Need help with my new 97 GMC Sierra 5.7L

Alexx · September 11, 2016

So yesterday I bought a new truck as a second car for work. Its got a load of miles (237k) but it was pretty damn cheap so I wasn't really worried. It's an automatic 4L60e tranny with the 350 vortec motor.

First of all, whenever you're on the highway and you give it a lot of gas, its seems to struggle and slip. It's fine if you ease into the throttle, but if you floor it, the truck doesn't like to accelerate.

Second of all, something looks like it's missing in the engine bay. Here's a pic: https://imgur.com/78K7Gmk

you can see some wire is unplugged and there's 2 holes empty.

Third of all, the AC doesn't blow cold. I can here the AC Compressor kick on, but the air is warm.

Also I noticed the car didn't really shift smoothly, so I dropped the tranny pan (it was a huge pain btw) and the fluid was really nasty. It was a dark brown. I checked the dipstick and even when the engine was running and hot, there was no fluid on the dipstick. I changed the fluid and it seems to shift fine now when driving normally, but still struggles when you floor it. Could it just be a tired transmission?

txab · September 11, 2016

That's where your refrigerant lines connect to the compressor and yes, your trans is worn out

Alexx · September 11, 2016

That's where your refrigerant lines connect to the compressor and yes, your trans is worn out

Ok so that's probably why the AC isn't cold... Could I just buy the lines and hook them up and get the system filled with freon? Or is it more complicated than that?

About the tranny, is there anything I can do to prolong the life of it? I'm not going to be driving this truck often, maybe 100 miles a month.

diyer2 · September 11, 2016

Cheap? From your post it may not end up being cheap to get a reliable truck.

If the trans is the problem and IMO it seems to be the case $2k to replace.

A/C $600/$1000.

These are guesses having the work done.

Alexx · September 11, 2016

Cheap? From your post it may not end up being cheap to get a reliable truck.

If the trans is the problem and IMO it seems to be the case $2k to replace.

A/C $600/$1000.

These are guesses having the work done.

I can do the work myself. If the tranny really is toast (it still shifts fine, just doesn't really like aggressive driving), I can replace it myself for under $500. I can deal without the AC if it comes to it.

barry G · September 12, 2016

a/c is cheap for these.

get whole new pump.. check ebay and stuff.

the best deal yet is getting anew one that needs the pressure relief in the back of your old one.

knocks off hundreds. I used a cutoff wheel and dissected my old one..just for the relief the new one needed.

As it turns out, it is an exact prt number and pressure. Original GM version does not fail.

I bought gauges, a vacuum pump and have used it more than once, yesterday was for my neighbors.

you get the pennies back...and choose any fluid you want.

the tranny, it is either ignore all of 'em to get an nv3500, or pay for a very good rebuild. the second time around really strengthens them.

as these wear, the slip equals heat..this dominoes to the darndest things, including fires elsewhere.

Don't delay on the tranny.

speaking of heat..after 96, the a/c is part of oil and radiator cooling. Quite noticable. Even changes oil pressure for the better.

Alexx · September 12, 2016

Well turns out I have a bigger problem in my hands...

I noticed that the tranny fluid level was low again, and so I added some more today, and when I parked my car I noticed that the tranny pan was leaking... a lot...

The car shifted great before it leaked out, so I'm guessing that I'm gonna need a new pan.