Couple of issues

1575 Views 5 Replies 4 Participants Last post by c_heskett, Apr 7, 2007

c_heskett

Discussion Starter · Apr 3, 2007

'02 LB7 Allison

1: Today I was driving on the interstate, about 70mph, cruise on, with a hell of a cross wind, and when I would go up a hill as it would accelerate..the more load it was under there was a pretty loud knock/ticking sound. Never heard it under normal driving before. I know it's hard to diagnose a sound you can't hear but thought you guys might have some ideas.

2:Under very light acceleration, when it shifts, right after it shifts sometimes it will surge. By surge I mean the engine will rev up for a split second. Almost like a diesel "bark" heh.

Any help is greatly appreciated

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RayIN

· #2 · Apr 7, 2007

#1 could be the TCM needs the latest service update (re-flash).
The answer to question #2 may be found by scrolling down to letter Q, here: http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11#100

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HuskerDiesel

· #3 · Apr 7, 2007

c_heskett said:
'02 LB7 Allison

1: Today I was driving on the interstate, about 70mph, cruise on, with a hell of a cross wind, and when I would go up a hill as it would accelerate..the more load it was under there was a pretty loud knock/ticking sound. Never heard it under normal driving before. I know it's hard to diagnose a sound you can't hear but thought you guys might have some ideas.

2:Under very light acceleration, when it shifts, right after it shifts sometimes it will surge. By surge I mean the engine will rev up for a split second. Almost like a diesel "bark" heh.

Any help is greatly appreciated

1- the knocking can be from a lick of lubrication in the diesel. the new ULS fuel for 2007 has limited lube factors for the older engines. Have you recently switched fuel stops?

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05_LLY

· #4 · Apr 7, 2007

ANy mods to the truck?

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c_heskett

Discussion Starter · #5 · Apr 7, 2007

Thanks for the replies guys. Since I've purchased the truck (only a month ago) I've been filling up at the local truck stop. They run that low sulfur stuff. Should I be running an additive?

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c_heskett

Discussion Starter · #6 · Apr 7, 2007

No mods that I know of. Don't see anything under the hood to make me think it has any mods. Just purchased the truck from a dealership about a month ago. "GM Certified" : ) It also does seem under powered compared to a couple of other duramax's that I've ridden in.

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