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Tue Dec 05, 2006 2:56 pm

The PO of my 72 Bus installed an automatic transmission in it. The transmission is from a 78 Bus. Does the transmission drive the speedometer on an automatic or is it the left front wheel that drives the speedometer, through a cable, of course. If I look under the Bus I can see a cable coming from the back of the left front hub but it may not be connected on the speedometer end. The reason I ask is because my speedo is off by 8 miles and hour and I have 15 inch rims on the Bus. I am actually going slower than what the speedometer says. Any ideas? Thank you for your replies!

Tue Dec 05, 2006 2:58 pm

Speedo is driven off of the left front wheel. If you are running a non stock tire size (15") that's the reason your speedo is off.

Tue Dec 05, 2006 3:29 pm

VDUBTech, I agree with you about the wheel size change. Doesn't a larger wheel cause the speedometer cable to turn slower? If that is the case than I am going faster than what the speedometer says. At 50 I am actually going 42. I think my speedometer needs calibration. Oh, and by the way, the needle is rock steady no matter where it points.

Tue Dec 05, 2006 3:44 pm

Oops my bad.....

peace

Tue Dec 05, 2006 4:28 pm

My Daughter paced me on the highway. When she was going 60 MPH I drove along side of her in the other lane and my speedometer said 68 MPH. Her car is a 2005 Mercedes so I doubt that her speedometer was off. Using a larger wheel and driving along side my Daughter shouldn't my speedometer have read less than 60 MPH when her speedometer was showing 60 MPH?

Tue Dec 05, 2006 5:21 pm

I wish I knew what to tell you. My speedo neddle bounces from 10 - 60, always has. :?: What's up with that?

Tue Dec 05, 2006 5:56 pm

I have a lowered 76 with a set of Kumho 195/50/15 tires on it.

It really is throwing my speedo off. I checked it with the wife riding beside me. When the speedo says 70 I am doing 55.

Also I just put in a new tach and found that I am running 3100 RPM at 55.

I now am wondering if cruising at 60 at 3500 is going to be bad for my motor.

Anybody know what the cruising RPM should be for a Bay to be safe on the motor?

Tue Dec 05, 2006 6:50 pm

Stop arguing.

When you try to pace one car against another, one car could be running faster than the speedo says, while the other car may be running slower than the speedo indicates.

A good way to test it would be to time it with your watch or a stopwatch while driving between two highway mile markers. If it takes 60 seconds per mile, then the car is going 60 mph.

Another way would be to go 100 in a 55 zone and have a cop arrest you. They always tell you how fast you were going. Whoops, I forgot, that won't work as a bus will barely do 55, unless you install a jet booster like I have.
Jerry