1992 Chevy 1500, transmissin in "limp home" mode


#1

I have a 1992 1500K extended cab 4WD with the 5.7L V8 engine (147,000 miles). It has been driving well since I bought it last winter. 2 days ago I took it on a longer road trip and it was doing great. Slowed down to take a 90 degree turn and the transmission suddenly hit “limp home” mode. It felt like it wasn’t up-shifting out of 2nd , high RPMs while driving no more than 30mph on flat road.
I have the proper amount of fluid and it is still red/pink and does not smell burnt. Someone suggested that I check the transmission fuse but in looking through the fuse box I can’t tell which is the tranny fuse.
Also, I can only find one fuse box on my truck. Is there a 2nd?
I feel like my next step is to take it to a transmission shop but I want to rule out whatever I can at home. I have zero experience with transmission work and don’t want to get scammed into a rebuild if I don’t need one. The transmission was working fine up until 2 days ago. No slipping, no hard shifting, and no noise


#2

Owner’s manual identifies which fuse is which and there might be an additional fuse box.
Otherwise pull and look at each fuse to see if they’re blown.
Then order an owner’s manual.
You can see a pdf of the owner’s manual at justgivemethedamnmanual.com


#3

Cool, I’ll check it out. I ordered the manual online since none of the auto parts stores near me have one in stock.


#4

The website you mentioned didn’t have a manual available for my model year. I guess I’ll wait until the one I ordered gets here. Thanks for your quick reply.


#5

Have you tried jumping between the A & B terminals on the DLC connector under the dash to see if any tranny codes are stored?

Tester


#6

I have very limited knowledge about how to read stored codes. The check engine light is not on but my understanding is that the car could still be storing codes? There is a Napa nearby, I could run it by there and see if they can plug their scan-tool into it.


#7

Try this (click) out. It’s quite simple.


#8

That does look simple enough. Would I just use a multi-meter to ground the terminal?


#9

Ah, never mind. I just saw that the preferred tool for this is a paperclip. :slight_smile:


#10

Many things are still much lower tech than one might think :wink: It you do get codes, post the specific 2-digit code numbers.


#11

Roger that. Thanks for the help.


#12

OK, I pulled the codes and it just ran the 12 code (diagnostic mode) over and over. I assume this means that there are no stored codes. Just for laughs I took the truck on a test drive and it started shifting into 3rd and 4th?!?!?!. It’s shifting hard but it is getting into gear. I’m thinking it’s time to take it to a shop. Thank you for all your help. I’ll get it to a shop on Tuesday and post what they say just to make sure it all sounds good.


#13

@fkoski‌

Please do NOT take it to AAMCO or any of those other big name franchised Transmission shops. They will sell you a rebuilt transmission, even if you don’t need it. And if they’re wrong with their diagnosis, the ugliness will begin.

Maybe you do need a rebuilt transmission, but AAMCO has a vested interest in selling transmissions . . .

By the way, if in the end, you do need a rebuilt transmission, I suggest having a genuine AC Delco unit installed. The 4L60E has had many changes and updates over the years, and if you get “the real thing” you’re likely to get those upgrades. Not only that, but I believe AC Delco units have a fairly good warranty.

If your transmission failed catastrophically . . . metal shavings, broken pieces, etc. . . . I suggest having the transmission cooler, torque converter and all the lines flushed. If any of the trans cooler hoses and lines look questionable . . . as in oily or greasy . . . replace them. It’ll be almost no additional labor, if the trans is coming out anyways.

If there’s any doubt about the torque converter, have it rebuilt or replaced.

This may sound drastic and expensive, but if you need a transmission, you want the best parts and the best and longest lasting repair possible, so that your truck will serve you for many more years to come

Good luck, and please keep us updated


#14

Thanks. I’m hoping it doesn’t come to needing a rebuild. Really not looking forward to spend $2000. I love this truck though, so I’ll do what I have to.


#15

@‌fkoski

Does the truck look pretty decent?

Is the engine still pretty strong?


#16

Engine runs strong and the truck looks great. I am the 3rd owner and the first two took amazing care of it. I’ve left it parked for the last 5 days and there isn’t a single drop of oil, antifreeze, or any other fluid on the ground under it. Other than the transmission issue the truck has given me no trouble.


#17

Hi everyone, had a development with the truck. I drove it to work this morning (approx 5 miles with 3 stops) so that I could get it to a shop on my lunch break. It shifted into 3rd and 4th but it was shifting “hard”. As soon as the engine hit operating temps (approx 4 miles) the transmission went back into “limp home” mode. I’m not sure what that means, if anything, but thought I would post it since you all have been so helpful.


#18

GM transmissions can do some weird stuff when the TPS starts going bad. The TPS won’t set a code, but it can start sending bad data to the computer. Transmission goes into a delayed, hard shift mode. Never had mine go into limp mode. But a TPS is a lot cheaper than a new transmission. Might want to try that to see if everything clears up.


#19

I’ll check it out. Wouldn’t I be having other issues if the TPS was bad?


#20

OK, the problem is definitely worse once the engine his operating temp. It will shift hard until the engine gets warm and then it will go into limp home mode.