2008 GMC Envoy Denali

[Husker6.5]

Gen 3 is like an obedient child. Gen 4 is like an ex-wife.

 

[Will L.]

Old mechanical diesel is a faithful dog or horse. It does what you tell it, when you tell it, without question- even to it’s own demise. Do I make it sound like I hate electrical, electronics, programming, and the like? Yeah? Good.

Here is a vfd I just a bit before I finished installing yesterday that is temporary to use while I replace 7 others permanently later this year. I am not writing the programming, but my bosses boss decided I am learning right now also. Hooray for plc function blocks. Haha

Nate my friend- you are nuts for doing this by choice.

 

[Husker6.5]

I feel for you, @Will L. ! I used to have to program/reprogram PLC's at my job as a maintenance tech at an organic cereal plant (we made Kashi and other Organic Certified cereals like Uncle Sam's on subcontract for major brands as one of only four Certified Organic cereal plants in the U.S. at the time back in 2008. We had crazy regulations for cleanliness, materials, etc. Like we couldn't touch food contact surfaces while working (yeah, right) and if we did we had to completely disinfect them after working on the equipment. Pretty much everything in the plant was made of stainless steel, so I learned how to weld both sheet and structural stainless (like angle iron) among other things. How about all bearings on shafts, slides were greased with a special edible-rated grease - as were drive chains with an edible-rated lubricating oil - but you don't dare eat the stuff, it was just rated to be used around food processing surfaces.

 

[Husker6.5]

And of course VFD's were used to control 3-phase motors throughout the plant for every kind of conceivable drive or conveyor belt system. They would burn out either from cereal dust build up on the cooling fins on the heat sinks on the back of the VFD for the SCR's, or because during wash down after finishing the job the $11/hr production workers didn't bother to properly bag/waterproof the VFD's and got water in them - which definitely didn't mix with the 277 or 480 voltage put to them when powered back up.

We would just toss and replace with a new/good used unit when one burned out, instead of trying to repair it. This was my supply of serious heat sinks to use with remote mounting PMDs/FSDs - far better than any aftermarket FSD coolers commercially sold by any vendor I've seen for heat soak and heat dispersion.

 

[n8in8or]

As of now I have called the tune “good enough”, I have gotten rid of the over-rich condition the new injectors gave me while not going too lean. I need to get back to work on the dually so it made sense to stop for now. Next month I’ll start again. I have found out that the way I was doing the MAF and VVE tuning is apparently antiquated and there is a better way of doing it, so I will give that a try and then once I have that optimized I will start working on tuning the spark. Even so, I am seeing improvements in miles per gallon (along with smiles per gallon). This afternoon we drove an hour away to an antique store. I reset the mileage before hitting the highway. I had the cruise set at 79mph, but I did have to slow down a couple times due to stupid traffic on I94. This is my mileage just before getting off the highway.



And this is what it was after the 55mph roads to get the rest of the way there, which included some stops and starts.



Then on the way home, we took mostly back roads to avoid I94 around rush hour, so this was mostly 55mph, but quite a few stops and starts.



Of course JUST before I took that picture it was reading 20.2, ha. I never would have thought that I’d gain that much fuel mileage from a tune. The best I got before was 16.2 with the cruise set at 76mph, and that was when it still had 3.42 gears. I’ll take it, now I need to take it to the drag strip and see what kind of a 1/4 mile it will run. Then it will get an exhaust and probably a better set of cylinder heads and then it should really haul.

 

[Husker6.5]

Boy, but look at that fuel gauge needle drop from photo to photo!

 

[n8in8or]

Boy, but look at that fuel gauge needle drop from photo to photo!

Why you gotta bring me down like that!?

 

[Husker6.5]

Just need a bigger tank to take advantage of the better MPG's!

 

[smokymtn65]

Your so far ahead of me, I did pull my first read off a 0411 I have to swap into my 98 with LS Droid. I have to get a 8.1 bin file to flash to it next. Let the learning begin. Of course get exhaust on it too.

 

[n8in8or]

Your so far ahead of me, I did pull my first read off a 0411 I have to swap into my 98 with LS Droid. I have to get a 8.1 bin file to flash to it next. Let the learning begin. Of course get exhaust on it too.

