RPM at 70 MPH 1998 Chevy K3500 5.7 Vortec
I have a 98 K3500 with the 5.7 V8 in it. I just put a Reman longblock (4-bolt
main). the only lights on the Dash is the ABS light (have the sensors to fix it
just haven't had time). when i a driving 70 the RPM's are 4k. that seems high
to me and it doesn't really sound like 4000. another issue is that when driving
70 it says 80. I replaced the VSS on the Transfer case even though there
were no codes. but still the same. I was thinking about replacing the Input
shaft speed sensor also but thought i would ask on here first.
I bought the pickup with a bad motor so I don't know if this is an issue but it
seams like it to me, what do you think?
4 grand at 70 is too high. It should be more like 2,000 rpm. Either the transmission is slipping badly or you are not in top gear.
F_O_R, sorry for makring your answer... this is new for me. I can feel it shifting through all 4 gears and when i shift into 3rd it goes and goes back to Overdrive when i go back, any other Ideas?
Unless you have stump puller rear axle gears you have a transmission problem. I would first verify the engine RPM's in case you have a tachometer problem.
it has 4.10 rear end in it. what are the best ways to check RPM? just a scanner ?
If you have the right kind of scanner you can read the engine speed.
So i got it scanned and here are the results: Idle : dash 1200 rpm, 0mph scanner 503 rpm, 0 vss hwy speed : dash 3900 rpm, 75mph scanner 2083 rpm, 60mph it looks like the sensor are working, does that lead you to think a bad cluster?
I don't know about the cluster. You may want to investigate the BCM. I will post a link.
http://knowhow.napaonline.com/bad-body-control-module-heres-tell/
I replaced the ignition switch and it is still having the same issue. What does the bcm look like on my 98? I did a little research and idc if it has one.
I believe it is under the dash on the drivers side. It would be a black box that would look something like this.
Do you know for sure it the 98 was equipmented with a bcm? I don't think it has one?
Update... I went to a junk yard and got a used cluster. The speedo is right now but the tach is still off. It was worth the $40 to verify. Looks like it is the stepper motors in the cluster. I'll update again once I replace it with a rebuilt cluster, in hopes of helping someone else.
