The Stovebolt Site Forums The Shop Area Engine Shop Speedo error

Hey Guy's,
It's been awhile. I got a problem with my 52 speedometer.It is spot on up to 35 and then starts to get fast. At 55 I'm really doing 45. Once in awhile it also starts to bounce around also. What do you think, speedo or speedo gear in the trany? I have a 3 speed and 16" tires. Thx.

Could be a cable issue in regards to the bounce. The innaccuracy is probably due to the 16" wheels, 1/2 tons were originally spec'd with 15" I think the next wheel choice would have been 17".

What does the odometer read, fast, slow or right on? The odometer is gear driven, so get it to read milage correctly then think about the speedometer.

The speedometer needle is driven off the end of the cable buy a magnet, the matching magnet is hooked to the needle assembly. If the magnets get weak, or the needle assembly gets dirty, it will not read correctly. The odometer will always read what the gears tell it.

joe

Uhm,
I thought my post was pretty clear. The speedo reads fast after 35. The odometer is weird though. Tens and single miles read fine but teens and above jump out of sequence. Also my drivers and service manuals state the truck uses 16" wheels as standard.

Is this post referring to a 1952 1/2 ton Chevrolet truck?

15" standard wheels?
17" next most common choice of wheels?
6.00x16 was base (standard)

15" would most likely have been third most common (after 6.50x16)

17"? 8-lugs, at least for 3/4-1 ton?

If the cable is lubricated sufficiently, Joe H's suggestion seems very reasonable.

I have had similar problems in a couple of vehicles. But it was also accompanied by a significant noise from the speedo. You didn't mention any noise. In my case it was the bushing where the cable connects to the speedo. The lube had dried out.

regards,
Leon

From what you have said, I would think that someone has taken the odometer apart. As far as the error is concerned, what is it like below 35. If it goes to the slow side then you probably have error due to the wrong drive gear ratio.

In general, weak magnets should make it read closer to the correct speed the slower you go. Two things come to mind when the the gauge shows faster then actual speed, one is dirt in the needle head, and the other is wrong gearing in the trans. To know which it is, you must drive a known distance using GPS or highway markers to determine what the odometer shows, at least 10 miles, 50 would be better. Remember, the odometer is a direct reading of the gearing.

Dirty cables and fittings should be corrected before testing to insure a smooth operation. Dry lubricant only in the cable, and sewing machine grade oils in the speedometer head.

If the odometer doesn't read accurately, correct the gearing or rebuild the speedometer head.

http://www.wallaceracing.com/speedo-calculator.php
http://www.transmissioncenter.net/speedometer_calibration_______va.htm
http://www.bgsoflex.com/speedo1.html