2004 8.1 Yukon

RedF

Adventurer


This shall be our new family run-around, road trip and occasional adventure rig. I just picked it up on Thursday. It fit the bill close enough for our expanding family and seems to have lots of life left in her. It has been affectionately dubbed the "Canyonero". It drives pretty nice, and the big block power is great.

As the title says, it has the 8.1 (it was advertised as having the "powerful 6 liter", I wonder if they didn't think they could market the 8.1?), 4.10 gearing, seats 7, has 170,000 Kms and has a bunch of options that I don't really care about.

She has some issues that I'd like to get resolved, and a few modifications that I'd like to do. This is specifically why I'm creating a thread here - as I know there are some "experts" on this platform that frequent here, and have been down this road before me.

Issues:

1) The HVAC is stuck on defrost. This is a best case scenario for a failure of this nature, but I'd like to get it fixed. I'm guessing it's a stuck door, but I don't know where to start looking, and I haven't had the time to research it. Input?

2) Autoride. It seems to be functional, but I know nothing about it, other than I'd rather not have it. Can I bump up the torsion bars without causing issues? Or is there a work-around? I would like a little more height, for a bit bigger tires in the future.

3) It smells a bit like wet dog inside, and there is dog hair embedded in the carpet. I've been working at it, and purchased an oxidizing spray that seems to be giving some results. This should be simple enough to correct, just tedious. If bad comes to worse, I'll remove all the seats and shampoo the carpets. Has anybody had good luck with any particular product? What about getting the hair out of the carpet? A vacuum will get it, but I have the make 40+ passes to pull it out, and there is a lot of carpet in this thing! No, I don't want to strip the carpet out. Once they are clean, I intend on putting floor liners down.

4) Motor. Is low(ish) hot oil pressure is normal for this motor? What does it like for spark plugs?

What I'd like to do:

1) Bigger tires. I'd like to move up to a 285/75R16, or thereabouts; looks like they should fit without issue. Stick with the PY0 rims? I have a set of H2 rims on my pickup that I could use, if the fitment is better. I'm thinking BFG ATs or Duratracs. Maybe Coopers.

2) Transmission/drivetrain. Is there anything that I need to be concerned about in the drivetrain on this truck, especially with the 8.1? Is it worth having a shift kit put in the transmission, or does electronic tuning net the same gains? I know GM neutered the motor with torque management to increase longevity.

3) Motor. I'm sure GM left power on the table with this motor. Is there an easy way to get it? Results? Cost?

4) Drivers seat. It has the typical wear and tear. I'll likely just leave it for now. Are replacement covers available?

5) Audio input. Is there a way to achieve an audio input into the stock head unit?

There is some easy stuff I'll nail down:
  • New windshield.
  • Flush the hydroboost.
  • Grease the front wheel bearings.
  • Headlight diode mod.
  • Misc. basic maintenance and repair as required.
  • Aux. lighitng.

Is there anything else I should consider? Looking forward to your input.
 

Fierokid

New member
I've got an 02 with a whipple supercharged 8.1. Oil pressure is very sensitive to RPM on mine, fairly low at idle but is just fine when cruising. My only problem I have had drivetrain wise is I have destroyed a rear axle in the 4ish years I've owned it. I know the Tcase suffers from "pump rub" but I haven't been hit with it yet. The 4L80 is a beast of a trans. Its had no problems pulling 10K all day long in the mountains of Utah.

The 8.1L is a beast of an engine but your the lucky 1% if it doesn't drink oil, it's very common but typical consumption is like a half quart an oil change I think? I don't really keep track of mine that well. Only other thing I have had to do is intake gasket when I did my tune up, and a fuel pressure regulator. All easy items.

There isn't much aftermarket support for this engine, it replaced the 454 and is totally different. Bolt hole locations are about all that the same between the blocks.. a set of 454 headers will fit the block but I couldn't find any that clear the frame except ones specifically made for the 8.1L. Look up Raylar Engineering, they do tons for the 8.1L but costs a pretty penny.

