matter how i shitfed still only 2nd and 3rd gear existed. Realizing this is a serios problem ..i reseached the interweb for info and found that this could be a electrical problem and needed to be put on a diagnostic machine. Took the Vehicle to "Gene's Transmission Shop" 1 mile from my home and asked him to check it out for me. When i picked the vehicle up the mechanic told me that it was definatly electrical and his Snap-on tester reported that the solenoid was fuctioning and that the computer was calling for the overdrive shift. But would not tell me exact cause of the problem. I believe he withheld the information because he knew that i wanted to do repairs myself and he wanted the 3hrs shop time and parts cost. After much reading i know that their could be several reasons for this problem. Such as Bad PCM/Bad Shifter Solenoid/Ignition switch/broken wiring/etc. Since i got my vehicle back from shop i have done a fluid and filter change myself which involved dropping the exaust from the manifolds to drop the pan. I examined the fluid carefully it was only slightly discolored and did not smell burnt ,there was no signs of burnt clutch remains or shards of metal although the magnet in the pan had an abundence of liquid metal attached to it which i would consider normal for the milage. Wish i had installed a drainplug before reinstalling the pan. If ANYONE could tell me what would be the most likely cause of this loss of 1st and overdrive or even an opinion on what i should do to remedy this problem PLEASE leave a post. I am without transit until i resolve this issue because i will not drive the vehicle (other than to test drive attemps at fixing) until it is fixed...Thank You for your help .....sincerly Grateful.

With the 4L60E transmission, this is called Failsafe mode (3rd gear starts unless the selector is placed in D2 or D1,then it has second gear starts). In failsafe mode, you will only have [R] [2] [3]. As seen from the shift pattern below, the most frequent cause is a bad 1-2 Shift Solenoid (approx $20 dealer part) under the transmission pan.

Solenoid
Gear 1-2 2-3
---- ---- ----
1st On On
2nd Off On
3rd Off Off
OD On Off

With the 4L60E transmission, this is called Failsafe mode (3rd gear starts unless the selector is placed in D2 or D1,then it has second gear starts). In failsafe mode, you will only have [R] [2] [3]. As seen from the shift pattern below, the most frequent cause is a bad 1-2 Shift Solenoid (approx $20 dealer part) under the transmission pan.

Solenoid
Gear 1-2 2-3
---- ---- ----
1st On On
2nd Off On
3rd Off Off
OD On Off


Thank you Brian ...could you possibly explain the location in more detail , i have had the pan off several times and seen lots of electronics in there . Do they just go bad or does sumint inparticular cause this failure?. will replace and post results A.S.A.P. and again Thank you Brian

Thank you Brian ...could you possibly explain the location in more detail , i have had the pan off several times and seen lots of electronics in there . Do they just go bad or does sumint inparticular cause this failure?. will replace and post results A.S.A.P. and again Thank you Brian

sorry I don't have access to a picture right now (picture worth a thousand words and all). anyway, the 1-2 shift solenoid is located in the front left-hand side of the valve body. the 2-3 shift solenoid is located immediately to the right. both solenoids will have a two-pin wire harness connection (+12VDV and Enable/Gnd).

as to the cause of failure ....
1) ensure that +12VDC is getting to the transmission. if not careful when replacing pan after fluid/filter change etc., the trans wiring harness can be pinched/crushed causing the trans fuse in the fuse box to blow. new wiring harness is $125+. doubtful failure since service personnel indicated ECM was calling for shift but none occurred.
2) bad Enable/Gnd wire from ECM to 1-2 solenoid - again doubtful since your service guy indicated the ECM was calling for a shift but none occurred.
3) bad solenoid - normal failure. can test solenoid by using jumper wire to short the Enable/Gnd lead to ground (or side of transmission) and listen for a click from the solenoid. use extreme caution when testing - key to ON not RUN; engine NOT running; short ONLY the Enable/Gnd lead and NOT the +12VDC.

I have the exact same problem!!!!!! Only mine is a 97. I think we have different electrical parts and computers--think I read that somewhere. We have replaced our solenoids and still have the same problem. I'll keep you posted if we find a fix!! Goodluck-and keep me updated also if you find the magic.!!!!

i have a couple of pictures, that will help,,, for some reason i'm unable to upload them to post here but can send as email attachments, they are a .jpg and a gif file....i you want them i will email them. just tell me where..

Thanks 99church --i am open to any and all suggestions at this point. I hope I am smart enough to figure out how to open these 'files' your gonna send. Not the best at this puter stuff. I try to stay close to the things I'm familiar with--grease and dishes. lol--thanks for the reply please send your info to : jgalbreath3790@charter.net-----thanks again :)

Thanks 99church --i am open to any and all suggestions at this point. I hope I am smart enough to figure out how to open these 'files' your gonna send. Not the best at this puter stuff. I try to stay close to the things I'm familiar with--grease and dishes. lol--thanks for the reply please send your info to : jgalbreath3790@charter.net-----thanks again :)


Just sent them to the above email address, both files are attachments, highlight one of the file names (electrical.jpg or 4l60e.gif) and you will get a warning box about viruses click open and it will display(there are no viruses in either files) i had to change the pwm tcc solenoid on our blazer ... piece of cake,,,,,,

could you please e-mail those files again. I didnt get them. Just reconfigured the e-mail so I should be ok now. I'll let you know if it works. Thanks again.:)

i have a couple of pictures, that will help,,, for some reason i'm unable to upload them to post here but can send as email attachments, they are a .jpg and a gif file....i you want them i will email them. just tell me where..


