New GM 3.0L Dmax

[supton]

How is a rear mounted cam drive going to affect NVH? On a longitudinal design, doesn't that put the noise maker closer to the driver?

Hmm. I turn my nose up at Ford trucks where they pull the cab to do engine work, but they do have a point, it makes it a heck of a lot easier to do the job. As someone pointed out here, perhaps if dropping the transmission was "easy" then maybe this isn't as much of a problem as I think it is. But I think I'll let it be someone else's problem...

 

[A_Harman]

I think the rear timing chain is good. Cam drives are put at the rear of the engine because the flywheel mass back there reduces torsional vibration inputs to the chain (or gear). I worked on a 28-liter V12 tank engine project at Cummins long, long ago, and it had a rear-mounted geartrain to drive the overhead cams.

On the other hand, I really don't understand the logic of driving the oil pump with a belt that needs to be replaced. Engines last pretty much as long as their oil pumps: once the oil pump stops running, the engine stops a few seconds later. Oil pump drives should be bomb-proof and definitely designed to last the life of the engine.

 

[supton]

Ah, that makes sense, use the flywheel mass to good effect. I know the crankshaft can have some twist to it, so I guess that variable can be eliminated.

 

[Nick1994]

Originally Posted by 1978elcamino
Their inline 5 cylinder that was in the Trailblazer and Colorado also had timing chains in the rear. Removal of the transmission was required.

Lifetime and GM do not belong together, IMO.

Trailblazer never had the 5 cylinder engine.

 

[nthach]

Originally Posted by A_Harman


On the other hand, I really don't understand the logic of driving the oil pump with a belt that needs to be replaced. .

If GM considered the oil pump drive belt to be separately serviced, they could have at least put it up front.

IIRC, some Mitsu/Hyundai engines had a separate belt driving the oil pump and it was serviced with the timing belt.

 

[Pew]

Originally Posted by nthach
IIRC, some Mitsu/Hyundai engines had a separate belt driving the oil pump and it was serviced with the timing belt.


Indeed. The 4B11/T has a separate timing chain. You still had to remove the timing chain cover to get to it though so it was a PITA. Luckily the chains weren't a service-interval item unless you had a 2008-early 2011 with the weaker timing chain design.

 

[Skippy722]

Chains in the back is asinine. Chain driven cams but a belt driven oil pump? Just why???? Guess the terrible ideas of GM's design department has bled over into engineering.

 

[kstanf150]

Originally Posted by 1978elcamino
Their inline 5 cylinder that was in the Trailblazer and Colorado also had timing chains in the rear. Removal of the transmission was required.

Lifetime and GM do not belong together, IMO.


Lifetime and GM ...³...³ðŸ¤”🤔🤔
I agree !!ðŸ‘
Good call 1978elcamino

 

[4WD]

Yep, H3 did … all GMT355 had the I5 in the lineup …

 

[CarbonSteel]

Why not gear driven? Meh, for all but open road drivers, modern diesels make zero sense for the average Joe.

I will not own another...

 

[4WD]

Welcome to Sonic, can I … clak, clak, Clack, CLACK, CLACK, CLACK (Ram pull-ups) ...
I drive off as stink is blowing across … Get drink at SpeedyStop

 

[HemiBenny]

Timing chain at the back of the engine, bad idea. The way the front of the truck looks,.........bad idea.

 

[clinebarger]

Originally Posted by 4WD
You can google rear timing chain and have some fun … I'm sure Trav and Chris have seen a mess or two



I have yet to mess with a rear timing chain arrangement, As labor intensive as it is to remove the front timing cover on some engines......It might actually be easier to pull the transmission. The Atlas wasn't any fun with the oil pump built into the cover. A 4wd Trailblazer calls for 17.1 hours.

 

[E365]

^ Bingo. With access to a lift, a transmission removal on a longitudinal engine/trans isn't a big deal.

A number of years ago I replaced the plastic timing chain guides on my BMW 318ti. Here's what it involved:

Remove air box and snorkel, remove valve cover, remove cooling fan assembly, drain coolant, remove thermostat, remove radiator hoses, remove main serpentine belt, remove AC belt, remove AC belt tensioner, remove crank position sensor, unbolt AC compressor so you can unbolt and remove the AC compressor bracket, remove AC belt pulley off main pulley, lock crank assembly in position with a special tool while you remove the main crank bolt, then you can pull off the timing case covers. I could see tighter engine bays and/or turbo vehicles needing even more work.

I HIGHLY doubt removing the transmission would have taken me much/any longer with access to a lift.

 

[clinebarger]

And access to a lift is part of vehicle repair today, It always was really. Manufactures don't care whether or not you can repair your vehicle at home.

 

[4WD]

Yep …
at Ford dealer today, getting $389 backup camera and spotted another cab off job going on …

 

[P10crew]

I just read an article by I think car and driver mag. They claim that when they test drove it that they got 46+ mpg.

 

[clinebarger]

Just because you see a cab pulled.....Doesn't mean the repair information called to pull the cab for that labor operation. It's so easy, Mechanics do it regardless.

Ford KNOWS it's easier....But they do not like the optics of cabs being pulled as it has a negative stereotype attached to it.

 

[P10crew]

Ha yeah we had one that had the cab pulled 4 times before we got rid of it at 150,000 miles
The last straw was when it gobbled up the turbo. This is the same truck that the transfer case exploded all over the interstate at 75 mph. S hit the bottom of the floor so hard that it knocked the dudes coffee cup out of the holder.

 

[clinebarger]

Was this a 6.4L or a 6.7L Powerstroke?