Hello, this is my 1st posting anywhere. I have a 1993 GMC 1500 2WD, 305, 4L60E. I bought this truck with a "bad" tranny, not shifting above 2nd gear. I asumed it was a bad transmission, so I pulled a recently rebuilt one from a 93 GMC Safari. Both tranny's are M30 versions. This tranny drove / shifted perfect in the van. After install, I have the EXACT same problem, in D, or OD, it shifts 1-2 perfect, then it tries to shift 2-3, but just revs up, so I shift manually. I have nothing above 2nd gear. My "Check Engine" light was on, so I ran a diag, and got a code 43. (Knock Sensor) I replaced the sensor, and reset the puter. (Unhooked battery for 5 minutes) No codes stored, runs great, but still nothing above 2nd gear. What am I missing? I changed torque converters too. Any help would be GREATLY appreciated. I have checked for 12V at trans fuse, and have it on both sides. All fusible links have 12V on both sides. I'm about ready to scrap this truck, so you are my last hope. Thanks. :confused:

You are thinking hardware, you need to start thinking sofware ! (Either the CPU is not telling the tranny to shift/or the tranny in not getting the message)

Mike D.

Thank You for your input, I am thinking about swapping computers with the 93 Safari I got the tranny from, the #'s match on it's PC, and mine, and the prom #'s match too. I'll give it a try. Any other sugguestions are welcome. Thanks!

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being that both trannies are doing the same thing. I would start at the speed sensor. It may have low or no voltage. Then I would start checking the connection of the main harness to the trans. Make sure there are no greenies. then go on to the computer.

i had one kill the direct clutch. 1-2 was fine, then it would neutral out for the 2-3. i've had 3 700R4s do this to me as well.

where is the direct clutch? It has to be a problem external to the tranny, as I have replaced it twice, with the same results. Thanks.

Sounds to me like you are putting the trans into "limp home mode" The 60E, and 65E when they get confused they will go into a mode that gives the truck 2nd gear only with full pressure to save the trans.

It is most likely caused by the speed sensor. Does your speedo work? If it does then you have a problem inside the trans, with either a shift solenoid or pressure switch.

Crazy question, do you have one of those remote starters on the truck?

Hello, this is my 2nd tranny, and I'm having the same results, however, the speed sensor is off my old tranny. I added a ground strap from - BATT to the frame in hopes of having a bad ground, no luck, I did a purge test on the tranny, and no luck, today I plan to replace the ECM/PROM and speed sensor. My speedo does work fine though. I do not have a remote start. :bounce2: :crybaby2: I just don't see how a perfectly good shifting transmission out of a GMC Safari could have lost a solenoid during install, and have the same exact problems my rebuilt tranny had. My old one has only 38K, with the updated valve body. It's really hard to believe that both tranny's have the exact same problem, and both were working fine. I was told that there are 2 computers inside the ECM box, one for motor, and one for tranny, and that sometimes the tranny board / TCM can go bad. But I get a code 12 on diag, so the ECM thinks it's good, it runs great, just won't shift. Any other sugguestions would be appreciated. Thanks for your post.

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Hello, this is my 2nd tranny, and I'm having the same results, however, the speed sensor is off my old tranny. I added a ground strap from - BATT to the frame in hopes of having a bad ground, no luck, I did a purge test on the tranny, and no luck, today I plan to replace the ECM/PROM and speed sensor. My speedo does work fine though. I do not have a remote start. :bounce2: :crybaby2: I just don't see how a perfectly good shifting transmission out of a GMC Safari could have lost a solenoid during install, and have the same exact problems my rebuilt tranny had. My old one has only 38K, with the updated valve body. It's really hard to believe that both tranny's have the exact same problem, and both were working fine. I was told that there are 2 computers inside the ECM box, one for motor, and one for tranny, and that sometimes the tranny board / TCM can go bad. But I get a code 12 on diag, so the ECM thinks it's good, it runs great, just won't shift. Any other sugguestions would be appreciated. Thanks for your post.

That is a good point, I think it is obviously an external problem....I would start with the speed sensor. But since your speedo works fine I am kind of lost.

Is there any other work "done" to this truck E.G., engine mods, stuff added to the harness like stereos and such.

When did this problem first start?

I had this problem once with a H1 hummer. I freaked out when it stopped shifting and almost panicked. I knew it would cost me my right arm and firstborn. I jumped under it and undid the big connector at the trans. Didn't see any thing but did this over and over several times. Worked O.K. for 2 years after that:grinpimp:

Well there was a system in it b4 I got it, but it drove fine then, there is keyless entry, and starter kill, but all was working fine. There is no system now, and all wiring was removed. I was driving from Tulsa, OK on I-44 and it just lost everything above 2nd?? Never shifted again. There are no mods at all. Just my family / work truck. It's got me lost too. I'd send it to a service dept if they weren't so expensive. I just can't afford it.