I have a 2004 Duramax 2500HD. After driving 35+ miles the oil pressure gauge starts climbing and pegs past 120 degrees. Turn off ignition and needle won’t return to zero. After a few days needle creeps back to zero. Water temp OK, trans temp OK. Found similar post concerning 2003 Tahoe (Whacky Gauges). Response was to replace stepper motors. $10.00 ea. Suggested he replace all six while he was at it. Last weekend while pulling my 5th wheel trailer the tach started acting up. First the R’s were up around 3500 RPM when I knew I was crusing around 2200 RPM then R's dropped down to 700 RPM when I was doing 55 in tow mode Overdrive out and doing about 2,200 RPM. I pulled over, shut her off and the tach stayed at 700 RPM. I started the engine back up and revved it up but the tach remained at 700 RPM. The next morning the tach was at zero and when I started her up tach worked as advertised. Is this also stepper motor problem? If so where do they live and where do I find a procedure for replacement? Probably not related and if not related I will post by itself but when the Allison tranny is cold (Below 40 degrees I have no reverse. Range shift inhibihited. Dealer replaced the module on outside of tranny for $230.00 but trouble persists. I drive a ½ mile in forward and then I have reverse. Thanks, John

 

Are you getting any sort of check engine light or check gauge light?

 

Nope. Everything else seems to be working fine.

 

ok it is either the stepper motors, which i am not sure of location or procudure. it could also be a guage pod problem. i would take it to a trusted mechanic not the dealer. as far as the tranny trouble, i have worked on the allison trans that you find in motorhomes and in big rigs. sometimes if the fluid is low that will happen. alot of the times the fluid just needs to warm up and get moving. the allison is a different breed of trans. you could also get it serviced that may help. if it doesnt then it may be a fluid pressure problem that a transmission shop should take a look at.