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8.1L/496 Tech

So would be it stupid to convert to propane? Gas is 3.99 for 87 here. Propane can be had at mid 2.xx a gallon.
 
Lots of the industrial 8.1L engines run on propane or natural gas. Generally speaking you use twice as much propane as gas to do the same amount of work, so it'll be a wash fuel cost wise and a loss in power and the cost of converting it. There is a reason why almost nobody runs propane anymore.
 
11mpg no matter what. Long freeway trip, all in town, all downhill at 50mph... it gets 11. They have a 9th injector and when the ecm senses low fuel usage it will kick on and spray gas down the side of the road.


That's just weight.

My 7800 lb truck with a 5.7 gets 12mpg. My 5500lb yukon gets 16mpg with AWD and a 6.0. Every 6.0 truck I've driven got 6-12 towing or empty. My 5.7 gets 6 towing 10k, my buddy gets 6mpg towing a 44' 5th wheel that weighs in at 18k with an 8.1.
You can get mid 20mpg in a RCSB cruising empty, because the truck will only be 4400lbs. Doesn't mean it has the power or chassis to tow.


GM should have sold a fuck-ton of 8.1's, but people were scared of big block fuel economy. In reality they do almost exactly the same as the 6.0 but with a hell of a lot more torque.

Buy a damn hybrid if you want fuel economy. :flipoff2:


The diesels are no better anymore. My 18 duramax gets 8mpg running 25500 gvw with a trailer. Burns a shit load of DEF when towing also.
 
What should hot idle oil pressure be on these? I get a good 40 when running and driving, but under 15 at idle. Running 10w30. 35k miles.

should I upgrade the oil pump, or just switch to thicker oil?

Its a 2006.

thank you
 
What should hot idle oil pressure be on these? I get a good 40 when running and driving, but under 15 at idle. Running 10w30. 35k miles.

should I upgrade the oil pump, or just switch to thicker oil?

Its a 2006.

thank you
My 2003 is around 20 at idle with 5W30 @ 187K with 180* TStat. I'll double check when I get back to Nor Cal.
20210811_092435.jpg
 
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Thats what my 02 8.1 XL does with 255k on the clock. I run 5w30 or 10w40 depending on what's on the shelf at work.
 
Thats what my 02 8.1 XL does with 255k on the clock. I run 5w30 or 10w40 depending on what's on the shelf at work.

the 15psi you mean?

i probably did this myself running it about 1800 miles not checking the oil.

Has it given you guys any trouble with those miles? Mine is pushing 1200 lb worth of wheels and tires alone, so I want to keep it as happy as possible.

ill look into an HV oil pum, might be worth it for me, assuming I didnt fubar the engine.
 
2002, 140k, 10w30, 20 idle, 45/50 driving.
 
I just picked up a 2002 Silverado 2500HD with the 8.1/Allison. 2WD. Goal is towing duties almost exclusively (32ft enclosed goose, 10k loaded).
I did not want a diesel nor a payment and this fit the bill.

It's got 130,000 miles. Engine runs smooth, plenty of power, the trans shifts super crisp and it doesn't make any weird noises. Got 14mpg driving it empty with cruise set on 70 for 320 miles, then 11.6 towing my empty car hauler in the TN mountains. So far I'm happy.

Needs a bit of interior work but I'm really wondering about the maintenance of the engine/trans combo. Water pump and hoses changed at 120,000. Tires in good shape and the battery looks recent. That's all I know.

What does irate say about stuff like valley gasket and the other scary things I read on various online forums?
Any ticking time bombs I need to address ASAP?
When do I need to be changing the Allison spin-on filter and the one in the pan ?
Front IFS pops/cracks a little when turning, I'm assuming it needs all bushings/ball-joints gone through ?

Thanks !

Cliffnotes : bought a 8.1 big block, happily putting gas in it but would like to keep doing so for a while, what to do to ensure it lasts ?

Obligatory driveway pic :

219BC83F-794F-4E32-BAE5-D681FA966110.jpeg
Update from when I opened the thread.

I end up driving around a lot more than originally planned. The long bed is awesome, I hate my DD with a short bed now.

Added better tow mirrors and they're awesome.

