Our Ford-O...or should I say Mile-O slips the whole quartermile Ain't build to handle over 400 ft lbs of torque

 Seppo from Järvenpää, Finland
www.hollowheads.net (just click the hole in the head to proceed)

I finally got the chance to run the truck down the interstate following another car with a known good speedo.  The Speedo in the truck was rebuilt by a known shop a couple years ago.  It was sent back once for being wildly too slow.  The rebuilder said to send the face of the speedo the second time which I did.  It came back and was better but still much too slow.  At a known 60 mph the speedo reads 48 mph. pretty crappy but worth knowing.  The speedo doesn't start to read until something like 15mph so it may just need to have the anchor of the spring moved if that is possible.

Anyhow the tach in the truck was reading 2800+ rpm, with 100 rpm hash marks it is difficult to be more precise.  With no slippage the truck would have been going 65 MPH at that engine speed.  Therefore the slippage is 65/60 => 8.3%.  This is probably not all lost energy,  The torque converter would be increasing torque with this much slippage and this torque was required to move the truck. 

Doug T

The Highlands, Louisville, Ky.

Doug,

        The commonly accepted number I've heard is 5%. That would be the number I'd use for the end of a quarter @ speed. I would think the amount in your truck would be less than that with a stock (?) converter, but I've been wrong before! I can usually get some idea by finding a cruise speed rpm, then backing off until the car/truck starts to slow down. the difference being slippage.

       I suppose as aerodynamic as the truck isn't, and given the weight you may well be higher than a car.  

    If you can get it apart, pull the needle and reset zero by letting it just rest aginst the stop on the bench, Blow out the area around the magnets sometimes foriegn material gets in there and affects the readings. 

Frank/Rebop

Bristol, In ( by Elkhart)