Just a tune will really wake these suckers up, theres a few places that are known, Black Bear tunes is the name I see come up the most though. I tend to find most of my information for the 8.1 on truck and towing forums. Just be aware that the trucks with the 8.1L didn't get the same transmission as us. They got the allison trans like the diesel guys got.
 

tennesseewj

Observer
1) The HVAC is stuck on defrost. This is a best case scenario for a failure of this nature, but I'd like to get it fixed. I'm guessing it's a stuck door, but I don't know where to start looking, and I haven't had the time to research it. Input?
Most likely the blower mode actuator. It's not terrible to change other than contorting your body to work behind the dash.

Sent from my Pixel 2 using Tapatalk
 

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zoomad75

Observer


This shall be our new family run-around, road trip and occasional adventure rig. I just picked it up on Thursday. It fit the bill close enough for our expanding family and seems to have lots of life left in her. It has been affectionately dubbed the "Canyonero". It drives pretty nice, and the big block power is great.

As the title says, it has the 8.1 (it was advertised as having the "powerful 6 liter", I wonder if they didn't think they could market the 8.1?), 4.10 gearing, seats 7, has 170,000 Kms and has a bunch of options that I don't really care about.

She has some issues that I'd like to get resolved, and a few modifications that I'd like to do. This is specifically why I'm creating a thread here - as I know there are some "experts" on this platform that frequent here, and have been down this road before me.

Issues:

1) The HVAC is stuck on defrost. This is a best case scenario for a failure of this nature, but I'd like to get it fixed. I'm guessing it's a stuck door, but I don't know where to start looking, and I haven't had the time to research it. Input?

2) Autoride. It seems to be functional, but I know nothing about it, other than I'd rather not have it. Can I bump up the torsion bars without causing issues? Or is there a work-around? I would like a little more height, for a bit bigger tires in the future.

3) It smells a bit like wet dog inside, and there is dog hair embedded in the carpet. I've been working at it, and purchased an oxidizing spray that seems to be giving some results. This should be simple enough to correct, just tedious. If bad comes to worse, I'll remove all the seats and shampoo the carpets. Has anybody had good luck with any particular product? What about getting the hair out of the carpet? A vacuum will get it, but I have the make 40+ passes to pull it out, and there is a lot of carpet in this thing! No, I don't want to strip the carpet out. Once they are clean, I intend on putting floor liners down.

4) Motor. Is low(ish) hot oil pressure is normal for this motor? What does it like for spark plugs?

What I'd like to do:

1) Bigger tires. I'd like to move up to a 285/75R16, or thereabouts; looks like they should fit without issue. Stick with the PY0 rims? I have a set of H2 rims on my pickup that I could use, if the fitment is better. I'm thinking BFG ATs or Duratracs. Maybe Coopers.

2) Transmission/drivetrain. Is there anything that I need to be concerned about in the drivetrain on this truck, especially with the 8.1? Is it worth having a shift kit put in the transmission, or does electronic tuning net the same gains? I know GM neutered the motor with torque management to increase longevity.

3) Motor. I'm sure GM left power on the table with this motor. Is there an easy way to get it? Results? Cost?

4) Drivers seat. It has the typical wear and tear. I'll likely just leave it for now. Are replacement covers available?

5) Audio input. Is there a way to achieve an audio input into the stock head unit?

There is some easy stuff I'll nail down:
  • New windshield.
  • Flush the hydroboost.
  • Grease the front wheel bearings.
  • Headlight diode mod.
  • Misc. basic maintenance and repair as required.
  • Aux. lighitng.
Is there anything else I should consider? Looking forward to your input.
I'll try to hit the questions in order with my thoughts.

Issues:

1. Mode door actuator. Fairly common. Might be an easy reach under the dash or tear it all apart to access. I can't remember.

2. Auto ride. Not to hard to disable if it's not working. Cranking up the bars for cheap lift is easy, but the more you crank them up the more your spring rate increases and ride quality suffers. Indexed torsion bar keys do the same thing without winding the spring tighter. Get an alignment after doing either, it tends to effect the camber.

3. Carpet smell and hair. Get the hair off first before you shampoo. We use a pumice type stone to remove dog hair. Got it from our detail supply vendor. Wipe the stone over the carpet and it lifts the hair. If you can't get the stone, break out the duct tape or packing tape. Make a loop of tape sticky side out and start patting. Either way is labor intensive, but works. Shampoo and let air dry.

