GM VORTEC 7400 Timing Gear & Chain Set

[overlander64]

Greetings Scott!

Originally Posted by scottanlily

I would say the rattle in the front of the engine is definately a cause for
concern and investigation .you can check your CMP (cam position) on a scan tool ,it should be 0 degrees .An out of range crank sensor (usually on a chevy astro 4.3)will cause your CMP to be incorrect .The noise is the key .Im
surprised still that its so thrashed ,Very unusual .One thing I have noted
on vortec big blocks is cold piston slap (another whole story).you have done
alot of timing chains though .By the way ,where the heck are you getting 93
octane fuel ???? One other thing ,the timing never changes unless somthing is wrong ,no adjustment is needed ,and you need a scan tool to set the base adjustment after a repair is performed like a timing chain .Have your
mechanic check the distributor and the drive gear for excessive damage or wear ,the distributor is plastic and can be worn severly as well as the gear
which means the camshaft dist drive gear also is trashed ,do this before comitting to the timing chain job as a new engine may be the best thing to do .

Scott of scottanlily

When my mechanic checked the codes and found both out of range crank sensor and cam position sensor registering, the progression of diagnosis included:

• Verify that the sensors were not malfunctioning -- I think that this may have been based upon the number of electronic circuit boards that have failed on this vehicle (primarily the electronic 4WD transfer case control, and the intermittent windshield wiper circuit control board).
  • The sensors passed inspection.
• The next item checked was the distributor.
  • The first check on the vehicle only turned up that the timing was significantly off of the mark and not as stable as it should be.
  • The second check was to remove and bench test the distributor, and nothing out of the ordinary was noted and it passed all bench tests.
• The truck was then road tested with the distributor timed to as near factory standard as possible -- they were finally able to get the timing set to specification.
  • While the timing wasn't wildly errant, the report was that the timing was unsteady.

One thing that I negelected to mention in my original post was one symptom that I hadn't associated with this until just now -- when the "service engine soon" light came on in January, the truck for the very first time took multiple tries to start -- it started on the third try; and since then it is not uncommon to take two tries to start. One reason that this didn't register immediately was that for the first time since I have owned the truck it has been sitting, and only driven twice a month as I generally walk to work. In the limited driving I have done since the diagnostics, it hasn't experienced the hard start problem.

Kevin

P.S.: Most of the major brand name gas stations around here carry 92 or 93 Octane premium (usually a gasohol blend). Since gasoline exceeded $2.00 per gallon, about the only time I use the premium is when I tow the Overlander.

[Mike Lewis]

If the chain slips and your left sitting along the road, a tow any distance at all, will cost more than the chain and gear set replacement !! Just do it. -----------------pieman

[azflycaster]

Years ago a friend ad a gear strip out on his Dodge Charger. When the crank and cam are out of sync, bad thing happen. He was lucky, no head damage, but 16 bent push rods.

[Killo1]

Originally Posted by spammer deleted

Hello, everybody!
We are a timing components manufacturer from China.
Company Name: Ningbo Liancheng Machinery Co., Ltd
Ownership: Family company.
Date Company Founded: 1986
Numbers of Employees:
150 in the LC section. 550 in the total family company.
ISO9001.2000 Certified since 1998.
Numbers of Factory: Three
We do not attent Guangzhou Fair or any other spare parts exhibition in automobile industry, just contact customer via internet.
Iron Casting: In our own company run by a Taiwanese, Japan technology.
Heat Treatment: completely controlled in our own company.
Currently: We are working with some renowned automobile companies in USA.
We welcome OEM, distributors of automobile parts to manufacture timing chain set in our company.
Currently, we have timing chain set of Chevrolet, Ford and Nissan ... we hope we can have more in the future.
We do not give retail service to end use.
Doncloud

GOOD TO KNOW. I was personally wondering where I could get 1 million timing chains from China for my new car I'm designing.