Found a bad radiator clamp from the PO, changed it and the coolant consumption problem I had went away. Been rock solid in that department. 180 empty to 200 degrees under heavy loads. Doesn't overheat at all.

Fuel consumption is 7 to 8 mpg towing, 10 around town, 12 on the hwy at 70/75mph.

The novelty wore off but the 8.1 doesn't impress me much anymore. Does the job but that's it. I guess it's impossible to replace a diesel with a gas engine.

Recently the fan clutch seems to stay on more often. Probably because it's so warm out there. When that happens it really makes the truck sluggish and it sounds like a damn airplane.

Front end pops haven't gone away. But now when I hit the brakes it veers to the left. I need to look into that. I checked the brakes and the calipers sliders and pistons are free and in good shape and the pads are worn evenly. It feels like there is play in the steering. Weird thing is, driving on the road it feels tight. Steering feels weird when you hit the brakes or when you maneuver at low speed.

It developed a little vibration on the rear end around 80mph. I had a flat tire and it was patched up. Maybe the did a shit job on the balancing. Need to get that checked. I wish I had my own tire changing and balancing machines.

About to change the oil for the third time soon, will do the Allison filter again.

Ideas on the front end ? I wish the WFO kit wasn't that expensive and I wasn't spending all my money on the buggy. This thing needs a solid front axle.
 
The novelty wore off but the 8.1 doesn't impress me much anymore. Does the job but that's it. I guess it's impossible to replace a diesel with a gas engine.

this is true. although on a pickup, it should do everything you need it to do. short of towing a 36k gooseneck maybe.
 
I find myself flooring it to pass on the highway while empty etc more than I would like.
 
Bringing this back up to pick the brains of the forum members...

2002 Silverado 2500HD with a 8.1

2 weeks ago I had to do an emergency stop on the hwy to avoid an idiot merging last mine. Full on panic stop, ABS engage etc... Barely missed him.
When I started moving again, the front axle was shaking like a mofo around 50mph for some reason. It never did so before.

I was 2 miles away from home to I pushed on and when I made it in the driveway I realized the right front brakes were locking up. Thick white smoke, heavy brake smell etc...

I let it cool overnight and the next day I took it for a drive. Came back home after 5 miles, same thing happening again.

On a whim, and since they needed pads and rotors anyway, I shotgun new calipers, pads, rotors and hoses in the front. Same results.

I did plenty of testing so here is what happens : When I press the brakes, the right front caliper locks up. Leave it alone for 45mn/1h and it slowly releases. Press the brakes again and the same thing starts over.

I did unbolt the master-cylinder from the booster, same problem.

The weird thing is, if I put a big screwdriver between the pads and rotor, I can pry the caliper open and everything is fine until I press the brakes again. So they're dragging, preventing me from spinning the tire by hand, but not clamping hard enough that I cannot push the pistons back in.

Maybe it's an issue with the pressure relief in the master (???), so I'm going to swap a new master tomorrow, but realistically, I'm out of ideas.

One thing to note, from time to time, I have the ABS light that comes on and off, due to a bad sensor (maybe ?), but I don't think it's ABS related because of the fact that the same problem happens every time I press the pedal. Same thing when the engine is off, ignition off, or on.

Thoughts ?

Thank you
 
Bringing this back up to pick the brains of the forum members...

2002 Silverado 2500HD with a 8.1

2 weeks ago I had to do an emergency stop on the hwy to avoid an idiot merging last mine. Full on panic stop, ABS engage etc... Barely missed him.
When I started moving again, the front axle was shaking like a mofo around 50mph for some reason. It never did so before.

I was 2 miles away from home to I pushed on and when I made it in the driveway I realized the right front brakes were locking up. Thick white smoke, heavy brake smell etc...

I let it cool overnight and the next day I took it for a drive. Came back home after 5 miles, same thing happening again.

On a whim, and since they needed pads and rotors anyway, I shotgun new calipers, pads, rotors and hoses in the front. Same results.

I did plenty of testing so here is what happens : When I press the brakes, the right front caliper locks up. Leave it alone for 45mn/1h and it slowly releases. Press the brakes again and the same thing starts over.

I did unbolt the master-cylinder from the booster, same problem.

