A couple engine/tranny issues!

[audiguy]

Hi guys, a couple things I've noticed on this Tahoe after driving it a bunch this weekend, would appreciate any tips...

- Tranny noise: This has happened twice now, both times after driving on the highway, then exiting onto local streets. Say it's stopped at a light, when I take off I hear a moderately loud grinding sound that lasts through the initial part of the take off, then goes away as the car gets up over say 5-10 mph. But every time I slow back down and then take back off, you hear that noise. Sounds like it's coming from the mid-rear portion of the vehicle, near the back of the tranny. If I then manually shift the tranny down to 3, then 2, then back to drive, the noise goes away. The truck seems to drive OK all along.

- Rough idle: Sitting at a stop light, while in gear, I noticed it idles pretty rough. The tach stays pretty steady around 500RPM, but you can feel the engine in your seat. Putting it in neutral smooths it out.

- Cold start noise: When the truck has been sitting like overnight, the first start of the day produces a pretty terrible sounding engine noise that lasts up to about 30 seconds, then sounds completely normal. Sounds almost like a diesel engine, a heavy knock.

I should point out that I have all new sparks (AC Delco), plug wires, intake filter, and fresh oil (synthetic 5W-30) + filter (AC Delco).

Would appreciate any thoughts on these issues!

 

[clkelley]

Welcome to the neighborhood!

On the grinding noise from take off, it sounds a little like you may have an interruption in flow of fluid through the valve body in the tranny. When was the last time you serviced the tranny, ie: changed the filter, etc.

For the rough idle, how many miles on the truck? I would start with cleaning the MAF sensor and throttle body, and if it persists, you may want to go ahead and change the o2 sensors, they can be on their way out without throwing codes and can cause tuning issues that could cause the rough idle.

The noise when cold is the valve train knock, what synthetic oil are you using? Are you certain that it is full synthetic? I had a similar tick in the wife's Denali and it went away after installing Amsoil. That being said, either way, it can be a good idea to also install a "Pre-oiler" set up to lubricate the valve train before cold starting. This will ensure that the valve train is good and lubricated before you start your engine.

Hope this helps...

 

[audiguy]

Hey thanks... truck has 105,000 miles. I will definitely clean the MAF and throttle body as a good first step. I was also thinking about adding seafoam just to give that a shot, although it sounds a bit hokey to me.

Re tranny - I don't really know the service history there, so I have to assume it's never been done. I already have the new filter and ATF, planning on dropping the pan and cleaning it up and replacing the filter sometime this week. I guess I'll see if that helps. Doesn't do this very often, but it's done it twice now.

I definitely put full synthetic... Mobil1 5W-30, same stuff I've used on all my cars for years. I will look into that pre-oiler setup thing, do you have any specific brand recommendations? It just sounds like an unhealthy noise to me!

 

[oldblue]

Had that kind of noise in my 01. sounded like teeth grinding coming from around mid to rear of truck.ended up being a shaft in my tranny was fractured found out when it snapped and broke rear housing. went out and bought a Monster tranmision brand tranny for $2000.00 loaded in the back of my pickup. it also included the torque converter. freinds said i went overboard buying a trans that will handle 650HP but i bet ill never have to worry about it again..
cottman was$2000.00 with only 1 yr warr. monster is 2yr for same money.:waytogo:

 

[audiguy]

Had that kind of noise in my 01. sounded like teeth grinding coming from around mid to rear of truck.ended up being a shaft in my tranny was fractured found out when it snapped and broke rear housing. went out and bought a Monster tranmision brand tranny for $2000.00 loaded in the back of my pickup. it also included the torque converter. freinds said i went overboard buying a trans that will handle 650HP but i bet ill never have to worry about it again..
cottman was$2000.00 with only 1 yr warr. monster is 2yr for same money.:waytogo:

And you were getting this sound intermittently, usually after getting off the highway? And it only lasted a second or two while accelerating from a stop?

I actually haven't heard the noise in a week or two, for whatever that's worth. Still planning on changing the tranny fluid and filter.

 

[oldblue]

sure did. the guy at monster told me the noise was a bearing starting to seize and heating up the shaft. hope yours is an easy fix. i think the worst thing that can go wrong in a car is the tranny! not many know how to fixem and they charge you an arm and a leg to fix them.Good Luck