Help 1997 tahoe

[Matt-man]

I just bought my first tahoe monday morning...the test dive went well and nothing was goin wrong with it. I drove it later that day and I herd a lil knocking noise when I first crunk it up and then it went away. So I changed the oil in it and it still does it. now it is getting a lil worse and you can hear it if you get on the gas but once you get goin it seems to be fine. Someone told me to check the torque converter im not sure so Im asking......and if I need a new motor where can I find one and would it be cheaper to rebuild the one I have? thanks Matt

 

[sasquatch094]

ooh boy, i wouldnt have quite the answer for the knocking noise, but sure as hell its not a pain to get a motor in your truck, its just a little time worthy if you have a job and u go to school like me. but i got my motor out of a 92 jimmy with a 350 thinking it work fine, but i had to replace both manifolds, y pipe, throttle body air cleaner and ect.. it was a pain.. but i have no answer to your "knock".. best of luck with you trying to find out whats wrong..

 

[CRXMotorsports]

97 Yukon here, bought from a fellow racer who had it since it was new. The story goes from him mind you (great guy, but no idea how knowledgable he is/was on these GM products) that the rear mainshaft bearing (towards tranny) was a wrong size on some of the 97s, it was a fraction of a millimeter, but that when the engine was cold you would hear the slapping from the play in it, and as the engine and everything came to temperature, it sealed itself and got quiet. I know my Yuk does it, and it goes away, hasn't gotten any worse the past 10,000 miles, nor have I seen oil levels dropping in my 3000mi intervals. (yes I monitor it) Hope that helps, if yours is getting worse, this may not be the problem, or what I have wrote could be just fabrication from a friend's mechanic, sounded good though yeah?

 

[96ProCompTahoe]

if it goes away when the truck starts to warm up its just the piston sleeves. for whatever reason they didn't put in full length sleeves, and they sort of clack until the truck starts to warm up. (info came from a buddy at NAPA)

Mine does it on cool mornings, but goes away when it warms up. If your continuously does it, take it in to a autozone or advance auto parts or whoever you have local and see if any codes are showing up.

 

[CRXMotorsports]

Could it be throwing codes w/o the CEL light coming on?

 

[SSport]

if it goes away when the truck starts to warm up its just the piston sleeves. for whatever reason they didn't put in full length sleeves, and they sort of clack until the truck starts to warm up. (info came from a buddy at NAPA)

Mine does it on cool mornings, but goes away when it warms up. If your continuously does it, take it in to a autozone or advance auto parts or whoever you have local and see if any codes are showing up.

Mine does the same thing. I'll agree with your explanation!

Could it be throwing codes w/o the CEL light coming on?

Yep. I had a motor go in a 06' SS Cobalt without one light coming on.

 

[Matt-man]

I took it to someone and they said the rods are knocking in it....im looking for another vortec motor to putt back in it and cant find one around here. He also said that running cheap gas builds up on the pistons and makes something called the vortec knock ( I dont know if thats true or not but anyways) and said that it builds up pressure on the bottom end on the motor and causes it to kncok as well. I also was wondering if a motor out of the newer body style tahoes would work in my 97?

 

[96ProCompTahoe]

Rod knock does not go away when it warms up. sounds like your getting screwed out of alot of money.

If you have a rod knocking, it will be really loud and will do it the entire time the engine is running.

 

[Matt-man]

Yea it still knocks as I drive.....it got worse after I drove it a week. and now it doesnt go away

 

[96ProCompTahoe]

sounds like you got screwed on that buy then. did you buy it from a dealer? i'd go back and make them fix it. I was just going off your first post of it going away when it warmed up.

was it low on oil or anything when you checked it out?

i'd drop in a 454...:yesnod:

 

[MarioAngeloBurke]

Stuck Lifters do the same thing. When they are cold when you first start your vehicle they do not expand like they should and leave slack between the Rod and Lifter causing a knocking noise. after they warm up the noise starts to quiet down. If you dont take care of it, the noise will get worse and cause damage. Quick temporary fix is to buy Lifter cleaner. Napa or Franklin Auto Parts (here) have the best cleaners. drive as instructions tell you about 500 miles or so. if the noise goes away keep running the cleaner with every oil change. If it doesn't you could have bent valves

 

[Matt-man]

No the oil and everything tested out ok and the pressure was good in it..I bought the truck for $2500 so I think even if I put a new motor and transmission in it it will be worth the money. It was a repo.

 

[Matt-man]

would a motor out of the newer style tahoe work in mine...like the body style after mine?

 

[96ProCompTahoe]

i think you'd have to change the wire harness and computer and all that good stuff since its a 5.3L instead of a 5.7L vortec.

 

[Matt-man]

Do you know if the bottom end is the same as the 5.7? I could just put the old heads and intake off of my tahoe on the newer short block if that would work...the rreason I ask is I have a friend who has one of these newer type engines and I waqs wondering if it would work b4 I got it

 

[Annihilator]

No, you have a Gen 1 SBC and the news ones are a Gen 3.