Sounds interesting. I hope you include that in your build thread. FYI, I saw that you can tune a 98 7.4 on HP Tuners, or is there another advantage for swapping to the 0411?

 

[smokymtn65]

Sounds interesting. I hope you include that in your build thread. FYI, I saw that you can tune a 98 7.4 on HP Tuners, or is there another advantage for swapping to the 0411?

Want to? LOL Actually more tune-ability more spark tables A lot more adjustment if I understand correctly.

 

[THEFERMANATOR]

Sounds interesting. I hope you include that in your build thread. FYI, I saw that you can tune a 98 7.4 on HP Tuners, or is there another advantage for swapping to the 0411?

Want to? LOL Actually more tune-ability more spark tables A lot more adjustment if I understand correctly.

The 98-00 black box is a PITA to tune to begin with. Very few tables to work with since it is only a 256kb memory chip vs the 0411's 512(double the memory). And the 0411 can be tuned for under $40. I bought my SX cable for $20 on sale through Amazon and can tune it for FREE using pcmhammer and tunerpro.

And do not use an 8.1l file. They used a 24/1x ignition pickup with CNP ignition, your 98 454 uses a 4/1x pickup and a distributor ignition. Make sure to use the 02 express van file from a 5.7l, correct the injector size data, and put in a 454 VE and spark table. Or use the VE & spark tables from the 8.1l as a starting point, but use the express van tune. You also need the express van tune so your fuel gauge will work as 98 is PCM controlled. You also have to make sure and use the correct maf settings. 8.1l has an 85mm maf, your 98 454 has a 75mm maf.

 

[MrMarty51]

The 98-00 black box is a PITA to tune to begin with. Very few tables to work with since it is only a 256kb memory chip vs the 0411's 512(double the memory). And the 0411 can be tuned for under $40. I bought my SX cable for $20 on sale through Amazon and can tune it for FREE using pcmhammer and tunerpro.

And do not use an 8.1l file. They used a 24/1x ignition pickup with CNP ignition, your 98 454 uses a 4/1x pickup and a distributor ignition. Make sure to use the 02 express van file from a 5.7l, correct the injector size data, and put in a 454 VE and spark table. Or use the VE & spark tables from the 8.1l as a starting point, but use the express van tune. You also need the express van tune so your fuel gauge will work as 98 is PCM controlled. You also have to make sure and use the correct maf settings. 8.1l has an 85mm maf, your 98 454 has a 75mm maf.

That just stuns Me every time You post. The information thats in Your head is totally amazing to Me.
I love this stuff but I dont understand a bit of it.

 

[n8in8or]

Last night we went 45 minutes to a county fair. No interstates, just 55mph and under roads. A couple stops and starts, plus some slower speeds that were too low for the converter clutch to lock. I was pretty pleased to see the number it put up this time.

 

[smokymtn65]

The 98-00 black box is a PITA to tune to begin with. Very few tables to work with since it is only a 256kb memory chip vs the 0411's 512(double the memory). And the 0411 can be tuned for under $40. I bought my SX cable for $20 on sale through Amazon and can tune it for FREE using pcmhammer and tunerpro.

And do not use an 8.1l file. They used a 24/1x ignition pickup with CNP ignition, your 98 454 uses a 4/1x pickup and a distributor ignition. Make sure to use the 02 express van file from a 5.7l, correct the injector size data, and put in a 454 VE and spark table. Or use the VE & spark tables from the 8.1l as a starting point, but use the express van tune. You also need the express van tune so your fuel gauge will work as 98 is PCM controlled. You also have to make sure and use the correct maf settings. 8.1l has an 85mm maf, your 98 454 has a 75mm maf.

Thanks @THEFERMANATOR

 

[smokymtn65]

@THEFERMANATOR do you have a link to the "sx" cord you used, I am two stepping now through my MX link

 

[THEFERMANATOR]

@THEFERMANATOR do you have a link to the "sx" cord you used, I am two stepping now through my MX link

It works with pcmhammer, it will not work for ls droid since it isn't bluetooth. The only downside is it is SLOW! You can catch them on sale for $20 every now and then.

https://www.amazon.com/ScanTool-OBDLink-USB-Professional-Diagnostics/dp/B005ZWM0R4/ref=sr_1_2?dchild=1&keywords=Obdlink+sx&qid=1631914016&sr=8-2

 

[n8in8or]

The last few weeks I’ve been cleaning the barn up. It was a WRECK after having three trucks crammed in here for over a year. Much sorting, organizing, putting away and cleaning needed to happen. I got it to a point I was happy with so I pulled the Envoy in for some repair and upgrades.

