Looking for info on miles per hour at a given RPM. I have a '01 SS which is all stock except of a Magnaflow cat convertor. Milage has steadly dropped over the last year. I'm noticing that it's turning 3,000 rpm's @ about 65-67mph which seems higher that it used to run.

Can anyone out there tell me what your 2001 SS tachs at 70mph?

 

Sounds like your torque converter isn't locking up. I turn around 2700 or so at 80+ I think.

 

I run 2300 or so at 70

 

That's what I would have guessed at 70 but I so rarely cruise at 70 (usually it's between 75 and 80) that I couldn't remember off the top of my head. Sounds like the OP still has 4th gear but the TC isn't locking up. IIRC if he didn't shift out of 3rd he'd be turning 3500+ RPM.

 

Something else to think about is that you might have lost fourth gear.

 

ok i am going to ask this first because no one asked because it is simple and also can effect it as well. did you do a tune up also did you do the filters as well as the oil when you noticed it. also when was your last trans service as well? it could have some thing sticking like a valve body due to dirty fluid? i would drop the pan and change filter and check every thing. also see if the fluid didnt smell like varnish. i am just asking before jumping for the most expencive items but i always ask for what is the record is first. to narrow the list down before going down the check list on what it could be. i dont mean to be rude to any body i just want to ask

 

could always have the car scaned for SES codes as there could be some in the PCM but not set the light. would give you an idea if something comes up.

 

imo z34 and i said it it could be some thing minor which the pcm not throwing a code or some thing simple as what i mentioned. i know our trans is computer and secondary vacume backup. to help it limp to a safe place hence the vacume back up but it also the pcm that runs the trans wich is called the tcm wich is a pain when it goes funky. when i was working for that dealer i have seen some models the tcm wich is trans controller moduel tcm that second computer next to the pcm goes. it will read a bunch of wiered things we go threw the list and see if every thing is fine and change the computer because it is stuck in a loop. when those go in the loop and try to reset it they just dont want to reset then replace it and go from there as test the car if iut will go threw the grears ok as well to see if it will go in revers as to see if it will go into fourth cruising for a short trip down the road and back

 

Monte07.... The 2001 doesnt have any vac lines at the trany. Nor does it have a separate TCM. Just the PCM. There is no back up vac system for the trany.

The 97 and older cars had a 4t60e that was vacuum controlled for the pressure and electronic for when to shift.

To the original poster just for codes. Also if u put it in to drive or tap the brake it will diss engage the tcc. This may help figure out the gear it is in.

 

that i didnt know that i am still not use to having a chevy. i have the experence with jappanes and korean as well as ford products use to work for a dealer that dealt with those types. not trully familuar with gm still learning i do admit i still have a learning curve for gm powertrain.