4. Oil pressure. How low is it hot? 10-20 isn't abnormal at idle. Gm spec is 10 psi per 1000 rpm. I'd change the oil and see how it changes. I've seen a change just because the oil has been over on an oil change interval. Oh and like was mentioned earlier check the oil level often. 8.1's are known thirsty beasts for oil. A quart lost in 2000 miles is not uncommon. Don't let it get low. Use ac delco platinum plugs when you change them.

What you want to do:

1. Wheels and tires. Very subjective. But as much as I like the pyo wheels, 16 tires are getting a little hard to get. The h2 wheels are 17" and open up the choices. I'm a fan of duratracs, but annoyed Goodyear is producing them overseas now.

2. Drivetrain. No shift kit needed. Fully electronic controls. Could be tuned but don't have to unless you really have some specific issues you want addressed. T-case could have the pump rub issue. Check the fluid level and if low look for a leak at the rear housing. Might as well change the fluid in all the gearboxes and start fresh.

3. Engine. Gm did leave power on the table Torque management and burst knock retard are what really keeps the 8.1 down. Have a tuner turn those off and the truck will wake up. Blackbear is known for a good tune I hear but never used them.

4. Seat. There is a place on the web selling new replacement leather seat covers. A search should yield a result there.

5. Audio input. I bought a kit that basically plugs into the stock antenna input to the stock radio. Came with a switch and an aux input jack. Turn it on and tune to a specific station, comes in loud and clear. Got mine on amazon.
 

lilkia

Active member
I have the 8.1 as well. Youre truck doesnt have the 4l80e it has the 4l85e with the 5 planetaries they started using it in late 02 You will not destroy that trans. Its rated for 16,000lb vehicles.
Increasing spring rate by cranking the keys is a myth. The spring rate doesnt change, all it does is reclock the position of the T bar and hence the lower control arm, anybody that says otherwise is wrong. If you disagree please explain how it increases the spring rate.
285s will fit fine.
Autoride is different on these than the 1500s its just an electric shock not air ride. Ditch em for 5100s and throw the resisitor in or yank the fuse no more trouble light.
Ill post more shortly I gotta go to work.
 

ajmaudio

Adventurer
As far as the wet dog smell... I know you don't want to yank the carpet.. but I would suggest doing it and replacing the padding under the carpet as it is likely going to keep causing the odor. The padding is cheap, and the OEM stuff comes off plenty easy after removing the carpet. Its not a terrible job on these trucks, I have done it dozens of times from my days customizing vehicles. An impact and or/air ratchet really speeds it up! Removing the carpet will also make it easier to really get it clean, and then rinse with clean water. Getting to soap out of the carpet with a rinse will help it not to accumulate dirt so fast. Its worth it.
 

lilkia

Active member
Immm baaaack. Anyways as for the smell go to your local rental shop and rent an ozone machine. Put in the burb turn it on shut the doors and let it run overnight and it will get rid of the stink. I second the notion of removing/replacing the carpet and (at least) the padding. I would remove the carpet before you shampoo it so the padding doesnt get wet and then mildewy. New carpet can be had for $300. My wife just bought a vacuum that has rubber fingers on the roller instead of brushes and holy crap does it grab dog hair! I thought our dyson was good. I think its a bissel or hoover. I havent used it in the vehicles yet but I imagine it will work just as well.

As to the keys. As I said before cranking the bolts doesnt change the spring rate at all it changes the geometry. The only way to change the spring rate is with a different Tbar. But with the stock keys you wont have enough bolt travel to level the 2500 burb/xl and the bolts will be pushed all the way up. It is better to get reclocked keys so its level and you wont have as much bolt thread sticking up past the block holding the key bolt

As for power. The 8.1 leaves a lot on the table in stock configuration. I have a black bear tune and it really makes a difference. Headers and open intake will also help. According to the dyno sheets Im sitting around to 430hp and 550ftlbs. Incredible engine but it is thirsty and does use some oil about a quart every 2-3000 miles depending on how you run. Much more impressive than the 7.4 or 6.0 and a world of difference over the 5.3.

Replacement seat covers are on ebay I think theyre about $200 for nice leather ones in tan or grey.

