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  1. #1

    Default what is your 3.8's rpm@ 60mph

    Okay good people I need to pick the collective brains here.I am currently looking at a 1983 Mustang convertible 3.8 2v auto trans with 110k on the odo.Car runs pretty good the shift between 1-2 is not noticeable and 2-3 the shift is soft but noticeable around 40mph.However I noticed that the rpm's seemed a bit high...60 mph-2800 rpm.Am I wrong thinking that is a bit high.I thought it would have been around 2250rpm or so.Also when I was going 55 or so and floored it accel was slight.Did not seem to kick down,It has been years since I had a 3.8 fox LTD so my memories are a bit fuzzy on performance but I seem to recall it was not stellar either longevity yes,performance no.The fluid in the transmission had a good color and no off odors.The car body is in good shape,no rust,needs paint,no dents.The interior is okay,needs cleaning.Needs a dash pad and a stereo.The top has many patches and will need replacing one day.Tires are new.A/C is there but seemed inop.The owner is asking 1200 ,i was thinking 950 or so.If the transmission is not an issue as evidenced by the rpm.

  2. #2

    Default

    Top gear cruise rpm depends hugely on the rear axle gearing, and a bit lesser on rear tire diameter, and whether factory-installed or somebody changed the rear axle's ring and pinion (not usual with granny's V6 Mustang, lol), but that rpm @ 60mph does seem a tad high for what's normally factory rear gearing, and might be from some transmission slippage. My '86 has a 3.8L V6 with a Holley 500cfm 2-barrel on it now, a C5 automatic transmission, 2.73:1 rear axle gearing, and revs right at about 2100rpm @ 60mph. After all this time and the mileage, the transmission you're describing sounds like it's working okay, but no doubt could use it's fluid and filter changed, it's bands adjusted, the vacuum modulator valve's screw adjusted inward for firm shifting, the kick down adjusted at the carburetor connection, and an external transmission cooler never hurts. All those things affect shifting, shift feel, and cruise rpm. Shifts should be noticeable, and kicking down should be very noticeable, either from 3rd to 2nd at highway speeds, or quite noticeably down to 1st gear at lower speeds.
    Last edited by Walking-Tall; 02-23-2017 at 12:28 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3

    Default

    Most 3.8's were a 3.27 ratio. With a non od trans, that seems about right to me. Could always throw a stick shift in it for a few $$$ and have more power and better gas mileage.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  4. #4

    Default

    NOT early or mid '80's 3.8's with automatics. Non-od automatic transmission equipped rarely got anything approaching 3.27's, lol

    OP, show us your door sticker, please
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  5. #5

    Default

    Thanks folks.
    I usually commute to work 30(45-60minutes) miles one way in a Buick Park Ave and I get a combined (40%town/60% hiway no interstate) mpg of 24.But in the last few months it has developed a hesitation in first gear around 4-7 mph.So I am thinking a rebuild is in my future.I did a fluid change last year when it was giving me some hard shifts which went away after the fluid change.The local transmission guy has months of backlog so I know when it dies I will need another vehicle.Hopefully one that gets decent gas mileage.From what I have read this Mustang should get about 22-23 combined mpg,does that sound right?Here is the CL link https://athensga.craigslist.org/cto/5968374099.html
    My other option is a 84 Marquis I am going to look at tomorrow.Here is the CL link for that one https://atlanta.craigslist.org/atl/cto/5994795380.html
    I am leaning towards the Mustang but I like unusual cars so the Marquis qualifies.There is only one Marquis around town and I have not seen it in a few months.

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