8.1 liter 2500 rev limit in Louisiana
12-06-2008, 09:57 PM
#1
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8.1 liter 2500 rev limit in Louisiana
I`m kind of new here so forgive Me if I`m in the wrong place.
I have an 03 2500HD CCSB 8.1 allison with 4.10 gear.
have added K&N drop in and modified air box, newly installed NGKs,flo-pro muffler, and Hypertec programer. also have replaced fuel pump [stock] and fuel filter.
most of the time the truck runs great , STRONG to say the least. but at times it seem like it hits the rev limiter around 43-4500 rpms just before the shift points falls on its face bad. will do this in 1-2 and 2-3 shifts from a dead stop. also when in park will only rev to aprox. 3500 rpms.
other times it will rev to 45-4800 rpms in park and will pull solid to the shift points. has no check engine light or stored codes. I moved rev limit to 6000 rpm but had no affect, and shift points are not adjustible with the allison.
problem was there before I changed anything and only changed one thing at a time.
thanks in advance for any help
I have an 03 2500HD CCSB 8.1 allison with 4.10 gear.
have added K&N drop in and modified air box, newly installed NGKs,flo-pro muffler, and Hypertec programer. also have replaced fuel pump [stock] and fuel filter.
most of the time the truck runs great , STRONG to say the least. but at times it seem like it hits the rev limiter around 43-4500 rpms just before the shift points falls on its face bad. will do this in 1-2 and 2-3 shifts from a dead stop. also when in park will only rev to aprox. 3500 rpms.
other times it will rev to 45-4800 rpms in park and will pull solid to the shift points. has no check engine light or stored codes. I moved rev limit to 6000 rpm but had no affect, and shift points are not adjustible with the allison.
problem was there before I changed anything and only changed one thing at a time.
thanks in advance for any help
Last edited by labmousedb; 12-08-2008 at 10:51 PM.
12-09-2008, 01:37 PM
#2
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you have 2 different rpm limit on your truck. In park or drive. So maybe the PNP switch on your truck is going bad and not sending the NEGITIVE voltage to that input to your computer. You can check that with a scan tool to see if it is the problem. IT normally wouldnt throw a code for it unless it happens alot.
Last edited by trever1t; 12-09-2008 at 06:22 PM.
12-09-2008, 10:20 PM
#3
I do not suggest setting the rev limiter higher than 5200 RPM. The 8.1 has a LONG stroke and there's a lot of mass slinging around in there. Also, the valve springs are ineffective about 4800 anyway, the valve are already floating at 4500.
If you manage to hit 6000 with it please get that on video (camera at ground level shooting the pan.)
If you manage to hit 6000 with it please get that on video (camera at ground level shooting the pan.)
12-09-2008, 10:24 PM
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I do not suggest setting the rev limiter higher than 5200 RPM. The 8.1 has a LONG stroke and there's a lot of mass slinging around in there. Also, the valve springs are ineffective about 4800 anyway, the valve are already floating at 4500.
If you manage to hit 6000 with it please get that on video (camera at ground level shooting the pan.)
If you manage to hit 6000 with it please get that on video (camera at ground level shooting the pan.)
i use to drive my old boss's 8.1 and i use to shift it at 5500 and it would bark on the 1-2 shift every now and again..
it had a hypercrapper on it also.
12-11-2008, 10:07 PM
#5
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Thread Starter
I have no plans on turning it that much, its an every day [gas hog] /driver and I just bought a 36 ft. Wilderness 5th wheel travel trailer. shouldnt there be a change in the shift position indicator if the PN switch was acting up.
could it be the torgue management. causing this? I think this engine trans combo could shift a bit earlier to be ohnest, seems when its running right it shifts right at the red line.
must say for a big truck its fun to drive, just wish it was more consistant.
also could this be an ealy sign of a crank sensor failure? think the 01-02 had a recall on that.
could it be the torgue management. causing this? I think this engine trans combo could shift a bit earlier to be ohnest, seems when its running right it shifts right at the red line.
must say for a big truck its fun to drive, just wish it was more consistant.
also could this be an ealy sign of a crank sensor failure? think the 01-02 had a recall on that.
12-23-2008, 09:50 PM
#6
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Thread Starter
guess I found problem last night, died in parking lot leaving work .
ebay fuel pump left Me stranded. replaced with New GM part is all better now.
question? there was a recall on 01-02 crank sensors, did this carry over to 03 or there any problems with crk. sensors on newer 8.1s?
ebay fuel pump left Me stranded. replaced with New GM part is all better now.
question? there was a recall on 01-02 crank sensors, did this carry over to 03 or there any problems with crk. sensors on newer 8.1s?
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