[steelbird312]

Originally Posted by spammer deleted

Hello, everybody!
We are a timing components manufacturer from China.
Company Name: Ningbo Liancheng Machinery Co., Ltd
Ownership: Family company.
Date Company Founded: 1986
Numbers of Employees:
150 in the LC section. 550 in the total family company.
ISO9001.2000 Certified since 1998.
Numbers of Factory: Three
We do not attent Guangzhou Fair or any other spare parts exhibition in automobile industry, just contact customer via internet.
Iron Casting: In our own company run by a Taiwanese, Japan technology.
Heat Treatment: completely controlled in our own company.
Currently: We are working with some renowned automobile companies in USA.
We welcome OEM, distributors of automobile parts to manufacture timing chain set in our company.
Currently, we have timing chain set of Chevrolet, Ford and Nissan ... we hope we can have more in the future.
We do not give retail service to end use.
Doncloud

So there!

[Silvertwinkie]

Here is currently some great conversation about China and what folks are feelin' about products from there:

http://www.airforums.com/forum...ons-29927.html

[overlander64]

I just returned from the Chevrolet garage, and my Suburban now has a new timing chain and gear set. Based on the visual of a timing chain that had more than 3" of deflection and several chipped teeth in the gears, I was running on borrowed time with the original chain and gears. I can't really fault the Suburban as the original lasted 183,500 miles with the cost for replacement being about three times the cost of replacing the timing belt in my old Toyota once -- and in 180,000 miles of driving, it (the Toyota) required three timing belts.

The difference in the Suburban's road manners is remarkable -- silky smooth acceleration with no hint of rough/noisy idle that I had been experiencing for more than six or seven months. If possible, it seems to be running smoother than it has since it was new in April of 1998.

Kevin

[Silvertwinkie]

Great to hear Kevin. I'm still floored that you needed a new timing chain and that it was that deflected and chipped teeth. I owned a GM that had 167k on it and ran like a top. I always thought that the timing chains were good for the life of the vehicle.

[59toaster]

Originally Posted by overlander64

The estaimate to replace the timing chain and gear set with GM factory components is between $900 and $1,100. The water pump was replaced with a new GM pump at 122,000 miles when it began leaking. The pully and tensioners were replaced when the truck was prepared for last summer's journey. The truck has been serviced by either one of two long-time GM dealers -- Pioneer Motors in Lancaster, WI or COAD Chevrolet-Cadillac-Pontiac-Buick in Anna, IL every 3,000 miles utilizing the severe service maintenance schedule. There is no evidence of oil burning, and compression and leak-down tests return well within the normal ranges for this engine. I am not opposed to replacing the timing chain in advance of failure as only my Oldsmobile escaped without related motor damage when the timing chain failed.

Kevin

$900-1100 for a TIMING CHAIN?!?!?!?!?!?!?!?!?!
I'm in the wrong buisness

You do know you can buy a brand new 350 engine for $1800 don't you?


I'll do the job for $500 including the the basic parts. Bring it on over.

Seriously...yes it is a pain in the butt job but it is not a $900 in labor pain in the butt job. Even with Chevy's ridiculous mark up you should be able to buy the chain for less the $100. The Cloyes aftermarket is $30 at Autozone. Feldpro front gasket set it about $30. Gallon of Anti Freeze $6 Gallon of Distilled water $1.25.

[overlander64]

Greetings Eric!

From what the service manager at the Chevrolet dealership told me, anything much over 150,000 miles on a 7.4 Liter and the timing chain/gear-set is a candidate for replacement -- particularly if the unit has seen much use towing. We have basically found this to be true with both our small-block V8s as well as the big block V8s -- my first '75 Cadillac had to have a timing gear and chain set at 155,000 miles, the '84 Oldsmobile 5.0 Liter made to in excess of 100,000 before its timing chain snapped while driving on the highway (I don't know how it happened, but there was no other damage to the motor -- just needed a new timing chain and gear set as well as a new timing chain cover).

I can't complain about the cost of operating the Suburban (other than the pesky automatic transfer case electronic module). In nine years and 183,500 miles I have only had a very few repair expenses beyond the timing gear and chain set -- one new water pump, one new fuel pump, one idler arm, one set tie rod ends, resurfacing front rotors three times, one new blower motor for front heat and air.

Kevin

[Silvertwinkie]

Wow...I just retired my 1980 Olds Delta, which was the one with 167k on it.

We also had a 1985 7.4L in our Suburban w/130k on it.

Maybe ours were flukes. I've never heard that about timing chains, but I am glad you got yours fixed before it left you stranded!

I've seen your truck a few times and know it's in great shape...well worth saving!