I have a 2005 Colorado crew cab 4x4 with 172 000 kms (107 000 miles). I was cruising down the highway and the truck kicked down to second gear to climb a hill (had cruise control on at 75 mph). Revs went up to around 5000 RPM and a terrible noise followed, something like a really bad tick or rattle. I was in the middle of nowhere so had to drive for another hour to get to a city and a GM dealership. (drove at 50 MPH to keep the revs low)
They think its a loose timing chain. They want $4300 total to fix it (front diff has to be dropped).
I can't find any info on timing chain stuff for Collys. You guys ever hear of the chain needing to be replaced? Anyone ever change one?
Timing chains do wear out although ours have a tensioner and 107k isn't alot. There may be a problem with the tensioner itself. Here's a link with pics that will help if you decide to do your own repairs. For what its worth you can also invest $15 in a Haynes manual. viewtopic.php?f=43&t=38604
Thanks for the link. A Hayne's manual was the first thing I bought.
I will hopefully have my truck back in my garage in the next week. I'll take the covers off and hopefully see what's causing all the racket. If I'm lucky it will be the tensioner or something silly like that. The engine still runs fine which gives me hope its nothing too critical.
I'd put a lower mileage motor in it before I spent that much on a chain replacement. Someone on here or 355nation was a dealer mechanic and said these motors are a major PITA on the timing chain stuff.
Ya thats what I hear. If I do it myself, it won't cost that much, just a lot of my time. I don't feel like doing an engine swap on a 3 year old truck. I definately thought it would last a bit longer than 107 000 miles...
I just received the summary from the dealership. Apparently they tested the actuator by sending a command to the actuator solenoid. There was NO change in cam position. I pulled the solenoid and it looks alright, although there are some metal fillings on the screens I would like to clean out.
So I guess either the solenoid or the actuator is toast. Would a busted actuator cause the terrible noise I heard? Looking through scott's timing chain "how to" it looks like there is a hydraulic chain tensioner on the lower right tensioner thing. I wonder if that could be toast as well. The engine actually sounds fine when its cold. It's only when it warms up that the sound gets really bad.
Does anyone know what the allowable timing chain lash is? Does anyone have a GM part # for the actuator? I have the number for the solenoid. Anyone have issues with the timing chain tensioner before?
I was just thinking about this, and I'm going to replace the tensioner and actuator. It's way too much of a job to try one or the other, so I might as well change everything.
So nevermind my previous questions. I have the valve cover off right now, so I'm on the way to getting the front cover off as well. I'll let you guys know how the actuator/tensioner replacement goes. Oh and I found everything I need on http://www.gmpartsdirect.com. Hopefully they can ship fairly quickly!
OK the fact that you said it only does it more when its hot leads me to beleive that maybe theres a problem with your exhaust camshaft timing sprocket or the VVT actuator. Most likely the sprocket im thinkin. Finding metal shaving in anything is not that great for the motor. I think you can get away with removing the exhaust sprocket without fully pullin out the chain if you use that special tool Gm techs use.
This tool allows you to hammer ina wedge that pushes in the timing chain tensioner and releases tension on the chain allowing you to remove the sprocket and replace it without having to pull off the timing chain cover and oil pan and front diff. But im not sure where you can buy it other than possibly from a tool distributor like Snap On or Mac or maybe Kent Moore.