# 8.1 chevy good and bad points



## Farm Boss (Jan 20, 2007)

Bought myself a '05 chev 2500 reg cab with the 8.1 allison combo. Has 39000, wondering what you guys with this truck have had for problems. Tell me the good and bad, and things I should be watching for! Thanks a ton!


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## B&B (Nov 4, 2006)

The 8.1's are very very reliable as they were originally designed to run in excess of 250,000 miles in class A motor home chassis before needing an overhaul or major repaires. '01-'02 had crank sensor problems but they've been proven dependable ever since. Normal for them to use some oil (like most GM big blocks). Excellent power/torque, 8-11 mpg is normal. You'll run out of traction long before power.

Run 10W-40 or 15W-40 synthetic oil to lessen the oil consumption no matter what is states on the oil fill cap or owners manual. The thicker oil has been a smart, time tested change for the 8.1's. They need the spark plugs changed every 25,000 miles regardless of maintenance schedule recommendations. Since they do consume some oil they like to leave oil deposits on the plugs, and will cut down on power/smoothness. Close the gap up on the plugs to .045 from the recommended .060, makes a noticeable difference in power. They also respond well to aftermarket power upgrades.

The Allison's work great. Change the spin on filter every 15,000 miles or so and change the fluid every 25,000 and it'll provide years of dependable service. Dont get in a big hurry in reverse, they're geared quite low.

Things to keep an eye on:


Factory rear rotors delaminate. Good quality aftermarkets rotors last longer. 
Rear calipers like to seize on their slide pins (lube caliper slides once a year to avoid problems)
If your plowing with it keep an eye on the frame right behind the upper control arm brackets for cracks if the truck doesn't have the extra frame gussets there. (Thread in the Chevy forum with more info on this issue)
Gage clusters give some problems. Not as expensive to fix as it once was.
Intermediate steering shafts can cause clunks and rattles in the steering.


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## plowman4life (Jan 16, 2008)

B&B;547449 said:


> The 8.1's are very very reliable as they were originally designed to run in excess of 250,000 miles in class A motor home chassis before needing an overhaul or major repaires. '01-'02 had crank sensor problems but they've been proven dependable ever since. Normal for them to use some oil (like most GM big blocks). Excellent power/torque, 8-11 mpg is normal. You'll run out of traction long before power.
> 
> Run 10W-40 or 15W-40 synthetic oil to lessen the oil consumption no matter what is states on the oil fill cap or owners manual. The thicker oil has been a smart, time tested change for the 8.1's. They need the spark plugs changed every 25,000 miles regardless of maintenance schedule recommendations. Since they do consume some oil they like to leave oil deposits on the plugs, and will cut down on power/smoothness. Close the gap up on the plugs to .045 from the recommended .060, makes a noticeable difference in power. They also respond well to aftermarket power upgrades.
> 
> ...


yea mine had the crank sensor problem. other than that. it was one awesome truck. i bought it brand new. died this winter at 185K + change. i did a lot of aftermarket things to it tho.

had a programmer. cold air intake. full gibson exhaust headers back. i did a front end conversion to the solid front axle. had an air locker. bunch of other stuff. put a lot of money into that truck.

absolutely run a 15W-40 in it. thats what i did. truck could have easily gone a lot longer than it did. but i had a little incident plowing that wrecked the engine and transfer case and i didnt want to fix it. wish i did. but o well.

i miss that truck ill tell u what. wasnt the best on gas but made up for it with power.

that is one truck you shouldnt worry about. keep it happy and it will last forever. **** its a chevy nothing works harder or lasts longer.


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## Triple L (Nov 1, 2005)

hay do mind me asking how much it costed you to do the solid front axle conversion on your truck and where you got the kit from... Did it make any difference ? thanks


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## exmark1 (Nov 30, 2005)

From experience watch the oil level! I had one with 60 K used a quart every 500-700 miles, so I traded it.


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## B&B (Nov 4, 2006)

exmark1;547648 said:


> From experience watch the oil level! I had one with 60 K used a quart every 500-700 miles, so I traded it.


What year was the truck exmark?


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## NCat496 (Mar 30, 2008)

I purchased 2 2007 GMC Sierra 2500HD Classic's with the 8.1/Allison combo and i had to order them and wait about 6 weeks for them because no one was buying the 496 because of gas prices. One problem that i have found with it is that one of the motor mounts seems to be bad because it makes a klunk noise when i am plowing or pulling a heavy trailer. unless anyone else knows what the problem is, i would like to know. Also i have talked to a few people that had the 496 and traded it in and went to the 6.6 diesel because of gas prices and they said that the 496 will out pull the 6.6, i cannot confirm that because i have not done the test.


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