Transmission?? or fuel pump?

[99 Mob Mobile]

i have a 99 tahoe 4x4 with 145k.. i do beleive the tranny was rebuilt not to long ago.. when i'm in town cruising around 10-40 I'll usually put it in third gear to disable the overdrive which makes the tranny shift alittle bit less.. I live in Maine and its been very cold out the last couple of days.. like 15 degrees..anyway when i was leaving the town i was in and i cruised up to 55 and left it in third by mistake so the rpms where turning 2200.. i had the radio on and i didnt hear it then whe n iwas going at a constant speed right at 55 my car almost felt like it was hitching alittle bit more of a shudder.. you almost think its the tranny but if it was that it be having problems by now.. It'll do that in all of the gears including drive.. but you have to be going at least 75mph to get the engine to turn that high and its not as noticable cause the vechical is traveling fast but you can still feel it and you feel it alot more at lower speeds when you have the rpms over 2000.. if you drive over 2000rpms if drives fine..only when your at a constant speed over 2000rpms.. if your taking off and it turns 4grand and it goes back to 1500 when you get to 60 you notice absulutly nothing.. its only when your at a constant speed with your rpms above 2000...

I'm clueless is to what it is..I would think if it was my tranny sliping I'd be noticing it at all speeds not just with the rpms revved up.. I go up hills and it drives fine.. My only guess its a bad regulater or something in the fuel pump but i really dont know what to think.. I have no warning lights.. everything works and it shifts as smooth as it can..

Its beyond me..

Fuel pump is original.. Filter was changed 3,000 miles ago..

[99 Mob Mobile]

oxygen sensor maybe??

[maxwedge]

Someone who is qualified need to drive the truck to feel the condition this could be a trans problem or something in the engine performance, could do a fuel pressure test, check for for misfire counts on a scanner, do a full trans scan to look at slippage errors or solenoid functions, this may not be a " dyer" type repair.

[99 Mob Mobile]

I dont beleive its in the transmission.. if it was i would be having alot more problems by now and it would both climbing hills.. My honest guess is that I have a fuel pressure problem or a bad co2 sensor.. I would like to think that i would have a check engine light on if it was something with the fuel pressure though... or a bad c02 sensor

[j cAT]

Originally Posted by 99 Mob Mobile

I dont beleive its in the transmission.. if it was i would be having alot more problems by now and it would both climbing hills.. My honest guess is that I have a fuel pressure problem or a bad co2 sensor.. I would like to think that i would have a check engine light on if it was something with the fuel pressure though... or a bad c02 sensor

check fuel pressure very easy/quick. disconnect vacuum line to fuel regulator should not have gas odor if so regulator, diaphram leak,. if ok check plugs/wires compare they all look normal color, resistance approximately the same, check vacuum lines esp. pcv hoses. possible that transmission pressure is low that can be checked quickly. check for codes, could be not enough failures to throw light on.maybe bad gas ice in tank......................

[maxwedge]

To check fuel pressure a gage must be connected to the fuel rail port, no other way here. How do you " quickly" check if the trans pressure is low?

[j cAT]

Originally Posted by maxwedge

To check fuel pressure a gage must be connected to the fuel rail port, no other way here. How do you " quickly" check if the trans pressure is low?

transmission line tap is drivers side directly above 1st pan bolt forward about 3-4inches straight up. pressure in park should be 200-225psi. I would bring to trans. repair shop for this quick check........

[maxwedge]

That is more like it, for a dyer in this thread that is not a " quick" check, agreed?

[j cAT]

Originally Posted by maxwedge

That is more like it, for a dyer in this thread that is not a " quick" check, agreed?

this transmission check is available in my area, and if you make appointment, they will do this for you, and with this info you will get a good idea of the transmissions condition . if the pressure is low and not corrected you will suffer transmission failure.this can be done quickly with no cost or very little expense at most . for most vehicle owners on this forum, checking the fuel pressure is not a quick check. if they bring in to a good repair shop, which most do, because they don't have pressure guage, it's then quick. this is all about diagnosis without removing / breakdown of componets to determine condition to help locate defect with minimum cost. I believe this method is the cheapest way to go, before spending money on guesses. repair shops like to replace parts only, or hook up scanner and not take measurements to ensure that they are replacing the defective part. also if repair shop don't undestand your need to perform these measurements or can't I would not use their services....................

[99 Mob Mobile]

I doubt its my transmission.. I did install a Jetchip performance mass air sensor and I do beleive that is throwing off my CO2 sensors.. it wouldnt suprise me cause thats kinda what it acts like

[maxwedge]

Originally Posted by 99 Mob Mobile

I doubt its my transmission.. I did install a Jetchip performance mass air sensor and I do beleive that is throwing off my CO2 sensors.. it wouldnt suprise me cause thats kinda what it acts like

In the future, the inclusion of this info is always helpful, as opposed to bringing it in at this point!

[muff34]

Originally Posted by maxwedge

In the future, the inclusion of this info is always helpful, as opposed to bringing it in at this point!

Ya right on!!!

[pokergypsy]

you might have some water in the trans fluid i did my rad and thear was some water in the trans line the dealer told me it was a tork cov but i put some trans cont.that takes out water from the fluid and no problems cant say if you have the same prob but its a cheep fix?

[j cAT]

Originally Posted by pokergypsy

you might have some water in the trans fluid i did my rad and thear was some water in the trans line the dealer told me it was a tork cov but i put some trans cont.that takes out water from the fluid and no problems cant say if you have the same prob but its a cheep fix?

i am having a hard time understanding this comment you replaced your radiator and somehow got water into the transmission by way of the radiator transmission cooling lines. but how did you correct this i cannot understand.......what is an trans cont. ?

[pokergypsy]

im sorry trans fluid addative.. as far as water geting in the trans line my guess is when they fixed the raddiator i think they put it in water to clean it? because when i put in back in i did see some water come out of the trans line and i guess i didnt take it all out and i hope you understand? now it fix my problem? im not saying its gonna fix everyones but it cant hurt?