As for radio. There are factory radios on ebay that have had aux inputs added. There are also videos on youtube on how to diy it if your handy. I did it on the truck its just a few cheap parts and some solder joints. It hooks into where the cassette player hooks in. Your sub may not have that being newer mine does.

I went with a sony double din unit that incorporates gps and rearview camera. Its touchscreen and has aux, bluetooth, and USB inputs. Seperate bass sub outputs as well. I think the new version is around $300. I went with component sets in all four doors and it sounds great. I have a new bass sub and new subwoofer but havent made time to intall them yet because it doesnt really need it.

Ill second the H2 wheels. I saw a brushed set that had the faces polished with the PY0 center caps and they look AWESOME! on the burbs. Im looking for a set (or 2) for the truck and maybe the burb for the next tire replacement. I have 285s on the PY0 for now.
 

RedF

Adventurer
I've got an 02 with a whipple supercharged 8.1. Oil pressure is very sensitive to RPM on mine, fairly low at idle but is just fine when cruising. My only problem I have had drivetrain wise is I have destroyed a rear axle in the 4ish years I've owned it. I know the Tcase suffers from "pump rub" but I haven't been hit with it yet. The 4L80 is a beast of a trans. Its had no problems pulling 10K all day long in the mountains of Utah.

The 8.1L is a beast of an engine but your the lucky 1% if it doesn't drink oil, it's very common but typical consumption is like a half quart an oil change I think? I don't really keep track of mine that well. Only other thing I have had to do is intake gasket when I did my tune up, and a fuel pressure regulator. All easy items.

There isn't much aftermarket support for this engine, it replaced the 454 and is totally different. Bolt hole locations are about all that the same between the blocks.. a set of 454 headers will fit the block but I couldn't find any that clear the frame except ones specifically made for the 8.1L. Look up Raylar Engineering, they do tons for the 8.1L but costs a pretty penny.

Just a tune will really wake these suckers up, theres a few places that are known, Black Bear tunes is the name I see come up the most though. I tend to find most of my information for the 8.1 on truck and towing forums. Just be aware that the trucks with the 8.1L didn't get the same transmission as us. They got the allison trans like the diesel guys got.
Must be a real beast with a supercharged 8.1! How many miles do you have on it with the blower? How hard do you drive it?

I've seen Raylar. They are expensive - even worse when the currency exchange is factored in.

I've heard many good things about Blackbear. I was going to get a tune for my 05 Silverado, but never got to it. Yes, I am aware that the trucks got the Allison, whereas the Suburbans and Avalanches got the 4 speed- supposedly because there isn't enough room under the truck for it; hence why the HD trucks sit 2" taller.

Most likely the blower mode actuator. It's not terrible to change other than contorting your body to work behind the dash.

Sent from my Pixel 2 using Tapatalk
I watched video about it - it looks super easy.

As for HVAC, dorman made a new improved version of HVAC controller I'd check out. Mine has gone bad too, but it'll change modes just not to the correct mode. Since yours isn't moving at all that sounds like the actuator.

( https://www.dormanproducts.com/p-98601-599-211.aspx )

Sent from my Pixel 3 XL using Tapatalk
I'll keep that in mind. Thanks.

I'll try to hit the questions in order with my thoughts.

Issues:

1. Mode door actuator. Fairly common. Might be an easy reach under the dash or tear it all apart to access. I can't remember.

2. Auto ride. Not to hard to disable if it's not working. Cranking up the bars for cheap lift is easy, but the more you crank them up the more your spring rate increases and ride quality suffers. Indexed torsion bar keys do the same thing without winding the spring tighter. Get an alignment after doing either, it tends to effect the camber.

3. Carpet smell and hair. Get the hair off first before you shampoo. We use a pumice type stone to remove dog hair. Got it from our detail supply vendor. Wipe the stone over the carpet and it lifts the hair. If you can't get the stone, break out the duct tape or packing tape. Make a loop of tape sticky side out and start patting. Either way is labor intensive, but works. Shampoo and let air dry.

4. Oil pressure. How low is it hot? 10-20 isn't abnormal at idle. Gm spec is 10 psi per 1000 rpm. I'd change the oil and see how it changes. I've seen a change just because the oil has been over on an oil change interval. Oh and like was mentioned earlier check the oil level often. 8.1's are known thirsty beasts for oil. A quart lost in 2000 miles is not uncommon. Don't let it get low. Use ac delco platinum plugs when you change them.

