12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

rpm vs mph

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Old 08-10-2009, 07:55 AM
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hey guys im wondering if my rpms sound right at 65mph im running 2500 rpm does that sound right? as far as i know the rear end is stock
 
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Old 08-10-2009, 11:59 AM
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I have a 96 with a 5 speed. At 65mph im hittin around 2100/2200 if that helps any,thats 4x4 with 4.10 rears also.
 
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Old 08-10-2009, 12:05 PM
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sounds like the converter isn't locking up. if the truck is 2WD it might have a 3.54 rear and not the 4.10.
 
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Old 08-10-2009, 12:57 PM
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its 2wd and the sticker in the glove box shows it to be 3.55 what would cause the converter to not lock up
 
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Old 08-10-2009, 01:22 PM
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low on transmission fluid,bad brake light switch, a bad lockup solenoid, bad converter, tranny needing servicing, tranny needing to be rebuilt. there are lots of reasons why one wouldn't lock up.

best way to test to see if the converter is locking up is to drive at approx 55mph in OD and after you are going on a nice flat road and the rpm's are steady push the brake pedal slightly. if the RPM's jump up a little bit like the tranny barely downshifting then it is locking and unlocking.

does the cruise control work? that will eliminate the bad brake switch.

check the tranny fluid while the truck is at operating temp in neutral on a level surface.
 
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Old 08-10-2009, 01:50 PM
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ok ill double check the fluid the cruise works and the guy i bought it from said he had it rebuilt about 30000 miles ago and just had it serviced a couple days before i bought it. i know he used to tow a show truck with it do you think they could have changed something in the tranny to help the towing?
 
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Old 08-10-2009, 10:22 PM
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tps? (only if it's a non lock-up problem) i just did the potentiometer install on the 98 and it fixed our hunting and erratic or no lock condition
 
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Old 08-10-2009, 10:29 PM
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hmm..my 97 4 by is at 2k at 75..not sure on the gear set..i was told 4.10's..and im on 33's..
 
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Old 08-10-2009, 10:38 PM
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Originally Posted by 97dirtydozen
hmm..my 97 4 by is at 2k at 75..not sure on the gear set..i was told 4.10's..and im on 33's..
x2, but I have 3.54s with the 33s on my 95 auto
 
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Old 08-10-2009, 10:39 PM
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Originally Posted by Johnny Z
I have a 96 with a 5 speed. At 65mph im hittin around 2100/2200 if that helps any,thats 4x4 with 4.10 rears also.
holy crap, at 70mph im directly at 2k with a 5 speed 3.54 gears 4x4 and that with 35" tires
 


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