Tranny Problem

I have a '97 Blazer LT with auto & 4WD. Got a code light that is a P0740. When the truck is cold it starts out in 1st and will shift up (I'm not sure if it's 2nd). When I stop at the first stop sign, it only starts out in 2nd or 3rd, and will stay there, even at cruising speed. It will not down shift after the first stop, or shift to high.

Is it curtains for my tranny (like a rebuild), or is a chip thing or something electrical that can be handled fairly easily.

Thanks for any help.

A code P0740 is a TCC lockup solenoid electrical circuit problem.
But it sounds like yours is going into fail safe mode.
You need to get it on a transmission capable scanner and get more details and info on what is going on.
You may have more codes or problems than the 740 code.
And member 97 is a year for bad ign switches which can cause many transmission problems.
MT

A code P0740 is a TCC lockup solenoid electrical circuit problem.
But it sounds like yours is going into fail safe mode.
You need to get it on a transmission capable scanner and get more details and info on what is going on.
You may have more codes or problems than the 740 code.
And member 97 is a year for bad ign switches which can cause many transmission problems.
MT

Funny you mentioned that. It is a '97. Around the same time I did have an ongoing ignition problem that had two symptoms. One was the key didn't work very well, and the second was I couldn't always get the key out after shutting the truck off. At the same time I had the trans problem of it not downshifting into 1st or ultimately shifting into "high".

Well, I thought I'd fix one at a time so I went to a steering column guy that said the key problem was twofold. First the key was cut wrong and not always working right, and second the sensor that keeps the key from being removed while driving was bad. So, he put in a new lock and removed the sensor. So now the ignition and key works great but still have the shifting problem.

Before I go and get a trans rebuild, are there any suggestions?

The ign key part is not the ign switch.
The ign key only turns the ign electrical switch on and off.
You need to have a look at and check the electrical part of the ign switch.
97 was a bad year for them and they cause many transmission and engine running problems.
Get out the old volt/ohm meter and check for good voltage out of switch to transmission computer.
Have you got in on a good transmission capable scanner yet?
MT

Get out the old volt/ohm meter and check for good voltage out of switch to transmission computer.
Have you got in on a good transmission capable scanner yet?
MT

I was never one to buy a one time tool. If I need to do that, I will. I'm not an avid mechanical whiz. About a year ago, I couldn't get the trans out of "Park" and the dealer changed some "switch" in the steering column. I also don't want to go to the dealer for repairs unless it's the absolute last resort. If nothing else, can a transmission shop diagnose the problem. Is it an electrical problem instead of a trans rebuild problem?

If you are going to do any mechanical work or electrical work a volt meter is a tool you will need a lot.
If you do not want to fix it yourself find a good repair shop.
Some transmission chain stores are to transmission rebuilt gong ho.
But from what you have described so far you have a bad ign switch.
But needs proper testing with a volt ohm meter to be sure.
Good luck
MT.

But from what you have described so far you have a bad ign switch.
But needs proper testing with a volt ohm meter to be sure.
Good luck
MT.

I do have a VOM, and am OK with using it. When you mentioned a transmission scanner, is when I choked up. So, do I have to take apart the steering column? Exactly what does the switch look like, and how is it checked, and what's it suppoosed to read. And finally, where and what does the transmission computer located/look like, and is it supposed to be checked?

Sorry about the stupid questions, I'm a cabinetmaker, not a mechanic.

You need a good service manual with a wiring diagram.
Factory service manual or a all data sub.is the best.
Also a lot of public libraries have car repair info.
Run a google search.
Check all power feeds to the ign switch and power output.

Check and test the ign switch.
Then if you still have problems find a good repair shop with a transmission capable scanner and have them check the transmission and engine pcm out.
Good Luck
MT

You need a good service manual with a wiring diagram.
Factory service manual or a all data sub.is the best.
Also a lot of public libraries have car repair info.
Run a google search.
Check all power feeds to the ign switch and power output.

Check and test the ign switch.
Then if you still have problems find a good repair shop with a transmission capable scanner and have them check the transmission and engine pcm out.
Good Luck
MT


Thanks for the advice. Time for overalls & floor jack. Maybe even a repair shop. I'll give it a go first.