What you want to do:

1. Wheels and tires. Very subjective. But as much as I like the pyo wheels, 16 tires are getting a little hard to get. The h2 wheels are 17" and open up the choices. I'm a fan of duratracs, but annoyed Goodyear is producing them overseas now.

2. Drivetrain. No shift kit needed. Fully electronic controls. Could be tuned but don't have to unless you really have some specific issues you want addressed. T-case could have the pump rub issue. Check the fluid level and if low look for a leak at the rear housing. Might as well change the fluid in all the gearboxes and start fresh.

3. Engine. Gm did leave power on the table Torque management and burst knock retard are what really keeps the 8.1 down. Have a tuner turn those off and the truck will wake up. Blackbear is known for a good tune I hear but never used them.

4. Seat. There is a place on the web selling new replacement leather seat covers. A search should yield a result there.

5. Audio input. I bought a kit that basically plugs into the stock antenna input to the stock radio. Came with a switch and an aux input jack. Turn it on and tune to a specific station, comes in loud and clear. Got mine on amazon.
I only want to adjust the torsion bars up to "new" height - or thereabouts. If the Autoride isn't causing issues, I'll leave it for now.

Thanks for the tip on the pumice stone.

It's about 15 PSI at a hot idle, maybe a little better. I have a scan gauge from my last vehicle, I think I'll plug it in and see what it says. I have the supplies to change the oil; that's a project for tomorrow, or the next day.

I've had good luck with Duratracs, but I'm leaning toward BFGs this time.

The Seat Shop? I have emailed them asking if they will ship to Canada - it's not an option on their website.

Do you happen to recall what product you purchased for the audio input? I have searched, but my Google-Fu isn't working this time.


I have the 8.1 as well. Youre truck doesnt have the 4l80e it has the 4l85e with the 5 planetaries they started using it in late 02 You will not destroy that trans. Its rated for 16,000lb vehicles.
Increasing spring rate by cranking the keys is a myth. The spring rate doesnt change, all it does is reclock the position of the T bar and hence the lower control arm, anybody that says otherwise is wrong. If you disagree please explain how it increases the spring rate.
285s will fit fine.
Autoride is different on these than the 1500s its just an electric shock not air ride. Ditch em for 5100s and throw the resisitor in or yank the fuse no more trouble light.
Ill post more shortly I gotta go to work.
So is the Autoride on the 2500 just changing the valving? Why bother!


I tried 285's on my 04 2500 and had to trim the bumper for street driving
The bumper or the air dam?


As far as the wet dog smell... I know you don't want to yank the carpet.. but I would suggest doing it and replacing the padding under the carpet as it is likely going to keep causing the odor. The padding is cheap, and the OEM stuff comes off plenty easy after removing the carpet. Its not a terrible job on these trucks, I have done it dozens of times from my days customizing vehicles. An impact and or/air ratchet really speeds it up! Removing the carpet will also make it easier to really get it clean, and then rinse with clean water. Getting to soap out of the carpet with a rinse will help it not to accumulate dirt so fast. Its worth it.
I hope it doesn't come to that, but one does what one must.
 

RedF

Adventurer
Immm baaaack. Anyways as for the smell go to your local rental shop and rent an ozone machine. Put in the burb turn it on shut the doors and let it run overnight and it will get rid of the stink. I second the notion of removing/replacing the carpet and (at least) the padding. I would remove the carpet before you shampoo it so the padding doesnt get wet and then mildewy. New carpet can be had for $300. My wife just bought a vacuum that has rubber fingers on the roller instead of brushes and holy crap does it grab dog hair! I thought our dyson was good. I think its a bissel or hoover. I havent used it in the vehicles yet but I imagine it will work just as well.

