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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 10-03-2002, 08:20 AM   #1
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Default Tach reading

I keep seeing a lot of big differences in what everyone says their car run on MPG. I get about 20-22 overall city and highway combined driving to and from work. I tach about 23-2500 when running 65-70 mph. Is this normal or not? What do y'all tach at various speeds?
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Old 10-03-2002, 08:28 AM   #2
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I can't remember what you drive.....but it shouldn't differ too much from model to model.
(you might want to put the pertinent info in your signature....click on profile above and enter whatever you want, it'll be a big help for everyone).

I usually run under 2000 rpms at 65mph. You seem to be running somewhat high, about where you would be running if you weren't shifting into overdrive. Check to see if there'* a difference between drive and overdrive. It should be significant. If it'* the same, you have a problem.
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Old 10-03-2002, 08:48 AM   #3
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I think I added pertinent info to my signature if I did it correctly...sorry about that I did not think about putting it in at the start. I had to have the transmission replaced at 69,000 miles ( had the tranny serviced at the dealer at 59000, GM and the dealer said sooo sorry) would having a rebuild in it change anything ?
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Old 10-03-2002, 08:50 AM   #4
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Depends on how competent your mech was. It really sounds to me like you're not shifting out of 3rd into OD. Give it a whirl like I suggested, and then come back and tell us what, if any, difference in rpm'* it makes. Do it at 60 or so mph. How long ago was the rebuild on the tranny? I'm not a real tranny expert, but this one looks pretty obvious.
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Old 10-03-2002, 09:00 AM   #5
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I now have 142,000 on the car. The tranny guy is one the best in our area. I'll check on the shift into OD and get back with you.........Either way, the rebuild has lasted longer than the factory........go figure
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Old 10-03-2002, 07:38 PM   #6
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Hey, forgot about that.....even on the newer ones, check the TCM connector on the front of the Tranny, Just to the right and below the EGR valve as you're facing the engine. I don't know what other symptoms you'd see if it were disconnected though.
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Old 10-03-2002, 10:39 PM   #7
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Try this, try going 65 and then setting your Cruise Control. See at what RPM the car runs at. Then try driving normally w/o Cruise Control, I bet because your foot is hitting the gas pedal a little more the rpm'* go up about 200 rpm. That is because the computer uses only as much as it needs to keep the car going 65. And since we are human and our feet get tired, kinda lean against the gas pedal and make the car do an extra 200 rpm. Just try it and see if it works. That' what I have observed in my car.
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Old 10-04-2002, 09:23 AM   #8
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60 MPH @ 1600 RPM
70 MPH @ 1800 RPM
80 MPH @ 2100 RPM

I've been getting about 27 MPG in combined city/highway mileage.
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Old 10-04-2002, 09:25 AM   #9
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That'* pretty close to me, too. Dylan'sdad'* problem sounds consistent with a loss of 4th gear (OD). I run the rpm'* he stated if I'm in 3rd.
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Old 10-04-2002, 12:41 PM   #10
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Ok folks, this is how it goes....

60 mph -2000 rpm
65 mph-21-2200 rpm all these are on cruise control
70 mph- 23-2400 rpm

If I manually shift from OD to D I can feel it shifting and watch the rpms go up and come back down, but if I tap the brake while running 70 with my foot on the gas, the only thing I notice is the brake grab, the rpms do not change. I think I may be going into OD but I am not sure about this lock up thing.............what to do now????

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