The weird thing is, if I put a big screwdriver between the pads and rotor, I can pry the caliper open and everything is fine until I press the brakes again. So they're dragging, preventing me from spinning the tire by hand, but not clamping hard enough that I cannot push the pistons back in.

Maybe it's an issue with the pressure relief in the master (???), so I'm going to swap a new master tomorrow, but realistically, I'm out of ideas.

One thing to note, from time to time, I have the ABS light that comes on and off, due to a bad sensor (maybe ?), but I don't think it's ABS related because of the fact that the same problem happens every time I press the pedal. Same thing when the engine is off, ignition off, or on.

Thoughts ?

Thank you
If it was an issue with the master cylinder both front calipers would drag.
 
ABS. One of the valves is stuck and won't fully release. Go down a gravel road and see if you can get it to pop free by activating it a bunch.:flipoff2:
I was hoping it wasn't that. How much of a pain is it to fix it ?
 
I was hoping it wasn't that. How much of a pain is it to fix it ?
I can't remember the issue, but I removed the abs fuse for a short amount of time on a '03 ½ ton. That fixed whatever the issue was.
When I went to fix it with the fuse installed my coworker slammed the brakes and it fixed itself.

It seems like the abs motor was running though.
 
A quick scan would help a lot to see whats being sent to the abs comp vrs reality.

Something is triggering it.
Abs systems work in multiple ways but mostly by either reducing applied psi or pulsing to keep the offending wheel the most traction and braking psi.

Its fine untill you push the pedal.......
Abs uses a tone ring in the wheel bearing to show the comp how fast each front wheel is rotating. If one wheel is not rotating while the other is and the vehic knows that is moving based on trans/tcase/vss/ engine rpm/trans gear selection and such it assume that wheel is not and is in fact skidding, So it pulses.


Not saying its THE answer but a vss wire or wheel bearing may be in order.

Read the vss with scanner and verify that they are reading and reading the same.
 
Obviously, real troubleshooting and a good scan tool are the best first steps. If it turns out to be the ABS module, there's a company out of Minnesota (I think) that rebuilds them and were priced well. If it gets to that point. Lmk and I'll try to dig up their name.
 
What is a good scan tool ?
I just bought an Autel MP808BT.

Should do the trick and it was somewhat fairly priced. I chose it over the MP808K for the wireless connection and the Key Programming ability.

Reading this has kinda made me want to find a low mileage reg cab 2500hd with the 8.1 and 6 speed for a dd

I'm happy with the Allison but i'd trade it for a 6sp in a heart beat if they weren't so hard to find.
 
I just bought an Autel MP808BT.

Should do the trick and it was somewhat fairly priced. I chose it over the MP808K for the wireless connection and the Key Programming ability.

Have to look into that.
 
Update on my junk, swapped out bed, tinted windows, swapped on nice set of stock wheels, rebuilt brakes all around, replaced exhaust manifold gaskets and hardware, steering rebuilt except for box (up next), cv axles, fuse block, and added cruise. Also eraser wheeled the steekers off. Been a fun project so far, mechanically its solid now so its time to make it nicer for long trips. Been knocking out 9.8-10/8 daily driving with a best of 11.8ish on a longer trip with cruise set on 63. Still have to find an interior shop to do the headliner and swap over the leather cover on the passenger side lower front cushion.

Here are a few pics of the process over the last 6 months.

061.jpg


06 bed 2.jpg





06 clean.jpg
 
Reading this has kinda made me want to find a low mileage reg cab 2500hd with the 8.1 and 6 speed for a dd

An 8.1L allison and ZF6 arent remotely comparable. Fuck autos behind these engines. I've settled for a NV4500 as the ZF6 are too much $, due to duramax prices and GMs retardation of no manuals early on.
 
An 8.1L allison and ZF6 arent remotely comparable. Fuck autos behind these engines. I've settled for a NV4500 as the ZF6 are too much $, due to duramax prices and GMs retardation of no manuals early on.
I feel the same way. I want a manual behind a big block. Kinda want the zf6 never been a fan of the nv4500.

IF I'm getting fucked on the price of fuel to feed the fucking thing I might as well enjoy it with a manual :smokin:
 
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