As to the keys. As I said before cranking the bolts doesnt change the spring rate at all it changes the geometry. The only way to change the spring rate is with a different Tbar. But with the stock keys you wont have enough bolt travel to level the 2500 burb/xl and the bolts will be pushed all the way up. It is better to get reclocked keys so its level and you wont have as much bolt thread sticking up past the block holding the key bolt

As for power. The 8.1 leaves a lot on the table in stock configuration. I have a black bear tune and it really makes a difference. Headers and open intake will also help. According to the dyno sheets Im sitting around to 430hp and 550ftlbs. Incredible engine but it is thirsty and does use some oil about a quart every 2-3000 miles depending on how you run. Much more impressive than the 7.4 or 6.0 and a world of difference over the 5.3.

Replacement seat covers are on ebay I think theyre about $200 for nice leather ones in tan or grey.

As for radio. There are factory radios on ebay that have had aux inputs added. There are also videos on youtube on how to diy it if your handy. I did it on the truck its just a few cheap parts and some solder joints. It hooks into where the cassette player hooks in. Your sub may not have that being newer mine does.

I went with a sony double din unit that incorporates gps and rearview camera. Its touchscreen and has aux, bluetooth, and USB inputs. Seperate bass sub outputs as well. I think the new version is around $300. I went with component sets in all four doors and it sounds great. I have a new bass sub and new subwoofer but havent made time to intall them yet because it doesnt really need it.

Ill second the H2 wheels. I saw a brushed set that had the faces polished with the PY0 center caps and they look AWESOME! on the burbs. Im looking for a set (or 2) for the truck and maybe the burb for the next tire replacement. I have 285s on the PY0 for now.
Good idea on the O zone machine. I'll look into that. I'll pull the carpet, but only if I have to... It's not that I'm afraid of doing it, or incapable; it's just one more thing on an ever-growing list.

I checked the oil before I test drove it and it was full, and checked again this morning. I know they use a little oil, and I'm watching for it.

What do you have done to yours for those HP and TQ numbers? That sounds fun! Have you had any issues because of it? The mileage doesn't bother me, my Silverado is a 6.0 with 4.10s and regularly returns single digit MPG.

My stereo does not have a cassette player. I have very little interest in replacing the head unit with an aftermarket part. The factory system sounds good to me. I've never really been into car audio.



Thanks for all the input thus far gents!
 

zoomad75

Observer
Cranked bars ride like crap, regardless of the definition why. Get keys if you want to have the cheap lift.

For the aux input kit here it is:
https://www.amazon.com/iSimple-IS31-Antenna-Modulator-Aftermarket/dp/B002U5XPBE/ref=sr_1_10?crid=13VZJ9N9YNFH&keywords=aux+input+adapter+for+car&qid=1561344177&s=gateway&sprefix=aux+input+ada,aps,194&sr=8-10

15 psi at idle isn't abnormal for the engine. Watch what it does after the oil change as it might come up slightly. But do keep an eye on the level.
 

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lilkia

Active member
Cranked bars ride like crap, regardless of the definition why. Get keys if you want to have the cheap lift.

For the aux input kit here it is:
https://www.amazon.com/iSimple-IS31-Antenna-Modulator-Aftermarket/dp/B002U5XPBE/ref=sr_1_10?crid=13VZJ9N9YNFH&keywords=aux+input+adapter+for+car&qid=1561344177&s=gateway&sprefix=aux+input+ada,aps,194&sr=8-10

15 psi at idle isn't abnormal for the engine. Watch what it does after the oil change as it might come up slightly. But do keep an eye on the level.
Do you not realize that changing keys are the exact same thing as cranked bars? Its the exact same thing. Whether you crank the bolts up on the existing keys or swap to new clocked keys it twists the Tbars which rotates the lower control arm down. There is absolutely no difference in ride at all between the two. In fact new keys allow you to crank the bars even further which would make it ride even worse according to you. So which is it new keys ride better or worse? You obviously have no experience with either.
 

XJLI

Adventurer
Do you not realize that changing keys are the exact same thing as cranked bars? Its the exact same thing. Whether you crank the bolts up on the existing keys or swap to new clocked keys it twists the Tbars which rotates the lower control arm down. There is absolutely no difference in ride at all between the two. In fact new keys allow you to crank the bars even further which would make it ride even worse according to you. So which is it new keys ride better or worse? You obviously have no experience with either.
Yup, the "bad ride" from a crank is either the shocks reaching the limit of travel, the control arms bottoming out on the travel stop, or both. I have my bars cranked 2" with no change in ride quality.
 
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