Last fall I was noticing a clunk coming from the rear on accel and decel. Fortunately it wasn’t in the axle itself. What I did find was the front bolts for the lower control arm were a little loose. I got out my service manual to look up the torque specs and was disappointed in what I found - they listed the spec for those bolts lower than the others, even though they are the same size and the same type of connection as the others. Typo!! This is the second time in a couple months that I’ve had a typo in a factory service manual bite me like this. So I tightened those bolts to the same spec as the other bolts, but that only lasted for a little bit….the damage was done, I had egg-shaped holes and/or worn bolts where they were crashing. So while I was cleaning the barn I formulated a repair plan. At first I planned on welding the worn part of the holes up and then regrind them round, but that would be hard to get right, so instead I decided welding some thick washers would be the best solution, plus a new set of bolts. While I had to take it apart I started thinking about upgrades I could do at the same time. PCM of NC offers lower control arm brackets for the axle that improve the anti-squat geometry on lowered trucks, so I ordered those. I also thought about the limited slip it has….it’s really tight. While that’s great for straight line traction, it’s a bummer for driving in slippery conditions - in the rain it doesn’t take much for the rear end to kick out going around a corner because the axle isn’t getting a chance to act as a differential…..a condition that probably isn’t helped by the poor anti-squat I currently have. I also had a problem on a snowy drive recently where it was understeering while trying to steer from a straight line in four wheel drive. I felt like the locked rear wheels were just pushing me forward with both pushing. Shortly after this I realized I had a better diff in my possession: the TrueTrac in the Tahoe….both axles are 9.5” 14 bolts. Bingo. This will be a better diff for a daily driver and the tight limited slip should work nice in the heavier Tahoe. So now I had my game plan….just need some time and space to do the work. Both things came together this past weekend so I got to it.

Before disassembling, I took a before pic of the lower control arm geometry. It’s actually pointing towards the ground. Not great for good anti-squat.



Here are before pics of the elongated bolt holes. The elongation is subtle, but it’s there, especially on the inside hole.



This is after welding the washers and grinding them smooth. Not the prettiest, most consistent welds, but that’s what happens when I’m welding from a creeper. It’ll hold and that’s the important part.



Here’s the axle just before filling it with oil and bolting the cover on. You can see the True Trac and the brackets that are welded and painted. I used KBS Rust Seal again. I am quite pleased with how well the paint has held up after 2 years of daily driving this truck in all Midwest seasons.



Here’s the lower control arm geometry after installation. Now it’s pointing up which should be much better for anti-squat. I didn’t take measurements to see what percentage I have now, but I know it has to be better. I also have some adjustability still if I need it (you’ll see that in the next pic).



And here’s the driver side bracket. I’m pointing to the bolt hole that the control arm originally pivoted on (an aluminum sleeve is bolted there now for bracket rigidity). You can see that I have a hole above and below where it’s bolted now in case I want to make some adjustments.



Oh and there was one more thing that I did: I’ve had a slight vibration I haven’t been able to get rid of so I’ve been suspecting the driveshaft, even though it was a new factory driveshaft. So while this was apart I took it to the local driveline shop. I didn’t talk to the guy that balanced it to see how much it was out, but they did remove the front weight and weld a different one in another spot, so it must have been off at least a little. I also took advantage of the adjustable control arms and set the pinion angle. It was a bit over 4 degrees down when I started, now it’s at 2 degrees down, so that may have also added a slight vibration.

Today during lunch I ran a quick errand as the first drive, just 5 miles or so. The roads had wet 2-tracks in the snow, so it was a bit slick. So far it feels like it isn’t trying to kick the rear end out as much around corners and when it does break traction it feels much more predictable and controllable, which makes sense to me based on this upgrade. I can’t wait to drive it more and hopefully feel satisfaction with these upgrades

 

[Husker6.5]

So, did you find a skidsteer somewhere in all that mess in the barn, @n8in8or ?

 

[n8in8or]

So, did you find a skidsteer somewhere in all that mess in the barn, @n8in8or ?

Skid steer? What skid steer?