Speedo reading 15 under? Any ideas on cause

[andy#34338]

Hello,

Just got the "Barn Car" 1960 on the road and the spedo is reading about 15 miles under (just an estimate do not know for sure how much). I do know it does not have correct trans/rear or motor (327/munci/mystery rear. Do rear end ratios or trans types effect the speedo?

Thanks Andy

http://www.geocities.com/andyww2/andy60.html

[Harmon C.]

Re: Speedo reading 15 under? Any ideas on cause

The rear end ratio will cause the speedo to be off if not matched to the speedo gear in the transmission.

[andy#34338]

Re: Speedo reading 15 under? Any ideas on cause

The rear has no numbers on it? I guess I can turn the rear wheels and count the rotation of the drive shaft to get that ratio but how do I know or match gear in trans? I am going to have the trans out for a couple of days doing a clutch job.

thanks
Andy

[Joe L.]

Re: Speedo reading 15 under? Any ideas on cause

andy-----

Here's waht you need to do:

1) Determine what your rear gear ratio is by the method which you described

2) Remove the current speedo driven gear from the transmission and determine what the tooth count and color of the gear is

If you post the above information on the board, I will be able to tell you which speedometer DRIVE and/or DRIVEN gears which you require, PROVIDING that you are using tires of near original diameter.

[Clem Z.]

Re: Speedo reading 15 under? Any ideas on cause

turning the rear wheel will not work if you have a open rear gear. the best way is to roll the car along the garage floor till the wheel makes 1 revolution while you count the turns of the drive shaft. you will need 2 people to do this,1 to push and watch the wheel turn and 1 to count the turns of the drive shaft. sometime you will need 3 to make things easier.

[andy#34338]

Lyle, Joe and Clem Will do all above and get back

Lyle, Joe and Clem.
I will do all of the above and get back to you in the next couple of days. I will try to figure out the raito tonight and start pulling the trans tomorrow night to change the clutch.
Thanks
Andy

60 Barn Not So Fresh Any More (cleaned up tons)
61 383

[andy#34338]

Speedo gear 24 teeth rear = 1 3/4 for 1 tire turn

Joe, Lyle and Clem,
Rear is not a posi, speedo gear has 24 teeth and
the yoke on the rear turned 1 3/4 times for a full turn of the tire (does that sound right)?

Joe the gear is plastic and kinda yellow in color (does that sound right)?

Thanks for the help

Andy

[Clem Z.]

Re: Speedo gear 24 teeth rear = 1 3/4 for 1 tire t

i would say the 1 3/4 is not correct but it could be 3.55 rear gear because the open diff could cause this to turn 1/2 the number of correct turns and that would be close to the 3.55

[Dennis F. King]

Re: Speedo reading 15 under? Any ideas on cause

Andy
If you live in an area that you personally know a police officer, ask him to pace you and get the read off of his certified speedometer. Better yet, if he can check you on his radar gun. I had mine done this way serveral years ago.
.02 cents worth, drive the car, have fun. Dennis