The Email Addy For Me Is whiteboytylenol@yahoo.com. those pics would be very much appreciated. thanks for the post 99Church.

The Email Addy For Me Is whiteboytylenol@yahoo.com. those pics would be very much appreciated. thanks for the post 99Church.


UPDATE!..ATTENTION Brian :)
.I have just replaced the solenoid,ordered from the local chevy dealer .(had to wait for part to install) and still no change with the exception that i took the vehicle for a 100 mile test drive (50 one way and 50 back).Seemed that the tranny slipped in to OD several times after the first 30 miles. this occured maybe 4 times...which i would have stayed in OD for the whole trip but i was on a toll road. Even though i had OD ,when i came to a stop at the tolls i had no 1st gear during take off (so i downshifted in 2nd) and once up to speed it still didnt shift into OD with proper timing (took a few miles before it kicked into OD) This intermitant OD might have existed before i changed the solenoid but i dont know because i didn't drive the vehicle once i knew there was a problem. This is starting to sound like a wireing problem (more so a ground problem).maybe you could tell me the most likely places that the wireing breaks down (connecters,contacts,etc.)If you have any questions that i could answer to help, please feel free to email me at whiteboytylenol@yahoo.com . Though i am trying to be as indepth as possible I may be leaving out critical information. Once again thank you so much for your time and effort .Sincerly greatful .

UPDATE!..ATTENTION Brian :)
.I have just replaced the solenoid,ordered from the local chevy dealer .(had to wait for part to install) and still no change with the exception that i took the vehicle for a 100 mile test drive (50 one way and 50 back).Seemed that the tranny slipped in to OD several times after the first 30 miles. this occured maybe 4 times...which i would have stayed in OD for the whole trip but i was on a toll road. Even though i had OD ,when i came to a stop at the tolls i had no 1st gear during take off (so i downshifted in 2nd) and once up to speed it still didnt shift into OD with proper timing (took a few miles before it kicked into OD) This intermitant OD might have existed before i changed the solenoid but i dont know because i didn't drive the vehicle once i knew there was a problem. This is starting to sound like a wireing problem (more so a ground problem).maybe you could tell me the most likely places that the wireing breaks down (connecters,contacts,etc.)If you have any questions that i could answer to help, please feel free to email me at whiteboytylenol@yahoo.com . Though i am trying to be as indepth as possible I may be leaving out critical information. Once again thank you so much for your time and effort .Sincerly greatful .


just re-sent pics , check the electrical connections at the tranny , i remember reading a post about a problem with those connectioins, also the ignition switch (it provides power to something on tranny) there is a post on that also,, i have both posts on my system in my blazer folder.. if you need em,,,,,,, good luck !

just re-sent pics,, check the elect connections at the trans i remember reading something about those being suspect, also the ignition switch, there is a prob ( i think it provides power to something on tranny) there are posts about both of these issues,, if you can't find , i have them on my system in my blazer folder.. if you need em, good luck

Sorry, no pics of the transmission wiring harness. However, you may be able to get your local Chevrolet Service Dept. to print one out for your year vehicle (believing that their parts dept will be getting your business).

Intermittent OD could be worn valve body; however, with no 1st, still sounds like an electrical trouble to me as well. Since 1st and OD share the same shift solenoid (1-2), this is the most logical place to start. Before the 1-2 solenoid was replaced, did you test it by shorting to ground and not hear a click? Verify the Enable/GND wire from the PCM to the 1-2 solenoid has continuity and is not pinched between the engine and firewall. The +12VDC to the 1-2 solenoid should be good as this is shared to all the solenoids in the valve body.

Had the same symptoms on my '97. Turned out to be the ignition switch...yes, the ignition switch. Figured that out by searching through this forum. Got it replaced, and problem fixed.



Sorry, no pics of the transmission wiring harness. However, you may be able to get your local Chevrolet Service Dept. to print one out for your year vehicle (believing that their parts dept will be getting your business).

Intermittent OD could be worn valve body; however, with no 1st, still sounds like an electrical trouble to me as well. Since 1st and OD share the same shift solenoid (1-2), this is the most logical place to start. Before the 1-2 solenoid was replaced, did you test it by shorting to ground and not hear a click? Verify the Enable/GND wire from the PCM to the 1-2 solenoid has continuity and is not pinched between the engine and firewall. The +12VDC to the 1-2 solenoid should be good as this is shared to all the solenoids in the valve body.

Thanks 99church --i am open to any and all suggestions at this point. I hope I am smart enough to figure out how to open these 'files' your gonna send. Not the best at this puter stuff. I try to stay close to the things I'm familiar with--grease and dishes. lol--thanks for the reply please send your info to : jgalbreath3790@charter.net-----thanks again :)


found a couple of items that may help . i just emailed them, 2 emails, one is about the ignition switch problem, the other is on the tranny and valve body

yo brian D thanks my trans did the same thing as wbtylenol 3 solenoids later trans shifted better than ever thanks again you saved me a nice chunk of change

glad you fixed the problem but this thread is almost a year old. please refrain from posting in older threads in the future.